Line data Source code
1 : /*-------------------------------------------------------------------------
2 : *
3 : * parallel.c
4 : * Infrastructure for launching parallel workers
5 : *
6 : * Portions Copyright (c) 1996-2024, PostgreSQL Global Development Group
7 : * Portions Copyright (c) 1994, Regents of the University of California
8 : *
9 : * IDENTIFICATION
10 : * src/backend/access/transam/parallel.c
11 : *
12 : *-------------------------------------------------------------------------
13 : */
14 :
15 : #include "postgres.h"
16 :
17 : #include "access/brin.h"
18 : #include "access/nbtree.h"
19 : #include "access/parallel.h"
20 : #include "access/session.h"
21 : #include "access/xact.h"
22 : #include "access/xlog.h"
23 : #include "catalog/index.h"
24 : #include "catalog/namespace.h"
25 : #include "catalog/pg_enum.h"
26 : #include "catalog/storage.h"
27 : #include "commands/async.h"
28 : #include "commands/vacuum.h"
29 : #include "executor/execParallel.h"
30 : #include "libpq/libpq.h"
31 : #include "libpq/pqformat.h"
32 : #include "libpq/pqmq.h"
33 : #include "miscadmin.h"
34 : #include "optimizer/optimizer.h"
35 : #include "pgstat.h"
36 : #include "storage/ipc.h"
37 : #include "storage/predicate.h"
38 : #include "storage/spin.h"
39 : #include "tcop/tcopprot.h"
40 : #include "utils/combocid.h"
41 : #include "utils/guc.h"
42 : #include "utils/inval.h"
43 : #include "utils/memutils.h"
44 : #include "utils/relmapper.h"
45 : #include "utils/snapmgr.h"
46 :
47 : /*
48 : * We don't want to waste a lot of memory on an error queue which, most of
49 : * the time, will process only a handful of small messages. However, it is
50 : * desirable to make it large enough that a typical ErrorResponse can be sent
51 : * without blocking. That way, a worker that errors out can write the whole
52 : * message into the queue and terminate without waiting for the user backend.
53 : */
54 : #define PARALLEL_ERROR_QUEUE_SIZE 16384
55 :
56 : /* Magic number for parallel context TOC. */
57 : #define PARALLEL_MAGIC 0x50477c7c
58 :
59 : /*
60 : * Magic numbers for per-context parallel state sharing. Higher-level code
61 : * should use smaller values, leaving these very large ones for use by this
62 : * module.
63 : */
64 : #define PARALLEL_KEY_FIXED UINT64CONST(0xFFFFFFFFFFFF0001)
65 : #define PARALLEL_KEY_ERROR_QUEUE UINT64CONST(0xFFFFFFFFFFFF0002)
66 : #define PARALLEL_KEY_LIBRARY UINT64CONST(0xFFFFFFFFFFFF0003)
67 : #define PARALLEL_KEY_GUC UINT64CONST(0xFFFFFFFFFFFF0004)
68 : #define PARALLEL_KEY_COMBO_CID UINT64CONST(0xFFFFFFFFFFFF0005)
69 : #define PARALLEL_KEY_TRANSACTION_SNAPSHOT UINT64CONST(0xFFFFFFFFFFFF0006)
70 : #define PARALLEL_KEY_ACTIVE_SNAPSHOT UINT64CONST(0xFFFFFFFFFFFF0007)
71 : #define PARALLEL_KEY_TRANSACTION_STATE UINT64CONST(0xFFFFFFFFFFFF0008)
72 : #define PARALLEL_KEY_ENTRYPOINT UINT64CONST(0xFFFFFFFFFFFF0009)
73 : #define PARALLEL_KEY_SESSION_DSM UINT64CONST(0xFFFFFFFFFFFF000A)
74 : #define PARALLEL_KEY_PENDING_SYNCS UINT64CONST(0xFFFFFFFFFFFF000B)
75 : #define PARALLEL_KEY_REINDEX_STATE UINT64CONST(0xFFFFFFFFFFFF000C)
76 : #define PARALLEL_KEY_RELMAPPER_STATE UINT64CONST(0xFFFFFFFFFFFF000D)
77 : #define PARALLEL_KEY_UNCOMMITTEDENUMS UINT64CONST(0xFFFFFFFFFFFF000E)
78 : #define PARALLEL_KEY_CLIENTCONNINFO UINT64CONST(0xFFFFFFFFFFFF000F)
79 :
80 : /* Fixed-size parallel state. */
81 : typedef struct FixedParallelState
82 : {
83 : /* Fixed-size state that workers must restore. */
84 : Oid database_id;
85 : Oid authenticated_user_id;
86 : Oid current_user_id;
87 : Oid outer_user_id;
88 : Oid temp_namespace_id;
89 : Oid temp_toast_namespace_id;
90 : int sec_context;
91 : bool is_superuser;
92 : PGPROC *parallel_leader_pgproc;
93 : pid_t parallel_leader_pid;
94 : ProcNumber parallel_leader_proc_number;
95 : TimestampTz xact_ts;
96 : TimestampTz stmt_ts;
97 : SerializableXactHandle serializable_xact_handle;
98 :
99 : /* Mutex protects remaining fields. */
100 : slock_t mutex;
101 :
102 : /* Maximum XactLastRecEnd of any worker. */
103 : XLogRecPtr last_xlog_end;
104 : } FixedParallelState;
105 :
106 : /*
107 : * Our parallel worker number. We initialize this to -1, meaning that we are
108 : * not a parallel worker. In parallel workers, it will be set to a value >= 0
109 : * and < the number of workers before any user code is invoked; each parallel
110 : * worker will get a different parallel worker number.
111 : */
112 : int ParallelWorkerNumber = -1;
113 :
114 : /* Is there a parallel message pending which we need to receive? */
115 : volatile sig_atomic_t ParallelMessagePending = false;
116 :
117 : /* Are we initializing a parallel worker? */
118 : bool InitializingParallelWorker = false;
119 :
120 : /* Pointer to our fixed parallel state. */
121 : static FixedParallelState *MyFixedParallelState;
122 :
123 : /* List of active parallel contexts. */
124 : static dlist_head pcxt_list = DLIST_STATIC_INIT(pcxt_list);
125 :
126 : /* Backend-local copy of data from FixedParallelState. */
127 : static pid_t ParallelLeaderPid;
128 :
129 : /*
130 : * List of internal parallel worker entry points. We need this for
131 : * reasons explained in LookupParallelWorkerFunction(), below.
132 : */
133 : static const struct
134 : {
135 : const char *fn_name;
136 : parallel_worker_main_type fn_addr;
137 : } InternalParallelWorkers[] =
138 :
139 : {
140 : {
141 : "ParallelQueryMain", ParallelQueryMain
142 : },
143 : {
144 : "_bt_parallel_build_main", _bt_parallel_build_main
145 : },
146 : {
147 : "_brin_parallel_build_main", _brin_parallel_build_main
148 : },
149 : {
150 : "parallel_vacuum_main", parallel_vacuum_main
151 : }
152 : };
153 :
154 : /* Private functions. */
155 : static void HandleParallelMessage(ParallelContext *pcxt, int i, StringInfo msg);
156 : static void WaitForParallelWorkersToExit(ParallelContext *pcxt);
157 : static parallel_worker_main_type LookupParallelWorkerFunction(const char *libraryname, const char *funcname);
158 : static void ParallelWorkerShutdown(int code, Datum arg);
159 :
160 :
161 : /*
162 : * Establish a new parallel context. This should be done after entering
163 : * parallel mode, and (unless there is an error) the context should be
164 : * destroyed before exiting the current subtransaction.
165 : */
166 : ParallelContext *
167 828 : CreateParallelContext(const char *library_name, const char *function_name,
168 : int nworkers)
169 : {
170 : MemoryContext oldcontext;
171 : ParallelContext *pcxt;
172 :
173 : /* It is unsafe to create a parallel context if not in parallel mode. */
174 : Assert(IsInParallelMode());
175 :
176 : /* Number of workers should be non-negative. */
177 : Assert(nworkers >= 0);
178 :
179 : /* We might be running in a short-lived memory context. */
180 828 : oldcontext = MemoryContextSwitchTo(TopTransactionContext);
181 :
182 : /* Initialize a new ParallelContext. */
183 828 : pcxt = palloc0(sizeof(ParallelContext));
184 828 : pcxt->subid = GetCurrentSubTransactionId();
185 828 : pcxt->nworkers = nworkers;
186 828 : pcxt->nworkers_to_launch = nworkers;
187 828 : pcxt->library_name = pstrdup(library_name);
188 828 : pcxt->function_name = pstrdup(function_name);
189 828 : pcxt->error_context_stack = error_context_stack;
190 828 : shm_toc_initialize_estimator(&pcxt->estimator);
191 828 : dlist_push_head(&pcxt_list, &pcxt->node);
192 :
193 : /* Restore previous memory context. */
194 828 : MemoryContextSwitchTo(oldcontext);
195 :
196 828 : return pcxt;
197 : }
198 :
199 : /*
200 : * Establish the dynamic shared memory segment for a parallel context and
201 : * copy state and other bookkeeping information that will be needed by
202 : * parallel workers into it.
203 : */
204 : void
205 828 : InitializeParallelDSM(ParallelContext *pcxt)
206 : {
207 : MemoryContext oldcontext;
208 828 : Size library_len = 0;
209 828 : Size guc_len = 0;
210 828 : Size combocidlen = 0;
211 828 : Size tsnaplen = 0;
212 828 : Size asnaplen = 0;
213 828 : Size tstatelen = 0;
214 828 : Size pendingsyncslen = 0;
215 828 : Size reindexlen = 0;
216 828 : Size relmapperlen = 0;
217 828 : Size uncommittedenumslen = 0;
218 828 : Size clientconninfolen = 0;
219 828 : Size segsize = 0;
220 : int i;
221 : FixedParallelState *fps;
222 828 : dsm_handle session_dsm_handle = DSM_HANDLE_INVALID;
223 828 : Snapshot transaction_snapshot = GetTransactionSnapshot();
224 828 : Snapshot active_snapshot = GetActiveSnapshot();
225 :
226 : /* We might be running in a very short-lived memory context. */
227 828 : oldcontext = MemoryContextSwitchTo(TopTransactionContext);
228 :
229 : /* Allow space to store the fixed-size parallel state. */
230 828 : shm_toc_estimate_chunk(&pcxt->estimator, sizeof(FixedParallelState));
231 828 : shm_toc_estimate_keys(&pcxt->estimator, 1);
232 :
233 : /*
234 : * Normally, the user will have requested at least one worker process, but
235 : * if by chance they have not, we can skip a bunch of things here.
236 : */
237 828 : if (pcxt->nworkers > 0)
238 : {
239 : /* Get (or create) the per-session DSM segment's handle. */
240 828 : session_dsm_handle = GetSessionDsmHandle();
241 :
242 : /*
243 : * If we weren't able to create a per-session DSM segment, then we can
244 : * continue but we can't safely launch any workers because their
245 : * record typmods would be incompatible so they couldn't exchange
246 : * tuples.
247 : */
248 828 : if (session_dsm_handle == DSM_HANDLE_INVALID)
249 0 : pcxt->nworkers = 0;
250 : }
251 :
252 828 : if (pcxt->nworkers > 0)
253 : {
254 : /* Estimate space for various kinds of state sharing. */
255 828 : library_len = EstimateLibraryStateSpace();
256 828 : shm_toc_estimate_chunk(&pcxt->estimator, library_len);
257 828 : guc_len = EstimateGUCStateSpace();
258 828 : shm_toc_estimate_chunk(&pcxt->estimator, guc_len);
259 828 : combocidlen = EstimateComboCIDStateSpace();
260 828 : shm_toc_estimate_chunk(&pcxt->estimator, combocidlen);
261 828 : if (IsolationUsesXactSnapshot())
262 : {
263 22 : tsnaplen = EstimateSnapshotSpace(transaction_snapshot);
264 22 : shm_toc_estimate_chunk(&pcxt->estimator, tsnaplen);
265 : }
266 828 : asnaplen = EstimateSnapshotSpace(active_snapshot);
267 828 : shm_toc_estimate_chunk(&pcxt->estimator, asnaplen);
268 828 : tstatelen = EstimateTransactionStateSpace();
269 828 : shm_toc_estimate_chunk(&pcxt->estimator, tstatelen);
270 828 : shm_toc_estimate_chunk(&pcxt->estimator, sizeof(dsm_handle));
271 828 : pendingsyncslen = EstimatePendingSyncsSpace();
272 828 : shm_toc_estimate_chunk(&pcxt->estimator, pendingsyncslen);
273 828 : reindexlen = EstimateReindexStateSpace();
274 828 : shm_toc_estimate_chunk(&pcxt->estimator, reindexlen);
275 828 : relmapperlen = EstimateRelationMapSpace();
276 828 : shm_toc_estimate_chunk(&pcxt->estimator, relmapperlen);
277 828 : uncommittedenumslen = EstimateUncommittedEnumsSpace();
278 828 : shm_toc_estimate_chunk(&pcxt->estimator, uncommittedenumslen);
279 828 : clientconninfolen = EstimateClientConnectionInfoSpace();
280 828 : shm_toc_estimate_chunk(&pcxt->estimator, clientconninfolen);
281 : /* If you add more chunks here, you probably need to add keys. */
282 828 : shm_toc_estimate_keys(&pcxt->estimator, 12);
283 :
284 : /* Estimate space need for error queues. */
285 : StaticAssertStmt(BUFFERALIGN(PARALLEL_ERROR_QUEUE_SIZE) ==
286 : PARALLEL_ERROR_QUEUE_SIZE,
287 : "parallel error queue size not buffer-aligned");
288 828 : shm_toc_estimate_chunk(&pcxt->estimator,
289 : mul_size(PARALLEL_ERROR_QUEUE_SIZE,
290 : pcxt->nworkers));
291 828 : shm_toc_estimate_keys(&pcxt->estimator, 1);
292 :
293 : /* Estimate how much we'll need for the entrypoint info. */
294 828 : shm_toc_estimate_chunk(&pcxt->estimator, strlen(pcxt->library_name) +
295 : strlen(pcxt->function_name) + 2);
296 828 : shm_toc_estimate_keys(&pcxt->estimator, 1);
297 : }
298 :
299 : /*
300 : * Create DSM and initialize with new table of contents. But if the user
301 : * didn't request any workers, then don't bother creating a dynamic shared
302 : * memory segment; instead, just use backend-private memory.
303 : *
304 : * Also, if we can't create a dynamic shared memory segment because the
305 : * maximum number of segments have already been created, then fall back to
306 : * backend-private memory, and plan not to use any workers. We hope this
307 : * won't happen very often, but it's better to abandon the use of
308 : * parallelism than to fail outright.
309 : */
310 828 : segsize = shm_toc_estimate(&pcxt->estimator);
311 828 : if (pcxt->nworkers > 0)
312 828 : pcxt->seg = dsm_create(segsize, DSM_CREATE_NULL_IF_MAXSEGMENTS);
313 828 : if (pcxt->seg != NULL)
314 828 : pcxt->toc = shm_toc_create(PARALLEL_MAGIC,
315 : dsm_segment_address(pcxt->seg),
316 : segsize);
317 : else
318 : {
319 0 : pcxt->nworkers = 0;
320 0 : pcxt->private_memory = MemoryContextAlloc(TopMemoryContext, segsize);
321 0 : pcxt->toc = shm_toc_create(PARALLEL_MAGIC, pcxt->private_memory,
322 : segsize);
323 : }
324 :
325 : /* Initialize fixed-size state in shared memory. */
326 : fps = (FixedParallelState *)
327 828 : shm_toc_allocate(pcxt->toc, sizeof(FixedParallelState));
328 828 : fps->database_id = MyDatabaseId;
329 828 : fps->authenticated_user_id = GetAuthenticatedUserId();
330 828 : fps->outer_user_id = GetCurrentRoleId();
331 828 : fps->is_superuser = current_role_is_superuser;
332 828 : GetUserIdAndSecContext(&fps->current_user_id, &fps->sec_context);
333 828 : GetTempNamespaceState(&fps->temp_namespace_id,
334 : &fps->temp_toast_namespace_id);
335 828 : fps->parallel_leader_pgproc = MyProc;
336 828 : fps->parallel_leader_pid = MyProcPid;
337 828 : fps->parallel_leader_proc_number = MyProcNumber;
338 828 : fps->xact_ts = GetCurrentTransactionStartTimestamp();
339 828 : fps->stmt_ts = GetCurrentStatementStartTimestamp();
340 828 : fps->serializable_xact_handle = ShareSerializableXact();
341 828 : SpinLockInit(&fps->mutex);
342 828 : fps->last_xlog_end = 0;
343 828 : shm_toc_insert(pcxt->toc, PARALLEL_KEY_FIXED, fps);
344 :
345 : /* We can skip the rest of this if we're not budgeting for any workers. */
346 828 : if (pcxt->nworkers > 0)
347 : {
348 : char *libraryspace;
349 : char *gucspace;
350 : char *combocidspace;
351 : char *tsnapspace;
352 : char *asnapspace;
353 : char *tstatespace;
354 : char *pendingsyncsspace;
355 : char *reindexspace;
356 : char *relmapperspace;
357 : char *error_queue_space;
358 : char *session_dsm_handle_space;
359 : char *entrypointstate;
360 : char *uncommittedenumsspace;
361 : char *clientconninfospace;
362 : Size lnamelen;
363 :
364 : /* Serialize shared libraries we have loaded. */
365 828 : libraryspace = shm_toc_allocate(pcxt->toc, library_len);
366 828 : SerializeLibraryState(library_len, libraryspace);
367 828 : shm_toc_insert(pcxt->toc, PARALLEL_KEY_LIBRARY, libraryspace);
368 :
369 : /* Serialize GUC settings. */
370 828 : gucspace = shm_toc_allocate(pcxt->toc, guc_len);
371 828 : SerializeGUCState(guc_len, gucspace);
372 828 : shm_toc_insert(pcxt->toc, PARALLEL_KEY_GUC, gucspace);
373 :
374 : /* Serialize combo CID state. */
375 828 : combocidspace = shm_toc_allocate(pcxt->toc, combocidlen);
376 828 : SerializeComboCIDState(combocidlen, combocidspace);
377 828 : shm_toc_insert(pcxt->toc, PARALLEL_KEY_COMBO_CID, combocidspace);
378 :
379 : /*
380 : * Serialize the transaction snapshot if the transaction isolation
381 : * level uses a transaction snapshot.
382 : */
383 828 : if (IsolationUsesXactSnapshot())
384 : {
385 22 : tsnapspace = shm_toc_allocate(pcxt->toc, tsnaplen);
386 22 : SerializeSnapshot(transaction_snapshot, tsnapspace);
387 22 : shm_toc_insert(pcxt->toc, PARALLEL_KEY_TRANSACTION_SNAPSHOT,
388 : tsnapspace);
389 : }
390 :
391 : /* Serialize the active snapshot. */
392 828 : asnapspace = shm_toc_allocate(pcxt->toc, asnaplen);
393 828 : SerializeSnapshot(active_snapshot, asnapspace);
394 828 : shm_toc_insert(pcxt->toc, PARALLEL_KEY_ACTIVE_SNAPSHOT, asnapspace);
395 :
396 : /* Provide the handle for per-session segment. */
397 828 : session_dsm_handle_space = shm_toc_allocate(pcxt->toc,
398 : sizeof(dsm_handle));
399 828 : *(dsm_handle *) session_dsm_handle_space = session_dsm_handle;
400 828 : shm_toc_insert(pcxt->toc, PARALLEL_KEY_SESSION_DSM,
401 : session_dsm_handle_space);
402 :
403 : /* Serialize transaction state. */
404 828 : tstatespace = shm_toc_allocate(pcxt->toc, tstatelen);
405 828 : SerializeTransactionState(tstatelen, tstatespace);
406 828 : shm_toc_insert(pcxt->toc, PARALLEL_KEY_TRANSACTION_STATE, tstatespace);
407 :
408 : /* Serialize pending syncs. */
409 828 : pendingsyncsspace = shm_toc_allocate(pcxt->toc, pendingsyncslen);
410 828 : SerializePendingSyncs(pendingsyncslen, pendingsyncsspace);
411 828 : shm_toc_insert(pcxt->toc, PARALLEL_KEY_PENDING_SYNCS,
412 : pendingsyncsspace);
413 :
414 : /* Serialize reindex state. */
415 828 : reindexspace = shm_toc_allocate(pcxt->toc, reindexlen);
416 828 : SerializeReindexState(reindexlen, reindexspace);
417 828 : shm_toc_insert(pcxt->toc, PARALLEL_KEY_REINDEX_STATE, reindexspace);
418 :
419 : /* Serialize relmapper state. */
420 828 : relmapperspace = shm_toc_allocate(pcxt->toc, relmapperlen);
421 828 : SerializeRelationMap(relmapperlen, relmapperspace);
422 828 : shm_toc_insert(pcxt->toc, PARALLEL_KEY_RELMAPPER_STATE,
423 : relmapperspace);
424 :
425 : /* Serialize uncommitted enum state. */
426 828 : uncommittedenumsspace = shm_toc_allocate(pcxt->toc,
427 : uncommittedenumslen);
428 828 : SerializeUncommittedEnums(uncommittedenumsspace, uncommittedenumslen);
429 828 : shm_toc_insert(pcxt->toc, PARALLEL_KEY_UNCOMMITTEDENUMS,
430 : uncommittedenumsspace);
431 :
432 : /* Serialize our ClientConnectionInfo. */
433 828 : clientconninfospace = shm_toc_allocate(pcxt->toc, clientconninfolen);
434 828 : SerializeClientConnectionInfo(clientconninfolen, clientconninfospace);
435 828 : shm_toc_insert(pcxt->toc, PARALLEL_KEY_CLIENTCONNINFO,
436 : clientconninfospace);
437 :
438 : /* Allocate space for worker information. */
439 828 : pcxt->worker = palloc0(sizeof(ParallelWorkerInfo) * pcxt->nworkers);
440 :
441 : /*
442 : * Establish error queues in dynamic shared memory.
443 : *
444 : * These queues should be used only for transmitting ErrorResponse,
445 : * NoticeResponse, and NotifyResponse protocol messages. Tuple data
446 : * should be transmitted via separate (possibly larger?) queues.
447 : */
448 : error_queue_space =
449 828 : shm_toc_allocate(pcxt->toc,
450 : mul_size(PARALLEL_ERROR_QUEUE_SIZE,
451 828 : pcxt->nworkers));
452 2726 : for (i = 0; i < pcxt->nworkers; ++i)
453 : {
454 : char *start;
455 : shm_mq *mq;
456 :
457 1898 : start = error_queue_space + i * PARALLEL_ERROR_QUEUE_SIZE;
458 1898 : mq = shm_mq_create(start, PARALLEL_ERROR_QUEUE_SIZE);
459 1898 : shm_mq_set_receiver(mq, MyProc);
460 1898 : pcxt->worker[i].error_mqh = shm_mq_attach(mq, pcxt->seg, NULL);
461 : }
462 828 : shm_toc_insert(pcxt->toc, PARALLEL_KEY_ERROR_QUEUE, error_queue_space);
463 :
464 : /*
465 : * Serialize entrypoint information. It's unsafe to pass function
466 : * pointers across processes, as the function pointer may be different
467 : * in each process in EXEC_BACKEND builds, so we always pass library
468 : * and function name. (We use library name "postgres" for functions
469 : * in the core backend.)
470 : */
471 828 : lnamelen = strlen(pcxt->library_name);
472 828 : entrypointstate = shm_toc_allocate(pcxt->toc, lnamelen +
473 828 : strlen(pcxt->function_name) + 2);
474 828 : strcpy(entrypointstate, pcxt->library_name);
475 828 : strcpy(entrypointstate + lnamelen + 1, pcxt->function_name);
476 828 : shm_toc_insert(pcxt->toc, PARALLEL_KEY_ENTRYPOINT, entrypointstate);
477 : }
478 :
479 : /* Restore previous memory context. */
480 828 : MemoryContextSwitchTo(oldcontext);
481 828 : }
482 :
483 : /*
484 : * Reinitialize the dynamic shared memory segment for a parallel context such
485 : * that we could launch workers for it again.
486 : */
487 : void
488 258 : ReinitializeParallelDSM(ParallelContext *pcxt)
489 : {
490 : FixedParallelState *fps;
491 :
492 : /* Wait for any old workers to exit. */
493 258 : if (pcxt->nworkers_launched > 0)
494 : {
495 258 : WaitForParallelWorkersToFinish(pcxt);
496 258 : WaitForParallelWorkersToExit(pcxt);
497 258 : pcxt->nworkers_launched = 0;
498 258 : if (pcxt->known_attached_workers)
499 : {
500 258 : pfree(pcxt->known_attached_workers);
501 258 : pcxt->known_attached_workers = NULL;
502 258 : pcxt->nknown_attached_workers = 0;
503 : }
504 : }
505 :
506 : /* Reset a few bits of fixed parallel state to a clean state. */
507 258 : fps = shm_toc_lookup(pcxt->toc, PARALLEL_KEY_FIXED, false);
508 258 : fps->last_xlog_end = 0;
509 :
510 : /* Recreate error queues (if they exist). */
511 258 : if (pcxt->nworkers > 0)
512 : {
513 : char *error_queue_space;
514 : int i;
515 :
516 : error_queue_space =
517 258 : shm_toc_lookup(pcxt->toc, PARALLEL_KEY_ERROR_QUEUE, false);
518 1080 : for (i = 0; i < pcxt->nworkers; ++i)
519 : {
520 : char *start;
521 : shm_mq *mq;
522 :
523 822 : start = error_queue_space + i * PARALLEL_ERROR_QUEUE_SIZE;
524 822 : mq = shm_mq_create(start, PARALLEL_ERROR_QUEUE_SIZE);
525 822 : shm_mq_set_receiver(mq, MyProc);
526 822 : pcxt->worker[i].error_mqh = shm_mq_attach(mq, pcxt->seg, NULL);
527 : }
528 : }
529 258 : }
530 :
531 : /*
532 : * Reinitialize parallel workers for a parallel context such that we could
533 : * launch a different number of workers. This is required for cases where
534 : * we need to reuse the same DSM segment, but the number of workers can
535 : * vary from run-to-run.
536 : */
537 : void
538 18 : ReinitializeParallelWorkers(ParallelContext *pcxt, int nworkers_to_launch)
539 : {
540 : /*
541 : * The number of workers that need to be launched must be less than the
542 : * number of workers with which the parallel context is initialized.
543 : */
544 : Assert(pcxt->nworkers >= nworkers_to_launch);
545 18 : pcxt->nworkers_to_launch = nworkers_to_launch;
546 18 : }
547 :
548 : /*
549 : * Launch parallel workers.
550 : */
551 : void
552 1086 : LaunchParallelWorkers(ParallelContext *pcxt)
553 : {
554 : MemoryContext oldcontext;
555 : BackgroundWorker worker;
556 : int i;
557 1086 : bool any_registrations_failed = false;
558 :
559 : /* Skip this if we have no workers. */
560 1086 : if (pcxt->nworkers == 0 || pcxt->nworkers_to_launch == 0)
561 0 : return;
562 :
563 : /* We need to be a lock group leader. */
564 1086 : BecomeLockGroupLeader();
565 :
566 : /* If we do have workers, we'd better have a DSM segment. */
567 : Assert(pcxt->seg != NULL);
568 :
569 : /* We might be running in a short-lived memory context. */
570 1086 : oldcontext = MemoryContextSwitchTo(TopTransactionContext);
571 :
572 : /* Configure a worker. */
573 1086 : memset(&worker, 0, sizeof(worker));
574 1086 : snprintf(worker.bgw_name, BGW_MAXLEN, "parallel worker for PID %d",
575 : MyProcPid);
576 1086 : snprintf(worker.bgw_type, BGW_MAXLEN, "parallel worker");
577 1086 : worker.bgw_flags =
578 : BGWORKER_SHMEM_ACCESS | BGWORKER_BACKEND_DATABASE_CONNECTION
579 : | BGWORKER_CLASS_PARALLEL;
580 1086 : worker.bgw_start_time = BgWorkerStart_ConsistentState;
581 1086 : worker.bgw_restart_time = BGW_NEVER_RESTART;
582 1086 : sprintf(worker.bgw_library_name, "postgres");
583 1086 : sprintf(worker.bgw_function_name, "ParallelWorkerMain");
584 1086 : worker.bgw_main_arg = UInt32GetDatum(dsm_segment_handle(pcxt->seg));
585 1086 : worker.bgw_notify_pid = MyProcPid;
586 :
587 : /*
588 : * Start workers.
589 : *
590 : * The caller must be able to tolerate ending up with fewer workers than
591 : * expected, so there is no need to throw an error here if registration
592 : * fails. It wouldn't help much anyway, because registering the worker in
593 : * no way guarantees that it will start up and initialize successfully.
594 : */
595 3806 : for (i = 0; i < pcxt->nworkers_to_launch; ++i)
596 : {
597 2720 : memcpy(worker.bgw_extra, &i, sizeof(int));
598 5382 : if (!any_registrations_failed &&
599 2662 : RegisterDynamicBackgroundWorker(&worker,
600 2662 : &pcxt->worker[i].bgwhandle))
601 : {
602 2640 : shm_mq_set_handle(pcxt->worker[i].error_mqh,
603 2640 : pcxt->worker[i].bgwhandle);
604 2640 : pcxt->nworkers_launched++;
605 : }
606 : else
607 : {
608 : /*
609 : * If we weren't able to register the worker, then we've bumped up
610 : * against the max_worker_processes limit, and future
611 : * registrations will probably fail too, so arrange to skip them.
612 : * But we still have to execute this code for the remaining slots
613 : * to make sure that we forget about the error queues we budgeted
614 : * for those workers. Otherwise, we'll wait for them to start,
615 : * but they never will.
616 : */
617 80 : any_registrations_failed = true;
618 80 : pcxt->worker[i].bgwhandle = NULL;
619 80 : shm_mq_detach(pcxt->worker[i].error_mqh);
620 80 : pcxt->worker[i].error_mqh = NULL;
621 : }
622 : }
623 :
624 : /*
625 : * Now that nworkers_launched has taken its final value, we can initialize
626 : * known_attached_workers.
627 : */
628 1086 : if (pcxt->nworkers_launched > 0)
629 : {
630 1066 : pcxt->known_attached_workers =
631 1066 : palloc0(sizeof(bool) * pcxt->nworkers_launched);
632 1066 : pcxt->nknown_attached_workers = 0;
633 : }
634 :
635 : /* Restore previous memory context. */
636 1086 : MemoryContextSwitchTo(oldcontext);
637 : }
638 :
639 : /*
640 : * Wait for all workers to attach to their error queues, and throw an error if
641 : * any worker fails to do this.
642 : *
643 : * Callers can assume that if this function returns successfully, then the
644 : * number of workers given by pcxt->nworkers_launched have initialized and
645 : * attached to their error queues. Whether or not these workers are guaranteed
646 : * to still be running depends on what code the caller asked them to run;
647 : * this function does not guarantee that they have not exited. However, it
648 : * does guarantee that any workers which exited must have done so cleanly and
649 : * after successfully performing the work with which they were tasked.
650 : *
651 : * If this function is not called, then some of the workers that were launched
652 : * may not have been started due to a fork() failure, or may have exited during
653 : * early startup prior to attaching to the error queue, so nworkers_launched
654 : * cannot be viewed as completely reliable. It will never be less than the
655 : * number of workers which actually started, but it might be more. Any workers
656 : * that failed to start will still be discovered by
657 : * WaitForParallelWorkersToFinish and an error will be thrown at that time,
658 : * provided that function is eventually reached.
659 : *
660 : * In general, the leader process should do as much work as possible before
661 : * calling this function. fork() failures and other early-startup failures
662 : * are very uncommon, and having the leader sit idle when it could be doing
663 : * useful work is undesirable. However, if the leader needs to wait for
664 : * all of its workers or for a specific worker, it may want to call this
665 : * function before doing so. If not, it must make some other provision for
666 : * the failure-to-start case, lest it wait forever. On the other hand, a
667 : * leader which never waits for a worker that might not be started yet, or
668 : * at least never does so prior to WaitForParallelWorkersToFinish(), need not
669 : * call this function at all.
670 : */
671 : void
672 144 : WaitForParallelWorkersToAttach(ParallelContext *pcxt)
673 : {
674 : int i;
675 :
676 : /* Skip this if we have no launched workers. */
677 144 : if (pcxt->nworkers_launched == 0)
678 0 : return;
679 :
680 : for (;;)
681 : {
682 : /*
683 : * This will process any parallel messages that are pending and it may
684 : * also throw an error propagated from a worker.
685 : */
686 12209982 : CHECK_FOR_INTERRUPTS();
687 :
688 24824896 : for (i = 0; i < pcxt->nworkers_launched; ++i)
689 : {
690 : BgwHandleStatus status;
691 : shm_mq *mq;
692 : int rc;
693 : pid_t pid;
694 :
695 12614914 : if (pcxt->known_attached_workers[i])
696 404946 : continue;
697 :
698 : /*
699 : * If error_mqh is NULL, then the worker has already exited
700 : * cleanly.
701 : */
702 12209968 : if (pcxt->worker[i].error_mqh == NULL)
703 : {
704 0 : pcxt->known_attached_workers[i] = true;
705 0 : ++pcxt->nknown_attached_workers;
706 0 : continue;
707 : }
708 :
709 12209968 : status = GetBackgroundWorkerPid(pcxt->worker[i].bgwhandle, &pid);
710 12209968 : if (status == BGWH_STARTED)
711 : {
712 : /* Has the worker attached to the error queue? */
713 12209826 : mq = shm_mq_get_queue(pcxt->worker[i].error_mqh);
714 12209826 : if (shm_mq_get_sender(mq) != NULL)
715 : {
716 : /* Yes, so it is known to be attached. */
717 126 : pcxt->known_attached_workers[i] = true;
718 126 : ++pcxt->nknown_attached_workers;
719 : }
720 : }
721 142 : else if (status == BGWH_STOPPED)
722 : {
723 : /*
724 : * If the worker stopped without attaching to the error queue,
725 : * throw an error.
726 : */
727 0 : mq = shm_mq_get_queue(pcxt->worker[i].error_mqh);
728 0 : if (shm_mq_get_sender(mq) == NULL)
729 0 : ereport(ERROR,
730 : (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE),
731 : errmsg("parallel worker failed to initialize"),
732 : errhint("More details may be available in the server log.")));
733 :
734 0 : pcxt->known_attached_workers[i] = true;
735 0 : ++pcxt->nknown_attached_workers;
736 : }
737 : else
738 : {
739 : /*
740 : * Worker not yet started, so we must wait. The postmaster
741 : * will notify us if the worker's state changes. Our latch
742 : * might also get set for some other reason, but if so we'll
743 : * just end up waiting for the same worker again.
744 : */
745 142 : rc = WaitLatch(MyLatch,
746 : WL_LATCH_SET | WL_EXIT_ON_PM_DEATH,
747 : -1, WAIT_EVENT_BGWORKER_STARTUP);
748 :
749 142 : if (rc & WL_LATCH_SET)
750 142 : ResetLatch(MyLatch);
751 : }
752 : }
753 :
754 : /* If all workers are known to have started, we're done. */
755 12209982 : if (pcxt->nknown_attached_workers >= pcxt->nworkers_launched)
756 : {
757 : Assert(pcxt->nknown_attached_workers == pcxt->nworkers_launched);
758 144 : break;
759 : }
760 : }
761 : }
762 :
763 : /*
764 : * Wait for all workers to finish computing.
765 : *
766 : * Even if the parallel operation seems to have completed successfully, it's
767 : * important to call this function afterwards. We must not miss any errors
768 : * the workers may have thrown during the parallel operation, or any that they
769 : * may yet throw while shutting down.
770 : *
771 : * Also, we want to update our notion of XactLastRecEnd based on worker
772 : * feedback.
773 : */
774 : void
775 2886 : WaitForParallelWorkersToFinish(ParallelContext *pcxt)
776 : {
777 : for (;;)
778 1548 : {
779 2886 : bool anyone_alive = false;
780 2886 : int nfinished = 0;
781 : int i;
782 :
783 : /*
784 : * This will process any parallel messages that are pending, which may
785 : * change the outcome of the loop that follows. It may also throw an
786 : * error propagated from a worker.
787 : */
788 2886 : CHECK_FOR_INTERRUPTS();
789 :
790 10474 : for (i = 0; i < pcxt->nworkers_launched; ++i)
791 : {
792 : /*
793 : * If error_mqh is NULL, then the worker has already exited
794 : * cleanly. If we have received a message through error_mqh from
795 : * the worker, we know it started up cleanly, and therefore we're
796 : * certain to be notified when it exits.
797 : */
798 7618 : if (pcxt->worker[i].error_mqh == NULL)
799 6000 : ++nfinished;
800 1618 : else if (pcxt->known_attached_workers[i])
801 : {
802 30 : anyone_alive = true;
803 30 : break;
804 : }
805 : }
806 :
807 2886 : if (!anyone_alive)
808 : {
809 : /* If all workers are known to have finished, we're done. */
810 2856 : if (nfinished >= pcxt->nworkers_launched)
811 : {
812 : Assert(nfinished == pcxt->nworkers_launched);
813 1338 : break;
814 : }
815 :
816 : /*
817 : * We didn't detect any living workers, but not all workers are
818 : * known to have exited cleanly. Either not all workers have
819 : * launched yet, or maybe some of them failed to start or
820 : * terminated abnormally.
821 : */
822 5650 : for (i = 0; i < pcxt->nworkers_launched; ++i)
823 : {
824 : pid_t pid;
825 : shm_mq *mq;
826 :
827 : /*
828 : * If the worker is BGWH_NOT_YET_STARTED or BGWH_STARTED, we
829 : * should just keep waiting. If it is BGWH_STOPPED, then
830 : * further investigation is needed.
831 : */
832 4132 : if (pcxt->worker[i].error_mqh == NULL ||
833 3176 : pcxt->worker[i].bgwhandle == NULL ||
834 1588 : GetBackgroundWorkerPid(pcxt->worker[i].bgwhandle,
835 : &pid) != BGWH_STOPPED)
836 4132 : continue;
837 :
838 : /*
839 : * Check whether the worker ended up stopped without ever
840 : * attaching to the error queue. If so, the postmaster was
841 : * unable to fork the worker or it exited without initializing
842 : * properly. We must throw an error, since the caller may
843 : * have been expecting the worker to do some work before
844 : * exiting.
845 : */
846 0 : mq = shm_mq_get_queue(pcxt->worker[i].error_mqh);
847 0 : if (shm_mq_get_sender(mq) == NULL)
848 0 : ereport(ERROR,
849 : (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE),
850 : errmsg("parallel worker failed to initialize"),
851 : errhint("More details may be available in the server log.")));
852 :
853 : /*
854 : * The worker is stopped, but is attached to the error queue.
855 : * Unless there's a bug somewhere, this will only happen when
856 : * the worker writes messages and terminates after the
857 : * CHECK_FOR_INTERRUPTS() near the top of this function and
858 : * before the call to GetBackgroundWorkerPid(). In that case,
859 : * or latch should have been set as well and the right things
860 : * will happen on the next pass through the loop.
861 : */
862 : }
863 : }
864 :
865 1548 : (void) WaitLatch(MyLatch, WL_LATCH_SET | WL_EXIT_ON_PM_DEATH, -1,
866 : WAIT_EVENT_PARALLEL_FINISH);
867 1548 : ResetLatch(MyLatch);
868 : }
869 :
870 1338 : if (pcxt->toc != NULL)
871 : {
872 : FixedParallelState *fps;
873 :
874 1338 : fps = shm_toc_lookup(pcxt->toc, PARALLEL_KEY_FIXED, false);
875 1338 : if (fps->last_xlog_end > XactLastRecEnd)
876 20 : XactLastRecEnd = fps->last_xlog_end;
877 : }
878 1338 : }
879 :
880 : /*
881 : * Wait for all workers to exit.
882 : *
883 : * This function ensures that workers have been completely shutdown. The
884 : * difference between WaitForParallelWorkersToFinish and this function is
885 : * that the former just ensures that last message sent by a worker backend is
886 : * received by the leader backend whereas this ensures the complete shutdown.
887 : */
888 : static void
889 1086 : WaitForParallelWorkersToExit(ParallelContext *pcxt)
890 : {
891 : int i;
892 :
893 : /* Wait until the workers actually die. */
894 3726 : for (i = 0; i < pcxt->nworkers_launched; ++i)
895 : {
896 : BgwHandleStatus status;
897 :
898 2640 : if (pcxt->worker == NULL || pcxt->worker[i].bgwhandle == NULL)
899 0 : continue;
900 :
901 2640 : status = WaitForBackgroundWorkerShutdown(pcxt->worker[i].bgwhandle);
902 :
903 : /*
904 : * If the postmaster kicked the bucket, we have no chance of cleaning
905 : * up safely -- we won't be able to tell when our workers are actually
906 : * dead. This doesn't necessitate a PANIC since they will all abort
907 : * eventually, but we can't safely continue this session.
908 : */
909 2640 : if (status == BGWH_POSTMASTER_DIED)
910 0 : ereport(FATAL,
911 : (errcode(ERRCODE_ADMIN_SHUTDOWN),
912 : errmsg("postmaster exited during a parallel transaction")));
913 :
914 : /* Release memory. */
915 2640 : pfree(pcxt->worker[i].bgwhandle);
916 2640 : pcxt->worker[i].bgwhandle = NULL;
917 : }
918 1086 : }
919 :
920 : /*
921 : * Destroy a parallel context.
922 : *
923 : * If expecting a clean exit, you should use WaitForParallelWorkersToFinish()
924 : * first, before calling this function. When this function is invoked, any
925 : * remaining workers are forcibly killed; the dynamic shared memory segment
926 : * is unmapped; and we then wait (uninterruptibly) for the workers to exit.
927 : */
928 : void
929 828 : DestroyParallelContext(ParallelContext *pcxt)
930 : {
931 : int i;
932 :
933 : /*
934 : * Be careful about order of operations here! We remove the parallel
935 : * context from the list before we do anything else; otherwise, if an
936 : * error occurs during a subsequent step, we might try to nuke it again
937 : * from AtEOXact_Parallel or AtEOSubXact_Parallel.
938 : */
939 828 : dlist_delete(&pcxt->node);
940 :
941 : /* Kill each worker in turn, and forget their error queues. */
942 828 : if (pcxt->worker != NULL)
943 : {
944 2646 : for (i = 0; i < pcxt->nworkers_launched; ++i)
945 : {
946 1818 : if (pcxt->worker[i].error_mqh != NULL)
947 : {
948 6 : TerminateBackgroundWorker(pcxt->worker[i].bgwhandle);
949 :
950 6 : shm_mq_detach(pcxt->worker[i].error_mqh);
951 6 : pcxt->worker[i].error_mqh = NULL;
952 : }
953 : }
954 : }
955 :
956 : /*
957 : * If we have allocated a shared memory segment, detach it. This will
958 : * implicitly detach the error queues, and any other shared memory queues,
959 : * stored there.
960 : */
961 828 : if (pcxt->seg != NULL)
962 : {
963 828 : dsm_detach(pcxt->seg);
964 828 : pcxt->seg = NULL;
965 : }
966 :
967 : /*
968 : * If this parallel context is actually in backend-private memory rather
969 : * than shared memory, free that memory instead.
970 : */
971 828 : if (pcxt->private_memory != NULL)
972 : {
973 0 : pfree(pcxt->private_memory);
974 0 : pcxt->private_memory = NULL;
975 : }
976 :
977 : /*
978 : * We can't finish transaction commit or abort until all of the workers
979 : * have exited. This means, in particular, that we can't respond to
980 : * interrupts at this stage.
981 : */
982 828 : HOLD_INTERRUPTS();
983 828 : WaitForParallelWorkersToExit(pcxt);
984 828 : RESUME_INTERRUPTS();
985 :
986 : /* Free the worker array itself. */
987 828 : if (pcxt->worker != NULL)
988 : {
989 828 : pfree(pcxt->worker);
990 828 : pcxt->worker = NULL;
991 : }
992 :
993 : /* Free memory. */
994 828 : pfree(pcxt->library_name);
995 828 : pfree(pcxt->function_name);
996 828 : pfree(pcxt);
997 828 : }
998 :
999 : /*
1000 : * Are there any parallel contexts currently active?
1001 : */
1002 : bool
1003 0 : ParallelContextActive(void)
1004 : {
1005 0 : return !dlist_is_empty(&pcxt_list);
1006 : }
1007 :
1008 : /*
1009 : * Handle receipt of an interrupt indicating a parallel worker message.
1010 : *
1011 : * Note: this is called within a signal handler! All we can do is set
1012 : * a flag that will cause the next CHECK_FOR_INTERRUPTS() to invoke
1013 : * HandleParallelMessages().
1014 : */
1015 : void
1016 3470 : HandleParallelMessageInterrupt(void)
1017 : {
1018 3470 : InterruptPending = true;
1019 3470 : ParallelMessagePending = true;
1020 3470 : SetLatch(MyLatch);
1021 3470 : }
1022 :
1023 : /*
1024 : * Handle any queued protocol messages received from parallel workers.
1025 : */
1026 : void
1027 3414 : HandleParallelMessages(void)
1028 : {
1029 : dlist_iter iter;
1030 : MemoryContext oldcontext;
1031 :
1032 : static MemoryContext hpm_context = NULL;
1033 :
1034 : /*
1035 : * This is invoked from ProcessInterrupts(), and since some of the
1036 : * functions it calls contain CHECK_FOR_INTERRUPTS(), there is a potential
1037 : * for recursive calls if more signals are received while this runs. It's
1038 : * unclear that recursive entry would be safe, and it doesn't seem useful
1039 : * even if it is safe, so let's block interrupts until done.
1040 : */
1041 3414 : HOLD_INTERRUPTS();
1042 :
1043 : /*
1044 : * Moreover, CurrentMemoryContext might be pointing almost anywhere. We
1045 : * don't want to risk leaking data into long-lived contexts, so let's do
1046 : * our work here in a private context that we can reset on each use.
1047 : */
1048 3414 : if (hpm_context == NULL) /* first time through? */
1049 116 : hpm_context = AllocSetContextCreate(TopMemoryContext,
1050 : "HandleParallelMessages",
1051 : ALLOCSET_DEFAULT_SIZES);
1052 : else
1053 3298 : MemoryContextReset(hpm_context);
1054 :
1055 3414 : oldcontext = MemoryContextSwitchTo(hpm_context);
1056 :
1057 : /* OK to process messages. Reset the flag saying there are more to do. */
1058 3414 : ParallelMessagePending = false;
1059 :
1060 6694 : dlist_foreach(iter, &pcxt_list)
1061 : {
1062 : ParallelContext *pcxt;
1063 : int i;
1064 :
1065 3286 : pcxt = dlist_container(ParallelContext, node, iter.cur);
1066 3286 : if (pcxt->worker == NULL)
1067 0 : continue;
1068 :
1069 13402 : for (i = 0; i < pcxt->nworkers_launched; ++i)
1070 : {
1071 : /*
1072 : * Read as many messages as we can from each worker, but stop when
1073 : * either (1) the worker's error queue goes away, which can happen
1074 : * if we receive a Terminate message from the worker; or (2) no
1075 : * more messages can be read from the worker without blocking.
1076 : */
1077 12756 : while (pcxt->worker[i].error_mqh != NULL)
1078 : {
1079 : shm_mq_result res;
1080 : Size nbytes;
1081 : void *data;
1082 :
1083 6192 : res = shm_mq_receive(pcxt->worker[i].error_mqh, &nbytes,
1084 : &data, true);
1085 6192 : if (res == SHM_MQ_WOULD_BLOCK)
1086 3552 : break;
1087 2640 : else if (res == SHM_MQ_SUCCESS)
1088 : {
1089 : StringInfoData msg;
1090 :
1091 2640 : initStringInfo(&msg);
1092 2640 : appendBinaryStringInfo(&msg, data, nbytes);
1093 2640 : HandleParallelMessage(pcxt, i, &msg);
1094 2634 : pfree(msg.data);
1095 : }
1096 : else
1097 0 : ereport(ERROR,
1098 : (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE),
1099 : errmsg("lost connection to parallel worker")));
1100 : }
1101 : }
1102 : }
1103 :
1104 3408 : MemoryContextSwitchTo(oldcontext);
1105 :
1106 : /* Might as well clear the context on our way out */
1107 3408 : MemoryContextReset(hpm_context);
1108 :
1109 3408 : RESUME_INTERRUPTS();
1110 3408 : }
1111 :
1112 : /*
1113 : * Handle a single protocol message received from a single parallel worker.
1114 : */
1115 : static void
1116 2640 : HandleParallelMessage(ParallelContext *pcxt, int i, StringInfo msg)
1117 : {
1118 : char msgtype;
1119 :
1120 2640 : if (pcxt->known_attached_workers != NULL &&
1121 2640 : !pcxt->known_attached_workers[i])
1122 : {
1123 2514 : pcxt->known_attached_workers[i] = true;
1124 2514 : pcxt->nknown_attached_workers++;
1125 : }
1126 :
1127 2640 : msgtype = pq_getmsgbyte(msg);
1128 :
1129 2640 : switch (msgtype)
1130 : {
1131 6 : case PqMsg_ErrorResponse:
1132 : case PqMsg_NoticeResponse:
1133 : {
1134 : ErrorData edata;
1135 : ErrorContextCallback *save_error_context_stack;
1136 :
1137 : /* Parse ErrorResponse or NoticeResponse. */
1138 6 : pq_parse_errornotice(msg, &edata);
1139 :
1140 : /* Death of a worker isn't enough justification for suicide. */
1141 6 : edata.elevel = Min(edata.elevel, ERROR);
1142 :
1143 : /*
1144 : * If desired, add a context line to show that this is a
1145 : * message propagated from a parallel worker. Otherwise, it
1146 : * can sometimes be confusing to understand what actually
1147 : * happened. (We don't do this in DEBUG_PARALLEL_REGRESS mode
1148 : * because it causes test-result instability depending on
1149 : * whether a parallel worker is actually used or not.)
1150 : */
1151 6 : if (debug_parallel_query != DEBUG_PARALLEL_REGRESS)
1152 : {
1153 6 : if (edata.context)
1154 0 : edata.context = psprintf("%s\n%s", edata.context,
1155 : _("parallel worker"));
1156 : else
1157 6 : edata.context = pstrdup(_("parallel worker"));
1158 : }
1159 :
1160 : /*
1161 : * Context beyond that should use the error context callbacks
1162 : * that were in effect when the ParallelContext was created,
1163 : * not the current ones.
1164 : */
1165 6 : save_error_context_stack = error_context_stack;
1166 6 : error_context_stack = pcxt->error_context_stack;
1167 :
1168 : /* Rethrow error or print notice. */
1169 6 : ThrowErrorData(&edata);
1170 :
1171 : /* Not an error, so restore previous context stack. */
1172 0 : error_context_stack = save_error_context_stack;
1173 :
1174 0 : break;
1175 : }
1176 :
1177 0 : case PqMsg_NotificationResponse:
1178 : {
1179 : /* Propagate NotifyResponse. */
1180 : int32 pid;
1181 : const char *channel;
1182 : const char *payload;
1183 :
1184 0 : pid = pq_getmsgint(msg, 4);
1185 0 : channel = pq_getmsgrawstring(msg);
1186 0 : payload = pq_getmsgrawstring(msg);
1187 0 : pq_endmessage(msg);
1188 :
1189 0 : NotifyMyFrontEnd(channel, payload, pid);
1190 :
1191 0 : break;
1192 : }
1193 :
1194 0 : case 'P': /* Parallel progress reporting */
1195 : {
1196 : /*
1197 : * Only incremental progress reporting is currently supported.
1198 : * However, it's possible to add more fields to the message to
1199 : * allow for handling of other backend progress APIs.
1200 : */
1201 0 : int index = pq_getmsgint(msg, 4);
1202 0 : int64 incr = pq_getmsgint64(msg);
1203 :
1204 0 : pq_getmsgend(msg);
1205 :
1206 0 : pgstat_progress_incr_param(index, incr);
1207 :
1208 0 : break;
1209 : }
1210 :
1211 2634 : case PqMsg_Terminate:
1212 : {
1213 2634 : shm_mq_detach(pcxt->worker[i].error_mqh);
1214 2634 : pcxt->worker[i].error_mqh = NULL;
1215 2634 : break;
1216 : }
1217 :
1218 0 : default:
1219 : {
1220 0 : elog(ERROR, "unrecognized message type received from parallel worker: %c (message length %d bytes)",
1221 : msgtype, msg->len);
1222 : }
1223 : }
1224 2634 : }
1225 :
1226 : /*
1227 : * End-of-subtransaction cleanup for parallel contexts.
1228 : *
1229 : * Here we remove only parallel contexts initiated within the current
1230 : * subtransaction.
1231 : */
1232 : void
1233 18024 : AtEOSubXact_Parallel(bool isCommit, SubTransactionId mySubId)
1234 : {
1235 18030 : while (!dlist_is_empty(&pcxt_list))
1236 : {
1237 : ParallelContext *pcxt;
1238 :
1239 6 : pcxt = dlist_head_element(ParallelContext, node, &pcxt_list);
1240 6 : if (pcxt->subid != mySubId)
1241 0 : break;
1242 6 : if (isCommit)
1243 0 : elog(WARNING, "leaked parallel context");
1244 6 : DestroyParallelContext(pcxt);
1245 : }
1246 18024 : }
1247 :
1248 : /*
1249 : * End-of-transaction cleanup for parallel contexts.
1250 : *
1251 : * We nuke all remaining parallel contexts.
1252 : */
1253 : void
1254 564956 : AtEOXact_Parallel(bool isCommit)
1255 : {
1256 564956 : while (!dlist_is_empty(&pcxt_list))
1257 : {
1258 : ParallelContext *pcxt;
1259 :
1260 0 : pcxt = dlist_head_element(ParallelContext, node, &pcxt_list);
1261 0 : if (isCommit)
1262 0 : elog(WARNING, "leaked parallel context");
1263 0 : DestroyParallelContext(pcxt);
1264 : }
1265 564956 : }
1266 :
1267 : /*
1268 : * Main entrypoint for parallel workers.
1269 : */
1270 : void
1271 2640 : ParallelWorkerMain(Datum main_arg)
1272 : {
1273 : dsm_segment *seg;
1274 : shm_toc *toc;
1275 : FixedParallelState *fps;
1276 : char *error_queue_space;
1277 : shm_mq *mq;
1278 : shm_mq_handle *mqh;
1279 : char *libraryspace;
1280 : char *entrypointstate;
1281 : char *library_name;
1282 : char *function_name;
1283 : parallel_worker_main_type entrypt;
1284 : char *gucspace;
1285 : char *combocidspace;
1286 : char *tsnapspace;
1287 : char *asnapspace;
1288 : char *tstatespace;
1289 : char *pendingsyncsspace;
1290 : char *reindexspace;
1291 : char *relmapperspace;
1292 : char *uncommittedenumsspace;
1293 : char *clientconninfospace;
1294 : char *session_dsm_handle_space;
1295 : Snapshot tsnapshot;
1296 : Snapshot asnapshot;
1297 :
1298 : /* Set flag to indicate that we're initializing a parallel worker. */
1299 2640 : InitializingParallelWorker = true;
1300 :
1301 : /* Establish signal handlers. */
1302 2640 : pqsignal(SIGTERM, die);
1303 2640 : BackgroundWorkerUnblockSignals();
1304 :
1305 : /* Determine and set our parallel worker number. */
1306 : Assert(ParallelWorkerNumber == -1);
1307 2640 : memcpy(&ParallelWorkerNumber, MyBgworkerEntry->bgw_extra, sizeof(int));
1308 :
1309 : /* Set up a memory context to work in, just for cleanliness. */
1310 2640 : CurrentMemoryContext = AllocSetContextCreate(TopMemoryContext,
1311 : "Parallel worker",
1312 : ALLOCSET_DEFAULT_SIZES);
1313 :
1314 : /*
1315 : * Attach to the dynamic shared memory segment for the parallel query, and
1316 : * find its table of contents.
1317 : *
1318 : * Note: at this point, we have not created any ResourceOwner in this
1319 : * process. This will result in our DSM mapping surviving until process
1320 : * exit, which is fine. If there were a ResourceOwner, it would acquire
1321 : * ownership of the mapping, but we have no need for that.
1322 : */
1323 2640 : seg = dsm_attach(DatumGetUInt32(main_arg));
1324 2640 : if (seg == NULL)
1325 0 : ereport(ERROR,
1326 : (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE),
1327 : errmsg("could not map dynamic shared memory segment")));
1328 2640 : toc = shm_toc_attach(PARALLEL_MAGIC, dsm_segment_address(seg));
1329 2640 : if (toc == NULL)
1330 0 : ereport(ERROR,
1331 : (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE),
1332 : errmsg("invalid magic number in dynamic shared memory segment")));
1333 :
1334 : /* Look up fixed parallel state. */
1335 2640 : fps = shm_toc_lookup(toc, PARALLEL_KEY_FIXED, false);
1336 2640 : MyFixedParallelState = fps;
1337 :
1338 : /* Arrange to signal the leader if we exit. */
1339 2640 : ParallelLeaderPid = fps->parallel_leader_pid;
1340 2640 : ParallelLeaderProcNumber = fps->parallel_leader_proc_number;
1341 2640 : before_shmem_exit(ParallelWorkerShutdown, PointerGetDatum(seg));
1342 :
1343 : /*
1344 : * Now we can find and attach to the error queue provided for us. That's
1345 : * good, because until we do that, any errors that happen here will not be
1346 : * reported back to the process that requested that this worker be
1347 : * launched.
1348 : */
1349 2640 : error_queue_space = shm_toc_lookup(toc, PARALLEL_KEY_ERROR_QUEUE, false);
1350 2640 : mq = (shm_mq *) (error_queue_space +
1351 2640 : ParallelWorkerNumber * PARALLEL_ERROR_QUEUE_SIZE);
1352 2640 : shm_mq_set_sender(mq, MyProc);
1353 2640 : mqh = shm_mq_attach(mq, seg, NULL);
1354 2640 : pq_redirect_to_shm_mq(seg, mqh);
1355 2640 : pq_set_parallel_leader(fps->parallel_leader_pid,
1356 : fps->parallel_leader_proc_number);
1357 :
1358 : /*
1359 : * Hooray! Primary initialization is complete. Now, we need to set up our
1360 : * backend-local state to match the original backend.
1361 : */
1362 :
1363 : /*
1364 : * Join locking group. We must do this before anything that could try to
1365 : * acquire a heavyweight lock, because any heavyweight locks acquired to
1366 : * this point could block either directly against the parallel group
1367 : * leader or against some process which in turn waits for a lock that
1368 : * conflicts with the parallel group leader, causing an undetected
1369 : * deadlock. (If we can't join the lock group, the leader has gone away,
1370 : * so just exit quietly.)
1371 : */
1372 2640 : if (!BecomeLockGroupMember(fps->parallel_leader_pgproc,
1373 : fps->parallel_leader_pid))
1374 0 : return;
1375 :
1376 : /*
1377 : * Restore transaction and statement start-time timestamps. This must
1378 : * happen before anything that would start a transaction, else asserts in
1379 : * xact.c will fire.
1380 : */
1381 2640 : SetParallelStartTimestamps(fps->xact_ts, fps->stmt_ts);
1382 :
1383 : /*
1384 : * Identify the entry point to be called. In theory this could result in
1385 : * loading an additional library, though most likely the entry point is in
1386 : * the core backend or in a library we just loaded.
1387 : */
1388 2640 : entrypointstate = shm_toc_lookup(toc, PARALLEL_KEY_ENTRYPOINT, false);
1389 2640 : library_name = entrypointstate;
1390 2640 : function_name = entrypointstate + strlen(library_name) + 1;
1391 :
1392 2640 : entrypt = LookupParallelWorkerFunction(library_name, function_name);
1393 :
1394 : /* Restore database connection. */
1395 2640 : BackgroundWorkerInitializeConnectionByOid(fps->database_id,
1396 : fps->authenticated_user_id,
1397 : 0);
1398 :
1399 : /*
1400 : * Set the client encoding to the database encoding, since that is what
1401 : * the leader will expect.
1402 : */
1403 2640 : SetClientEncoding(GetDatabaseEncoding());
1404 :
1405 : /*
1406 : * Load libraries that were loaded by original backend. We want to do
1407 : * this before restoring GUCs, because the libraries might define custom
1408 : * variables.
1409 : */
1410 2640 : libraryspace = shm_toc_lookup(toc, PARALLEL_KEY_LIBRARY, false);
1411 2640 : StartTransactionCommand();
1412 2640 : RestoreLibraryState(libraryspace);
1413 :
1414 : /* Restore GUC values from launching backend. */
1415 2640 : gucspace = shm_toc_lookup(toc, PARALLEL_KEY_GUC, false);
1416 2640 : RestoreGUCState(gucspace);
1417 2640 : CommitTransactionCommand();
1418 :
1419 : /* Crank up a transaction state appropriate to a parallel worker. */
1420 2640 : tstatespace = shm_toc_lookup(toc, PARALLEL_KEY_TRANSACTION_STATE, false);
1421 2640 : StartParallelWorkerTransaction(tstatespace);
1422 :
1423 : /* Restore combo CID state. */
1424 2640 : combocidspace = shm_toc_lookup(toc, PARALLEL_KEY_COMBO_CID, false);
1425 2640 : RestoreComboCIDState(combocidspace);
1426 :
1427 : /* Attach to the per-session DSM segment and contained objects. */
1428 : session_dsm_handle_space =
1429 2640 : shm_toc_lookup(toc, PARALLEL_KEY_SESSION_DSM, false);
1430 2640 : AttachSession(*(dsm_handle *) session_dsm_handle_space);
1431 :
1432 : /*
1433 : * If the transaction isolation level is REPEATABLE READ or SERIALIZABLE,
1434 : * the leader has serialized the transaction snapshot and we must restore
1435 : * it. At lower isolation levels, there is no transaction-lifetime
1436 : * snapshot, but we need TransactionXmin to get set to a value which is
1437 : * less than or equal to the xmin of every snapshot that will be used by
1438 : * this worker. The easiest way to accomplish that is to install the
1439 : * active snapshot as the transaction snapshot. Code running in this
1440 : * parallel worker might take new snapshots via GetTransactionSnapshot()
1441 : * or GetLatestSnapshot(), but it shouldn't have any way of acquiring a
1442 : * snapshot older than the active snapshot.
1443 : */
1444 2640 : asnapspace = shm_toc_lookup(toc, PARALLEL_KEY_ACTIVE_SNAPSHOT, false);
1445 2640 : tsnapspace = shm_toc_lookup(toc, PARALLEL_KEY_TRANSACTION_SNAPSHOT, true);
1446 2640 : asnapshot = RestoreSnapshot(asnapspace);
1447 2640 : tsnapshot = tsnapspace ? RestoreSnapshot(tsnapspace) : asnapshot;
1448 2640 : RestoreTransactionSnapshot(tsnapshot,
1449 2640 : fps->parallel_leader_pgproc);
1450 2640 : PushActiveSnapshot(asnapshot);
1451 :
1452 : /*
1453 : * We've changed which tuples we can see, and must therefore invalidate
1454 : * system caches.
1455 : */
1456 2640 : InvalidateSystemCaches();
1457 :
1458 : /*
1459 : * Restore current role id. Skip verifying whether session user is
1460 : * allowed to become this role and blindly restore the leader's state for
1461 : * current role.
1462 : */
1463 2640 : SetCurrentRoleId(fps->outer_user_id, fps->is_superuser);
1464 :
1465 : /* Restore user ID and security context. */
1466 2640 : SetUserIdAndSecContext(fps->current_user_id, fps->sec_context);
1467 :
1468 : /* Restore temp-namespace state to ensure search path matches leader's. */
1469 2640 : SetTempNamespaceState(fps->temp_namespace_id,
1470 : fps->temp_toast_namespace_id);
1471 :
1472 : /* Restore pending syncs. */
1473 2640 : pendingsyncsspace = shm_toc_lookup(toc, PARALLEL_KEY_PENDING_SYNCS,
1474 : false);
1475 2640 : RestorePendingSyncs(pendingsyncsspace);
1476 :
1477 : /* Restore reindex state. */
1478 2640 : reindexspace = shm_toc_lookup(toc, PARALLEL_KEY_REINDEX_STATE, false);
1479 2640 : RestoreReindexState(reindexspace);
1480 :
1481 : /* Restore relmapper state. */
1482 2640 : relmapperspace = shm_toc_lookup(toc, PARALLEL_KEY_RELMAPPER_STATE, false);
1483 2640 : RestoreRelationMap(relmapperspace);
1484 :
1485 : /* Restore uncommitted enums. */
1486 2640 : uncommittedenumsspace = shm_toc_lookup(toc, PARALLEL_KEY_UNCOMMITTEDENUMS,
1487 : false);
1488 2640 : RestoreUncommittedEnums(uncommittedenumsspace);
1489 :
1490 : /* Restore the ClientConnectionInfo. */
1491 2640 : clientconninfospace = shm_toc_lookup(toc, PARALLEL_KEY_CLIENTCONNINFO,
1492 : false);
1493 2640 : RestoreClientConnectionInfo(clientconninfospace);
1494 :
1495 : /*
1496 : * Initialize SystemUser now that MyClientConnectionInfo is restored. Also
1497 : * ensure that auth_method is actually valid, aka authn_id is not NULL.
1498 : */
1499 2640 : if (MyClientConnectionInfo.authn_id)
1500 4 : InitializeSystemUser(MyClientConnectionInfo.authn_id,
1501 : hba_authname(MyClientConnectionInfo.auth_method));
1502 :
1503 : /* Attach to the leader's serializable transaction, if SERIALIZABLE. */
1504 2640 : AttachSerializableXact(fps->serializable_xact_handle);
1505 :
1506 : /*
1507 : * We've initialized all of our state now; nothing should change
1508 : * hereafter.
1509 : */
1510 2640 : InitializingParallelWorker = false;
1511 2640 : EnterParallelMode();
1512 :
1513 : /*
1514 : * Time to do the real work: invoke the caller-supplied code.
1515 : */
1516 2640 : entrypt(seg, toc);
1517 :
1518 : /* Must exit parallel mode to pop active snapshot. */
1519 2634 : ExitParallelMode();
1520 :
1521 : /* Must pop active snapshot so snapmgr.c doesn't complain. */
1522 2634 : PopActiveSnapshot();
1523 :
1524 : /* Shut down the parallel-worker transaction. */
1525 2634 : EndParallelWorkerTransaction();
1526 :
1527 : /* Detach from the per-session DSM segment. */
1528 2634 : DetachSession();
1529 :
1530 : /* Report success. */
1531 2634 : pq_putmessage(PqMsg_Terminate, NULL, 0);
1532 : }
1533 :
1534 : /*
1535 : * Update shared memory with the ending location of the last WAL record we
1536 : * wrote, if it's greater than the value already stored there.
1537 : */
1538 : void
1539 2634 : ParallelWorkerReportLastRecEnd(XLogRecPtr last_xlog_end)
1540 : {
1541 2634 : FixedParallelState *fps = MyFixedParallelState;
1542 :
1543 : Assert(fps != NULL);
1544 2634 : SpinLockAcquire(&fps->mutex);
1545 2634 : if (fps->last_xlog_end < last_xlog_end)
1546 120 : fps->last_xlog_end = last_xlog_end;
1547 2634 : SpinLockRelease(&fps->mutex);
1548 2634 : }
1549 :
1550 : /*
1551 : * Make sure the leader tries to read from our error queue one more time.
1552 : * This guards against the case where we exit uncleanly without sending an
1553 : * ErrorResponse to the leader, for example because some code calls proc_exit
1554 : * directly.
1555 : *
1556 : * Also explicitly detach from dsm segment so that subsystems using
1557 : * on_dsm_detach() have a chance to send stats before the stats subsystem is
1558 : * shut down as part of a before_shmem_exit() hook.
1559 : *
1560 : * One might think this could instead be solved by carefully ordering the
1561 : * attaching to dsm segments, so that the pgstats segments get detached from
1562 : * later than the parallel query one. That turns out to not work because the
1563 : * stats hash might need to grow which can cause new segments to be allocated,
1564 : * which then will be detached from earlier.
1565 : */
1566 : static void
1567 2640 : ParallelWorkerShutdown(int code, Datum arg)
1568 : {
1569 2640 : SendProcSignal(ParallelLeaderPid,
1570 : PROCSIG_PARALLEL_MESSAGE,
1571 : ParallelLeaderProcNumber);
1572 :
1573 2640 : dsm_detach((dsm_segment *) DatumGetPointer(arg));
1574 2640 : }
1575 :
1576 : /*
1577 : * Look up (and possibly load) a parallel worker entry point function.
1578 : *
1579 : * For functions contained in the core code, we use library name "postgres"
1580 : * and consult the InternalParallelWorkers array. External functions are
1581 : * looked up, and loaded if necessary, using load_external_function().
1582 : *
1583 : * The point of this is to pass function names as strings across process
1584 : * boundaries. We can't pass actual function addresses because of the
1585 : * possibility that the function has been loaded at a different address
1586 : * in a different process. This is obviously a hazard for functions in
1587 : * loadable libraries, but it can happen even for functions in the core code
1588 : * on platforms using EXEC_BACKEND (e.g., Windows).
1589 : *
1590 : * At some point it might be worthwhile to get rid of InternalParallelWorkers[]
1591 : * in favor of applying load_external_function() for core functions too;
1592 : * but that raises portability issues that are not worth addressing now.
1593 : */
1594 : static parallel_worker_main_type
1595 2640 : LookupParallelWorkerFunction(const char *libraryname, const char *funcname)
1596 : {
1597 : /*
1598 : * If the function is to be loaded from postgres itself, search the
1599 : * InternalParallelWorkers array.
1600 : */
1601 2640 : if (strcmp(libraryname, "postgres") == 0)
1602 : {
1603 : int i;
1604 :
1605 2884 : for (i = 0; i < lengthof(InternalParallelWorkers); i++)
1606 : {
1607 2884 : if (strcmp(InternalParallelWorkers[i].fn_name, funcname) == 0)
1608 2640 : return InternalParallelWorkers[i].fn_addr;
1609 : }
1610 :
1611 : /* We can only reach this by programming error. */
1612 0 : elog(ERROR, "internal function \"%s\" not found", funcname);
1613 : }
1614 :
1615 : /* Otherwise load from external library. */
1616 0 : return (parallel_worker_main_type)
1617 0 : load_external_function(libraryname, funcname, true, NULL);
1618 : }
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