Line data Source code
1 : /*-------------------------------------------------------------------------
2 : *
3 : * pqmq.c
4 : * Use the frontend/backend protocol for communication over a shm_mq
5 : *
6 : * Portions Copyright (c) 1996-2026, PostgreSQL Global Development Group
7 : * Portions Copyright (c) 1994, Regents of the University of California
8 : *
9 : * src/backend/libpq/pqmq.c
10 : *
11 : *-------------------------------------------------------------------------
12 : */
13 :
14 : #include "postgres.h"
15 :
16 : #include "access/parallel.h"
17 : #include "commands/repack.h"
18 : #include "libpq/libpq.h"
19 : #include "libpq/pqformat.h"
20 : #include "libpq/pqmq.h"
21 : #include "miscadmin.h"
22 : #include "pgstat.h"
23 : #include "replication/logicalworker.h"
24 : #include "storage/latch.h"
25 : #include "tcop/tcopprot.h"
26 : #include "utils/builtins.h"
27 : #include "utils/wait_event.h"
28 :
29 : static shm_mq_handle *pq_mq_handle = NULL;
30 : static bool pq_mq_busy = false;
31 : static pid_t pq_mq_parallel_leader_pid = 0;
32 : static ProcNumber pq_mq_parallel_leader_proc_number = INVALID_PROC_NUMBER;
33 :
34 : static void pq_cleanup_redirect_to_shm_mq(dsm_segment *seg, Datum arg);
35 : static void mq_comm_reset(void);
36 : static int mq_flush(void);
37 : static int mq_flush_if_writable(void);
38 : static bool mq_is_send_pending(void);
39 : static int mq_putmessage(char msgtype, const char *s, size_t len);
40 : static void mq_putmessage_noblock(char msgtype, const char *s, size_t len);
41 :
42 : static const PQcommMethods PqCommMqMethods = {
43 : .comm_reset = mq_comm_reset,
44 : .flush = mq_flush,
45 : .flush_if_writable = mq_flush_if_writable,
46 : .is_send_pending = mq_is_send_pending,
47 : .putmessage = mq_putmessage,
48 : .putmessage_noblock = mq_putmessage_noblock
49 : };
50 :
51 : /*
52 : * Arrange to redirect frontend/backend protocol messages to a shared-memory
53 : * message queue.
54 : */
55 : void
56 2028 : pq_redirect_to_shm_mq(dsm_segment *seg, shm_mq_handle *mqh)
57 : {
58 2028 : PqCommMethods = &PqCommMqMethods;
59 2028 : pq_mq_handle = mqh;
60 2028 : whereToSendOutput = DestRemote;
61 2028 : FrontendProtocol = PG_PROTOCOL_LATEST;
62 2028 : on_dsm_detach(seg, pq_cleanup_redirect_to_shm_mq, (Datum) 0);
63 2028 : }
64 :
65 : /*
66 : * When the DSM that contains our shm_mq goes away, we need to stop sending
67 : * messages to it.
68 : */
69 : static void
70 2028 : pq_cleanup_redirect_to_shm_mq(dsm_segment *seg, Datum arg)
71 : {
72 2028 : if (pq_mq_handle != NULL)
73 : {
74 2028 : pfree(pq_mq_handle);
75 2028 : pq_mq_handle = NULL;
76 : }
77 2028 : whereToSendOutput = DestNone;
78 2028 : }
79 :
80 : /*
81 : * Arrange to SendProcSignal() to the parallel leader each time we transmit
82 : * message data via the shm_mq.
83 : */
84 : void
85 2028 : pq_set_parallel_leader(pid_t pid, ProcNumber procNumber)
86 : {
87 : Assert(PqCommMethods == &PqCommMqMethods);
88 2028 : pq_mq_parallel_leader_pid = pid;
89 2028 : pq_mq_parallel_leader_proc_number = procNumber;
90 2028 : }
91 :
92 : static void
93 0 : mq_comm_reset(void)
94 : {
95 : /* Nothing to do. */
96 0 : }
97 :
98 : static int
99 16 : mq_flush(void)
100 : {
101 : /* Nothing to do. */
102 16 : return 0;
103 : }
104 :
105 : static int
106 0 : mq_flush_if_writable(void)
107 : {
108 : /* Nothing to do. */
109 0 : return 0;
110 : }
111 :
112 : static bool
113 0 : mq_is_send_pending(void)
114 : {
115 : /* There's never anything pending. */
116 0 : return 0;
117 : }
118 :
119 : /*
120 : * Transmit a libpq protocol message to the shared memory message queue
121 : * selected via pq_mq_handle. We don't include a length word, because the
122 : * receiver will know the length of the message from shm_mq_receive().
123 : */
124 : static int
125 2020 : mq_putmessage(char msgtype, const char *s, size_t len)
126 : {
127 : shm_mq_iovec iov[2];
128 : shm_mq_result result;
129 :
130 : /*
131 : * If we're sending a message, and we have to wait because the queue is
132 : * full, and then we get interrupted, and that interrupt results in trying
133 : * to send another message, we respond by detaching the queue. There's no
134 : * way to return to the original context, but even if there were, just
135 : * queueing the message would amount to indefinitely postponing the
136 : * response to the interrupt. So we do this instead.
137 : */
138 2020 : if (pq_mq_busy)
139 : {
140 0 : if (pq_mq_handle != NULL)
141 : {
142 0 : shm_mq_detach(pq_mq_handle);
143 0 : pq_mq_handle = NULL;
144 : }
145 0 : return EOF;
146 : }
147 :
148 : /*
149 : * If the message queue is already gone, just ignore the message. This
150 : * doesn't necessarily indicate a problem; for example, DEBUG messages can
151 : * be generated late in the shutdown sequence, after all DSMs have already
152 : * been detached.
153 : */
154 2020 : if (pq_mq_handle == NULL)
155 0 : return 0;
156 :
157 2020 : pq_mq_busy = true;
158 :
159 2020 : iov[0].data = &msgtype;
160 2020 : iov[0].len = 1;
161 2020 : iov[1].data = s;
162 2020 : iov[1].len = len;
163 :
164 : for (;;)
165 : {
166 : /*
167 : * Immediately notify the receiver by passing force_flush as true so
168 : * that the shared memory value is updated before we send the parallel
169 : * message signal right after this.
170 : */
171 6 : Assert(pq_mq_handle != NULL);
172 2026 : result = shm_mq_sendv(pq_mq_handle, iov, 2, true, true);
173 :
174 2026 : if (pq_mq_parallel_leader_pid != 0)
175 : {
176 2026 : if (IsLogicalParallelApplyWorker())
177 8 : SendProcSignal(pq_mq_parallel_leader_pid,
178 : PROCSIG_PARALLEL_APPLY_MESSAGE,
179 : pq_mq_parallel_leader_proc_number);
180 2018 : else if (AmRepackWorker())
181 0 : SendProcSignal(pq_mq_parallel_leader_pid,
182 : PROCSIG_REPACK_MESSAGE,
183 : pq_mq_parallel_leader_proc_number);
184 : else
185 : {
186 : Assert(IsParallelWorker());
187 2018 : SendProcSignal(pq_mq_parallel_leader_pid,
188 : PROCSIG_PARALLEL_MESSAGE,
189 : pq_mq_parallel_leader_proc_number);
190 : }
191 : }
192 :
193 2026 : if (result != SHM_MQ_WOULD_BLOCK)
194 2020 : break;
195 :
196 6 : (void) WaitLatch(MyLatch, WL_LATCH_SET | WL_EXIT_ON_PM_DEATH, 0,
197 : WAIT_EVENT_MESSAGE_QUEUE_PUT_MESSAGE);
198 6 : ResetLatch(MyLatch);
199 6 : CHECK_FOR_INTERRUPTS();
200 : }
201 :
202 2020 : pq_mq_busy = false;
203 :
204 : Assert(result == SHM_MQ_SUCCESS || result == SHM_MQ_DETACHED);
205 2020 : if (result != SHM_MQ_SUCCESS)
206 4 : return EOF;
207 2016 : return 0;
208 : }
209 :
210 : static void
211 0 : mq_putmessage_noblock(char msgtype, const char *s, size_t len)
212 : {
213 : /*
214 : * While the shm_mq machinery does support sending a message in
215 : * non-blocking mode, there's currently no way to try sending beginning to
216 : * send the message that doesn't also commit us to completing the
217 : * transmission. This could be improved in the future, but for now we
218 : * don't need it.
219 : */
220 0 : elog(ERROR, "not currently supported");
221 : }
222 :
223 : /*
224 : * Parse an ErrorResponse or NoticeResponse payload and populate an ErrorData
225 : * structure with the results.
226 : */
227 : void
228 11 : pq_parse_errornotice(StringInfo msg, ErrorData *edata)
229 : {
230 : /* Initialize edata with reasonable defaults. */
231 264 : MemSet(edata, 0, sizeof(ErrorData));
232 11 : edata->elevel = ERROR;
233 11 : edata->assoc_context = CurrentMemoryContext;
234 :
235 : /* Loop over fields and extract each one. */
236 : for (;;)
237 88 : {
238 99 : char code = pq_getmsgbyte(msg);
239 : const char *value;
240 :
241 99 : if (code == '\0')
242 : {
243 11 : pq_getmsgend(msg);
244 11 : break;
245 : }
246 88 : value = pq_getmsgrawstring(msg);
247 :
248 88 : switch (code)
249 : {
250 11 : case PG_DIAG_SEVERITY:
251 : /* ignore, trusting we'll get a nonlocalized version */
252 11 : break;
253 11 : case PG_DIAG_SEVERITY_NONLOCALIZED:
254 11 : if (strcmp(value, "DEBUG") == 0)
255 : {
256 : /*
257 : * We can't reconstruct the exact DEBUG level, but
258 : * presumably it was >= client_min_messages, so select
259 : * DEBUG1 to ensure we'll pass it on to the client.
260 : */
261 0 : edata->elevel = DEBUG1;
262 : }
263 11 : else if (strcmp(value, "LOG") == 0)
264 : {
265 : /*
266 : * It can't be LOG_SERVER_ONLY, or the worker wouldn't
267 : * have sent it to us; so LOG is the correct value.
268 : */
269 0 : edata->elevel = LOG;
270 : }
271 11 : else if (strcmp(value, "INFO") == 0)
272 0 : edata->elevel = INFO;
273 11 : else if (strcmp(value, "NOTICE") == 0)
274 0 : edata->elevel = NOTICE;
275 11 : else if (strcmp(value, "WARNING") == 0)
276 0 : edata->elevel = WARNING;
277 11 : else if (strcmp(value, "ERROR") == 0)
278 11 : edata->elevel = ERROR;
279 0 : else if (strcmp(value, "FATAL") == 0)
280 0 : edata->elevel = FATAL;
281 0 : else if (strcmp(value, "PANIC") == 0)
282 0 : edata->elevel = PANIC;
283 : else
284 0 : elog(ERROR, "unrecognized error severity: \"%s\"", value);
285 11 : break;
286 11 : case PG_DIAG_SQLSTATE:
287 11 : if (strlen(value) != 5)
288 0 : elog(ERROR, "invalid SQLSTATE: \"%s\"", value);
289 11 : edata->sqlerrcode = MAKE_SQLSTATE(value[0], value[1], value[2],
290 : value[3], value[4]);
291 11 : break;
292 11 : case PG_DIAG_MESSAGE_PRIMARY:
293 11 : edata->message = pstrdup(value);
294 11 : break;
295 1 : case PG_DIAG_MESSAGE_DETAIL:
296 1 : edata->detail = pstrdup(value);
297 1 : break;
298 3 : case PG_DIAG_MESSAGE_HINT:
299 3 : edata->hint = pstrdup(value);
300 3 : break;
301 0 : case PG_DIAG_STATEMENT_POSITION:
302 0 : edata->cursorpos = pg_strtoint32(value);
303 0 : break;
304 0 : case PG_DIAG_INTERNAL_POSITION:
305 0 : edata->internalpos = pg_strtoint32(value);
306 0 : break;
307 0 : case PG_DIAG_INTERNAL_QUERY:
308 0 : edata->internalquery = pstrdup(value);
309 0 : break;
310 7 : case PG_DIAG_CONTEXT:
311 7 : edata->context = pstrdup(value);
312 7 : break;
313 0 : case PG_DIAG_SCHEMA_NAME:
314 0 : edata->schema_name = pstrdup(value);
315 0 : break;
316 0 : case PG_DIAG_TABLE_NAME:
317 0 : edata->table_name = pstrdup(value);
318 0 : break;
319 0 : case PG_DIAG_COLUMN_NAME:
320 0 : edata->column_name = pstrdup(value);
321 0 : break;
322 0 : case PG_DIAG_DATATYPE_NAME:
323 0 : edata->datatype_name = pstrdup(value);
324 0 : break;
325 0 : case PG_DIAG_CONSTRAINT_NAME:
326 0 : edata->constraint_name = pstrdup(value);
327 0 : break;
328 11 : case PG_DIAG_SOURCE_FILE:
329 11 : edata->filename = pstrdup(value);
330 11 : break;
331 11 : case PG_DIAG_SOURCE_LINE:
332 11 : edata->lineno = pg_strtoint32(value);
333 11 : break;
334 11 : case PG_DIAG_SOURCE_FUNCTION:
335 11 : edata->funcname = pstrdup(value);
336 11 : break;
337 0 : default:
338 0 : elog(ERROR, "unrecognized error field code: %d", code);
339 : break;
340 : }
341 : }
342 11 : }
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