Line data Source code
1 : /*
2 : * task.c
3 : * framework for parallelizing pg_upgrade's once-in-each-database tasks
4 : *
5 : * This framework provides an efficient way of running the various
6 : * once-in-each-database tasks required by pg_upgrade. Specifically, it
7 : * parallelizes these tasks by managing a set of slots that follow a simple
8 : * state machine and by using libpq's asynchronous APIs to establish the
9 : * connections and run the queries. Callers simply need to create a callback
10 : * function and build/execute an UpgradeTask. A simple example follows:
11 : *
12 : * static void
13 : * my_process_cb(DbInfo *dbinfo, PGresult *res, void *arg)
14 : * {
15 : * for (int i = 0; i < PQntuples(res); i++)
16 : * {
17 : * ... process results ...
18 : * }
19 : * }
20 : *
21 : * void
22 : * my_task(ClusterInfo *cluster)
23 : * {
24 : * UpgradeTask *task = upgrade_task_create();
25 : *
26 : * upgrade_task_add_step(task,
27 : * "... query text ...",
28 : * my_process_cb,
29 : * true, // let the task free the PGresult
30 : * NULL); // "arg" pointer for callback
31 : * upgrade_task_run(task, cluster);
32 : * upgrade_task_free(task);
33 : * }
34 : *
35 : * Note that multiple steps can be added to a given task. When there are
36 : * multiple steps, the task will run all of the steps consecutively in the same
37 : * database connection before freeing the connection and moving on. In other
38 : * words, it only ever initiates one connection to each database in the
39 : * cluster for a given run.
40 : *
41 : * Copyright (c) 2024-2026, PostgreSQL Global Development Group
42 : * src/bin/pg_upgrade/task.c
43 : */
44 :
45 : #include "postgres_fe.h"
46 :
47 : #include "common/connect.h"
48 : #include "fe_utils/string_utils.h"
49 : #include "pg_upgrade.h"
50 :
51 : /*
52 : * dbs_complete stores the number of databases that we have completed
53 : * processing. When this value equals the number of databases in the cluster,
54 : * the task is finished.
55 : */
56 : static int dbs_complete;
57 :
58 : /*
59 : * dbs_processing stores the index of the next database in the cluster's array
60 : * of databases that will be picked up for processing. It will always be
61 : * greater than or equal to dbs_complete.
62 : */
63 : static int dbs_processing;
64 :
65 : /*
66 : * This struct stores the information for a single step of a task. Note that
67 : * the query string is stored in the "queries" PQExpBuffer for the UpgradeTask.
68 : * All steps in a task are run in a single connection before moving on to the
69 : * next database (which requires a new connection).
70 : */
71 : typedef struct UpgradeTaskStep
72 : {
73 : UpgradeTaskProcessCB process_cb; /* processes the results of the query */
74 : bool free_result; /* should we free the result? */
75 : void *arg; /* pointer passed to process_cb */
76 : } UpgradeTaskStep;
77 :
78 : /*
79 : * This struct is a thin wrapper around an array of steps, i.e.,
80 : * UpgradeTaskStep, plus a PQExpBuffer for all the query strings.
81 : */
82 : struct UpgradeTask
83 : {
84 : UpgradeTaskStep *steps;
85 : int num_steps;
86 : PQExpBuffer queries;
87 : };
88 :
89 : /*
90 : * The different states for a parallel slot.
91 : */
92 : typedef enum UpgradeTaskSlotState
93 : {
94 : FREE, /* slot available for use in a new database */
95 : CONNECTING, /* waiting for connection to be established */
96 : RUNNING_QUERIES, /* running/processing queries in the task */
97 : } UpgradeTaskSlotState;
98 :
99 : /*
100 : * We maintain an array of user_opts.jobs slots to execute the task.
101 : */
102 : typedef struct UpgradeTaskSlot
103 : {
104 : UpgradeTaskSlotState state; /* state of the slot */
105 : int db_idx; /* index of the database assigned to slot */
106 : int step_idx; /* index of the current step of task */
107 : PGconn *conn; /* current connection managed by slot */
108 : bool ready; /* slot is ready for processing */
109 : bool select_mode; /* select() mode: true->read, false->write */
110 : int sock; /* file descriptor for connection's socket */
111 : } UpgradeTaskSlot;
112 :
113 : /*
114 : * Initializes an UpgradeTask.
115 : */
116 : UpgradeTask *
117 93 : upgrade_task_create(void)
118 : {
119 93 : UpgradeTask *task = pg_malloc0_object(UpgradeTask);
120 :
121 93 : task->queries = createPQExpBuffer();
122 :
123 : /* All tasks must first set a secure search_path. */
124 93 : upgrade_task_add_step(task, ALWAYS_SECURE_SEARCH_PATH_SQL, NULL, true, NULL);
125 :
126 93 : return task;
127 : }
128 :
129 : /*
130 : * Frees all storage associated with an UpgradeTask.
131 : */
132 : void
133 93 : upgrade_task_free(UpgradeTask *task)
134 : {
135 93 : destroyPQExpBuffer(task->queries);
136 93 : pg_free(task->steps);
137 93 : pg_free(task);
138 93 : }
139 :
140 : /*
141 : * Adds a step to an UpgradeTask. The steps will be executed in each database
142 : * in the order in which they are added.
143 : *
144 : * task: task object that must have been initialized via upgrade_task_create()
145 : * query: the query text
146 : * process_cb: function that processes the results of the query
147 : * free_result: should we free the PGresult, or leave it to the caller?
148 : * arg: pointer to task-specific data that is passed to each callback
149 : */
150 : void
151 216 : upgrade_task_add_step(UpgradeTask *task, const char *query,
152 : UpgradeTaskProcessCB process_cb, bool free_result,
153 : void *arg)
154 : {
155 : UpgradeTaskStep *new_step;
156 :
157 216 : task->steps = pg_realloc_array(task->steps, UpgradeTaskStep,
158 : ++task->num_steps);
159 :
160 216 : new_step = &task->steps[task->num_steps - 1];
161 216 : new_step->process_cb = process_cb;
162 216 : new_step->free_result = free_result;
163 216 : new_step->arg = arg;
164 :
165 216 : appendPQExpBuffer(task->queries, "%s;", query);
166 216 : }
167 :
168 : /*
169 : * Build a connection string for the slot's current database and asynchronously
170 : * start a new connection, but do not wait for the connection to be
171 : * established.
172 : */
173 : static void
174 282 : start_conn(const ClusterInfo *cluster, UpgradeTaskSlot *slot)
175 : {
176 : PQExpBufferData conn_opts;
177 282 : DbInfo *dbinfo = &cluster->dbarr.dbs[slot->db_idx];
178 :
179 : /* Build connection string with proper quoting */
180 282 : initPQExpBuffer(&conn_opts);
181 282 : appendPQExpBufferStr(&conn_opts, "dbname=");
182 282 : appendConnStrVal(&conn_opts, dbinfo->db_name);
183 282 : appendPQExpBufferStr(&conn_opts, " user=");
184 282 : appendConnStrVal(&conn_opts, os_info.user);
185 282 : appendPQExpBuffer(&conn_opts, " port=%d", cluster->port);
186 282 : if (cluster->sockdir)
187 : {
188 282 : appendPQExpBufferStr(&conn_opts, " host=");
189 282 : appendConnStrVal(&conn_opts, cluster->sockdir);
190 : }
191 282 : if (!protocol_negotiation_supported(cluster))
192 0 : appendPQExpBufferStr(&conn_opts, " max_protocol_version=3.0");
193 :
194 282 : slot->conn = PQconnectStart(conn_opts.data);
195 :
196 282 : if (!slot->conn)
197 0 : pg_fatal("out of memory");
198 :
199 282 : termPQExpBuffer(&conn_opts);
200 282 : }
201 :
202 : /*
203 : * Run the process_cb callback function to process the result of a query, and
204 : * free the result if the caller indicated we should do so.
205 : */
206 : static void
207 660 : process_query_result(const ClusterInfo *cluster, UpgradeTaskSlot *slot,
208 : const UpgradeTask *task)
209 : {
210 660 : UpgradeTaskStep *steps = &task->steps[slot->step_idx];
211 660 : UpgradeTaskProcessCB process_cb = steps->process_cb;
212 660 : DbInfo *dbinfo = &cluster->dbarr.dbs[slot->db_idx];
213 660 : PGresult *res = PQgetResult(slot->conn);
214 :
215 1320 : if (PQstatus(slot->conn) == CONNECTION_BAD ||
216 660 : (PQresultStatus(res) != PGRES_TUPLES_OK &&
217 0 : PQresultStatus(res) != PGRES_COMMAND_OK))
218 0 : pg_fatal("connection failure: %s", PQerrorMessage(slot->conn));
219 :
220 : /*
221 : * We assume that a NULL process_cb callback function means there's
222 : * nothing to process. This is primarily intended for the initial step in
223 : * every task that sets a safe search_path.
224 : */
225 660 : if (process_cb)
226 378 : (*process_cb) (dbinfo, res, steps->arg);
227 :
228 660 : if (steps->free_result)
229 610 : PQclear(res);
230 660 : }
231 :
232 : /*
233 : * Advances the state machine for a given slot as necessary.
234 : */
235 : static void
236 1248 : process_slot(const ClusterInfo *cluster, UpgradeTaskSlot *slot, const UpgradeTask *task)
237 : {
238 : PostgresPollingStatusType status;
239 :
240 1248 : if (!slot->ready)
241 0 : return;
242 :
243 1248 : switch (slot->state)
244 : {
245 375 : case FREE:
246 :
247 : /*
248 : * If all of the databases in the cluster have been processed or
249 : * are currently being processed by other slots, we are done.
250 : */
251 375 : if (dbs_processing >= cluster->dbarr.ndbs)
252 93 : return;
253 :
254 : /*
255 : * Claim the next database in the cluster's array and initiate a
256 : * new connection.
257 : */
258 282 : slot->db_idx = dbs_processing++;
259 282 : slot->state = CONNECTING;
260 282 : start_conn(cluster, slot);
261 :
262 282 : return;
263 :
264 564 : case CONNECTING:
265 :
266 : /* Check for connection failure. */
267 564 : status = PQconnectPoll(slot->conn);
268 564 : if (status == PGRES_POLLING_FAILED)
269 0 : pg_fatal("connection failure: %s", PQerrorMessage(slot->conn));
270 :
271 : /* Check whether the connection is still establishing. */
272 564 : if (status != PGRES_POLLING_OK)
273 : {
274 282 : slot->select_mode = (status == PGRES_POLLING_READING);
275 282 : return;
276 : }
277 :
278 : /*
279 : * Move on to running/processing the queries in the task.
280 : */
281 282 : slot->state = RUNNING_QUERIES;
282 282 : slot->select_mode = true; /* wait until ready for reading */
283 282 : if (!PQsendQuery(slot->conn, task->queries->data))
284 0 : pg_fatal("connection failure: %s", PQerrorMessage(slot->conn));
285 :
286 282 : return;
287 :
288 309 : case RUNNING_QUERIES:
289 :
290 : /*
291 : * Consume any available data and clear the read-ready indicator
292 : * for the connection.
293 : */
294 309 : if (!PQconsumeInput(slot->conn))
295 0 : pg_fatal("connection failure: %s", PQerrorMessage(slot->conn));
296 :
297 : /*
298 : * Process any results that are ready so that we can free up this
299 : * slot for another database as soon as possible.
300 : */
301 969 : for (; slot->step_idx < task->num_steps; slot->step_idx++)
302 : {
303 : /* If no more results are available yet, move on. */
304 687 : if (PQisBusy(slot->conn))
305 27 : return;
306 :
307 660 : process_query_result(cluster, slot, task);
308 : }
309 :
310 : /*
311 : * If we just finished processing the result of the last step in
312 : * the task, free the slot. We recursively call this function on
313 : * the newly-freed slot so that we can start initiating the next
314 : * connection immediately instead of waiting for the next loop
315 : * through the slots.
316 : */
317 282 : dbs_complete++;
318 282 : PQfinish(slot->conn);
319 282 : memset(slot, 0, sizeof(UpgradeTaskSlot));
320 282 : slot->ready = true;
321 :
322 282 : process_slot(cluster, slot, task);
323 :
324 282 : return;
325 : }
326 : }
327 :
328 : /*
329 : * Returns -1 on error, else the number of ready descriptors.
330 : */
331 : static int
332 966 : select_loop(int maxFd, fd_set *input, fd_set *output)
333 : {
334 966 : fd_set save_input = *input;
335 966 : fd_set save_output = *output;
336 :
337 966 : if (maxFd == 0)
338 93 : return 0;
339 :
340 : for (;;)
341 0 : {
342 : int i;
343 :
344 873 : *input = save_input;
345 873 : *output = save_output;
346 :
347 873 : i = select(maxFd + 1, input, output, NULL, NULL);
348 :
349 : #ifndef WIN32
350 873 : if (i < 0 && errno == EINTR)
351 0 : continue;
352 : #else
353 : if (i == SOCKET_ERROR && WSAGetLastError() == WSAEINTR)
354 : continue;
355 : #endif
356 873 : return i;
357 : }
358 : }
359 :
360 : /*
361 : * Wait on the slots to either finish connecting or to receive query results if
362 : * possible. This avoids a tight loop in upgrade_task_run().
363 : */
364 : static void
365 966 : wait_on_slots(UpgradeTaskSlot *slots, int numslots)
366 : {
367 : fd_set input;
368 : fd_set output;
369 966 : int maxFd = 0;
370 :
371 16422 : FD_ZERO(&input);
372 16422 : FD_ZERO(&output);
373 :
374 1932 : for (int i = 0; i < numslots; i++)
375 : {
376 : /*
377 : * We assume the previous call to process_slot() handled everything
378 : * that was marked ready in the previous call to wait_on_slots(), if
379 : * any.
380 : */
381 966 : slots[i].ready = false;
382 :
383 : /*
384 : * This function should only ever see free slots as we are finishing
385 : * processing the last few databases, at which point we don't have any
386 : * databases left for them to process. We'll never use these slots
387 : * again, so we can safely ignore them.
388 : */
389 966 : if (slots[i].state == FREE)
390 93 : continue;
391 :
392 : /*
393 : * Add the socket to the set.
394 : */
395 873 : slots[i].sock = PQsocket(slots[i].conn);
396 873 : if (slots[i].sock < 0)
397 0 : pg_fatal("invalid socket");
398 873 : FD_SET(slots[i].sock, slots[i].select_mode ? &input : &output);
399 873 : maxFd = Max(maxFd, slots[i].sock);
400 : }
401 :
402 : /*
403 : * If we found socket(s) to wait on, wait.
404 : */
405 966 : if (select_loop(maxFd, &input, &output) == -1)
406 0 : pg_fatal("%s() failed: %m", "select");
407 :
408 : /*
409 : * Mark which sockets appear to be ready.
410 : */
411 1932 : for (int i = 0; i < numslots; i++)
412 1341 : slots[i].ready |= (FD_ISSET(slots[i].sock, &input) ||
413 1341 : FD_ISSET(slots[i].sock, &output));
414 966 : }
415 :
416 : /*
417 : * Runs all the steps of the task in every database in the cluster using
418 : * user_opts.jobs parallel slots.
419 : */
420 : void
421 93 : upgrade_task_run(const UpgradeTask *task, const ClusterInfo *cluster)
422 : {
423 93 : int jobs = Max(1, user_opts.jobs);
424 93 : UpgradeTaskSlot *slots = pg_malloc0_array(UpgradeTaskSlot, jobs);
425 :
426 93 : dbs_complete = 0;
427 93 : dbs_processing = 0;
428 :
429 : /*
430 : * Process every slot the first time round.
431 : */
432 186 : for (int i = 0; i < jobs; i++)
433 93 : slots[i].ready = true;
434 :
435 1059 : while (dbs_complete < cluster->dbarr.ndbs)
436 : {
437 1932 : for (int i = 0; i < jobs; i++)
438 966 : process_slot(cluster, &slots[i], task);
439 :
440 966 : wait_on_slots(slots, jobs);
441 : }
442 :
443 93 : pg_free(slots);
444 93 : }
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