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) 1996-2025, 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 "libpq/libpq.h"
18 : #include "libpq/pqformat.h"
19 : #include "libpq/pqmq.h"
20 : #include "miscadmin.h"
21 : #include "pgstat.h"
22 : #include "replication/logicalworker.h"
23 : #include "tcop/tcopprot.h"
24 : #include "utils/builtins.h"
25 :
26 : static shm_mq_handle *pq_mq_handle = NULL;
27 : static bool pq_mq_busy = false;
28 : static pid_t pq_mq_parallel_leader_pid = 0;
29 : static ProcNumber pq_mq_parallel_leader_proc_number = INVALID_PROC_NUMBER;
30 :
31 : static void pq_cleanup_redirect_to_shm_mq(dsm_segment *seg, Datum arg);
32 : static void mq_comm_reset(void);
33 : static int mq_flush(void);
34 : static int mq_flush_if_writable(void);
35 : static bool mq_is_send_pending(void);
36 : static int mq_putmessage(char msgtype, const char *s, size_t len);
37 : static void mq_putmessage_noblock(char msgtype, const char *s, size_t len);
38 :
39 : static const PQcommMethods PqCommMqMethods = {
40 : .comm_reset = mq_comm_reset,
41 : .flush = mq_flush,
42 : .flush_if_writable = mq_flush_if_writable,
43 : .is_send_pending = mq_is_send_pending,
44 : .putmessage = mq_putmessage,
45 : .putmessage_noblock = mq_putmessage_noblock
46 : };
47 :
48 : /*
49 : * Arrange to redirect frontend/backend protocol messages to a shared-memory
50 : * message queue.
51 : */
52 : void
53 2750 : pq_redirect_to_shm_mq(dsm_segment *seg, shm_mq_handle *mqh)
54 : {
55 2750 : PqCommMethods = &PqCommMqMethods;
56 2750 : pq_mq_handle = mqh;
57 2750 : whereToSendOutput = DestRemote;
58 2750 : FrontendProtocol = PG_PROTOCOL_LATEST;
59 2750 : on_dsm_detach(seg, pq_cleanup_redirect_to_shm_mq, (Datum) 0);
60 2750 : }
61 :
62 : /*
63 : * When the DSM that contains our shm_mq goes away, we need to stop sending
64 : * messages to it.
65 : */
66 : static void
67 2750 : pq_cleanup_redirect_to_shm_mq(dsm_segment *seg, Datum arg)
68 : {
69 2750 : if (pq_mq_handle != NULL)
70 : {
71 2750 : pfree(pq_mq_handle);
72 2750 : pq_mq_handle = NULL;
73 : }
74 2750 : whereToSendOutput = DestNone;
75 2750 : }
76 :
77 : /*
78 : * Arrange to SendProcSignal() to the parallel leader each time we transmit
79 : * message data via the shm_mq.
80 : */
81 : void
82 2750 : pq_set_parallel_leader(pid_t pid, ProcNumber procNumber)
83 : {
84 : Assert(PqCommMethods == &PqCommMqMethods);
85 2750 : pq_mq_parallel_leader_pid = pid;
86 2750 : pq_mq_parallel_leader_proc_number = procNumber;
87 2750 : }
88 :
89 : static void
90 0 : mq_comm_reset(void)
91 : {
92 : /* Nothing to do. */
93 0 : }
94 :
95 : static int
96 22 : mq_flush(void)
97 : {
98 : /* Nothing to do. */
99 22 : return 0;
100 : }
101 :
102 : static int
103 0 : mq_flush_if_writable(void)
104 : {
105 : /* Nothing to do. */
106 0 : return 0;
107 : }
108 :
109 : static bool
110 0 : mq_is_send_pending(void)
111 : {
112 : /* There's never anything pending. */
113 0 : return 0;
114 : }
115 :
116 : /*
117 : * Transmit a libpq protocol message to the shared memory message queue
118 : * selected via pq_mq_handle. We don't include a length word, because the
119 : * receiver will know the length of the message from shm_mq_receive().
120 : */
121 : static int
122 2740 : mq_putmessage(char msgtype, const char *s, size_t len)
123 : {
124 : shm_mq_iovec iov[2];
125 : shm_mq_result result;
126 :
127 : /*
128 : * If we're sending a message, and we have to wait because the queue is
129 : * full, and then we get interrupted, and that interrupt results in trying
130 : * to send another message, we respond by detaching the queue. There's no
131 : * way to return to the original context, but even if there were, just
132 : * queueing the message would amount to indefinitely postponing the
133 : * response to the interrupt. So we do this instead.
134 : */
135 2740 : if (pq_mq_busy)
136 : {
137 0 : if (pq_mq_handle != NULL)
138 : {
139 0 : shm_mq_detach(pq_mq_handle);
140 0 : pfree(pq_mq_handle);
141 0 : pq_mq_handle = NULL;
142 : }
143 0 : return EOF;
144 : }
145 :
146 : /*
147 : * If the message queue is already gone, just ignore the message. This
148 : * doesn't necessarily indicate a problem; for example, DEBUG messages can
149 : * be generated late in the shutdown sequence, after all DSMs have already
150 : * been detached.
151 : */
152 2740 : if (pq_mq_handle == NULL)
153 0 : return 0;
154 :
155 2740 : pq_mq_busy = true;
156 :
157 2740 : iov[0].data = &msgtype;
158 2740 : iov[0].len = 1;
159 2740 : iov[1].data = s;
160 2740 : iov[1].len = len;
161 :
162 : for (;;)
163 : {
164 : /*
165 : * Immediately notify the receiver by passing force_flush as true so
166 : * that the shared memory value is updated before we send the parallel
167 : * message signal right after this.
168 : */
169 8 : Assert(pq_mq_handle != NULL);
170 2748 : result = shm_mq_sendv(pq_mq_handle, iov, 2, true, true);
171 :
172 2748 : if (pq_mq_parallel_leader_pid != 0)
173 : {
174 2748 : if (IsLogicalParallelApplyWorker())
175 10 : SendProcSignal(pq_mq_parallel_leader_pid,
176 : PROCSIG_PARALLEL_APPLY_MESSAGE,
177 : pq_mq_parallel_leader_proc_number);
178 : else
179 : {
180 : Assert(IsParallelWorker());
181 2738 : SendProcSignal(pq_mq_parallel_leader_pid,
182 : PROCSIG_PARALLEL_MESSAGE,
183 : pq_mq_parallel_leader_proc_number);
184 : }
185 : }
186 :
187 2748 : if (result != SHM_MQ_WOULD_BLOCK)
188 2740 : break;
189 :
190 8 : (void) WaitLatch(MyLatch, WL_LATCH_SET | WL_EXIT_ON_PM_DEATH, 0,
191 : WAIT_EVENT_MESSAGE_QUEUE_PUT_MESSAGE);
192 8 : ResetLatch(MyLatch);
193 8 : CHECK_FOR_INTERRUPTS();
194 : }
195 :
196 2740 : pq_mq_busy = false;
197 :
198 : Assert(result == SHM_MQ_SUCCESS || result == SHM_MQ_DETACHED);
199 2740 : if (result != SHM_MQ_SUCCESS)
200 6 : return EOF;
201 2734 : return 0;
202 : }
203 :
204 : static void
205 0 : mq_putmessage_noblock(char msgtype, const char *s, size_t len)
206 : {
207 : /*
208 : * While the shm_mq machinery does support sending a message in
209 : * non-blocking mode, there's currently no way to try sending beginning to
210 : * send the message that doesn't also commit us to completing the
211 : * transmission. This could be improved in the future, but for now we
212 : * don't need it.
213 : */
214 0 : elog(ERROR, "not currently supported");
215 : }
216 :
217 : /*
218 : * Parse an ErrorResponse or NoticeResponse payload and populate an ErrorData
219 : * structure with the results.
220 : */
221 : void
222 14 : pq_parse_errornotice(StringInfo msg, ErrorData *edata)
223 : {
224 : /* Initialize edata with reasonable defaults. */
225 336 : MemSet(edata, 0, sizeof(ErrorData));
226 14 : edata->elevel = ERROR;
227 14 : edata->assoc_context = CurrentMemoryContext;
228 :
229 : /* Loop over fields and extract each one. */
230 : for (;;)
231 110 : {
232 124 : char code = pq_getmsgbyte(msg);
233 : const char *value;
234 :
235 124 : if (code == '\0')
236 : {
237 14 : pq_getmsgend(msg);
238 14 : break;
239 : }
240 110 : value = pq_getmsgrawstring(msg);
241 :
242 110 : switch (code)
243 : {
244 14 : case PG_DIAG_SEVERITY:
245 : /* ignore, trusting we'll get a nonlocalized version */
246 14 : break;
247 14 : case PG_DIAG_SEVERITY_NONLOCALIZED:
248 14 : if (strcmp(value, "DEBUG") == 0)
249 : {
250 : /*
251 : * We can't reconstruct the exact DEBUG level, but
252 : * presumably it was >= client_min_messages, so select
253 : * DEBUG1 to ensure we'll pass it on to the client.
254 : */
255 0 : edata->elevel = DEBUG1;
256 : }
257 14 : else if (strcmp(value, "LOG") == 0)
258 : {
259 : /*
260 : * It can't be LOG_SERVER_ONLY, or the worker wouldn't
261 : * have sent it to us; so LOG is the correct value.
262 : */
263 0 : edata->elevel = LOG;
264 : }
265 14 : else if (strcmp(value, "INFO") == 0)
266 0 : edata->elevel = INFO;
267 14 : else if (strcmp(value, "NOTICE") == 0)
268 0 : edata->elevel = NOTICE;
269 14 : else if (strcmp(value, "WARNING") == 0)
270 0 : edata->elevel = WARNING;
271 14 : else if (strcmp(value, "ERROR") == 0)
272 14 : edata->elevel = ERROR;
273 0 : else if (strcmp(value, "FATAL") == 0)
274 0 : edata->elevel = FATAL;
275 0 : else if (strcmp(value, "PANIC") == 0)
276 0 : edata->elevel = PANIC;
277 : else
278 0 : elog(ERROR, "unrecognized error severity: \"%s\"", value);
279 14 : break;
280 14 : case PG_DIAG_SQLSTATE:
281 14 : if (strlen(value) != 5)
282 0 : elog(ERROR, "invalid SQLSTATE: \"%s\"", value);
283 14 : edata->sqlerrcode = MAKE_SQLSTATE(value[0], value[1], value[2],
284 : value[3], value[4]);
285 14 : break;
286 14 : case PG_DIAG_MESSAGE_PRIMARY:
287 14 : edata->message = pstrdup(value);
288 14 : break;
289 2 : case PG_DIAG_MESSAGE_DETAIL:
290 2 : edata->detail = pstrdup(value);
291 2 : break;
292 2 : case PG_DIAG_MESSAGE_HINT:
293 2 : edata->hint = pstrdup(value);
294 2 : break;
295 0 : case PG_DIAG_STATEMENT_POSITION:
296 0 : edata->cursorpos = pg_strtoint32(value);
297 0 : break;
298 0 : case PG_DIAG_INTERNAL_POSITION:
299 0 : edata->internalpos = pg_strtoint32(value);
300 0 : break;
301 0 : case PG_DIAG_INTERNAL_QUERY:
302 0 : edata->internalquery = pstrdup(value);
303 0 : break;
304 8 : case PG_DIAG_CONTEXT:
305 8 : edata->context = pstrdup(value);
306 8 : break;
307 0 : case PG_DIAG_SCHEMA_NAME:
308 0 : edata->schema_name = pstrdup(value);
309 0 : break;
310 0 : case PG_DIAG_TABLE_NAME:
311 0 : edata->table_name = pstrdup(value);
312 0 : break;
313 0 : case PG_DIAG_COLUMN_NAME:
314 0 : edata->column_name = pstrdup(value);
315 0 : break;
316 0 : case PG_DIAG_DATATYPE_NAME:
317 0 : edata->datatype_name = pstrdup(value);
318 0 : break;
319 0 : case PG_DIAG_CONSTRAINT_NAME:
320 0 : edata->constraint_name = pstrdup(value);
321 0 : break;
322 14 : case PG_DIAG_SOURCE_FILE:
323 14 : edata->filename = pstrdup(value);
324 14 : break;
325 14 : case PG_DIAG_SOURCE_LINE:
326 14 : edata->lineno = pg_strtoint32(value);
327 14 : break;
328 14 : case PG_DIAG_SOURCE_FUNCTION:
329 14 : edata->funcname = pstrdup(value);
330 14 : break;
331 0 : default:
332 0 : elog(ERROR, "unrecognized error field code: %d", (int) code);
333 : break;
334 : }
335 : }
336 14 : }
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