/* ---------- * backend_status.c * Backend status reporting infrastructure. * * Copyright (c) 2001-2024, PostgreSQL Global Development Group * * * IDENTIFICATION * src/backend/utils/activity/backend_status.c * ---------- */ #include "postgres.h" #include "access/xact.h" #include "libpq/libpq-be.h" #include "miscadmin.h" #include "pg_trace.h" #include "pgstat.h" #include "port/atomics.h" /* for memory barriers */ #include "storage/ipc.h" #include "storage/proc.h" /* for MyProc */ #include "storage/procarray.h" #include "storage/sinvaladt.h" #include "utils/ascii.h" #include "utils/guc.h" /* for application_name */ #include "utils/memutils.h" /* ---------- * Total number of backends including auxiliary * * We reserve a slot for each possible PGPROC entry, including aux processes. * (But not including PGPROC entries reserved for prepared xacts; they are not * real processes.) * ---------- */ #define NumBackendStatSlots (MaxBackends + NUM_AUXILIARY_PROCS) /* ---------- * GUC parameters * ---------- */ bool pgstat_track_activities = false; int pgstat_track_activity_query_size = 1024; /* exposed so that backend_progress.c can access it */ PgBackendStatus *MyBEEntry = NULL; static PgBackendStatus *BackendStatusArray = NULL; static char *BackendAppnameBuffer = NULL; static char *BackendClientHostnameBuffer = NULL; static char *BackendActivityBuffer = NULL; static Size BackendActivityBufferSize = 0; #ifdef USE_SSL static PgBackendSSLStatus *BackendSslStatusBuffer = NULL; #endif #ifdef ENABLE_GSS static PgBackendGSSStatus *BackendGssStatusBuffer = NULL; #endif /* Status for backends including auxiliary */ static LocalPgBackendStatus *localBackendStatusTable = NULL; /* Total number of backends including auxiliary */ static int localNumBackends = 0; static MemoryContext backendStatusSnapContext; static void pgstat_beshutdown_hook(int code, Datum arg); static void pgstat_read_current_status(void); static void pgstat_setup_backend_status_context(void); /* * Report shared-memory space needed by CreateSharedBackendStatus. */ Size BackendStatusShmemSize(void) { Size size; /* BackendStatusArray: */ size = mul_size(sizeof(PgBackendStatus), NumBackendStatSlots); /* BackendAppnameBuffer: */ size = add_size(size, mul_size(NAMEDATALEN, NumBackendStatSlots)); /* BackendClientHostnameBuffer: */ size = add_size(size, mul_size(NAMEDATALEN, NumBackendStatSlots)); /* BackendActivityBuffer: */ size = add_size(size, mul_size(pgstat_track_activity_query_size, NumBackendStatSlots)); #ifdef USE_SSL /* BackendSslStatusBuffer: */ size = add_size(size, mul_size(sizeof(PgBackendSSLStatus), NumBackendStatSlots)); #endif #ifdef ENABLE_GSS /* BackendGssStatusBuffer: */ size = add_size(size, mul_size(sizeof(PgBackendGSSStatus), NumBackendStatSlots)); #endif return size; } /* * Initialize the shared status array and several string buffers * during postmaster startup. */ void CreateSharedBackendStatus(void) { Size size; bool found; int i; char *buffer; /* Create or attach to the shared array */ size = mul_size(sizeof(PgBackendStatus), NumBackendStatSlots); BackendStatusArray = (PgBackendStatus *) ShmemInitStruct("Backend Status Array", size, &found); if (!found) { /* * We're the first - initialize. */ MemSet(BackendStatusArray, 0, size); } /* Create or attach to the shared appname buffer */ size = mul_size(NAMEDATALEN, NumBackendStatSlots); BackendAppnameBuffer = (char *) ShmemInitStruct("Backend Application Name Buffer", size, &found); if (!found) { MemSet(BackendAppnameBuffer, 0, size); /* Initialize st_appname pointers. */ buffer = BackendAppnameBuffer; for (i = 0; i < NumBackendStatSlots; i++) { BackendStatusArray[i].st_appname = buffer; buffer += NAMEDATALEN; } } /* Create or attach to the shared client hostname buffer */ size = mul_size(NAMEDATALEN, NumBackendStatSlots); BackendClientHostnameBuffer = (char *) ShmemInitStruct("Backend Client Host Name Buffer", size, &found); if (!found) { MemSet(BackendClientHostnameBuffer, 0, size); /* Initialize st_clienthostname pointers. */ buffer = BackendClientHostnameBuffer; for (i = 0; i < NumBackendStatSlots; i++) { BackendStatusArray[i].st_clienthostname = buffer; buffer += NAMEDATALEN; } } /* Create or attach to the shared activity buffer */ BackendActivityBufferSize = mul_size(pgstat_track_activity_query_size, NumBackendStatSlots); BackendActivityBuffer = (char *) ShmemInitStruct("Backend Activity Buffer", BackendActivityBufferSize, &found); if (!found) { MemSet(BackendActivityBuffer, 0, BackendActivityBufferSize); /* Initialize st_activity pointers. */ buffer = BackendActivityBuffer; for (i = 0; i < NumBackendStatSlots; i++) { BackendStatusArray[i].st_activity_raw = buffer; buffer += pgstat_track_activity_query_size; } } #ifdef USE_SSL /* Create or attach to the shared SSL status buffer */ size = mul_size(sizeof(PgBackendSSLStatus), NumBackendStatSlots); BackendSslStatusBuffer = (PgBackendSSLStatus *) ShmemInitStruct("Backend SSL Status Buffer", size, &found); if (!found) { PgBackendSSLStatus *ptr; MemSet(BackendSslStatusBuffer, 0, size); /* Initialize st_sslstatus pointers. */ ptr = BackendSslStatusBuffer; for (i = 0; i < NumBackendStatSlots; i++) { BackendStatusArray[i].st_sslstatus = ptr; ptr++; } } #endif #ifdef ENABLE_GSS /* Create or attach to the shared GSSAPI status buffer */ size = mul_size(sizeof(PgBackendGSSStatus), NumBackendStatSlots); BackendGssStatusBuffer = (PgBackendGSSStatus *) ShmemInitStruct("Backend GSS Status Buffer", size, &found); if (!found) { PgBackendGSSStatus *ptr; MemSet(BackendGssStatusBuffer, 0, size); /* Initialize st_gssstatus pointers. */ ptr = BackendGssStatusBuffer; for (i = 0; i < NumBackendStatSlots; i++) { BackendStatusArray[i].st_gssstatus = ptr; ptr++; } } #endif } /* * Initialize pgstats backend activity state, and set up our on-proc-exit * hook. Called from InitPostgres and AuxiliaryProcessMain. MyProcNumber must * be set, but we must not have started any transaction yet (since the exit * hook must run after the last transaction exit). * * NOTE: MyDatabaseId isn't set yet; so the shutdown hook has to be careful. */ void pgstat_beinit(void) { /* Initialize MyBEEntry */ Assert(MyProcNumber != INVALID_PROC_NUMBER); Assert(MyProcNumber >= 0 && MyProcNumber < NumBackendStatSlots); MyBEEntry = &BackendStatusArray[MyProcNumber]; /* Set up a process-exit hook to clean up */ on_shmem_exit(pgstat_beshutdown_hook, 0); } /* ---------- * pgstat_bestart() - * * Initialize this backend's entry in the PgBackendStatus array. * Called from InitPostgres. * * Apart from auxiliary processes, MyDatabaseId, session userid, and * application_name must already be set (hence, this cannot be combined * with pgstat_beinit). Note also that we must be inside a transaction * if this isn't an aux process, as we may need to do encoding conversion * on some strings. *---------- */ void pgstat_bestart(void) { volatile PgBackendStatus *vbeentry = MyBEEntry; PgBackendStatus lbeentry; #ifdef USE_SSL PgBackendSSLStatus lsslstatus; #endif #ifdef ENABLE_GSS PgBackendGSSStatus lgssstatus; #endif /* pgstats state must be initialized from pgstat_beinit() */ Assert(vbeentry != NULL); /* * To minimize the time spent modifying the PgBackendStatus entry, and * avoid risk of errors inside the critical section, we first copy the * shared-memory struct to a local variable, then modify the data in the * local variable, then copy the local variable back to shared memory. * Only the last step has to be inside the critical section. * * Most of the data we copy from shared memory is just going to be * overwritten, but the struct's not so large that it's worth the * maintenance hassle to copy only the needful fields. */ memcpy(&lbeentry, unvolatize(PgBackendStatus *, vbeentry), sizeof(PgBackendStatus)); /* These structs can just start from zeroes each time, though */ #ifdef USE_SSL memset(&lsslstatus, 0, sizeof(lsslstatus)); #endif #ifdef ENABLE_GSS memset(&lgssstatus, 0, sizeof(lgssstatus)); #endif /* * Now fill in all the fields of lbeentry, except for strings that are * out-of-line data. Those have to be handled separately, below. */ lbeentry.st_procpid = MyProcPid; lbeentry.st_backendType = MyBackendType; lbeentry.st_proc_start_timestamp = MyStartTimestamp; lbeentry.st_activity_start_timestamp = 0; lbeentry.st_state_start_timestamp = 0; lbeentry.st_xact_start_timestamp = 0; lbeentry.st_databaseid = MyDatabaseId; /* We have userid for client-backends, wal-sender and bgworker processes */ if (lbeentry.st_backendType == B_BACKEND || lbeentry.st_backendType == B_WAL_SENDER || lbeentry.st_backendType == B_BG_WORKER) lbeentry.st_userid = GetSessionUserId(); else lbeentry.st_userid = InvalidOid; /* * We may not have a MyProcPort (eg, if this is the autovacuum process). * If so, use all-zeroes client address, which is dealt with specially in * pg_stat_get_backend_client_addr and pg_stat_get_backend_client_port. */ if (MyProcPort) memcpy(&lbeentry.st_clientaddr, &MyProcPort->raddr, sizeof(lbeentry.st_clientaddr)); else MemSet(&lbeentry.st_clientaddr, 0, sizeof(lbeentry.st_clientaddr)); #ifdef USE_SSL if (MyProcPort && MyProcPort->ssl_in_use) { lbeentry.st_ssl = true; lsslstatus.ssl_bits = be_tls_get_cipher_bits(MyProcPort); strlcpy(lsslstatus.ssl_version, be_tls_get_version(MyProcPort), NAMEDATALEN); strlcpy(lsslstatus.ssl_cipher, be_tls_get_cipher(MyProcPort), NAMEDATALEN); be_tls_get_peer_subject_name(MyProcPort, lsslstatus.ssl_client_dn, NAMEDATALEN); be_tls_get_peer_serial(MyProcPort, lsslstatus.ssl_client_serial, NAMEDATALEN); be_tls_get_peer_issuer_name(MyProcPort, lsslstatus.ssl_issuer_dn, NAMEDATALEN); } else { lbeentry.st_ssl = false; } #else lbeentry.st_ssl = false; #endif #ifdef ENABLE_GSS if (MyProcPort && MyProcPort->gss != NULL) { const char *princ = be_gssapi_get_princ(MyProcPort); lbeentry.st_gss = true; lgssstatus.gss_auth = be_gssapi_get_auth(MyProcPort); lgssstatus.gss_enc = be_gssapi_get_enc(MyProcPort); lgssstatus.gss_delegation = be_gssapi_get_delegation(MyProcPort); if (princ) strlcpy(lgssstatus.gss_princ, princ, NAMEDATALEN); } else { lbeentry.st_gss = false; } #else lbeentry.st_gss = false; #endif lbeentry.st_state = STATE_UNDEFINED; lbeentry.st_progress_command = PROGRESS_COMMAND_INVALID; lbeentry.st_progress_command_target = InvalidOid; lbeentry.st_query_id = UINT64CONST(0); /* * we don't zero st_progress_param here to save cycles; nobody should * examine it until st_progress_command has been set to something other * than PROGRESS_COMMAND_INVALID */ /* * We're ready to enter the critical section that fills the shared-memory * status entry. We follow the protocol of bumping st_changecount before * and after; and make sure it's even afterwards. We use a volatile * pointer here to ensure the compiler doesn't try to get cute. */ PGSTAT_BEGIN_WRITE_ACTIVITY(vbeentry); /* make sure we'll memcpy the same st_changecount back */ lbeentry.st_changecount = vbeentry->st_changecount; memcpy(unvolatize(PgBackendStatus *, vbeentry), &lbeentry, sizeof(PgBackendStatus)); /* * We can write the out-of-line strings and structs using the pointers * that are in lbeentry; this saves some de-volatilizing messiness. */ lbeentry.st_appname[0] = '\0'; if (MyProcPort && MyProcPort->remote_hostname) strlcpy(lbeentry.st_clienthostname, MyProcPort->remote_hostname, NAMEDATALEN); else lbeentry.st_clienthostname[0] = '\0'; lbeentry.st_activity_raw[0] = '\0'; /* Also make sure the last byte in each string area is always 0 */ lbeentry.st_appname[NAMEDATALEN - 1] = '\0'; lbeentry.st_clienthostname[NAMEDATALEN - 1] = '\0'; lbeentry.st_activity_raw[pgstat_track_activity_query_size - 1] = '\0'; #ifdef USE_SSL memcpy(lbeentry.st_sslstatus, &lsslstatus, sizeof(PgBackendSSLStatus)); #endif #ifdef ENABLE_GSS memcpy(lbeentry.st_gssstatus, &lgssstatus, sizeof(PgBackendGSSStatus)); #endif PGSTAT_END_WRITE_ACTIVITY(vbeentry); /* Update app name to current GUC setting */ if (application_name) pgstat_report_appname(application_name); } /* * Clear out our entry in the PgBackendStatus array. */ static void pgstat_beshutdown_hook(int code, Datum arg) { volatile PgBackendStatus *beentry = MyBEEntry; /* * Clear my status entry, following the protocol of bumping st_changecount * before and after. We use a volatile pointer here to ensure the * compiler doesn't try to get cute. */ PGSTAT_BEGIN_WRITE_ACTIVITY(beentry); beentry->st_procpid = 0; /* mark invalid */ PGSTAT_END_WRITE_ACTIVITY(beentry); /* so that functions can check if backend_status.c is up via MyBEEntry */ MyBEEntry = NULL; } /* * Discard any data collected in the current transaction. Any subsequent * request will cause new snapshots to be read. * * This is also invoked during transaction commit or abort to discard the * no-longer-wanted snapshot. */ void pgstat_clear_backend_activity_snapshot(void) { /* Release memory, if any was allocated */ if (backendStatusSnapContext) { MemoryContextDelete(backendStatusSnapContext); backendStatusSnapContext = NULL; } /* Reset variables */ localBackendStatusTable = NULL; localNumBackends = 0; } static void pgstat_setup_backend_status_context(void) { if (!backendStatusSnapContext) backendStatusSnapContext = AllocSetContextCreate(TopMemoryContext, "Backend Status Snapshot", ALLOCSET_SMALL_SIZES); } /* ---------- * pgstat_report_activity() - * * Called from tcop/postgres.c to report what the backend is actually doing * (but note cmd_str can be NULL for certain cases). * * All updates of the status entry follow the protocol of bumping * st_changecount before and after. We use a volatile pointer here to * ensure the compiler doesn't try to get cute. * ---------- */ void pgstat_report_activity(BackendState state, const char *cmd_str) { volatile PgBackendStatus *beentry = MyBEEntry; TimestampTz start_timestamp; TimestampTz current_timestamp; int len = 0; TRACE_POSTGRESQL_STATEMENT_STATUS(cmd_str); if (!beentry) return; if (!pgstat_track_activities) { if (beentry->st_state != STATE_DISABLED) { volatile PGPROC *proc = MyProc; /* * track_activities is disabled, but we last reported a * non-disabled state. As our final update, change the state and * clear fields we will not be updating anymore. */ PGSTAT_BEGIN_WRITE_ACTIVITY(beentry); beentry->st_state = STATE_DISABLED; beentry->st_state_start_timestamp = 0; beentry->st_activity_raw[0] = '\0'; beentry->st_activity_start_timestamp = 0; /* st_xact_start_timestamp and wait_event_info are also disabled */ beentry->st_xact_start_timestamp = 0; beentry->st_query_id = UINT64CONST(0); proc->wait_event_info = 0; PGSTAT_END_WRITE_ACTIVITY(beentry); } return; } /* * To minimize the time spent modifying the entry, and avoid risk of * errors inside the critical section, fetch all the needed data first. */ start_timestamp = GetCurrentStatementStartTimestamp(); if (cmd_str != NULL) { /* * Compute length of to-be-stored string unaware of multi-byte * characters. For speed reasons that'll get corrected on read, rather * than computed every write. */ len = Min(strlen(cmd_str), pgstat_track_activity_query_size - 1); } current_timestamp = GetCurrentTimestamp(); /* * If the state has changed from "active" or "idle in transaction", * calculate the duration. */ if ((beentry->st_state == STATE_RUNNING || beentry->st_state == STATE_FASTPATH || beentry->st_state == STATE_IDLEINTRANSACTION || beentry->st_state == STATE_IDLEINTRANSACTION_ABORTED) && state != beentry->st_state) { long secs; int usecs; TimestampDifference(beentry->st_state_start_timestamp, current_timestamp, &secs, &usecs); if (beentry->st_state == STATE_RUNNING || beentry->st_state == STATE_FASTPATH) pgstat_count_conn_active_time((PgStat_Counter) secs * 1000000 + usecs); else pgstat_count_conn_txn_idle_time((PgStat_Counter) secs * 1000000 + usecs); } /* * Now update the status entry */ PGSTAT_BEGIN_WRITE_ACTIVITY(beentry); beentry->st_state = state; beentry->st_state_start_timestamp = current_timestamp; /* * If a new query is started, we reset the query identifier as it'll only * be known after parse analysis, to avoid reporting last query's * identifier. */ if (state == STATE_RUNNING) beentry->st_query_id = UINT64CONST(0); if (cmd_str != NULL) { memcpy((char *) beentry->st_activity_raw, cmd_str, len); beentry->st_activity_raw[len] = '\0'; beentry->st_activity_start_timestamp = start_timestamp; } PGSTAT_END_WRITE_ACTIVITY(beentry); } /* -------- * pgstat_report_query_id() - * * Called to update top-level query identifier. * -------- */ void pgstat_report_query_id(uint64 query_id, bool force) { volatile PgBackendStatus *beentry = MyBEEntry; /* * if track_activities is disabled, st_query_id should already have been * reset */ if (!beentry || !pgstat_track_activities) return; /* * We only report the top-level query identifiers. The stored query_id is * reset when a backend calls pgstat_report_activity(STATE_RUNNING), or * with an explicit call to this function using the force flag. If the * saved query identifier is not zero it means that it's not a top-level * command, so ignore the one provided unless it's an explicit call to * reset the identifier. */ if (beentry->st_query_id != 0 && !force) return; /* * Update my status entry, following the protocol of bumping * st_changecount before and after. We use a volatile pointer here to * ensure the compiler doesn't try to get cute. */ PGSTAT_BEGIN_WRITE_ACTIVITY(beentry); beentry->st_query_id = query_id; PGSTAT_END_WRITE_ACTIVITY(beentry); } /* ---------- * pgstat_report_appname() - * * Called to update our application name. * ---------- */ void pgstat_report_appname(const char *appname) { volatile PgBackendStatus *beentry = MyBEEntry; int len; if (!beentry) return; /* This should be unnecessary if GUC did its job, but be safe */ len = pg_mbcliplen(appname, strlen(appname), NAMEDATALEN - 1); /* * Update my status entry, following the protocol of bumping * st_changecount before and after. We use a volatile pointer here to * ensure the compiler doesn't try to get cute. */ PGSTAT_BEGIN_WRITE_ACTIVITY(beentry); memcpy((char *) beentry->st_appname, appname, len); beentry->st_appname[len] = '\0'; PGSTAT_END_WRITE_ACTIVITY(beentry); } /* * Report current transaction start timestamp as the specified value. * Zero means there is no active transaction. */ void pgstat_report_xact_timestamp(TimestampTz tstamp) { volatile PgBackendStatus *beentry = MyBEEntry; if (!pgstat_track_activities || !beentry) return; /* * Update my status entry, following the protocol of bumping * st_changecount before and after. We use a volatile pointer here to * ensure the compiler doesn't try to get cute. */ PGSTAT_BEGIN_WRITE_ACTIVITY(beentry); beentry->st_xact_start_timestamp = tstamp; PGSTAT_END_WRITE_ACTIVITY(beentry); } /* ---------- * pgstat_read_current_status() - * * Copy the current contents of the PgBackendStatus array to local memory, * if not already done in this transaction. * ---------- */ static void pgstat_read_current_status(void) { volatile PgBackendStatus *beentry; LocalPgBackendStatus *localtable; LocalPgBackendStatus *localentry; char *localappname, *localclienthostname, *localactivity; #ifdef USE_SSL PgBackendSSLStatus *localsslstatus; #endif #ifdef ENABLE_GSS PgBackendGSSStatus *localgssstatus; #endif ProcNumber procNumber; if (localBackendStatusTable) return; /* already done */ pgstat_setup_backend_status_context(); /* * Allocate storage for local copy of state data. We can presume that * none of these requests overflow size_t, because we already calculated * the same values using mul_size during shmem setup. However, with * probably-silly values of pgstat_track_activity_query_size and * max_connections, the localactivity buffer could exceed 1GB, so use * "huge" allocation for that one. */ localtable = (LocalPgBackendStatus *) MemoryContextAlloc(backendStatusSnapContext, sizeof(LocalPgBackendStatus) * NumBackendStatSlots); localappname = (char *) MemoryContextAlloc(backendStatusSnapContext, NAMEDATALEN * NumBackendStatSlots); localclienthostname = (char *) MemoryContextAlloc(backendStatusSnapContext, NAMEDATALEN * NumBackendStatSlots); localactivity = (char *) MemoryContextAllocHuge(backendStatusSnapContext, (Size) pgstat_track_activity_query_size * (Size) NumBackendStatSlots); #ifdef USE_SSL localsslstatus = (PgBackendSSLStatus *) MemoryContextAlloc(backendStatusSnapContext, sizeof(PgBackendSSLStatus) * NumBackendStatSlots); #endif #ifdef ENABLE_GSS localgssstatus = (PgBackendGSSStatus *) MemoryContextAlloc(backendStatusSnapContext, sizeof(PgBackendGSSStatus) * NumBackendStatSlots); #endif localNumBackends = 0; beentry = BackendStatusArray; localentry = localtable; for (procNumber = 0; procNumber < NumBackendStatSlots; procNumber++) { /* * Follow the protocol of retrying if st_changecount changes while we * copy the entry, or if it's odd. (The check for odd is needed to * cover the case where we are able to completely copy the entry while * the source backend is between increment steps.) We use a volatile * pointer here to ensure the compiler doesn't try to get cute. */ for (;;) { int before_changecount; int after_changecount; pgstat_begin_read_activity(beentry, before_changecount); localentry->backendStatus.st_procpid = beentry->st_procpid; /* Skip all the data-copying work if entry is not in use */ if (localentry->backendStatus.st_procpid > 0) { memcpy(&localentry->backendStatus, unvolatize(PgBackendStatus *, beentry), sizeof(PgBackendStatus)); /* * For each PgBackendStatus field that is a pointer, copy the * pointed-to data, then adjust the local copy of the pointer * field to point at the local copy of the data. * * strcpy is safe even if the string is modified concurrently, * because there's always a \0 at the end of the buffer. */ strcpy(localappname, (char *) beentry->st_appname); localentry->backendStatus.st_appname = localappname; strcpy(localclienthostname, (char *) beentry->st_clienthostname); localentry->backendStatus.st_clienthostname = localclienthostname; strcpy(localactivity, (char *) beentry->st_activity_raw); localentry->backendStatus.st_activity_raw = localactivity; #ifdef USE_SSL if (beentry->st_ssl) { memcpy(localsslstatus, beentry->st_sslstatus, sizeof(PgBackendSSLStatus)); localentry->backendStatus.st_sslstatus = localsslstatus; } #endif #ifdef ENABLE_GSS if (beentry->st_gss) { memcpy(localgssstatus, beentry->st_gssstatus, sizeof(PgBackendGSSStatus)); localentry->backendStatus.st_gssstatus = localgssstatus; } #endif } pgstat_end_read_activity(beentry, after_changecount); if (pgstat_read_activity_complete(before_changecount, after_changecount)) break; /* Make sure we can break out of loop if stuck... */ CHECK_FOR_INTERRUPTS(); } /* Only valid entries get included into the local array */ if (localentry->backendStatus.st_procpid > 0) { /* * The BackendStatusArray index is exactly the ProcNumber of the * source backend. Note that this means localBackendStatusTable * is in order by proc_number. pgstat_get_beentry_by_proc_number() * depends on that. */ localentry->proc_number = procNumber; ProcNumberGetTransactionIds(procNumber, &localentry->backend_xid, &localentry->backend_xmin, &localentry->backend_subxact_count, &localentry->backend_subxact_overflowed); localentry++; localappname += NAMEDATALEN; localclienthostname += NAMEDATALEN; localactivity += pgstat_track_activity_query_size; #ifdef USE_SSL localsslstatus++; #endif #ifdef ENABLE_GSS localgssstatus++; #endif localNumBackends++; } beentry++; } /* Set the pointer only after completion of a valid table */ localBackendStatusTable = localtable; } /* ---------- * pgstat_get_backend_current_activity() - * * Return a string representing the current activity of the backend with * the specified PID. This looks directly at the BackendStatusArray, * and so will provide current information regardless of the age of our * transaction's snapshot of the status array. * * It is the caller's responsibility to invoke this only for backends whose * state is expected to remain stable while the result is in use. The * only current use is in deadlock reporting, where we can expect that * the target backend is blocked on a lock. (There are corner cases * where the target's wait could get aborted while we are looking at it, * but the very worst consequence is to return a pointer to a string * that's been changed, so we won't worry too much.) * * Note: return strings for special cases match pg_stat_get_backend_activity. * ---------- */ const char * pgstat_get_backend_current_activity(int pid, bool checkUser) { PgBackendStatus *beentry; int i; beentry = BackendStatusArray; for (i = 1; i <= MaxBackends; i++) { /* * Although we expect the target backend's entry to be stable, that * doesn't imply that anyone else's is. To avoid identifying the * wrong backend, while we check for a match to the desired PID we * must follow the protocol of retrying if st_changecount changes * while we examine the entry, or if it's odd. (This might be * unnecessary, since fetching or storing an int is almost certainly * atomic, but let's play it safe.) We use a volatile pointer here to * ensure the compiler doesn't try to get cute. */ volatile PgBackendStatus *vbeentry = beentry; bool found; for (;;) { int before_changecount; int after_changecount; pgstat_begin_read_activity(vbeentry, before_changecount); found = (vbeentry->st_procpid == pid); pgstat_end_read_activity(vbeentry, after_changecount); if (pgstat_read_activity_complete(before_changecount, after_changecount)) break; /* Make sure we can break out of loop if stuck... */ CHECK_FOR_INTERRUPTS(); } if (found) { /* Now it is safe to use the non-volatile pointer */ if (checkUser && !superuser() && beentry->st_userid != GetUserId()) return ""; else if (*(beentry->st_activity_raw) == '\0') return ""; else { /* this'll leak a bit of memory, but that seems acceptable */ return pgstat_clip_activity(beentry->st_activity_raw); } } beentry++; } /* If we get here, caller is in error ... */ return ""; } /* ---------- * pgstat_get_crashed_backend_activity() - * * Return a string representing the current activity of the backend with * the specified PID. Like the function above, but reads shared memory with * the expectation that it may be corrupt. On success, copy the string * into the "buffer" argument and return that pointer. On failure, * return NULL. * * This function is only intended to be used by the postmaster to report the * query that crashed a backend. In particular, no attempt is made to * follow the correct concurrency protocol when accessing the * BackendStatusArray. But that's OK, in the worst case we'll return a * corrupted message. We also must take care not to trip on ereport(ERROR). * ---------- */ const char * pgstat_get_crashed_backend_activity(int pid, char *buffer, int buflen) { volatile PgBackendStatus *beentry; int i; beentry = BackendStatusArray; /* * We probably shouldn't get here before shared memory has been set up, * but be safe. */ if (beentry == NULL || BackendActivityBuffer == NULL) return NULL; for (i = 1; i <= MaxBackends; i++) { if (beentry->st_procpid == pid) { /* Read pointer just once, so it can't change after validation */ const char *activity = beentry->st_activity_raw; const char *activity_last; /* * We mustn't access activity string before we verify that it * falls within the BackendActivityBuffer. To make sure that the * entire string including its ending is contained within the * buffer, subtract one activity length from the buffer size. */ activity_last = BackendActivityBuffer + BackendActivityBufferSize - pgstat_track_activity_query_size; if (activity < BackendActivityBuffer || activity > activity_last) return NULL; /* If no string available, no point in a report */ if (activity[0] == '\0') return NULL; /* * Copy only ASCII-safe characters so we don't run into encoding * problems when reporting the message; and be sure not to run off * the end of memory. As only ASCII characters are reported, it * doesn't seem necessary to perform multibyte aware clipping. */ ascii_safe_strlcpy(buffer, activity, Min(buflen, pgstat_track_activity_query_size)); return buffer; } beentry++; } /* PID not found */ return NULL; } /* ---------- * pgstat_get_my_query_id() - * * Return current backend's query identifier. */ uint64 pgstat_get_my_query_id(void) { if (!MyBEEntry) return 0; /* * There's no need for a lock around pgstat_begin_read_activity / * pgstat_end_read_activity here as it's only called from * pg_stat_get_activity which is already protected, or from the same * backend which means that there won't be concurrent writes. */ return MyBEEntry->st_query_id; } /* ---------- * cmp_lbestatus * * Comparison function for bsearch() on an array of LocalPgBackendStatus. * The proc_number field is used to compare the arguments. * ---------- */ static int cmp_lbestatus(const void *a, const void *b) { const LocalPgBackendStatus *lbestatus1 = (const LocalPgBackendStatus *) a; const LocalPgBackendStatus *lbestatus2 = (const LocalPgBackendStatus *) b; return lbestatus1->proc_number - lbestatus2->proc_number; } /* ---------- * pgstat_get_beentry_by_proc_number() - * * Support function for the SQL-callable pgstat* functions. Returns * our local copy of the current-activity entry for one backend, * or NULL if the given beid doesn't identify any known session. * * The argument is the ProcNumber of the desired session * (note that this is unlike pgstat_get_local_beentry_by_index()). * * NB: caller is responsible for a check if the user is permitted to see * this info (especially the querystring). * ---------- */ PgBackendStatus * pgstat_get_beentry_by_proc_number(ProcNumber procNumber) { LocalPgBackendStatus *ret = pgstat_get_local_beentry_by_proc_number(procNumber); if (ret) return &ret->backendStatus; return NULL; } /* ---------- * pgstat_get_local_beentry_by_proc_number() - * * Like pgstat_get_beentry_by_proc_number() but with locally computed additions * (like xid and xmin values of the backend) * * The argument is the ProcNumber of the desired session * (note that this is unlike pgstat_get_local_beentry_by_index()). * * NB: caller is responsible for checking if the user is permitted to see this * info (especially the querystring). * ---------- */ LocalPgBackendStatus * pgstat_get_local_beentry_by_proc_number(ProcNumber procNumber) { LocalPgBackendStatus key; pgstat_read_current_status(); /* * Since the localBackendStatusTable is in order by proc_number, we can * use bsearch() to search it efficiently. */ key.proc_number = procNumber; return bsearch(&key, localBackendStatusTable, localNumBackends, sizeof(LocalPgBackendStatus), cmp_lbestatus); } /* ---------- * pgstat_get_local_beentry_by_index() - * * Like pgstat_get_beentry_by_proc_number() but with locally computed * additions (like xid and xmin values of the backend) * * The idx argument is a 1-based index in the localBackendStatusTable * (note that this is unlike pgstat_get_beentry_by_proc_number()). * Returns NULL if the argument is out of range (no current caller does that). * * NB: caller is responsible for a check if the user is permitted to see * this info (especially the querystring). * ---------- */ LocalPgBackendStatus * pgstat_get_local_beentry_by_index(int idx) { pgstat_read_current_status(); if (idx < 1 || idx > localNumBackends) return NULL; return &localBackendStatusTable[idx - 1]; } /* ---------- * pgstat_fetch_stat_numbackends() - * * Support function for the SQL-callable pgstat* functions. Returns * the number of sessions known in the localBackendStatusTable, i.e. * the maximum 1-based index to pass to pgstat_get_local_beentry_by_index(). * ---------- */ int pgstat_fetch_stat_numbackends(void) { pgstat_read_current_status(); return localNumBackends; } /* * Convert a potentially unsafely truncated activity string (see * PgBackendStatus.st_activity_raw's documentation) into a correctly truncated * one. * * The returned string is allocated in the caller's memory context and may be * freed. */ char * pgstat_clip_activity(const char *raw_activity) { char *activity; int rawlen; int cliplen; /* * Some callers, like pgstat_get_backend_current_activity(), do not * guarantee that the buffer isn't concurrently modified. We try to take * care that the buffer is always terminated by a NUL byte regardless, but * let's still be paranoid about the string's length. In those cases the * underlying buffer is guaranteed to be pgstat_track_activity_query_size * large. */ activity = pnstrdup(raw_activity, pgstat_track_activity_query_size - 1); /* now double-guaranteed to be NUL terminated */ rawlen = strlen(activity); /* * All supported server-encodings make it possible to determine the length * of a multi-byte character from its first byte (this is not the case for * client encodings, see GB18030). As st_activity is always stored using * server encoding, this allows us to perform multi-byte aware truncation, * even if the string earlier was truncated in the middle of a multi-byte * character. */ cliplen = pg_mbcliplen(activity, rawlen, pgstat_track_activity_query_size - 1); activity[cliplen] = '\0'; return activity; }