From aa2c3209969fe4b6d193b37d92959dfd3809c804 Mon Sep 17 00:00:00 2001 From: Mike Palmiotto Date: Mon, 16 Mar 2020 23:05:33 +0000 Subject: [PATCH v2 09/12] Add Backends to subprocess struct --- src/backend/postmaster/postmaster.c | 407 +++++++++++++++------------- src/backend/postmaster/subprocess.c | 11 + src/include/postmaster/postmaster.h | 6 + src/include/postmaster/subprocess.h | 1 + 4 files changed, 235 insertions(+), 190 deletions(-) diff --git a/src/backend/postmaster/postmaster.c b/src/backend/postmaster/postmaster.c index 8343a81923..f979d505df 100644 --- a/src/backend/postmaster/postmaster.c +++ b/src/backend/postmaster/postmaster.c @@ -359,7 +359,6 @@ static void BackendInitialize(Port *port); static void BackendRun(Port *port) pg_attribute_noreturn(); static void ExitPostmaster(int status) pg_attribute_noreturn(); static int ServerLoop(void); -static int BackendStartup(Port *port); static int ProcessStartupPacket(Port *port, bool secure_done); static void SendNegotiateProtocolVersion(List *unrecognized_protocol_options); static void processCancelRequest(Port *port, void *pkt); @@ -409,7 +408,6 @@ typedef struct } win32_deadchild_waitinfo; #endif /* WIN32 */ -static pid_t backend_forkexec(Port *port); static pid_t internal_forkexec(int argc, char *argv[], Port *port); /* Type for a socket that can be inherited to a client process */ @@ -512,6 +510,8 @@ int postmaster_alive_fds[2] = {-1, -1}; HANDLE PostmasterHandle; #endif +static Port *ConnProcPort = NULL; + /* * Postmaster main entry point */ @@ -1671,19 +1671,18 @@ ServerLoop(void) break; if (FD_ISSET(ListenSocket[i], &rmask)) { - Port *port; + ConnProcPort = ConnCreate(ListenSocket[i]); - port = ConnCreate(ListenSocket[i]); - if (port) + if (ConnProcPort) { - BackendStartup(port); + StartSubprocess(ClientBackendType); /* * We no longer need the open socket or port structure * in this process */ - StreamClose(port->sock); - ConnFree(port); + StreamClose(ConnProcPort->sock); + ConnFree(ConnProcPort); } } } @@ -3215,6 +3214,174 @@ reaper(SIGNAL_ARGS) errno = save_errno; } +/* + * BackendPrep + * + * Do all of the pre-fork setup for a new Backend. +*/ +int +BackendPrep(int argc, char *argv[]) +{ + /* + * Create backend data structure. Better before the fork() so we can + * handle failure cleanly. + */ + Backend *bn; + + bn = (Backend *) malloc(sizeof(Backend)); + if (!bn) + { + ereport(LOG, + (errcode(ERRCODE_OUT_OF_MEMORY), + errmsg("out of memory"))); + } + + /* + * Compute the cancel key that will be assigned to this backend. The + * backend will have its own copy in the forked-off process' value of + * MyCancelKey, so that it can transmit the key to the frontend. + */ + if (!RandomCancelKey(&MyCancelKey)) + { + free(bn); + ereport(LOG, + (errcode(ERRCODE_INTERNAL_ERROR), + errmsg("could not generate random cancel key"))); + } + + bn->cancel_key = MyCancelKey; + + /* Pass down canAcceptConnections state */ + ConnProcPort->canAcceptConnections = canAcceptConnections(BACKEND_TYPE_NORMAL); + bn->dead_end = (ConnProcPort->canAcceptConnections != CAC_OK && + ConnProcPort->canAcceptConnections != CAC_WAITBACKUP); + + /* + * Unless it's a dead_end child, assign it a child slot number + */ + if (!bn->dead_end) + bn->child_slot = MyPMChildSlot = AssignPostmasterChildSlot(); + else + bn->child_slot = 0; + + /* Hasn't asked to be notified about any bgworkers yet */ + bn->bgworker_notify = false; + + /* + * Push the Backend to the stack as-is so it can be retreived by the parent + * on the other side of the fork/exec. They will modify this entry in place. + */ + dlist_push_head(&BackendList, &bn->elem); + + return 0; +} + +/* + * BackendMain + * + * Child code when forking a Backend. + */ +void BackendMain(pg_attribute_unused() int argc, pg_attribute_unused() char *argv[]) +{ + /* + * Perform additional initialization and collect startup packet. + * + * We want to do this before InitProcess() for a couple of reasons: 1. + * so that we aren't eating up a PGPROC slot while waiting on the + * client. 2. so that if InitProcess() fails due to being out of + * PGPROC slots, we have already initialized libpq and are able to + * report the error to the client. + */ +#ifndef EXEC_BACKEND + BackendInitialize(ConnProcPort); +#endif + + /* And run the backend */ + BackendRun(ConnProcPort); /* does not return */ +} + +/* + * BackendPostmasterMain + * + * Parent code when forking a Backend. + */ +void BackendPostmasterMain(pg_attribute_unused() int argc, pg_attribute_unused() char *argv[]) +{ + dlist_mutable_iter iter; + + /* + * Find our backend node by popping the element with a matching child slot + * off the list. This was pushed to the stack (incomplete) by BackendPrep. + * We need to fix it up and push back. + */ + dlist_foreach_modify(iter, &BackendList) + { + Backend *bp = dlist_container(Backend, elem, iter.cur); + + /* MyPMChildSlot is guaranteed to match the child MyPMChildSlot */ + if (bp->child_slot == MyPMChildSlot) + { + /* + * Everything's been successful, it's safe to add this backend to our list + * of backends. + */ + bp->pid = MyChildProcPid; + bp->bkend_type = BACKEND_TYPE_NORMAL; /* Can change later to WALSND */ + +#ifdef EXEC_BACKEND + if (!bp->dead_end) + ShmemBackendArrayAdd(bp); +#endif + break; /* There is only one entry and we've found it */ + } + } + + /* in parent, successful fork */ + ereport(DEBUG2, + (errmsg_internal("forked new backend, pid=%d socket=%d", + (int) MyChildProcPid, (int) MyProcPort->sock))); +} + +/* + * BackendForkFailure + * + * Backend cleanup in case a failure occurs forking a new Backend. + */ +bool +BackendForkFailure(int child_errno) +{ + dlist_mutable_iter iter; + + dlist_foreach_modify(iter, &BackendList) + { + Backend *bp = dlist_container(Backend, elem, iter.cur); + + if (bp->child_slot == MyPMChildSlot) + { + if (!bp->dead_end) + { + if (!ReleasePostmasterChildSlot(bp->child_slot)) + { + /* Could not release child slot! Panic! */ + return true; + } +#ifdef EXEC_BACKEND + ShmemBackendArrayRemove(bp); +#endif + } + dlist_delete(iter.cur); + free(bp); + break; + } + } + + report_fork_failure_to_client(MyProcPort, child_errno); + + /* Don't panic */ + return false; +} + + /* * Scan the bgworkers list and see if the given PID (which has just stopped * or crashed) is in it. Handle its shutdown if so, and return true. If not a @@ -4075,122 +4242,6 @@ TerminateChildren(int signal) signal_child(PgStatPID, signal); } -/* - * BackendStartup -- start backend process - * - * returns: STATUS_ERROR if the fork failed, STATUS_OK otherwise. - * - * Note: if you change this code, also consider StartAutovacuumWorker. - */ -static int -BackendStartup(Port *port) -{ - Backend *bn; /* for backend cleanup */ - pid_t pid; - - /* - * Create backend data structure. Better before the fork() so we can - * handle failure cleanly. - */ - bn = (Backend *) malloc(sizeof(Backend)); - if (!bn) - { - ereport(LOG, - (errcode(ERRCODE_OUT_OF_MEMORY), - errmsg("out of memory"))); - return STATUS_ERROR; - } - - /* - * Compute the cancel key that will be assigned to this backend. The - * backend will have its own copy in the forked-off process' value of - * MyCancelKey, so that it can transmit the key to the frontend. - */ - if (!RandomCancelKey(&MyCancelKey)) - { - free(bn); - ereport(LOG, - (errcode(ERRCODE_INTERNAL_ERROR), - errmsg("could not generate random cancel key"))); - return STATUS_ERROR; - } - - bn->cancel_key = MyCancelKey; - - /* Pass down canAcceptConnections state */ - port->canAcceptConnections = canAcceptConnections(BACKEND_TYPE_NORMAL); - bn->dead_end = (port->canAcceptConnections != CAC_OK && - port->canAcceptConnections != CAC_WAITBACKUP); - - /* - * Unless it's a dead_end child, assign it a child slot number - */ - if (!bn->dead_end) - bn->child_slot = MyPMChildSlot = AssignPostmasterChildSlot(); - else - bn->child_slot = 0; - - /* Hasn't asked to be notified about any bgworkers yet */ - bn->bgworker_notify = false; - -#ifdef EXEC_BACKEND - pid = backend_forkexec(port); -#else /* !EXEC_BACKEND */ - pid = fork_process(); - if (pid == 0) /* child */ - { - free(bn); - - /* Detangle from postmaster */ - InitPostmasterChild(); - - /* Close the postmaster's sockets */ - ClosePostmasterPorts(false); - - /* Perform additional initialization and collect startup packet */ - BackendInitialize(port); - - /* And run the backend */ - BackendRun(port); - } -#endif /* EXEC_BACKEND */ - - if (pid < 0) - { - /* in parent, fork failed */ - int save_errno = errno; - - if (!bn->dead_end) - (void) ReleasePostmasterChildSlot(bn->child_slot); - free(bn); - errno = save_errno; - ereport(LOG, - (errmsg("could not fork new process for connection: %m"))); - report_fork_failure_to_client(port, save_errno); - return STATUS_ERROR; - } - - /* in parent, successful fork */ - ereport(DEBUG2, - (errmsg_internal("forked new backend, pid=%d socket=%d", - (int) pid, (int) port->sock))); - - /* - * Everything's been successful, it's safe to add this backend to our list - * of backends. - */ - bn->pid = pid; - bn->bkend_type = BACKEND_TYPE_NORMAL; /* Can change later to WALSND */ - dlist_push_head(&BackendList, &bn->elem); - -#ifdef EXEC_BACKEND - if (!bn->dead_end) - ShmemBackendArrayAdd(bn); -#endif - - return STATUS_OK; -} - /* * Try to report backend fork() failure to client before we close the * connection. Since we do not care to risk blocking the postmaster on @@ -4483,33 +4534,12 @@ postmaster_forkexec(int argc, char *argv[]) Port port; /* This entry point passes dummy values for the Port variables */ - memset(&port, 0, sizeof(port)); - return internal_forkexec(argc, argv, &port); -} - -/* - * backend_forkexec -- fork/exec off a backend process - * - * Some operating systems (WIN32) don't have fork() so we have to simulate - * it by storing parameters that need to be passed to the child and - * then create a new child process. - * - * returns the pid of the fork/exec'd process, or -1 on failure - */ -static pid_t -backend_forkexec(Port *port) -{ - char *av[4]; - int ac = 0; - - av[ac++] = "postgres"; - av[ac++] = "--forkbackend"; - av[ac++] = NULL; /* filled in by internal_forkexec */ - - av[ac] = NULL; - Assert(ac < lengthof(av)); + if (!ConnProcPort) + memset(&port, 0, sizeof(port)); + else + port = *ConnProcPort; - return internal_forkexec(ac, av, port); + return internal_forkexec(argc, argv, &port); } #ifndef WIN32 @@ -4849,6 +4879,7 @@ SubPostmasterMain(int argc, char *argv[]) /* Read in the variables file */ memset(&port, 0, sizeof(Port)); read_backend_variables(argv[2], &port); + ConnProcPort = &port; /* Close the postmaster's sockets (as soon as we know them) */ ClosePostmasterPorts(strcmp(argv[1], "--forklog") == 0); @@ -4890,11 +4921,7 @@ SubPostmasterMain(int argc, char *argv[]) * sometimes impossible to attach to shared memory at the desired address. * Return the setting to its old value (usually '1' or '2') when finished. */ - if (strcmp(argv[1], "--forkbackend") == 0 || - strcmp(argv[1], "--forkavlauncher") == 0 || - strcmp(argv[1], "--forkavworker") == 0 || - strcmp(argv[1], "--forkboot") == 0 || - strncmp(argv[1], "--forkbgworker=", 15) == 0) + if (MySubprocess->needs_shmem) PGSharedMemoryReAttach(); else PGSharedMemoryNoReAttach(); @@ -4943,11 +4970,23 @@ SubPostmasterMain(int argc, char *argv[]) */ process_shared_preload_libraries(); - /* Run backend or appropriate child */ - if (strcmp(argv[1], "--forkbackend") == 0) + if (MySubprocess->needs_aux_proc) { - Assert(argc == 3); /* shouldn't be any more args */ + /* Restore basic shared memory pointers */ + InitShmemAccess(UsedShmemSegAddr); + /* Need a PGPROC to run CreateSharedMemoryAndSemaphores */ + InitAuxiliaryProcess(); + + /* Attach process to shared data structures */ + CreateSharedMemoryAndSemaphores(); + + AuxiliaryProcessMain(argc - 2, argv + 2); /* does not return */ + } + + /* Run backend or appropriate child */ + if (MySubprocessType == ClientBackendType) + { /* * Need to reinitialize the SSL library in the backend, since the * context structures contain function pointers and cannot be passed @@ -4981,32 +5020,6 @@ SubPostmasterMain(int argc, char *argv[]) * report the error to the client. */ BackendInitialize(&port); - - /* Restore basic shared memory pointers */ - InitShmemAccess(UsedShmemSegAddr); - - /* Need a PGPROC to run CreateSharedMemoryAndSemaphores */ - InitProcess(); - - /* Attach process to shared data structures */ - CreateSharedMemoryAndSemaphores(); - - /* And run the backend */ - BackendRun(&port); /* does not return */ - } - - if (MySubprocess->needs_aux_proc) - { - /* Restore basic shared memory pointers */ - InitShmemAccess(UsedShmemSegAddr); - - /* Need a PGPROC to run CreateSharedMemoryAndSemaphores */ - InitAuxiliaryProcess(); - - /* Attach process to shared data structures */ - CreateSharedMemoryAndSemaphores(); - - AuxiliaryProcessMain(argc - 2, argv + 2); /* does not return */ } if (MySubprocessType == BgWorkerType) @@ -5027,15 +5040,29 @@ SubPostmasterMain(int argc, char *argv[]) CreateSharedMemoryAndSemaphores(); } - if (MySubprocessType == BgWorkerType) + switch (MySubprocessType) { - /* Fetch MyBgworkerEntry from shared memory */ - shmem_slot = atoi(argv[1] + 15); - MyBgworkerEntry = BackgroundWorkerEntry(shmem_slot); + case AutoVacuumLauncherType: + case AutoVacuumWorkerType: + MySubprocess->entrypoint(argc - 2, argv + 2); + break; + case BgWorkerType: + /* Fetch MyBgworkerEntry from shared memory */ + shmem_slot = atoi(argv[1] + 15); + MyBgworkerEntry = BackgroundWorkerEntry(shmem_slot); + /* fallthrough */ + case PgArchiverType: + case PgstatCollectorType: + case SysLoggerType: + case ClientBackendType: + MySubprocess->entrypoint(argc, argv); + break; + default: + ereport(LOG, + (errmsg("could not start unknown process type (%d) under postmaster", + MySubprocessType))); } - MySubprocess->entrypoint(argc - 2, argv + 2); - abort(); /* shouldn't get here */ } #endif /* EXEC_BACKEND */ diff --git a/src/backend/postmaster/subprocess.c b/src/backend/postmaster/subprocess.c index d4df791aeb..9d7ce86918 100644 --- a/src/backend/postmaster/subprocess.c +++ b/src/backend/postmaster/subprocess.c @@ -170,6 +170,17 @@ static PgSubprocess process_types[] = { .entrypoint = BackgroundWorkerMain, .fork_failure = BackgroundWorkerForkFailure, .postmaster_main = BackgroundWorkerPostmasterMain + }, + { + .name = "backend", + .desc = "backend", + .needs_aux_proc = false, + .needs_shmem = true, + .keep_postmaster_memcontext = true, + .fork_prep = BackendPrep, + .entrypoint = BackendMain, + .fork_failure = BackendForkFailure, + .postmaster_main = BackendPostmasterMain } }; diff --git a/src/include/postmaster/postmaster.h b/src/include/postmaster/postmaster.h index b1411c1ed2..6bc0af7c2b 100644 --- a/src/include/postmaster/postmaster.h +++ b/src/include/postmaster/postmaster.h @@ -91,6 +91,12 @@ extern bool PostmasterMarkPIDForWorkerNotify(int); extern bool RandomCancelKey(int32 *cancel_key); +extern int BackendPrep(int argc, char *argv[]); +extern void BackendMain(int argc, char *argv[]); +extern void BackendPostmasterMain(int argc, char *argv[]); +extern bool BackendForkFailure(int child_errno); +extern void BackgroundWorkerMain(int argc, char *argv[]); + #ifdef EXEC_BACKEND extern pid_t postmaster_forkexec(int argc, char *argv[]); extern void SubPostmasterMain(int argc, char *argv[]) pg_attribute_noreturn(); diff --git a/src/include/postmaster/subprocess.h b/src/include/postmaster/subprocess.h index 706d60e4d6..06e67efecc 100644 --- a/src/include/postmaster/subprocess.h +++ b/src/include/postmaster/subprocess.h @@ -29,6 +29,7 @@ typedef enum PgArchiverType, SysLoggerType, BgWorkerType, + ClientBackendType, NUMSUBPROCESSTYPES /* Must be last! */ } SubprocessType; -- 2.17.0