--- /dev/null
+/*-------------------------------------------------------------------------
+ *
+ * autoprewarm.c
+ * Periodically dump information about the blocks present in
+ * shared_buffers, and reload them on server restart.
+ *
+ * Due to locking considerations, we can't actually begin prewarming
+ * until the server reaches a consistent state. We need the catalogs
+ * to be consistent so that we can figure out which relation to lock,
+ * and we need to lock the relations so that we don't try to prewarm
+ * pages from a relation that is in the process of being dropped.
+ *
+ * While prewarming, autoprewarm will use two workers. There's a
+ * master worker that reads and sorts the list of blocks to be
+ * prewarmed and then launches a per-database worker for each
+ * relevant database in turn. The former keeps running after the
+ * initial prewarm is complete to update the dump file periodically.
+ *
+ * Copyright (c) 2016-2017, PostgreSQL Global Development Group
+ *
+ * IDENTIFICATION
+ * contrib/pg_prewarm/autoprewarm.c
+ *
+ *-------------------------------------------------------------------------
+ */
+
+#include "postgres.h"
+#include <unistd.h>
+
+#include "access/heapam.h"
+#include "access/xact.h"
+#include "catalog/pg_class.h"
+#include "catalog/pg_type.h"
+#include "miscadmin.h"
+#include "pgstat.h"
+#include "postmaster/bgworker.h"
+#include "storage/buf_internals.h"
+#include "storage/dsm.h"
+#include "storage/ipc.h"
+#include "storage/latch.h"
+#include "storage/lwlock.h"
+#include "storage/proc.h"
+#include "storage/procsignal.h"
+#include "storage/shmem.h"
+#include "storage/smgr.h"
+#include "tcop/tcopprot.h"
+#include "utils/acl.h"
+#include "utils/guc.h"
+#include "utils/memutils.h"
+#include "utils/rel.h"
+#include "utils/relfilenodemap.h"
+#include "utils/resowner.h"
+
+#define AUTOPREWARM_FILE "autoprewarm.blocks"
+
+/* Metadata for each block we dump. */
+typedef struct BlockInfoRecord
+{
+ Oid database;
+ Oid tablespace;
+ Oid filenode;
+ ForkNumber forknum;
+ BlockNumber blocknum;
+} BlockInfoRecord;
+
+/* Shared state information for autoprewarm bgworker. */
+typedef struct AutoPrewarmSharedState
+{
+ LWLock lock; /* mutual exclusion */
+ pid_t bgworker_pid; /* for main bgworker */
+ pid_t pid_using_dumpfile; /* for autoprewarm or block dump */
+
+ /* Following items are for communication with per-database worker */
+ dsm_handle block_info_handle;
+ Oid database;
+ int64 prewarm_start_idx;
+ int64 prewarm_stop_idx;
+ int64 prewarmed_blocks;
+} AutoPrewarmSharedState;
+
+void _PG_init(void);
+void autoprewarm_main(Datum main_arg);
+void autoprewarm_database_main(Datum main_arg);
+
+PG_FUNCTION_INFO_V1(autoprewarm_start_worker);
+PG_FUNCTION_INFO_V1(autoprewarm_dump_now);
+
+static void apw_load_buffers(void);
+static int64 apw_dump_now(bool is_bgworker, bool dump_unlogged);
+static void apw_start_master_worker(void);
+static void apw_start_database_worker(void);
+static bool apw_init_shmem(void);
+static void apw_detach_shmem(int code, Datum arg);
+static int apw_compare_blockinfo(const void *p, const void *q);
+static void apw_sigterm_handler(SIGNAL_ARGS);
+static void apw_sighup_handler(SIGNAL_ARGS);
+
+/* Flags set by signal handlers */
+static volatile sig_atomic_t got_sigterm = false;
+static volatile sig_atomic_t got_sighup = false;
+
+/* Pointer to shared-memory state. */
+static AutoPrewarmSharedState *apw_state = NULL;
+
+/* GUC variables. */
+static bool autoprewarm = true; /* start worker? */
+static int autoprewarm_interval; /* dump interval */
+
+/*
+ * Module load callback.
+ */
+void
+_PG_init(void)
+{
+ DefineCustomIntVariable("pg_prewarm.autoprewarm_interval",
+ "Sets the interval between dumps of shared buffers",
+ "If set to zero, time-based dumping is disabled.",
+ &autoprewarm_interval,
+ 300,
+ 0, INT_MAX / 1000,
+ PGC_SIGHUP,
+ GUC_UNIT_S,
+ NULL,
+ NULL,
+ NULL);
+
+ if (!process_shared_preload_libraries_in_progress)
+ return;
+
+ /* can't define PGC_POSTMASTER variable after startup */
+ DefineCustomBoolVariable("pg_prewarm.autoprewarm",
+ "Starts the autoprewarm worker.",
+ NULL,
+ &autoprewarm,
+ true,
+ PGC_POSTMASTER,
+ 0,
+ NULL,
+ NULL,
+ NULL);
+
+ EmitWarningsOnPlaceholders("pg_prewarm");
+
+ RequestAddinShmemSpace(MAXALIGN(sizeof(AutoPrewarmSharedState)));
+
+ /* Register autoprewarm worker, if enabled. */
+ if (autoprewarm)
+ apw_start_master_worker();
+}
+
+/*
+ * Main entry point for the master autoprewarm process. Per-database workers
+ * have a separate entry point.
+ */
+void
+autoprewarm_main(Datum main_arg)
+{
+ bool first_time = true;
+ TimestampTz last_dump_time = 0;
+
+ /* Establish signal handlers; once that's done, unblock signals. */
+ pqsignal(SIGTERM, apw_sigterm_handler);
+ pqsignal(SIGHUP, apw_sighup_handler);
+ pqsignal(SIGUSR1, procsignal_sigusr1_handler);
+ BackgroundWorkerUnblockSignals();
+
+ /* Create (if necessary) and attach to our shared memory area. */
+ if (apw_init_shmem())
+ first_time = false;
+
+ /* Set on-detach hook so that our PID will be cleared on exit. */
+ on_shmem_exit(apw_detach_shmem, 0);
+
+ /*
+ * Store our PID in the shared memory area --- unless there's already
+ * another worker running, in which case just exit.
+ */
+ LWLockAcquire(&apw_state->lock, LW_EXCLUSIVE);
+ if (apw_state->bgworker_pid != InvalidPid)
+ {
+ LWLockRelease(&apw_state->lock);
+ ereport(LOG,
+ (errmsg("autoprewarm worker is already running under PID %d",
+ apw_state->bgworker_pid)));
+ return;
+ }
+ apw_state->bgworker_pid = MyProcPid;
+ LWLockRelease(&apw_state->lock);
+
+ /*
+ * Preload buffers from the dump file only if we just created the shared
+ * memory region. Otherwise, it's either already been done or shouldn't
+ * be done - e.g. because the old dump file has been overwritten since the
+ * server was started.
+ *
+ * There's not much point in performing a dump immediately after we finish
+ * preloading; so, if we do end up preloading, consider the last dump time
+ * to be equal to the current time.
+ */
+ if (first_time)
+ {
+ apw_load_buffers();
+ last_dump_time = GetCurrentTimestamp();
+ }
+
+ /* Periodically dump buffers until terminated. */
+ while (!got_sigterm)
+ {
+ int rc;
+
+ /* In case of a SIGHUP, just reload the configuration. */
+ if (got_sighup)
+ {
+ got_sighup = false;
+ ProcessConfigFile(PGC_SIGHUP);
+ }
+
+ if (autoprewarm_interval <= 0)
+ {
+ /* We're only dumping at shutdown, so just wait forever. */
+ rc = WaitLatch(&MyProc->procLatch,
+ WL_LATCH_SET | WL_POSTMASTER_DEATH,
+ -1L,
+ PG_WAIT_EXTENSION);
+ }
+ else
+ {
+ long delay_in_ms = 0;
+ TimestampTz next_dump_time = 0;
+ long secs = 0;
+ int usecs = 0;
+
+ /* Compute the next dump time. */
+ next_dump_time =
+ TimestampTzPlusMilliseconds(last_dump_time,
+ autoprewarm_interval * 1000);
+ TimestampDifference(GetCurrentTimestamp(), next_dump_time,
+ &secs, &usecs);
+ delay_in_ms = secs + (usecs / 1000);
+
+ /* Perform a dump if it's time. */
+ if (delay_in_ms <= 0)
+ {
+ last_dump_time = GetCurrentTimestamp();
+ apw_dump_now(true, false);
+ continue;
+ }
+
+ /* Sleep until the next dump time. */
+ rc = WaitLatch(&MyProc->procLatch,
+ WL_LATCH_SET | WL_TIMEOUT | WL_POSTMASTER_DEATH,
+ delay_in_ms,
+ PG_WAIT_EXTENSION);
+ }
+
+ /* Reset the latch, bail out if postmaster died, otherwise loop. */
+ ResetLatch(&MyProc->procLatch);
+ if (rc & WL_POSTMASTER_DEATH)
+ proc_exit(1);
+ }
+
+ /*
+ * Dump one last time. We assume this is probably the result of a system
+ * shutdown, although it's possible that we've merely been terminated.
+ */
+ apw_dump_now(true, true);
+}
+
+/*
+ * Read the dump file and launch per-database workers one at a time to
+ * prewarm the buffers found there.
+ */
+static void
+apw_load_buffers(void)
+{
+ FILE *file = NULL;
+ int64 num_elements,
+ i;
+ BlockInfoRecord *blkinfo;
+ dsm_segment *seg;
+
+ /*
+ * Skip the prewarm if the dump file is in use; otherwise, prevent any
+ * other process from writing it while we're using it.
+ */
+ LWLockAcquire(&apw_state->lock, LW_EXCLUSIVE);
+ if (apw_state->pid_using_dumpfile == InvalidPid)
+ apw_state->pid_using_dumpfile = MyProcPid;
+ else
+ {
+ LWLockRelease(&apw_state->lock);
+ ereport(LOG,
+ (errmsg("skipping prewarm because block dump file is being written by PID %d",
+ apw_state->pid_using_dumpfile)));
+ return;
+ }
+ LWLockRelease(&apw_state->lock);
+
+ /*
+ * Open the block dump file. Exit quietly if it doesn't exist, but report
+ * any other error.
+ */
+ file = AllocateFile(AUTOPREWARM_FILE, "r");
+ if (!file)
+ {
+ if (errno == ENOENT)
+ {
+ LWLockAcquire(&apw_state->lock, LW_EXCLUSIVE);
+ apw_state->pid_using_dumpfile = InvalidPid;
+ LWLockRelease(&apw_state->lock);
+ return; /* No file to load. */
+ }
+ ereport(ERROR,
+ (errcode_for_file_access(),
+ errmsg("could not read file \"%s\": %m",
+ AUTOPREWARM_FILE)));
+ }
+
+ /* First line of the file is a record count. */
+ if (fscanf(file, "<<" INT64_FORMAT ">>\n", &num_elements) != 1)
+ ereport(ERROR,
+ (errcode_for_file_access(),
+ errmsg("could not read from file \"%s\": %m",
+ AUTOPREWARM_FILE)));
+
+ /* Allocate a dynamic shared memory segment to store the record data. */
+ seg = dsm_create(sizeof(BlockInfoRecord) * num_elements, 0);
+ blkinfo = (BlockInfoRecord *) dsm_segment_address(seg);
+
+ /* Read records, one per line. */
+ for (i = 0; i < num_elements; i++)
+ {
+ unsigned forknum;
+
+ if (fscanf(file, "%u,%u,%u,%u,%u\n", &blkinfo[i].database,
+ &blkinfo[i].tablespace, &blkinfo[i].filenode,
+ &forknum, &blkinfo[i].blocknum) != 5)
+ ereport(ERROR,
+ (errmsg("autoprewarm block dump file is corrupted at line " INT64_FORMAT,
+ i + 1)));
+ blkinfo[i].forknum = forknum;
+ }
+
+ FreeFile(file);
+
+ /* Sort the blocks to be loaded. */
+ pg_qsort(blkinfo, num_elements, sizeof(BlockInfoRecord),
+ apw_compare_blockinfo);
+
+ /* Populate shared memory state. */
+ apw_state->block_info_handle = dsm_segment_handle(seg);
+ apw_state->prewarm_start_idx = apw_state->prewarm_stop_idx = 0;
+ apw_state->prewarmed_blocks = 0;
+
+ /* Get the info position of the first block of the next database. */
+ while (apw_state->prewarm_start_idx < num_elements)
+ {
+ uint32 i = apw_state->prewarm_start_idx;
+ Oid current_db = blkinfo[i].database;
+
+ /*
+ * Advance the prewarm_stop_idx to the first BlockRecordInfo that does
+ * not belong to this database.
+ */
+ i++;
+ while (i < num_elements)
+ {
+ if (current_db != blkinfo[i].database)
+ {
+ /*
+ * Combine BlockRecordInfos for global objects withs those of
+ * the database.
+ */
+ if (current_db != InvalidOid)
+ break;
+ current_db = blkinfo[i].database;
+ }
+
+ i++;
+ }
+
+ /*
+ * If we reach this point with current_db == InvalidOid, then only
+ * BlockRecordInfos belonging to global objects exist. We can't
+ * prewarm without a database connection, so just bail out.
+ */
+ if (current_db == InvalidOid)
+ break;
+
+ /* Configure stop point and database for next per-database worker. */
+ apw_state->prewarm_stop_idx = i;
+ apw_state->database = current_db;
+ Assert(apw_state->prewarm_start_idx < apw_state->prewarm_stop_idx);
+
+ /* If we've run out of free buffers, don't launch another worker. */
+ if (!have_free_buffer())
+ break;
+
+ /*
+ * Start a per-database worker to load blocks for this database; this
+ * function will return once the per-database worker exits.
+ */
+ apw_start_database_worker();
+
+ /* Prepare for next database. */
+ apw_state->prewarm_start_idx = apw_state->prewarm_stop_idx;
+ }
+
+ /* Clean up. */
+ dsm_detach(seg);
+ LWLockAcquire(&apw_state->lock, LW_EXCLUSIVE);
+ apw_state->block_info_handle = DSM_HANDLE_INVALID;
+ apw_state->pid_using_dumpfile = InvalidPid;
+ LWLockRelease(&apw_state->lock);
+
+ /* Report our success. */
+ ereport(LOG,
+ (errmsg("autoprewarm successfully prewarmed " INT64_FORMAT
+ " of " INT64_FORMAT " previously-loaded blocks",
+ apw_state->prewarmed_blocks, num_elements)));
+}
+
+/*
+ * Prewarm all blocks for one database (and possibly also global objects, if
+ * those got grouped with this database).
+ */
+void
+autoprewarm_database_main(Datum main_arg)
+{
+ uint32 pos;
+ BlockInfoRecord *block_info;
+ Relation rel = NULL;
+ BlockNumber nblocks = 0;
+ BlockInfoRecord *old_blk = NULL;
+ dsm_segment *seg;
+
+ /* Establish signal handlers; once that's done, unblock signals. */
+ pqsignal(SIGTERM, die);
+ BackgroundWorkerUnblockSignals();
+
+ /* Connect to correct database and get block information. */
+ apw_init_shmem();
+ seg = dsm_attach(apw_state->block_info_handle);
+ if (seg == NULL)
+ ereport(ERROR,
+ (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE),
+ errmsg("could not map dynamic shared memory segment")));
+ BackgroundWorkerInitializeConnectionByOid(apw_state->database, InvalidOid);
+ block_info = (BlockInfoRecord *) dsm_segment_address(seg);
+ pos = apw_state->prewarm_start_idx;
+
+ /*
+ * Loop until we run out of blocks to prewarm or until we run out of free
+ * buffers.
+ */
+ while (pos < apw_state->prewarm_stop_idx && have_free_buffer())
+ {
+ BlockInfoRecord *blk = &block_info[pos++];
+ Buffer buf;
+
+ CHECK_FOR_INTERRUPTS();
+
+ /*
+ * Quit if we've reached records for another database. If previous
+ * blocks are of some global objects, then continue pre-warming.
+ */
+ if (old_blk != NULL && old_blk->database != blk->database &&
+ old_blk->database != 0)
+ break;
+
+ /*
+ * As soon as we encounter a block of a new relation, close the old
+ * relation. Note that rel will be NULL if try_relation_open failed
+ * previously; in that case, there is nothing to close.
+ */
+ if (old_blk != NULL && old_blk->filenode != blk->filenode &&
+ rel != NULL)
+ {
+ relation_close(rel, AccessShareLock);
+ rel = NULL;
+ CommitTransactionCommand();
+ }
+
+ /*
+ * Try to open each new relation, but only once, when we first
+ * encounter it. If it's been dropped, skip the associated blocks.
+ */
+ if (old_blk == NULL || old_blk->filenode != blk->filenode)
+ {
+ Oid reloid;
+
+ Assert(rel == NULL);
+ StartTransactionCommand();
+ reloid = RelidByRelfilenode(blk->tablespace, blk->filenode);
+ if (OidIsValid(reloid))
+ rel = try_relation_open(reloid, AccessShareLock);
+
+ if (!rel)
+ CommitTransactionCommand();
+ }
+ if (!rel)
+ {
+ old_blk = blk;
+ continue;
+ }
+
+ /* Once per fork, check for fork existence and size. */
+ if (old_blk == NULL ||
+ old_blk->filenode != blk->filenode ||
+ old_blk->forknum != blk->forknum)
+ {
+ RelationOpenSmgr(rel);
+
+ /*
+ * smgrexists is not safe for illegal forknum, hence check whether
+ * the passed forknum is valid before using it in smgrexists.
+ */
+ if (blk->forknum > InvalidForkNumber &&
+ blk->forknum <= MAX_FORKNUM &&
+ smgrexists(rel->rd_smgr, blk->forknum))
+ nblocks = RelationGetNumberOfBlocksInFork(rel, blk->forknum);
+ else
+ nblocks = 0;
+ }
+
+ /* Check whether blocknum is valid and within fork file size. */
+ if (blk->blocknum >= nblocks)
+ {
+ /* Move to next forknum. */
+ old_blk = blk;
+ continue;
+ }
+
+ /* Prewarm buffer. */
+ buf = ReadBufferExtended(rel, blk->forknum, blk->blocknum, RBM_NORMAL,
+ NULL);
+ if (BufferIsValid(buf))
+ {
+ apw_state->prewarmed_blocks++;
+ ReleaseBuffer(buf);
+ }
+
+ old_blk = blk;
+ }
+
+ dsm_detach(seg);
+
+ /* Release lock on previous relation. */
+ if (rel)
+ {
+ relation_close(rel, AccessShareLock);
+ CommitTransactionCommand();
+ }
+}
+
+/*
+ * Dump information on blocks in shared buffers. We use a text format here
+ * so that it's easy to understand and even change the file contents if
+ * necessary.
+ */
+static int64
+apw_dump_now(bool is_bgworker, bool dump_unlogged)
+{
+ uint32 i;
+ int ret;
+ int64 num_blocks;
+ BlockInfoRecord *block_info_array;
+ BufferDesc *bufHdr;
+ FILE *file;
+ char transient_dump_file_path[MAXPGPATH];
+ pid_t pid;
+
+ LWLockAcquire(&apw_state->lock, LW_EXCLUSIVE);
+ pid = apw_state->pid_using_dumpfile;
+ if (apw_state->pid_using_dumpfile == InvalidPid)
+ apw_state->pid_using_dumpfile = MyProcPid;
+ LWLockRelease(&apw_state->lock);
+
+ if (pid != InvalidPid)
+ {
+ if (!is_bgworker)
+ ereport(ERROR,
+ (errmsg("could not perform block dump because dump file is being used by PID %d",
+ apw_state->pid_using_dumpfile)));
+
+ ereport(LOG,
+ (errmsg("skipping block dump because it is already being performed by PID %d",
+ apw_state->pid_using_dumpfile)));
+ return 0;
+ }
+
+ block_info_array =
+ (BlockInfoRecord *) palloc(sizeof(BlockInfoRecord) * NBuffers);
+
+ for (num_blocks = 0, i = 0; i < NBuffers; i++)
+ {
+ uint32 buf_state;
+
+ CHECK_FOR_INTERRUPTS();
+
+ bufHdr = GetBufferDescriptor(i);
+
+ /* Lock each buffer header before inspecting. */
+ buf_state = LockBufHdr(bufHdr);
+
+ /*
+ * Unlogged tables will be automatically truncated after a crash or
+ * unclean shutdown. In such cases we need not prewarm them. Dump them
+ * only if requested by caller.
+ */
+ if (buf_state & BM_TAG_VALID &&
+ ((buf_state & BM_PERMANENT) || dump_unlogged))
+ {
+ block_info_array[num_blocks].database = bufHdr->tag.rnode.dbNode;
+ block_info_array[num_blocks].tablespace = bufHdr->tag.rnode.spcNode;
+ block_info_array[num_blocks].filenode = bufHdr->tag.rnode.relNode;
+ block_info_array[num_blocks].forknum = bufHdr->tag.forkNum;
+ block_info_array[num_blocks].blocknum = bufHdr->tag.blockNum;
+ ++num_blocks;
+ }
+
+ UnlockBufHdr(bufHdr, buf_state);
+ }
+
+ snprintf(transient_dump_file_path, MAXPGPATH, "%s.tmp", AUTOPREWARM_FILE);
+ file = AllocateFile(transient_dump_file_path, "w");
+ if (!file)
+ ereport(ERROR,
+ (errcode_for_file_access(),
+ errmsg("could not open file \"%s\": %m",
+ transient_dump_file_path)));
+
+ ret = fprintf(file, "<<" INT64_FORMAT ">>\n", num_blocks);
+ if (ret < 0)
+ {
+ int save_errno = errno;
+
+ FreeFile(file);
+ unlink(transient_dump_file_path);
+ errno = save_errno;
+ ereport(ERROR,
+ (errcode_for_file_access(),
+ errmsg("could not write to file \"%s\" : %m",
+ transient_dump_file_path)));
+ }
+
+ for (i = 0; i < num_blocks; i++)
+ {
+ CHECK_FOR_INTERRUPTS();
+
+ ret = fprintf(file, "%u,%u,%u,%u,%u\n",
+ block_info_array[i].database,
+ block_info_array[i].tablespace,
+ block_info_array[i].filenode,
+ (uint32) block_info_array[i].forknum,
+ block_info_array[i].blocknum);
+ if (ret < 0)
+ {
+ int save_errno = errno;
+
+ FreeFile(file);
+ unlink(transient_dump_file_path);
+ errno = save_errno;
+ ereport(ERROR,
+ (errcode_for_file_access(),
+ errmsg("could not write to file \"%s\" : %m",
+ transient_dump_file_path)));
+ }
+ }
+
+ pfree(block_info_array);
+
+ /*
+ * Rename transient_dump_file_path to AUTOPREWARM_FILE to make things
+ * permanent.
+ */
+ ret = FreeFile(file);
+ if (ret != 0)
+ {
+ int save_errno = errno;
+
+ unlink(transient_dump_file_path);
+ errno = save_errno;
+ ereport(ERROR,
+ (errcode_for_file_access(),
+ errmsg("could not close file \"%s\" : %m",
+ transient_dump_file_path)));
+ }
+
+ (void) durable_rename(transient_dump_file_path, AUTOPREWARM_FILE, ERROR);
+ apw_state->pid_using_dumpfile = InvalidPid;
+
+ ereport(DEBUG1,
+ (errmsg("wrote block details for " INT64_FORMAT " blocks",
+ num_blocks)));
+ return num_blocks;
+}
+
+/*
+ * SQL-callable function to launch autoprewarm.
+ */
+Datum
+autoprewarm_start_worker(PG_FUNCTION_ARGS)
+{
+ pid_t pid;
+
+ if (!autoprewarm)
+ ereport(ERROR,
+ (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE),
+ errmsg("autoprewarm is disabled")));
+
+ apw_init_shmem();
+ LWLockAcquire(&apw_state->lock, LW_EXCLUSIVE);
+ pid = apw_state->bgworker_pid;
+ LWLockRelease(&apw_state->lock);
+
+ if (pid != InvalidPid)
+ ereport(ERROR,
+ (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE),
+ errmsg("autoprewarm worker is already running under PID %d",
+ pid)));
+
+ apw_start_master_worker();
+
+ PG_RETURN_VOID();
+}
+
+/*
+ * SQL-callable function to perform an immediate block dump.
+ */
+Datum
+autoprewarm_dump_now(PG_FUNCTION_ARGS)
+{
+ int64 num_blocks;
+
+ apw_init_shmem();
+
+ PG_ENSURE_ERROR_CLEANUP(apw_detach_shmem, 0);
+ {
+ num_blocks = apw_dump_now(false, true);
+ }
+ PG_END_ENSURE_ERROR_CLEANUP(apw_detach_shmem, 0);
+
+ PG_RETURN_INT64(num_blocks);
+}
+
+/*
+ * Allocate and initialize autoprewarm related shared memory, if not already
+ * done, and set up backend-local pointer to that state. Returns true if an
+ * existing shared memory segment was found.
+ */
+static bool
+apw_init_shmem(void)
+{
+ bool found;
+
+ LWLockAcquire(AddinShmemInitLock, LW_EXCLUSIVE);
+ apw_state = ShmemInitStruct("autoprewarm",
+ sizeof(AutoPrewarmSharedState),
+ &found);
+ if (!found)
+ {
+ /* First time through ... */
+ LWLockInitialize(&apw_state->lock, LWLockNewTrancheId());
+ apw_state->bgworker_pid = InvalidPid;
+ apw_state->pid_using_dumpfile = InvalidPid;
+ }
+ LWLockRelease(AddinShmemInitLock);
+
+ return found;
+}
+
+/*
+ * Clear our PID from autoprewarm shared state.
+ */
+static void
+apw_detach_shmem(int code, Datum arg)
+{
+ LWLockAcquire(&apw_state->lock, LW_EXCLUSIVE);
+ if (apw_state->pid_using_dumpfile == MyProcPid)
+ apw_state->pid_using_dumpfile = InvalidPid;
+ if (apw_state->bgworker_pid == MyProcPid)
+ apw_state->bgworker_pid = InvalidPid;
+ LWLockRelease(&apw_state->lock);
+}
+
+/*
+ * Start autoprewarm master worker process.
+ */
+static void
+apw_start_master_worker(void)
+{
+ BackgroundWorker worker;
+ BackgroundWorkerHandle *handle;
+ BgwHandleStatus status;
+ pid_t pid;
+
+ MemSet(&worker, 0, sizeof(BackgroundWorker));
+ worker.bgw_flags = BGWORKER_SHMEM_ACCESS;
+ worker.bgw_start_time = BgWorkerStart_ConsistentState;
+ strcpy(worker.bgw_library_name, "pg_prewarm");
+ strcpy(worker.bgw_function_name, "autoprewarm_main");
+ strcpy(worker.bgw_name, "autoprewarm");
+
+ if (process_shared_preload_libraries_in_progress)
+ {
+ RegisterBackgroundWorker(&worker);
+ return;
+ }
+
+ /* must set notify PID to wait for startup */
+ worker.bgw_notify_pid = MyProcPid;
+
+ if (!RegisterDynamicBackgroundWorker(&worker, &handle))
+ ereport(ERROR,
+ (errcode(ERRCODE_INSUFFICIENT_RESOURCES),
+ errmsg("could not register background process"),
+ errhint("You may need to increase max_worker_processes.")));
+
+ status = WaitForBackgroundWorkerStartup(handle, &pid);
+ if (status != BGWH_STARTED)
+ ereport(ERROR,
+ (errcode(ERRCODE_INSUFFICIENT_RESOURCES),
+ errmsg("could not start background process"),
+ errhint("More details may be available in the server log.")));
+}
+
+/*
+ * Start autoprewarm per-database worker process.
+ */
+static void
+apw_start_database_worker(void)
+{
+ BackgroundWorker worker;
+ BackgroundWorkerHandle *handle;
+
+ MemSet(&worker, 0, sizeof(BackgroundWorker));
+ worker.bgw_flags =
+ BGWORKER_SHMEM_ACCESS | BGWORKER_BACKEND_DATABASE_CONNECTION;
+ worker.bgw_start_time = BgWorkerStart_ConsistentState;
+ strcpy(worker.bgw_library_name, "pg_prewarm");
+ strcpy(worker.bgw_function_name, "autoprewarm_database_main");
+ strcpy(worker.bgw_name, "autoprewarm");
+
+ /* must set notify PID to wait for shutdown */
+ worker.bgw_notify_pid = MyProcPid;
+
+ if (!RegisterDynamicBackgroundWorker(&worker, &handle))
+ ereport(ERROR,
+ (errcode(ERRCODE_INSUFFICIENT_RESOURCES),
+ errmsg("registering dynamic bgworker autoprewarm failed"),
+ errhint("Consider increasing configuration parameter \"max_worker_processes\".")));
+
+ /*
+ * Ignore return value; if it fails, postmaster has died, but we have
+ * checks for that elsewhere.
+ */
+ WaitForBackgroundWorkerShutdown(handle);
+}
+
+/* Compare member elements to check whether they are not equal. */
+#define cmp_member_elem(fld) \
+do { \
+ if (a->fld < b->fld) \
+ return -1; \
+ else if (a->fld > b->fld) \
+ return 1; \
+} while(0);
+
+/*
+ * apw_compare_blockinfo
+ *
+ * We depend on all records for a particular database being consecutive
+ * in the dump file; each per-database worker will preload blocks until
+ * it sees a block for some other database. Sorting by tablespace,
+ * filenode, forknum, and blocknum isn't critical for correctness, but
+ * helps us get a sequential I/O pattern.
+ */
+static int
+apw_compare_blockinfo(const void *p, const void *q)
+{
+ BlockInfoRecord *a = (BlockInfoRecord *) p;
+ BlockInfoRecord *b = (BlockInfoRecord *) q;
+
+ cmp_member_elem(database);
+ cmp_member_elem(tablespace);
+ cmp_member_elem(filenode);
+ cmp_member_elem(forknum);
+ cmp_member_elem(blocknum);
+
+ return 0;
+}
+
+/*
+ * Signal handler for SIGTERM
+ */
+static void
+apw_sigterm_handler(SIGNAL_ARGS)
+{
+ int save_errno = errno;
+
+ got_sigterm = true;
+
+ if (MyProc)
+ SetLatch(&MyProc->procLatch);
+
+ errno = save_errno;
+}
+
+/*
+ * Signal handler for SIGHUP
+ */
+static void
+apw_sighup_handler(SIGNAL_ARGS)
+{
+ int save_errno = errno;
+
+ got_sighup = true;
+
+ if (MyProc)
+ SetLatch(&MyProc->procLatch);
+
+ errno = save_errno;
+}
projects / postgresql / commitdiff