postgresql/contrib/pg_prewarm/autoprewarm.c
Tom Lane f10f0ae420 Replace RelationOpenSmgr() with RelationGetSmgr().
The idea behind this patch is to design out bugs like the one fixed
by commit 9d523119f.  Previously, once one did RelationOpenSmgr(rel),
it was considered okay to access rel->rd_smgr directly for some
not-very-clear interval.  But since that pointer will be cleared by
relcache flushes, we had bugs arising from overreliance on a previous
RelationOpenSmgr call still being effective.

Now, very little code except that in rel.h and relcache.c should ever
touch the rd_smgr field directly.  The normal coding rule is to use
RelationGetSmgr(rel) and not expect the result to be valid for longer
than one smgr function call.  There are a couple of places where using
the function every single time seemed like overkill, but they are now
annotated with large warning comments.

Amul Sul, after an idea of mine.

Discussion: https://postgr.es/m/CANiYTQsU7yMFpQYnv=BrcRVqK_3U3mtAzAsJCaqtzsDHfsUbdQ@mail.gmail.com
2021-07-12 17:01:36 -04:00

904 lines
24 KiB
C

/*-------------------------------------------------------------------------
*
* 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
* leader 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) 2016-2021, PostgreSQL Global Development Group
*
* IDENTIFICATION
* contrib/pg_prewarm/autoprewarm.c
*
*-------------------------------------------------------------------------
*/
#include "postgres.h"
#include <unistd.h>
#include "access/relation.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 "postmaster/interrupt.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/datetime.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;
int prewarm_start_idx;
int prewarm_stop_idx;
int 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 int apw_dump_now(bool is_bgworker, bool dump_unlogged);
static void apw_start_leader_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);
/* 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_leader_worker();
}
/*
* Main entry point for the leader autoprewarm process. Per-database workers
* have a separate entry point.
*/
void
autoprewarm_main(Datum main_arg)
{
bool first_time = true;
bool final_dump_allowed = true;
TimestampTz last_dump_time = 0;
/* Establish signal handlers; once that's done, unblock signals. */
pqsignal(SIGTERM, SignalHandlerForShutdownRequest);
pqsignal(SIGHUP, SignalHandlerForConfigReload);
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 %lu",
(unsigned long) 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 apw_load_buffers() is terminated early by a shutdown request,
* prevent dumping out our state below the loop, because we'd effectively
* just truncate the saved state to however much we'd managed to preload.
*/
if (first_time)
{
apw_load_buffers();
final_dump_allowed = !ShutdownRequestPending;
last_dump_time = GetCurrentTimestamp();
}
/* Periodically dump buffers until terminated. */
while (!ShutdownRequestPending)
{
/* In case of a SIGHUP, just reload the configuration. */
if (ConfigReloadPending)
{
ConfigReloadPending = false;
ProcessConfigFile(PGC_SIGHUP);
}
if (autoprewarm_interval <= 0)
{
/* We're only dumping at shutdown, so just wait forever. */
(void) WaitLatch(MyLatch,
WL_LATCH_SET | WL_EXIT_ON_PM_DEATH,
-1L,
PG_WAIT_EXTENSION);
}
else
{
TimestampTz next_dump_time;
long delay_in_ms;
/* Compute the next dump time. */
next_dump_time =
TimestampTzPlusMilliseconds(last_dump_time,
autoprewarm_interval * 1000);
delay_in_ms =
TimestampDifferenceMilliseconds(GetCurrentTimestamp(),
next_dump_time);
/* 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. */
(void) WaitLatch(MyLatch,
WL_LATCH_SET | WL_TIMEOUT | WL_EXIT_ON_PM_DEATH,
delay_in_ms,
PG_WAIT_EXTENSION);
}
/* Reset the latch, loop. */
ResetLatch(MyLatch);
}
/*
* 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.
*/
if (final_dump_allowed)
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;
int 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 %lu",
(unsigned long) 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, "<<%d>>\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 %d",
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)
{
int j = apw_state->prewarm_start_idx;
Oid current_db = blkinfo[j].database;
/*
* Advance the prewarm_stop_idx to the first BlockInfoRecord that does
* not belong to this database.
*/
j++;
while (j < num_elements)
{
if (current_db != blkinfo[j].database)
{
/*
* Combine BlockInfoRecords for global objects with those of
* the database.
*/
if (current_db != InvalidOid)
break;
current_db = blkinfo[j].database;
}
j++;
}
/*
* If we reach this point with current_db == InvalidOid, then only
* BlockInfoRecords 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 = j;
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;
/*
* Likewise, don't launch if we've already been told to shut down.
* (The launch would fail anyway, but we might as well skip it.)
*/
if (ShutdownRequestPending)
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, if we were able to finish. */
if (!ShutdownRequestPending)
ereport(LOG,
(errmsg("autoprewarm successfully prewarmed %d of %d 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)
{
int 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, 0);
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)
{
/*
* 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(RelationGetSmgr(rel), 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.
* Returns the number of blocks dumped.
*/
static int
apw_dump_now(bool is_bgworker, bool dump_unlogged)
{
int num_blocks;
int i;
int ret;
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 %lu",
(unsigned long) apw_state->pid_using_dumpfile)));
ereport(LOG,
(errmsg("skipping block dump because it is already being performed by PID %lu",
(unsigned long) 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, "<<%d>>\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_internal("wrote block details for %d 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 %lu",
(unsigned long) pid)));
apw_start_leader_worker();
PG_RETURN_VOID();
}
/*
* SQL-callable function to perform an immediate block dump.
*
* Note: this is declared to return int8, as insurance against some
* very distant day when we might make NBuffers wider than int.
*/
Datum
autoprewarm_dump_now(PG_FUNCTION_ARGS)
{
int 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((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);
LWLockRegisterTranche(apw_state->lock.tranche, "autoprewarm");
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 leader worker process.
*/
static void
apw_start_leader_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 leader");
strcpy(worker.bgw_type, "autoprewarm leader");
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;
worker.bgw_restart_time = BGW_NEVER_RESTART;
strcpy(worker.bgw_library_name, "pg_prewarm");
strcpy(worker.bgw_function_name, "autoprewarm_database_main");
strcpy(worker.bgw_name, "autoprewarm worker");
strcpy(worker.bgw_type, "autoprewarm worker");
/* 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)
{
const BlockInfoRecord *a = (const BlockInfoRecord *) p;
const BlockInfoRecord *b = (const BlockInfoRecord *) q;
cmp_member_elem(database);
cmp_member_elem(tablespace);
cmp_member_elem(filenode);
cmp_member_elem(forknum);
cmp_member_elem(blocknum);
return 0;
}