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postgresql/src/backend/replication/walreceiver.c

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/*-------------------------------------------------------------------------
*
* walreceiver.c
*
* The WAL receiver process (walreceiver) is new as of Postgres 9.0. It
* is the process in the standby server that takes charge of receiving
* XLOG records from a primary server during streaming replication.
*
* When the startup process determines that it's time to start streaming,
* it instructs postmaster to start walreceiver. Walreceiver first connects
* to the primary server (it will be served by a walsender process
* in the primary server), and then keeps receiving XLOG records and
* writing them to the disk as long as the connection is alive. As XLOG
* records are received and flushed to disk, it updates the
* WalRcv->receivedUpto variable in shared memory, to inform the startup
* process of how far it can proceed with XLOG replay.
*
* If the primary server ends streaming, but doesn't disconnect, walreceiver
* goes into "waiting" mode, and waits for the startup process to give new
* instructions. The startup process will treat that the same as
* disconnection, and will rescan the archive/pg_xlog directory. But when the
* startup process wants to try streaming replication again, it will just
* nudge the existing walreceiver process that's waiting, instead of launching
* a new one.
*
* Normal termination is by SIGTERM, which instructs the walreceiver to
* exit(0). Emergency termination is by SIGQUIT; like any postmaster child
* process, the walreceiver will simply abort and exit on SIGQUIT. A close
* of the connection and a FATAL error are treated not as a crash but as
* normal operation.
*
* This file contains the server-facing parts of walreceiver. The libpq-
* specific parts are in the libpqwalreceiver module. It's loaded
* dynamically to avoid linking the server with libpq.
*
* Portions Copyright (c) 2010-2013, PostgreSQL Global Development Group
*
*
* IDENTIFICATION
* src/backend/replication/walreceiver.c
*
*-------------------------------------------------------------------------
*/
#include "postgres.h"
#include <signal.h>
#include <unistd.h>
#include "access/timeline.h"
#include "access/xlog_internal.h"
#include "libpq/pqformat.h"
#include "libpq/pqsignal.h"
#include "miscadmin.h"
#include "replication/walreceiver.h"
#include "replication/walsender.h"
#include "storage/ipc.h"
#include "storage/pmsignal.h"
#include "storage/procarray.h"
#include "utils/guc.h"
#include "utils/ps_status.h"
#include "utils/resowner.h"
#include "utils/timestamp.h"
/* GUC variables */
int wal_receiver_status_interval;
int wal_receiver_timeout;
bool hot_standby_feedback;
/* libpqreceiver hooks to these when loaded */
walrcv_connect_type walrcv_connect = NULL;
walrcv_identify_system_type walrcv_identify_system = NULL;
walrcv_startstreaming_type walrcv_startstreaming = NULL;
walrcv_endstreaming_type walrcv_endstreaming = NULL;
walrcv_readtimelinehistoryfile_type walrcv_readtimelinehistoryfile = NULL;
walrcv_receive_type walrcv_receive = NULL;
walrcv_send_type walrcv_send = NULL;
walrcv_disconnect_type walrcv_disconnect = NULL;
#define NAPTIME_PER_CYCLE 100 /* max sleep time between cycles (100ms) */
/*
* These variables are used similarly to openLogFile/SegNo/Off,
* but for walreceiver to write the XLOG. recvFileTLI is the TimeLineID
* corresponding the filename of recvFile, used for error messages.
*/
static int recvFile = -1;
static TimeLineID recvFileTLI = 0;
static XLogSegNo recvSegNo = 0;
static uint32 recvOff = 0;
/*
* Flags set by interrupt handlers of walreceiver for later service in the
* main loop.
*/
static volatile sig_atomic_t got_SIGHUP = false;
static volatile sig_atomic_t got_SIGTERM = false;
/*
* LogstreamResult indicates the byte positions that we have already
* written/fsynced.
*/
static struct
{
XLogRecPtr Write; /* last byte + 1 written out in the standby */
XLogRecPtr Flush; /* last byte + 1 flushed in the standby */
} LogstreamResult;
static StringInfoData reply_message;
static StringInfoData incoming_message;
/*
* About SIGTERM handling:
*
* We can't just exit(1) within SIGTERM signal handler, because the signal
* might arrive in the middle of some critical operation, like while we're
* holding a spinlock. We also can't just set a flag in signal handler and
* check it in the main loop, because we perform some blocking operations
* like libpqrcv_PQexec(), which can take a long time to finish.
*
* We use a combined approach: When WalRcvImmediateInterruptOK is true, it's
* safe for the signal handler to elog(FATAL) immediately. Otherwise it just
* sets got_SIGTERM flag, which is checked in the main loop when convenient.
*
* This is very much like what regular backends do with ImmediateInterruptOK,
* ProcessInterrupts() etc.
*/
static volatile bool WalRcvImmediateInterruptOK = false;
/* Prototypes for private functions */
static void ProcessWalRcvInterrupts(void);
static void EnableWalRcvImmediateExit(void);
static void DisableWalRcvImmediateExit(void);
static void WalRcvFetchTimeLineHistoryFiles(TimeLineID first, TimeLineID last);
static void WalRcvWaitForStartPosition(XLogRecPtr *startpoint, TimeLineID *startpointTLI);
static void WalRcvDie(int code, Datum arg);
static void XLogWalRcvProcessMsg(unsigned char type, char *buf, Size len);
static void XLogWalRcvWrite(char *buf, Size nbytes, XLogRecPtr recptr);
static void XLogWalRcvFlush(bool dying);
static void XLogWalRcvSendReply(bool force, bool requestReply);
static void XLogWalRcvSendHSFeedback(void);
static void ProcessWalSndrMessage(XLogRecPtr walEnd, TimestampTz sendTime);
/* Signal handlers */
static void WalRcvSigHupHandler(SIGNAL_ARGS);
static void WalRcvSigUsr1Handler(SIGNAL_ARGS);
static void WalRcvShutdownHandler(SIGNAL_ARGS);
static void WalRcvQuickDieHandler(SIGNAL_ARGS);
static void
ProcessWalRcvInterrupts(void)
{
/*
* Although walreceiver interrupt handling doesn't use the same scheme as
* regular backends, call CHECK_FOR_INTERRUPTS() to make sure we receive
* any incoming signals on Win32.
*/
CHECK_FOR_INTERRUPTS();
if (got_SIGTERM)
{
WalRcvImmediateInterruptOK = false;
ereport(FATAL,
(errcode(ERRCODE_ADMIN_SHUTDOWN),
errmsg("terminating walreceiver process due to administrator command")));
}
}
static void
EnableWalRcvImmediateExit(void)
{
WalRcvImmediateInterruptOK = true;
ProcessWalRcvInterrupts();
}
static void
DisableWalRcvImmediateExit(void)
{
WalRcvImmediateInterruptOK = false;
ProcessWalRcvInterrupts();
}
/* Main entry point for walreceiver process */
void
WalReceiverMain(void)
{
char conninfo[MAXCONNINFO];
XLogRecPtr startpoint;
TimeLineID startpointTLI;
TimeLineID primaryTLI;
bool first_stream;
/* use volatile pointer to prevent code rearrangement */
volatile WalRcvData *walrcv = WalRcv;
TimestampTz last_recv_timestamp;
bool ping_sent;
/*
* WalRcv should be set up already (if we are a backend, we inherit this
* by fork() or EXEC_BACKEND mechanism from the postmaster).
*/
Assert(walrcv != NULL);
/*
* Mark walreceiver as running in shared memory.
*
* Do this as early as possible, so that if we fail later on, we'll set
* state to STOPPED. If we die before this, the startup process will keep
* waiting for us to start up, until it times out.
*/
SpinLockAcquire(&walrcv->mutex);
Assert(walrcv->pid == 0);
switch (walrcv->walRcvState)
{
case WALRCV_STOPPING:
/* If we've already been requested to stop, don't start up. */
walrcv->walRcvState = WALRCV_STOPPED;
/* fall through */
case WALRCV_STOPPED:
SpinLockRelease(&walrcv->mutex);
proc_exit(1);
break;
case WALRCV_STARTING:
/* The usual case */
break;
case WALRCV_WAITING:
case WALRCV_STREAMING:
case WALRCV_RESTARTING:
default:
/* Shouldn't happen */
elog(PANIC, "walreceiver still running according to shared memory state");
}
/* Advertise our PID so that the startup process can kill us */
walrcv->pid = MyProcPid;
walrcv->walRcvState = WALRCV_STREAMING;
/* Fetch information required to start streaming */
strlcpy(conninfo, (char *) walrcv->conninfo, MAXCONNINFO);
startpoint = walrcv->receiveStart;
startpointTLI = walrcv->receiveStartTLI;
/* Initialise to a sanish value */
walrcv->lastMsgSendTime = walrcv->lastMsgReceiptTime = walrcv->latestWalEndTime = GetCurrentTimestamp();
SpinLockRelease(&walrcv->mutex);
/* Arrange to clean up at walreceiver exit */
on_shmem_exit(WalRcvDie, 0);
OwnLatch(&walrcv->latch);
/*
* If possible, make this process a group leader, so that the postmaster
* can signal any child processes too. (walreceiver probably never has
* any child processes, but for consistency we make all postmaster child
* processes do this.)
*/
#ifdef HAVE_SETSID
if (setsid() < 0)
elog(FATAL, "setsid() failed: %m");
#endif
/* Properly accept or ignore signals the postmaster might send us */
pqsignal(SIGHUP, WalRcvSigHupHandler); /* set flag to read config
* file */
pqsignal(SIGINT, SIG_IGN);
pqsignal(SIGTERM, WalRcvShutdownHandler); /* request shutdown */
pqsignal(SIGQUIT, WalRcvQuickDieHandler); /* hard crash time */
pqsignal(SIGALRM, SIG_IGN);
pqsignal(SIGPIPE, SIG_IGN);
pqsignal(SIGUSR1, WalRcvSigUsr1Handler);
pqsignal(SIGUSR2, SIG_IGN);
/* Reset some signals that are accepted by postmaster but not here */
pqsignal(SIGCHLD, SIG_DFL);
pqsignal(SIGTTIN, SIG_DFL);
pqsignal(SIGTTOU, SIG_DFL);
pqsignal(SIGCONT, SIG_DFL);
pqsignal(SIGWINCH, SIG_DFL);
/* We allow SIGQUIT (quickdie) at all times */
sigdelset(&BlockSig, SIGQUIT);
/* Load the libpq-specific functions */
load_file("libpqwalreceiver", false);
if (walrcv_connect == NULL || walrcv_startstreaming == NULL ||
walrcv_endstreaming == NULL ||
walrcv_identify_system == NULL ||
walrcv_readtimelinehistoryfile == NULL ||
walrcv_receive == NULL || walrcv_send == NULL ||
walrcv_disconnect == NULL)
elog(ERROR, "libpqwalreceiver didn't initialize correctly");
/*
* Create a resource owner to keep track of our resources (not clear that
* we need this, but may as well have one).
*/
CurrentResourceOwner = ResourceOwnerCreate(NULL, "Wal Receiver");
/* Unblock signals (they were blocked when the postmaster forked us) */
PG_SETMASK(&UnBlockSig);
/* Establish the connection to the primary for XLOG streaming */
EnableWalRcvImmediateExit();
walrcv_connect(conninfo);
DisableWalRcvImmediateExit();
first_stream = true;
for (;;)
{
/*
* Check that we're connected to a valid server using the
* IDENTIFY_SYSTEM replication command,
*/
EnableWalRcvImmediateExit();
walrcv_identify_system(&primaryTLI);
DisableWalRcvImmediateExit();
/*
* Confirm that the current timeline of the primary is the same or
* ahead of ours.
*/
if (primaryTLI < startpointTLI)
ereport(ERROR,
(errmsg("highest timeline %u of the primary is behind recovery timeline %u",
primaryTLI, startpointTLI)));
/*
* Get any missing history files. We do this always, even when we're
* not interested in that timeline, so that if we're promoted to become
* the master later on, we don't select the same timeline that was
* already used in the current master. This isn't bullet-proof - you'll
* need some external software to manage your cluster if you need to
* ensure that a unique timeline id is chosen in every case, but let's
* avoid the confusion of timeline id collisions where we can.
*/
WalRcvFetchTimeLineHistoryFiles(startpointTLI, primaryTLI);
/*
* Start streaming.
*
* We'll try to start at the requested starting point and timeline,
* even if it's different from the server's latest timeline. In case
* we've already reached the end of the old timeline, the server will
* finish the streaming immediately, and we will go back to await
* orders from the startup process. If recovery_target_timeline is
* 'latest', the startup process will scan pg_xlog and find the new
* history file, bump recovery target timeline, and ask us to restart
* on the new timeline.
*/
ThisTimeLineID = startpointTLI;
if (walrcv_startstreaming(startpointTLI, startpoint))
{
bool endofwal = false;
if (first_stream)
ereport(LOG,
(errmsg("started streaming WAL from primary at %X/%X on timeline %u",
(uint32) (startpoint >> 32), (uint32) startpoint,
startpointTLI)));
else
ereport(LOG,
(errmsg("restarted WAL streaming at %X/%X on timeline %u",
(uint32) (startpoint >> 32), (uint32) startpoint,
startpointTLI)));
first_stream = false;
/* Initialize LogstreamResult and buffers for processing messages */
LogstreamResult.Write = LogstreamResult.Flush = GetXLogReplayRecPtr(NULL);
initStringInfo(&reply_message);
initStringInfo(&incoming_message);
/* Initialize the last recv timestamp */
last_recv_timestamp = GetCurrentTimestamp();
ping_sent = false;
/* Loop until end-of-streaming or error */
while (!endofwal)
{
char *buf;
int len;
/*
* Emergency bailout if postmaster has died. This is to avoid
* the necessity for manual cleanup of all postmaster children.
*/
if (!PostmasterIsAlive())
exit(1);
/*
* Exit walreceiver if we're not in recovery. This should not
* happen, but cross-check the status here.
*/
if (!RecoveryInProgress())
ereport(FATAL,
(errmsg("cannot continue WAL streaming, recovery has already ended")));
/* Process any requests or signals received recently */
ProcessWalRcvInterrupts();
if (got_SIGHUP)
{
got_SIGHUP = false;
ProcessConfigFile(PGC_SIGHUP);
}
/* Wait a while for data to arrive */
len = walrcv_receive(NAPTIME_PER_CYCLE, &buf);
if (len != 0)
{
/*
* Process the received data, and any subsequent data we
* can read without blocking.
*/
for (;;)
{
if (len > 0)
{
/* Something was received from master, so reset timeout */
last_recv_timestamp = GetCurrentTimestamp();
ping_sent = false;
XLogWalRcvProcessMsg(buf[0], &buf[1], len - 1);
}
else if (len == 0)
break;
else if (len < 0)
{
ereport(LOG,
(errmsg("replication terminated by primary server"),
errdetail("End of WAL reached on timeline %u at %X/%X",
startpointTLI,
(uint32) (LogstreamResult.Write >> 32), (uint32) LogstreamResult.Write)));
endofwal = true;
break;
}
len = walrcv_receive(0, &buf);
}
/* Let the master know that we received some data. */
XLogWalRcvSendReply(false, false);
/*
* If we've written some records, flush them to disk and
* let the startup process and primary server know about
* them.
*/
XLogWalRcvFlush(false);
}
else
{
/*
* We didn't receive anything new. If we haven't heard
* anything from the server for more than
* wal_receiver_timeout / 2, ping the server. Also, if it's
* been longer than wal_receiver_status_interval since the
* last update we sent, send a status update to the master
* anyway, to report any progress in applying WAL.
*/
bool requestReply = false;
/*
* Check if time since last receive from standby has
* reached the configured limit.
*/
if (wal_receiver_timeout > 0)
{
TimestampTz now = GetCurrentTimestamp();
TimestampTz timeout;
timeout =
TimestampTzPlusMilliseconds(last_recv_timestamp,
wal_receiver_timeout);
if (now >= timeout)
ereport(ERROR,
(errmsg("terminating walreceiver due to timeout")));
/*
* We didn't receive anything new, for half of receiver
* replication timeout. Ping the server.
*/
if (!ping_sent)
{
timeout = TimestampTzPlusMilliseconds(last_recv_timestamp,
(wal_receiver_timeout/2));
if (now >= timeout)
{
requestReply = true;
ping_sent = true;
}
}
}
XLogWalRcvSendReply(requestReply, requestReply);
XLogWalRcvSendHSFeedback();
}
}
/*
* The backend finished streaming. Exit streaming COPY-mode from
* our side, too.
*/
EnableWalRcvImmediateExit();
walrcv_endstreaming();
DisableWalRcvImmediateExit();
}
else
ereport(LOG,
(errmsg("primary server contains no more WAL on requested timeline %u",
startpointTLI)));
/*
* End of WAL reached on the requested timeline. Close the last
* segment, and await for new orders from the startup process.
*/
if (recvFile >= 0)
{
XLogWalRcvFlush(false);
if (close(recvFile) != 0)
ereport(PANIC,
(errcode_for_file_access(),
errmsg("could not close log segment %s: %m",
XLogFileNameP(recvFileTLI, recvSegNo))));
}
recvFile = -1;
elog(DEBUG1, "walreceiver ended streaming and awaits new instructions");
WalRcvWaitForStartPosition(&startpoint, &startpointTLI);
}
/* not reached */
}
/*
* Wait for startup process to set receiveStart and receiveStartTLI.
*/
static void
WalRcvWaitForStartPosition(XLogRecPtr *startpoint, TimeLineID *startpointTLI)
{
/* use volatile pointer to prevent code rearrangement */
volatile WalRcvData *walrcv = WalRcv;
int state;
SpinLockAcquire(&walrcv->mutex);
state = walrcv->walRcvState;
if (state != WALRCV_STREAMING)
{
SpinLockRelease(&walrcv->mutex);
if (state == WALRCV_STOPPING)
proc_exit(0);
else
elog(FATAL, "unexpected walreceiver state");
}
walrcv->walRcvState = WALRCV_WAITING;
walrcv->receiveStart = InvalidXLogRecPtr;
walrcv->receiveStartTLI = 0;
SpinLockRelease(&walrcv->mutex);
if (update_process_title)
set_ps_display("idle", false);
/*
* nudge startup process to notice that we've stopped streaming and are
* now waiting for instructions.
*/
WakeupRecovery();
for (;;)
{
ResetLatch(&walrcv->latch);
/*
* Emergency bailout if postmaster has died. This is to avoid the
* necessity for manual cleanup of all postmaster children.
*/
if (!PostmasterIsAlive())
exit(1);
ProcessWalRcvInterrupts();
SpinLockAcquire(&walrcv->mutex);
Assert(walrcv->walRcvState == WALRCV_RESTARTING ||
walrcv->walRcvState == WALRCV_WAITING ||
walrcv->walRcvState == WALRCV_STOPPING);
if (walrcv->walRcvState == WALRCV_RESTARTING)
{
/* we don't expect primary_conninfo to change */
*startpoint = walrcv->receiveStart;
*startpointTLI = walrcv->receiveStartTLI;
walrcv->walRcvState = WALRCV_STREAMING;
SpinLockRelease(&walrcv->mutex);
break;
}
if (walrcv->walRcvState == WALRCV_STOPPING)
{
/*
* We should've received SIGTERM if the startup process wants
* us to die, but might as well check it here too.
*/
SpinLockRelease(&walrcv->mutex);
exit(1);
}
SpinLockRelease(&walrcv->mutex);
WaitLatch(&walrcv->latch, WL_LATCH_SET | WL_POSTMASTER_DEATH, 0);
}
if (update_process_title)
{
char activitymsg[50];
snprintf(activitymsg, sizeof(activitymsg), "restarting at %X/%X",
(uint32) (*startpoint >> 32),
(uint32) *startpoint);
set_ps_display(activitymsg, false);
}
}
/*
* Fetch any missing timeline history files between 'first' and 'last'
* (inclusive) from the server.
*/
static void
WalRcvFetchTimeLineHistoryFiles(TimeLineID first, TimeLineID last)
{
TimeLineID tli;
for (tli = first; tli <= last; tli++)
{
/* there's no history file for timeline 1 */
if (tli != 1 && !existsTimeLineHistory(tli))
{
char *fname;
char *content;
int len;
char expectedfname[MAXFNAMELEN];
ereport(LOG,
(errmsg("fetching timeline history file for timeline %u from primary server",
tli)));
EnableWalRcvImmediateExit();
walrcv_readtimelinehistoryfile(tli, &fname, &content, &len);
DisableWalRcvImmediateExit();
/*
* Check that the filename on the master matches what we calculated
* ourselves. This is just a sanity check, it should always match.
*/
TLHistoryFileName(expectedfname, tli);
if (strcmp(fname, expectedfname) != 0)
ereport(ERROR,
(errcode(ERRCODE_PROTOCOL_VIOLATION),
errmsg_internal("primary reported unexpected filename for timeline history file of timeline %u",
tli)));
/*
* Write the file to pg_xlog.
*/
writeTimeLineHistoryFile(tli, content, len);
pfree(fname);
pfree(content);
}
}
}
/*
* Mark us as STOPPED in shared memory at exit.
*/
static void
WalRcvDie(int code, Datum arg)
{
/* use volatile pointer to prevent code rearrangement */
volatile WalRcvData *walrcv = WalRcv;
/* Ensure that all WAL records received are flushed to disk */
XLogWalRcvFlush(true);
DisownLatch(&walrcv->latch);
SpinLockAcquire(&walrcv->mutex);
Assert(walrcv->walRcvState == WALRCV_STREAMING ||
walrcv->walRcvState == WALRCV_RESTARTING ||
walrcv->walRcvState == WALRCV_STARTING ||
walrcv->walRcvState == WALRCV_WAITING ||
walrcv->walRcvState == WALRCV_STOPPING);
Assert(walrcv->pid == MyProcPid);
walrcv->walRcvState = WALRCV_STOPPED;
walrcv->pid = 0;
SpinLockRelease(&walrcv->mutex);
/* Terminate the connection gracefully. */
if (walrcv_disconnect != NULL)
walrcv_disconnect();
/* Wake up the startup process to notice promptly that we're gone */
WakeupRecovery();
}
/* SIGHUP: set flag to re-read config file at next convenient time */
static void
WalRcvSigHupHandler(SIGNAL_ARGS)
{
got_SIGHUP = true;
}
/* SIGUSR1: used by latch mechanism */
static void
WalRcvSigUsr1Handler(SIGNAL_ARGS)
{
latch_sigusr1_handler();
}
/* SIGTERM: set flag for main loop, or shutdown immediately if safe */
static void
WalRcvShutdownHandler(SIGNAL_ARGS)
{
int save_errno = errno;
got_SIGTERM = true;
SetLatch(&WalRcv->latch);
/* Don't joggle the elbow of proc_exit */
if (!proc_exit_inprogress && WalRcvImmediateInterruptOK)
ProcessWalRcvInterrupts();
errno = save_errno;
}
/*
* WalRcvQuickDieHandler() occurs when signalled SIGQUIT by the postmaster.
*
* Some backend has bought the farm, so we need to stop what we're doing and
* exit.
*/
static void
WalRcvQuickDieHandler(SIGNAL_ARGS)
{
PG_SETMASK(&BlockSig);
/*
* We DO NOT want to run proc_exit() callbacks -- we're here because
* shared memory may be corrupted, so we don't want to try to clean up our
* transaction. Just nail the windows shut and get out of town. Now that
* there's an atexit callback to prevent third-party code from breaking
* things by calling exit() directly, we have to reset the callbacks
* explicitly to make this work as intended.
*/
on_exit_reset();
/*
* Note we do exit(2) not exit(0). This is to force the postmaster into a
* system reset cycle if some idiot DBA sends a manual SIGQUIT to a random
* backend. This is necessary precisely because we don't clean up our
* shared memory state. (The "dead man switch" mechanism in pmsignal.c
* should ensure the postmaster sees this as a crash, too, but no harm in
* being doubly sure.)
*/
exit(2);
}
/*
* Accept the message from XLOG stream, and process it.
*/
static void
XLogWalRcvProcessMsg(unsigned char type, char *buf, Size len)
{
int hdrlen;
XLogRecPtr dataStart;
XLogRecPtr walEnd;
TimestampTz sendTime;
bool replyRequested;
resetStringInfo(&incoming_message);
switch (type)
{
case 'w': /* WAL records */
{
/* copy message to StringInfo */
hdrlen = sizeof(int64) + sizeof(int64) + sizeof(int64);
if (len < hdrlen)
ereport(ERROR,
(errcode(ERRCODE_PROTOCOL_VIOLATION),
errmsg_internal("invalid WAL message received from primary")));
appendBinaryStringInfo(&incoming_message, buf, hdrlen);
/* read the fields */
dataStart = pq_getmsgint64(&incoming_message);
walEnd = pq_getmsgint64(&incoming_message);
sendTime = IntegerTimestampToTimestampTz(
pq_getmsgint64(&incoming_message));
ProcessWalSndrMessage(walEnd, sendTime);
buf += hdrlen;
len -= hdrlen;
XLogWalRcvWrite(buf, len, dataStart);
break;
}
case 'k': /* Keepalive */
{
/* copy message to StringInfo */
hdrlen = sizeof(int64) + sizeof(int64) + sizeof(char);
if (len != hdrlen)
ereport(ERROR,
(errcode(ERRCODE_PROTOCOL_VIOLATION),
errmsg_internal("invalid keepalive message received from primary")));
appendBinaryStringInfo(&incoming_message, buf, hdrlen);
/* read the fields */
walEnd = pq_getmsgint64(&incoming_message);
sendTime = IntegerTimestampToTimestampTz(
pq_getmsgint64(&incoming_message));
replyRequested = pq_getmsgbyte(&incoming_message);
ProcessWalSndrMessage(walEnd, sendTime);
/* If the primary requested a reply, send one immediately */
if (replyRequested)
XLogWalRcvSendReply(true, false);
break;
}
default:
ereport(ERROR,
(errcode(ERRCODE_PROTOCOL_VIOLATION),
errmsg_internal("invalid replication message type %d",
type)));
}
}
/*
* Write XLOG data to disk.
*/
static void
XLogWalRcvWrite(char *buf, Size nbytes, XLogRecPtr recptr)
{
int startoff;
int byteswritten;
while (nbytes > 0)
{
int segbytes;
if (recvFile < 0 || !XLByteInSeg(recptr, recvSegNo))
{
bool use_existent;
/*
* fsync() and close current file before we switch to next one. We
* would otherwise have to reopen this file to fsync it later
*/
if (recvFile >= 0)
{
XLogWalRcvFlush(false);
/*
* XLOG segment files will be re-read by recovery in startup
* process soon, so we don't advise the OS to release cache
* pages associated with the file like XLogFileClose() does.
*/
if (close(recvFile) != 0)
ereport(PANIC,
(errcode_for_file_access(),
errmsg("could not close log segment %s: %m",
XLogFileNameP(recvFileTLI, recvSegNo))));
}
recvFile = -1;
/* Create/use new log file */
XLByteToSeg(recptr, recvSegNo);
use_existent = true;
recvFile = XLogFileInit(recvSegNo, &use_existent, true);
recvFileTLI = ThisTimeLineID;
recvOff = 0;
}
/* Calculate the start offset of the received logs */
startoff = recptr % XLogSegSize;
if (startoff + nbytes > XLogSegSize)
segbytes = XLogSegSize - startoff;
else
segbytes = nbytes;
/* Need to seek in the file? */
if (recvOff != startoff)
{
if (lseek(recvFile, (off_t) startoff, SEEK_SET) < 0)
ereport(PANIC,
(errcode_for_file_access(),
errmsg("could not seek in log segment %s, to offset %u: %m",
XLogFileNameP(recvFileTLI, recvSegNo),
startoff)));
recvOff = startoff;
}
/* OK to write the logs */
errno = 0;
byteswritten = write(recvFile, buf, segbytes);
if (byteswritten <= 0)
{
/* if write didn't set errno, assume no disk space */
if (errno == 0)
errno = ENOSPC;
ereport(PANIC,
(errcode_for_file_access(),
errmsg("could not write to log segment %s "
"at offset %u, length %lu: %m",
XLogFileNameP(recvFileTLI, recvSegNo),
recvOff, (unsigned long) segbytes)));
}
/* Update state for write */
recptr += byteswritten;
recvOff += byteswritten;
nbytes -= byteswritten;
buf += byteswritten;
LogstreamResult.Write = recptr;
}
}
/*
* Flush the log to disk.
*
* If we're in the midst of dying, it's unwise to do anything that might throw
* an error, so we skip sending a reply in that case.
*/
static void
XLogWalRcvFlush(bool dying)
{
if (LogstreamResult.Flush < LogstreamResult.Write)
{
/* use volatile pointer to prevent code rearrangement */
volatile WalRcvData *walrcv = WalRcv;
issue_xlog_fsync(recvFile, recvSegNo);
LogstreamResult.Flush = LogstreamResult.Write;
/* Update shared-memory status */
SpinLockAcquire(&walrcv->mutex);
if (walrcv->receivedUpto < LogstreamResult.Flush)
{
walrcv->latestChunkStart = walrcv->receivedUpto;
walrcv->receivedUpto = LogstreamResult.Flush;
walrcv->receivedTLI = ThisTimeLineID;
}
SpinLockRelease(&walrcv->mutex);
/* Signal the startup process and walsender that new WAL has arrived */
WakeupRecovery();
if (AllowCascadeReplication())
WalSndWakeup();
/* Report XLOG streaming progress in PS display */
if (update_process_title)
{
char activitymsg[50];
snprintf(activitymsg, sizeof(activitymsg), "streaming %X/%X",
(uint32) (LogstreamResult.Write >> 32),
(uint32) LogstreamResult.Write);
set_ps_display(activitymsg, false);
}
/* Also let the master know that we made some progress */
if (!dying)
XLogWalRcvSendReply(false, false);
}
}
/*
* Send reply message to primary, indicating our current XLOG positions, oldest
* xmin and the current time.
*
* If 'force' is not set, the message is only sent if enough time has
* passed since last status update to reach wal_receiver_status_interval.
* If wal_receiver_status_interval is disabled altogether and 'force' is
* false, this is a no-op.
*
* If 'requestReply' is true, requests the server to reply immediately upon
* receiving this message. This is used for heartbearts, when approaching
* wal_receiver_timeout.
*/
static void
XLogWalRcvSendReply(bool force, bool requestReply)
{
static XLogRecPtr writePtr = 0;
static XLogRecPtr flushPtr = 0;
XLogRecPtr applyPtr;
static TimestampTz sendTime = 0;
TimestampTz now;
/*
* If the user doesn't want status to be reported to the master, be sure
* to exit before doing anything at all.
*/
if (!force && wal_receiver_status_interval <= 0)
return;
/* Get current timestamp. */
now = GetCurrentTimestamp();
/*
* We can compare the write and flush positions to the last message we
* sent without taking any lock, but the apply position requires a spin
* lock, so we don't check that unless something else has changed or 10
* seconds have passed. This means that the apply log position will
* appear, from the master's point of view, to lag slightly, but since
* this is only for reporting purposes and only on idle systems, that's
* probably OK.
*/
if (!force
&& writePtr == LogstreamResult.Write
&& flushPtr == LogstreamResult.Flush
&& !TimestampDifferenceExceeds(sendTime, now,
wal_receiver_status_interval * 1000))
return;
sendTime = now;
/* Construct a new message */
writePtr = LogstreamResult.Write;
flushPtr = LogstreamResult.Flush;
applyPtr = GetXLogReplayRecPtr(NULL);
resetStringInfo(&reply_message);
pq_sendbyte(&reply_message, 'r');
pq_sendint64(&reply_message, writePtr);
pq_sendint64(&reply_message, flushPtr);
pq_sendint64(&reply_message, applyPtr);
pq_sendint64(&reply_message, GetCurrentIntegerTimestamp());
pq_sendbyte(&reply_message, requestReply ? 1 : 0);
/* Send it */
elog(DEBUG2, "sending write %X/%X flush %X/%X apply %X/%X%s",
(uint32) (writePtr >> 32), (uint32) writePtr,
(uint32) (flushPtr >> 32), (uint32) flushPtr,
(uint32) (applyPtr >> 32), (uint32) applyPtr,
requestReply ? " (reply requested)" : "");
walrcv_send(reply_message.data, reply_message.len);
}
/*
* Send hot standby feedback message to primary, plus the current time,
* in case they don't have a watch.
*/
static void
XLogWalRcvSendHSFeedback(void)
{
TimestampTz now;
TransactionId nextXid;
uint32 nextEpoch;
TransactionId xmin;
static TimestampTz sendTime = 0;
/*
* If the user doesn't want status to be reported to the master, be sure
* to exit before doing anything at all.
*/
if (wal_receiver_status_interval <= 0 || !hot_standby_feedback)
return;
/* Get current timestamp. */
now = GetCurrentTimestamp();
/*
* Send feedback at most once per wal_receiver_status_interval.
*/
if (!TimestampDifferenceExceeds(sendTime, now,
wal_receiver_status_interval * 1000))
return;
sendTime = now;
/*
* If Hot Standby is not yet active there is nothing to send. Check this
* after the interval has expired to reduce number of calls.
*/
if (!HotStandbyActive())
return;
/*
* Make the expensive call to get the oldest xmin once we are certain
* everything else has been checked.
*/
xmin = GetOldestXmin(true, false);
/*
* Get epoch and adjust if nextXid and oldestXmin are different sides of
* the epoch boundary.
*/
GetNextXidAndEpoch(&nextXid, &nextEpoch);
if (nextXid < xmin)
nextEpoch--;
elog(DEBUG2, "sending hot standby feedback xmin %u epoch %u",
xmin, nextEpoch);
/* Construct the the message and send it. */
resetStringInfo(&reply_message);
pq_sendbyte(&reply_message, 'h');
pq_sendint64(&reply_message, GetCurrentIntegerTimestamp());
pq_sendint(&reply_message, xmin, 4);
pq_sendint(&reply_message, nextEpoch, 4);
walrcv_send(reply_message.data, reply_message.len);
}
/*
* Update shared memory status upon receiving a message from primary.
*
* 'walEnd' and 'sendTime' are the end-of-WAL and timestamp of the latest
* message, reported by primary.
*/
static void
ProcessWalSndrMessage(XLogRecPtr walEnd, TimestampTz sendTime)
{
/* use volatile pointer to prevent code rearrangement */
volatile WalRcvData *walrcv = WalRcv;
TimestampTz lastMsgReceiptTime = GetCurrentTimestamp();
/* Update shared-memory status */
SpinLockAcquire(&walrcv->mutex);
if (walrcv->latestWalEnd < walEnd)
walrcv->latestWalEndTime = sendTime;
walrcv->latestWalEnd = walEnd;
walrcv->lastMsgSendTime = sendTime;
walrcv->lastMsgReceiptTime = lastMsgReceiptTime;
SpinLockRelease(&walrcv->mutex);
if (log_min_messages <= DEBUG2)
elog(DEBUG2, "sendtime %s receipttime %s replication apply delay %d ms transfer latency %d ms",
timestamptz_to_str(sendTime),
timestamptz_to_str(lastMsgReceiptTime),
GetReplicationApplyDelay(),
GetReplicationTransferLatency());
}
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