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Suppress useless wakeups in walreceiver.

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Instead of waking up 10 times per second to check for various timeout
conditions, keep track of when we next have periodic work to do.

Author: Thomas Munro <thomas.munro@gmail.com>
Author: Nathan Bossart <nathandbossart@gmail.com>
Reviewed-by: Kyotaro Horiguchi <horikyota.ntt@gmail.com>
Reviewed-by: Bharath Rupireddy <bharath.rupireddyforpostgres@gmail.com>
Reviewed-by: Alvaro Herrera <alvherre@alvh.no-ip.org>
Discussion: https://postgr.es/m/CA%2BhUKGJGhX4r2LPUE3Oy9BX71Eum6PBcS8L3sJpScR9oKaTVaA%40mail.gmail.com
pull/138/head^2
Thomas Munro 3 years ago
parent bd95816f74
commit 05a7be9355
2 changed files with 115 additions and 57 deletions
Show all changes Ignore whitespace when comparing lines Ignore changes in amount of whitespace Ignore changes in whitespace at EOL
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  1. 155
      src/backend/replication/walreceiver.c
  2. 1
      src/tools/pgindent/typedefs.list

155
src/backend/replication/walreceiver.c
Unescape View File

@ -95,8 +95,6 @@ bool hot_standby_feedback;
static WalReceiverConn *wrconn = NULL;
WalReceiverFunctionsType *WalReceiverFunctions = NULL;
#define NAPTIME_PER_CYCLE 100 /* max sleep time between cycles (100ms) */
/*
* These variables are used similarly to openLogFile/SegNo,
* but for walreceiver to write the XLOG. recvFileTLI is the TimeLineID
@ -116,6 +114,23 @@ static struct
XLogRecPtr Flush; /* last byte + 1 flushed in the standby */
} LogstreamResult;
/*
* Reasons to wake up and perform periodic tasks.
*/
typedef enum WalRcvWakeupReason
{
WALRCV_WAKEUP_TERMINATE,
WALRCV_WAKEUP_PING,
WALRCV_WAKEUP_REPLY,
WALRCV_WAKEUP_HSFEEDBACK,
NUM_WALRCV_WAKEUPS
} WalRcvWakeupReason;
/*
* Wake up times for periodic tasks.
*/
static TimestampTz wakeup[NUM_WALRCV_WAKEUPS];
static StringInfoData reply_message;
static StringInfoData incoming_message;
@ -132,6 +147,7 @@ static void XLogWalRcvClose(XLogRecPtr recptr, TimeLineID tli);
static void XLogWalRcvSendReply(bool force, bool requestReply);
static void XLogWalRcvSendHSFeedback(bool immed);
static void ProcessWalSndrMessage(XLogRecPtr walEnd, TimestampTz sendTime);
static void WalRcvComputeNextWakeup(WalRcvWakeupReason reason, TimestampTz now);
/*
* Process any interrupts the walreceiver process may have received.
@ -179,9 +195,7 @@ WalReceiverMain(void)
TimeLineID primaryTLI;
bool first_stream;
WalRcvData *walrcv = WalRcv;
TimestampTz last_recv_timestamp;
TimestampTz starttime;
bool ping_sent;
TimestampTz now;
char *err;
char *sender_host = NULL;
int sender_port = 0;
@ -192,7 +206,7 @@ WalReceiverMain(void)
*/
Assert(walrcv != NULL);
starttime = GetCurrentTimestamp();
now = GetCurrentTimestamp();
/*
* Mark walreceiver as running in shared memory.
@ -248,7 +262,7 @@ WalReceiverMain(void)
/* Initialise to a sanish value */
walrcv->lastMsgSendTime =
walrcv->lastMsgReceiptTime = walrcv->latestWalEndTime = starttime;
walrcv->lastMsgReceiptTime = walrcv->latestWalEndTime = now;
/* Report the latch to use to awaken this process */
walrcv->latch = &MyProc->procLatch;
@ -414,9 +428,10 @@ WalReceiverMain(void)
initStringInfo(&reply_message);
initStringInfo(&incoming_message);
/* Initialize the last recv timestamp */
last_recv_timestamp = GetCurrentTimestamp();
ping_sent = false;
/* Initialize nap wakeup times. */
now = GetCurrentTimestamp();
for (int i = 0; i < NUM_WALRCV_WAKEUPS; ++i)
WalRcvComputeNextWakeup(i, now);
/* Loop until end-of-streaming or error */
for (;;)
@ -426,6 +441,8 @@ WalReceiverMain(void)
bool endofwal = false;
pgsocket wait_fd = PGINVALID_SOCKET;
int rc;
TimestampTz nextWakeup;
int nap;
/*
* Exit walreceiver if we're not in recovery. This should not
@ -443,11 +460,15 @@ WalReceiverMain(void)
{
ConfigReloadPending = false;
ProcessConfigFile(PGC_SIGHUP);
now = GetCurrentTimestamp();
for (int i = 0; i < NUM_WALRCV_WAKEUPS; ++i)
WalRcvComputeNextWakeup(i, now);
XLogWalRcvSendHSFeedback(true);
}
/* See if we can read data immediately */
len = walrcv_receive(wrconn, &buf, &wait_fd);
now = GetCurrentTimestamp();
if (len != 0)
{
/*
@ -459,11 +480,12 @@ WalReceiverMain(void)
if (len > 0)
{
/*
* Something was received from primary, so reset
* timeout
* Something was received from primary, so adjust
* the ping and terminate wakeup times.
*/
last_recv_timestamp = GetCurrentTimestamp();
ping_sent = false;
WalRcvComputeNextWakeup(WALRCV_WAKEUP_TERMINATE,
now);
WalRcvComputeNextWakeup(WALRCV_WAKEUP_PING, now);
XLogWalRcvProcessMsg(buf[0], &buf[1], len - 1,
startpointTLI);
}
@ -480,6 +502,7 @@ WalReceiverMain(void)
break;
}
len = walrcv_receive(wrconn, &buf, &wait_fd);
now = GetCurrentTimestamp();
}
/* Let the primary know that we received some data. */
@ -497,6 +520,20 @@ WalReceiverMain(void)
if (endofwal)
break;
/* Find the soonest wakeup time, to limit our nap. */
nextWakeup = PG_INT64_MAX;
for (int i = 0; i < NUM_WALRCV_WAKEUPS; ++i)
nextWakeup = Min(wakeup[i], nextWakeup);
/*
* Calculate the nap time. WaitLatchOrSocket() doesn't accept
* timeouts longer than INT_MAX milliseconds, so we limit the
* result accordingly. Also, we round up to the next
* millisecond to avoid waking up too early and spinning until
* one of the wakeup times.
*/
nap = (int) Min(INT_MAX, Max(0, (nextWakeup - now + 999) / 1000));
/*
* Ideally we would reuse a WaitEventSet object repeatedly
* here to avoid the overheads of WaitLatchOrSocket on epoll
@ -513,8 +550,9 @@ WalReceiverMain(void)
WL_EXIT_ON_PM_DEATH | WL_SOCKET_READABLE |
WL_TIMEOUT | WL_LATCH_SET,
wait_fd,
NAPTIME_PER_CYCLE,
nap,
WAIT_EVENT_WAL_RECEIVER_MAIN);
now = GetCurrentTimestamp();
if (rc & WL_LATCH_SET)
{
ResetLatch(MyLatch);
@ -550,34 +588,19 @@ WalReceiverMain(void)
* Check if time since last receive from primary 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)
if (now >= wakeup[WALRCV_WAKEUP_TERMINATE])
ereport(ERROR,
(errcode(ERRCODE_CONNECTION_FAILURE),
errmsg("terminating walreceiver due to timeout")));
/*
* We didn't receive anything new, for half of
* receiver replication timeout. Ping the server.
* 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)
if (now >= wakeup[WALRCV_WAKEUP_PING])
{
requestReply = true;
ping_sent = true;
}
}
wakeup[WALRCV_WAKEUP_PING] = PG_INT64_MAX;
}
XLogWalRcvSendReply(requestReply, requestReply);
@ -1076,7 +1099,6 @@ XLogWalRcvSendReply(bool force, bool requestReply)
static XLogRecPtr writePtr = 0;
static XLogRecPtr flushPtr = 0;
XLogRecPtr applyPtr;
static TimestampTz sendTime = 0;
TimestampTz now;
/*
@ -1101,10 +1123,11 @@ XLogWalRcvSendReply(bool force, bool requestReply)
if (!force
&& writePtr == LogstreamResult.Write
&& flushPtr == LogstreamResult.Flush
&& !TimestampDifferenceExceeds(sendTime, now,
wal_receiver_status_interval * 1000))
&& now < wakeup[WALRCV_WAKEUP_REPLY])
return;
sendTime = now;
/* Make sure we wake up when it's time to send another reply. */
WalRcvComputeNextWakeup(WALRCV_WAKEUP_REPLY, now);
/* Construct a new message */
writePtr = LogstreamResult.Write;
@ -1149,7 +1172,6 @@ XLogWalRcvSendHSFeedback(bool immed)
catalog_xmin_epoch;
TransactionId xmin,
catalog_xmin;
static TimestampTz sendTime = 0;
/* initially true so we always send at least one feedback message */
static bool primary_has_standby_xmin = true;
@ -1165,16 +1187,12 @@ XLogWalRcvSendHSFeedback(bool immed)
/* Get current timestamp. */
now = GetCurrentTimestamp();
if (!immed)
{
/*
* Send feedback at most once per wal_receiver_status_interval.
*/
if (!TimestampDifferenceExceeds(sendTime, now,
wal_receiver_status_interval * 1000))
/* Send feedback at most once per wal_receiver_status_interval. */
if (!immed && now < wakeup[WALRCV_WAKEUP_HSFEEDBACK])
return;
sendTime = now;
}
/* Make sure we wake up when it's time to send feedback again. */
WalRcvComputeNextWakeup(WALRCV_WAKEUP_HSFEEDBACK, now);
/*
* If Hot Standby is not yet accepting connections there is nothing to
@ -1285,6 +1303,45 @@ ProcessWalSndrMessage(XLogRecPtr walEnd, TimestampTz sendTime)
}
}
/*
* Compute the next wakeup time for a given wakeup reason. Can be called to
* initialize a wakeup time, to adjust it for the next wakeup, or to
* reinitialize it when GUCs have changed.
*/
static void
WalRcvComputeNextWakeup(WalRcvWakeupReason reason, TimestampTz now)
{
switch (reason)
{
case WALRCV_WAKEUP_TERMINATE:
if (wal_receiver_timeout <= 0)
wakeup[reason] = PG_INT64_MAX;
else
wakeup[reason] = now + wal_receiver_timeout * INT64CONST(1000);
break;
case WALRCV_WAKEUP_PING:
if (wal_receiver_timeout <= 0)
wakeup[reason] = PG_INT64_MAX;
else
wakeup[reason] = now + (wal_receiver_timeout / 2) * INT64CONST(1000);
break;
case WALRCV_WAKEUP_HSFEEDBACK:
if (!hot_standby_feedback || wal_receiver_status_interval <= 0)
wakeup[reason] = PG_INT64_MAX;
else
wakeup[reason] = now + wal_receiver_status_interval * INT64CONST(1000000);
break;
case WALRCV_WAKEUP_REPLY:
if (wal_receiver_status_interval <= 0)
wakeup[reason] = PG_INT64_MAX;
else
wakeup[reason] = now + wal_receiver_status_interval * INT64CONST(1000000);
break;
default:
break;
}
}
/*
* Wake up the walreceiver main loop.
*

1
src/tools/pgindent/typedefs.list
Unescape View File

@ -2927,6 +2927,7 @@ WALInsertLock
WALInsertLockPadded
WALOpenSegment
WALReadError
WalRcvWakeupReason
WALSegmentCloseCB
WALSegmentContext
WALSegmentOpenCB

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