On Tue, 07 Jan 2020 15:57:29 +0900 (JST)
Kyotaro Horiguchi <horikyota....@gmail.com> wrote:
> At Mon, 23 Dec 2019 15:38:16 +0100, Jehan-Guillaume de Rorthais
> <j...@dalibo.com> wrote in
> > 1. we could decide to remove this filter to expose the data even when no
> > wal receiver is active. It's the same behavior than pg_stat_subscription
> > view. It could introduce regression from tools point of view, but adds some
> > useful information. I would vote 0 for it.
>
> A subscription exists since it is defined and regardless whether it is
> active or not. It is strange that we see a line in the view if
> replication is not configured. But it is reasonable to show if it is
> configured. We could do that by checking PrimaryConnInfo. (I would
> vote +0.5 for it).
Thanks. I put this on hold for now, I'm waiting for some more opinons as
there's no strong position yet.
> > 2. we could extend it with new replayed lsn/tli fields. I would vote +1 for
> > it.
>
> +1. As of now a walsender lives for just one timeline, because it ends
> for disconnection from walsender when the master moves to a new
> timeline. That being said, we already have the columns for TLI for
> both starting and received-up-to LSN so we would need it also for
> replayed LSN for a consistent looking.
I added applied_lsn and applied_tli to the pg_stat_get_wal_receiver function
output columns.
However, note that applying xlog is the responsibility of the startup process,
not the wal receiver one. Is it OK that pg_stat_get_wal_receiver
returns stats not directly related to the wal receiver?
> The function is going to show "streaming" but conninfo is not shown
> until connection establishes. That state is currently hidden by the
> PID filtering of the view. We might need to keep the WALRCV_STARTING
> state until connection establishes.
Indeed, fixed.
> sender_host and sender_port have bogus values until connection is
> actually established when conninfo is changed. They as well as
> conninfo should be hidden until connection is established, too, I
> think.
Fixed as well.
Please find the new version of the patch in attachment.
Thank you for your review!
>From d1e5d6c33e193626f05911462e66a6c96366bfa6 Mon Sep 17 00:00:00 2001
From: Jehan-Guillaume de Rorthais <j...@dalibo.com>
Date: Tue, 31 Dec 2019 18:29:13 +0100
Subject: [PATCH] Always expose available stats from wal receiver
Makes admin function pg_stat_get_wal_receiver() return available data
from WalRcv in shared memory, whatever the state of the wal receiver
process.
This allows supervision or HA tools to gather various physical
replication stats even when the wal receiver is stopped. For example,
the latest timeline the wal receiver was receiving before shutting
down.
The behavior of the pg_stat_wal_receiver view has been kept to avoid
regressions: it returns no row when the wal receiver is shut down.
---
src/backend/replication/walreceiver.c | 61 ++++++++++++----------
src/include/catalog/pg_proc.dat | 6 +--
src/test/recovery/t/004_timeline_switch.pl | 12 ++++-
3 files changed, 48 insertions(+), 31 deletions(-)
diff --git a/src/backend/replication/walreceiver.c b/src/backend/replication/walreceiver.c
index a5e85d32f3..e4273b7f55 100644
--- a/src/backend/replication/walreceiver.c
+++ b/src/backend/replication/walreceiver.c
@@ -226,7 +226,6 @@ WalReceiverMain(void)
}
/* Advertise our PID so that the startup process can kill us */
walrcv->pid = MyProcPid;
- walrcv->walRcvState = WALRCV_STREAMING;
/* Fetch information required to start streaming */
walrcv->ready_to_display = false;
@@ -295,6 +294,7 @@ WalReceiverMain(void)
strlcpy((char *) walrcv->sender_host, sender_host, NI_MAXHOST);
walrcv->sender_port = sender_port;
+ walrcv->walRcvState = WALRCV_STREAMING;
walrcv->ready_to_display = true;
SpinLockRelease(&walrcv->mutex);
@@ -1368,6 +1368,8 @@ pg_stat_get_wal_receiver(PG_FUNCTION_ARGS)
TimeLineID receive_start_tli;
XLogRecPtr received_lsn;
TimeLineID received_tli;
+ XLogRecPtr applied_lsn;
+ TimeLineID applied_tli;
TimestampTz last_send_time;
TimestampTz last_receipt_time;
XLogRecPtr latest_end_lsn;
@@ -1379,6 +1381,7 @@ pg_stat_get_wal_receiver(PG_FUNCTION_ARGS)
/* Take a lock to ensure value consistency */
SpinLockAcquire(&WalRcv->mutex);
+ applied_lsn = GetXLogReplayRecPtr(&applied_tli);
pid = (int) WalRcv->pid;
ready_to_display = WalRcv->ready_to_display;
state = WalRcv->walRcvState;
@@ -1396,13 +1399,6 @@ pg_stat_get_wal_receiver(PG_FUNCTION_ARGS)
strlcpy(conninfo, (char *) WalRcv->conninfo, sizeof(conninfo));
SpinLockRelease(&WalRcv->mutex);
- /*
- * No WAL receiver (or not ready yet), just return a tuple with NULL
- * values
- */
- if (pid == 0 || !ready_to_display)
- PG_RETURN_NULL();
-
/* determine result type */
if (get_call_result_type(fcinfo, NULL, &tupdesc) != TYPEFUNC_COMPOSITE)
elog(ERROR, "return type must be a row type");
@@ -1411,7 +1407,10 @@ pg_stat_get_wal_receiver(PG_FUNCTION_ARGS)
nulls = palloc0(sizeof(bool) * tupdesc->natts);
/* Fetch values */
- values[0] = Int32GetDatum(pid);
+ if (pid == 0)
+ nulls[0] = true;
+ else
+ values[0] = Int32GetDatum(pid);
if (!is_member_of_role(GetUserId(), DEFAULT_ROLE_READ_ALL_STATS))
{
@@ -1436,38 +1435,46 @@ pg_stat_get_wal_receiver(PG_FUNCTION_ARGS)
else
values[4] = LSNGetDatum(received_lsn);
values[5] = Int32GetDatum(received_tli);
- if (last_send_time == 0)
+ if (XLogRecPtrIsInvalid(applied_lsn)) {
nulls[6] = true;
- else
- values[6] = TimestampTzGetDatum(last_send_time);
- if (last_receipt_time == 0)
nulls[7] = true;
- else
- values[7] = TimestampTzGetDatum(last_receipt_time);
- if (XLogRecPtrIsInvalid(latest_end_lsn))
+ }
+ else {
+ values[6] = LSNGetDatum(applied_lsn);
+ values[7] = Int32GetDatum(applied_tli);
+ }
+ if (last_send_time == 0)
nulls[8] = true;
else
- values[8] = LSNGetDatum(latest_end_lsn);
- if (latest_end_time == 0)
+ values[8] = TimestampTzGetDatum(last_send_time);
+ if (last_receipt_time == 0)
nulls[9] = true;
else
- values[9] = TimestampTzGetDatum(latest_end_time);
- if (*slotname == '\0')
+ values[9] = TimestampTzGetDatum(last_receipt_time);
+ if (XLogRecPtrIsInvalid(latest_end_lsn))
nulls[10] = true;
else
- values[10] = CStringGetTextDatum(slotname);
- if (*sender_host == '\0')
+ values[10] = LSNGetDatum(latest_end_lsn);
+ if (latest_end_time == 0)
nulls[11] = true;
else
- values[11] = CStringGetTextDatum(sender_host);
- if (sender_port == 0)
+ values[11] = TimestampTzGetDatum(latest_end_time);
+ if (*slotname == '\0')
nulls[12] = true;
else
- values[12] = Int32GetDatum(sender_port);
- if (*conninfo == '\0')
+ values[12] = CStringGetTextDatum(slotname);
+ if (*sender_host == '\0' || !ready_to_display)
nulls[13] = true;
else
- values[13] = CStringGetTextDatum(conninfo);
+ values[13] = CStringGetTextDatum(sender_host);
+ if (sender_port == 0 || !ready_to_display)
+ nulls[14] = true;
+ else
+ values[14] = Int32GetDatum(sender_port);
+ if (*conninfo == '\0' || !ready_to_display)
+ nulls[15] = true;
+ else
+ values[15] = CStringGetTextDatum(conninfo);
}
/* Returns the record as Datum */
diff --git a/src/include/catalog/pg_proc.dat b/src/include/catalog/pg_proc.dat
index fcf2a1214c..f6a6bc5b7b 100644
--- a/src/include/catalog/pg_proc.dat
+++ b/src/include/catalog/pg_proc.dat
@@ -5180,9 +5180,9 @@
{ oid => '3317', descr => 'statistics: information about WAL receiver',
proname => 'pg_stat_get_wal_receiver', proisstrict => 'f', provolatile => 's',
proparallel => 'r', prorettype => 'record', proargtypes => '',
- proallargtypes => '{int4,text,pg_lsn,int4,pg_lsn,int4,timestamptz,timestamptz,pg_lsn,timestamptz,text,text,int4,text}',
- proargmodes => '{o,o,o,o,o,o,o,o,o,o,o,o,o,o}',
- proargnames => '{pid,status,receive_start_lsn,receive_start_tli,received_lsn,received_tli,last_msg_send_time,last_msg_receipt_time,latest_end_lsn,latest_end_time,slot_name,sender_host,sender_port,conninfo}',
+ proallargtypes => '{int4,text,pg_lsn,int4,pg_lsn,int4,pg_lsn,int4,timestamptz,timestamptz,pg_lsn,timestamptz,text,text,int4,text}',
+ proargmodes => '{o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o}',
+ proargnames => '{pid,status,receive_start_lsn,receive_start_tli,received_lsn,received_tli,applied_lsn,applied_tli,last_msg_send_time,last_msg_receipt_time,latest_end_lsn,latest_end_time,slot_name,sender_host,sender_port,conninfo}',
prosrc => 'pg_stat_get_wal_receiver' },
{ oid => '6118', descr => 'statistics: information about subscription',
proname => 'pg_stat_get_subscription', proisstrict => 'f', provolatile => 's',
diff --git a/src/test/recovery/t/004_timeline_switch.pl b/src/test/recovery/t/004_timeline_switch.pl
index 7e952d3667..cdcdd2d981 100644
--- a/src/test/recovery/t/004_timeline_switch.pl
+++ b/src/test/recovery/t/004_timeline_switch.pl
@@ -6,7 +6,7 @@ use warnings;
use File::Path qw(rmtree);
use PostgresNode;
use TestLib;
-use Test::More tests => 2;
+use Test::More tests => 4;
$ENV{PGDATABASE} = 'postgres';
@@ -37,6 +37,11 @@ $node_master->safe_psql('postgres',
$node_master->wait_for_catchup($node_standby_1, 'replay',
$node_master->lsn('write'));
+# Check received timeline from pg_stat_get_wal_receiver() on standby 1
+my $node_standby_1_lsn = $node_standby_1->safe_psql('postgres',
+ 'SELECT received_tli FROM pg_stat_get_wal_receiver()');
+is($node_standby_1_lsn, 1, 'check received timeline on standby 1');
+
# Stop and remove master
$node_master->teardown_node;
@@ -66,3 +71,8 @@ $node_standby_1->wait_for_catchup($node_standby_2, 'replay',
my $result =
$node_standby_2->safe_psql('postgres', "SELECT count(*) FROM tab_int");
is($result, qq(2000), 'check content of standby 2');
+
+# Check received timeline from pg_stat_get_wal_receiver() on standby 2
+my $node_standby_2_lsn = $node_standby_2->safe_psql('postgres',
+ 'SELECT received_tli FROM pg_stat_get_wal_receiver()');
+is($node_standby_2_lsn, 2, 'check received timeline on standby 2');
--
2.20.1
