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walreceiver: tweak pg_stat_wal_receiver behavior

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There are two problems in the original coding: one is that if one
walreceiver process exits, the ready_to_display flag remains set in
shared memory, exposing the conninfo of the next walreceiver before
obfuscating.  Fix by having WalRcvDie reset the flag.

Second, the sleep-and-retry behavior that waited until walreceiver had
set ready_to_display wasn't liked; the preference is to have it return
no data instead, so let's do that.

Bugs in 9ed551e0a reported by Fujii Masao and Michël Paquier.

Author: Michaël Paquier
This commit is contained in:
Alvaro Herrera 2016-07-01 13:53:46 -04:00
parent 9e703987a8
commit 1bdae16fca
1 changed files with 6 additions and 16 deletions
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22
src/backend/replication/walreceiver.c
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@ -246,6 +246,7 @@ WalReceiverMain(void)
walrcv->walRcvState = WALRCV_STREAMING;
/* Fetch information required to start streaming */
walrcv->ready_to_display = false;
strlcpy(conninfo, (char *) walrcv->conninfo, MAXCONNINFO);
strlcpy(slotname, (char *) walrcv->slotname, NAMEDATALEN);
startpoint = walrcv->receiveStart;
@ -770,6 +771,7 @@ WalRcvDie(int code, Datum arg)
Assert(walrcv->pid == MyProcPid);
walrcv->walRcvState = WALRCV_STOPPED;
walrcv->pid = 0;
walrcv->ready_to_display = false;
SpinLockRelease(&walrcv->mutex);
/* Terminate the connection gracefully. */
@ -1343,24 +1345,12 @@ pg_stat_get_wal_receiver(PG_FUNCTION_ARGS)
char *slotname;
char *conninfo;
/* No WAL receiver, just return a tuple with NULL values */
if (walrcv->pid == 0)
PG_RETURN_NULL();
/*
* Users attempting to read this data mustn't be shown security sensitive
* data, so sleep until everything has been properly obfuscated.
* No WAL receiver (or not ready yet), just return a tuple with NULL
* values
*/
retry:
SpinLockAcquire(&walrcv->mutex);
if (!walrcv->ready_to_display)
{
SpinLockRelease(&walrcv->mutex);
CHECK_FOR_INTERRUPTS();
pg_usleep(1000);
goto retry;
}
SpinLockRelease(&walrcv->mutex);
if (walrcv->pid == 0 || !walrcv->ready_to_display)
PG_RETURN_NULL();
/* determine result type */
if (get_call_result_type(fcinfo, NULL, &tupdesc) != TYPEFUNC_COMPOSITE)