From 5f374fe7a83304fd339789da22599bd102dac9e5 Mon Sep 17 00:00:00 2001
From: Robert Haas <rhaas@postgresql.org>
Date: Fri, 19 May 2017 16:19:51 -0400
Subject: [PATCH] libpq: Try next host if one of them times out.
If one host in a multi-host connection string times out, move on to
the next specified host instead of giving up entirely.
Takayuki Tsunakawa, reviewed by Michael Paquier. I added
a minor adjustment to the documentation.
Discussion: http://postgr.es/m/0A3221C70F24FB45833433255569204D1F6F42F5@G01JPEXMBYT05
---
doc/src/sgml/libpq.sgml | 7 ++++---
src/interfaces/libpq/fe-connect.c | 29 +++++++++++++++++++++++++----
src/interfaces/libpq/fe-misc.c | 10 ++++------
3 files changed, 33 insertions(+), 13 deletions(-)
diff --git a/doc/src/sgml/libpq.sgml b/doc/src/sgml/libpq.sgml
index d20d3140821..493cc12d61e 100644
--- a/doc/src/sgml/libpq.sgml
+++ b/doc/src/sgml/libpq.sgml
@@ -1041,9 +1041,10 @@ postgresql://%2Fvar%2Flib%2Fpostgresql/dbname
string). Zero or not specified means wait indefinitely. It is not
recommended to use a timeout of less than 2 seconds.
This timeout applies separately to each connection attempt.
- For example, if you specify two hosts and both of them are unreachable,
- and <literal>connect_timeout</> is 5, the total time spent waiting for a
- connection might be up to 10 seconds.
+ For example, if you specify two hosts and <literal>connect_timeout</>
+ is 5, each host will time out if no connection is made within 5
+ seconds, so the total time spent waiting for a connection might be
+ up to 10 seconds.
</para>
</listitem>
</varlistentry>
diff --git a/src/interfaces/libpq/fe-connect.c b/src/interfaces/libpq/fe-connect.c
index 8e3ef4b9f75..f2c9bf7a883 100644
--- a/src/interfaces/libpq/fe-connect.c
+++ b/src/interfaces/libpq/fe-connect.c
@@ -1720,6 +1720,7 @@ connectDBComplete(PGconn *conn)
{
PostgresPollingStatusType flag = PGRES_POLLING_WRITING;
time_t finish_time = ((time_t) -1);
+ int timeout = 0;
if (conn == NULL || conn->status == CONNECTION_BAD)
return 0;
@@ -1729,8 +1730,7 @@ connectDBComplete(PGconn *conn)
*/
if (conn->connect_timeout != NULL)
{
- int timeout = atoi(conn->connect_timeout);
-
+ timeout = atoi(conn->connect_timeout);
if (timeout > 0)
{
/*
@@ -1745,6 +1745,8 @@ connectDBComplete(PGconn *conn)
for (;;)
{
+ int ret = 0;
+
/*
* Wait, if necessary. Note that the initial state (just after
* PQconnectStart) is to wait for the socket to select for writing.
@@ -1761,7 +1763,8 @@ connectDBComplete(PGconn *conn)
return 1; /* success! */
case PGRES_POLLING_READING:
- if (pqWaitTimed(1, 0, conn, finish_time))
+ ret = pqWaitTimed(1, 0, conn, finish_time);
+ if (ret == -1)
{
conn->status = CONNECTION_BAD;
return 0;
@@ -1769,7 +1772,8 @@ connectDBComplete(PGconn *conn)
break;
case PGRES_POLLING_WRITING:
- if (pqWaitTimed(0, 1, conn, finish_time))
+ ret = pqWaitTimed(0, 1, conn, finish_time);
+ if (ret == -1)
{
conn->status = CONNECTION_BAD;
return 0;
@@ -1782,6 +1786,23 @@ connectDBComplete(PGconn *conn)
return 0;
}
+ if (ret == 1) /* connect_timeout elapsed */
+ {
+ /* If there are no more hosts, return (the error message is already set) */
+ if (++conn->whichhost >= conn->nconnhost)
+ {
+ conn->whichhost = 0;
+ conn->status = CONNECTION_BAD;
+ return 0;
+ }
+ /* Attempt connection to the next host, starting the connect_timeout timer */
+ pqDropConnection(conn, true);
+ conn->addr_cur = conn->connhost[conn->whichhost].addrlist;
+ conn->status = CONNECTION_NEEDED;
+ if (conn->connect_timeout != NULL)
+ finish_time = time(NULL) + timeout;
+ }
+
/*
* Now try to advance the state machine.
*/
diff --git a/src/interfaces/libpq/fe-misc.c b/src/interfaces/libpq/fe-misc.c
index 756c6d77790..1d6ea93a0a9 100644
--- a/src/interfaces/libpq/fe-misc.c
+++ b/src/interfaces/libpq/fe-misc.c
@@ -991,11 +991,9 @@ pqWait(int forRead, int forWrite, PGconn *conn)
/*
* pqWaitTimed: wait, but not past finish_time.
*
- * If finish_time is exceeded then we return failure (EOF). This is like
- * the response for a kernel exception because we don't want the caller
- * to try to read/write in that case.
- *
* finish_time = ((time_t) -1) disables the wait limit.
+ *
+ * Returns -1 on failure, 0 if the socket is readable/writable, 1 if it timed out.
*/
int
pqWaitTimed(int forRead, int forWrite, PGconn *conn, time_t finish_time)
@@ -1005,13 +1003,13 @@ pqWaitTimed(int forRead, int forWrite, PGconn *conn, time_t finish_time)
result = pqSocketCheck(conn, forRead, forWrite, finish_time);
if (result < 0)
- return EOF; /* errorMessage is already set */
+ return -1; /* errorMessage is already set */
if (result == 0)
{
printfPQExpBuffer(&conn->errorMessage,
libpq_gettext("timeout expired\n"));
- return EOF;
+ return 1;
}
return 0;
--
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