From 5f374fe7a83304fd339789da22599bd102dac9e5 Mon Sep 17 00:00:00 2001 From: Robert Haas 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 d20d314082..493cc12d61 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 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 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. diff --git a/src/interfaces/libpq/fe-connect.c b/src/interfaces/libpq/fe-connect.c index 8e3ef4b9f7..f2c9bf7a88 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 756c6d7779..1d6ea93a0a 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; -- 2.40.0