Add a server version check to pg_basebackup and pg_receivexlog.

These programs don't work against 9.0 or earlier servers, so check that when
the connection is made. That's better than a cryptic error message you got
before.

Also, these programs won't work with a 9.3 server, because the WAL streaming
protocol was changed in a non-backwards-compatible way. As a general rule,
we don't make any guarantee that an old client will work with a new server,
so check that. However, allow a 9.1 client to connect to a 9.2 server, to
avoid breaking environments that currently work; a 9.1 client happens to
work with a 9.2 server, even though we didn't make any great effort to
ensure that.

This patch is for the 9.1 and 9.2 branches, I'll commit a similar patch to
master later. Although this isn't a critical bug fix, it seems safe enough
to back-patch. The error message you got when connecting to a 9.3devel
server without this patch was cryptic enough to warrant backpatching.

diff --git a/src/bin/pg_basebackup/pg_basebackup.c b/src/bin/pg_basebackup/pg_basebackup.c
index 472df3a1fbfb2dc8fee7c26b326df82f396ed5f2..d68e742920c7dc52e05d28cb200b32091c453202 100644 (file)
--- a/src/bin/pg_basebackup/pg_basebackup.c
+++ b/src/bin/pg_basebackup/pg_basebackup.c
@@ -816,12 +816,33 @@ BaseBackup(void)
        int                     i;
        char            xlogstart[64];
        char            xlogend[64];
+       int                     minServerMajor,
+                               maxServerMajor;
+       int                     serverMajor;
 
        /*
         * Connect in replication mode to the server
         */
        conn = GetConnection();
 
+       /*
+        * Check server version. BASE_BACKUP command was introduced in 9.1, so
+        * we can't work with servers older than 9.1. We don't officially support
+        * servers newer than the client, but the 9.1 version happens to work with
+        * a 9.2 server. This version check was added to 9.1 branch in a minor
+        * release, so allow connecting to a 9.2 server, to avoid breaking
+        * environments that worked before this version check was added.
+        */
+       minServerMajor = 901;
+       maxServerMajor = 902;
+       serverMajor = PQserverVersion(conn) / 100;
+       if (serverMajor < minServerMajor || serverMajor > maxServerMajor)
+       {
+               fprintf(stderr, _("%s: unsupported server version %s\n"),
+                               progname, PQparameterStatus(conn, "server_version"));
+               disconnect_and_exit(1);
+       }
+
        /*
         * Start the actual backup
         */