bk commit into 5.0 tree (guilhem:1.2031) BUG#2122

[guilhem]

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ChangeSet
  1.2031 05/10/11 15:01:24 guilhem@stripped +1 -0
  To help people avoid BUG#2122 "changing hostname confuses master or slave" until it's fixed,
  we now issue a warning (at slave's server startup only) when a relay log is named
  using the implicit hostname-relay-bin naming. Like we already do for binlogs.

  sql/slave.cc
    1.260 05/10/11 15:01:20 guilhem@stripped +18 -1
    To help people avoid BUG#2122 "changing hostname confuses master or slave" until it's fixed,
    we now issue a warning (at slave's server startup only) when a relay log is named
    using the implicit hostname-relay-bin naming. Like I had already added a similar startup warning
    when a binlog is named using the implicit hostname-bin naming.
    name_warning_sent is so that at most one warning per startup is sent.

# This is a BitKeeper patch.  What follows are the unified diffs for the
# set of deltas contained in the patch.  The rest of the patch, the part
# that BitKeeper cares about, is below these diffs.
# User:	guilhem
# Host:	gbichot3.local
# Root:	/home/mysql_src/mysql-5.0

--- 1.259/sql/slave.cc	2005-10-08 16:39:40 +02:00
+++ 1.260/sql/slave.cc	2005-10-11 15:01:20 +02:00
@@ -1722,9 +1722,26 @@
   {
     char buf[FN_REFLEN];
     const char *ln;
+    static bool name_warning_sent= 0;
     ln= rli->relay_log.generate_name(opt_relay_logname, "-relay-bin",
                                      1, buf);
-
+    /* We send the warning only at startup, not after every RESET SLAVE */
+    if (!opt_relay_logname && !opt_relaylog_index_name && !name_warning_sent)
+    {
+      /*
+        User didn't give us info to name the relay log index file.
+        Picking `hostname`-relay-bin.index like we do, causes replication to
+        fail if this slave's hostname is changed later. So, we would like to
+        instead require a name. But as we don't want to break many existing
+        setups, we only give warning, not error.
+      */
+      sql_print_warning("Neither --relay-log nor --relay-log-index were used;"
+                        " so replication "
+                        "may break when this MySQL server acts as a "
+                        "slave and has his hostname changed!! Please "
+                        "use '--relay-log=%s' to avoid this problem.", ln);
+      name_warning_sent= 1;
+    }
     /*
       note, that if open() fails, we'll still have index file open
       but a destructor will take care of that