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ctdb-recovery: Recovery lock setting can now include helper command

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The underlying change is to allow the cluster mutex argstring to
optionally contain a helper command.  When the argument string starts
with '!' then the first word is the helper command to run.  This is
now the standard way of changing the helper from the default.

CTDB_CLUSTER_MUTEX_HELPER show now only be used to change the location
of the default helper when testing.

Signed-off-by: Martin Schwenke <martin@meltin.net>
Reviewed-by: Amitay Isaacs <amitay@gmail.com>
This commit is contained in:
Martin Schwenke 2016-02-16 16:39:40 +11:00 committed by Amitay Isaacs
parent 918b0d9a9c
commit 46684867b1
5 changed files with 58 additions and 22 deletions
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6
ctdb/config/events.d/01.reclock
View File

@ -7,6 +7,12 @@
. $CTDB_BASE/functions
loadconfig
# If CTDB_RECOVERY_LOCK specifies a helper then exit because this
# script can't do anything useful.
case "$CTDB_RECOVERY_LOCK" in
!*) exit 0 ;;
esac
case "$1" in
init)
ctdb_counter_init

20
ctdb/doc/ctdb.7.xml
View File

@ -98,14 +98,26 @@
</para>
<para>
The recovery lock is implemented using a file residing in shared
storage (usually) on a cluster filesystem. To support a
recovery lock the cluster filesystem must support lock
coherence. See
By default, the recovery lock is implemented using a file
(specified by <parameter>CTDB_RECOVERY_LOCK</parameter>)
residing in shared storage (usually) on a cluster filesystem.
To support a recovery lock the cluster filesystem must support
lock coherence. See
<citerefentry><refentrytitle>ping_pong</refentrytitle>
<manvolnum>1</manvolnum></citerefentry> for more details.
</para>
<para>
The recovery lock can also be implemented using an arbitrary
cluster mutex call-out by using an exclamation point ('!') as
the first character of
<parameter>CTDB_RECOVERY_LOCK</parameter>. For example, a value
of <command>!/usr/local/bin/myhelper recovery</command> would
run the given helper with the specified arguments. See the
source code relating to cluster mutexes for clues about writing
call-outs.
</para>
<para>
If a cluster becomes partitioned (for example, due to a
communication failure) and a different recovery master is

7
ctdb/doc/ctdbd.1.xml
View File

@ -365,12 +365,11 @@
</varlistentry>
<varlistentry>
<term>--reclock=<parameter>FILE</parameter></term>
<term>--reclock=<parameter>LOCK</parameter></term>
<listitem>
<para>
FILE is the name of the recovery lock file, stored in
<emphasis>shared storage</emphasis>, that CTDB uses to
prevent split brains.
LOCK specifies the cluster-wide mutex used to detect and
prevent a partitioned cluster (or "split brain").
</para>
<para>
For information about the recovery lock please see the

8
ctdb/doc/ctdbd.conf.5.xml
View File

@ -379,10 +379,14 @@
</varlistentry>
<varlistentry>
<term>CTDB_RECOVERY_LOCK=<parameter>FILENAME</parameter></term>
<term>CTDB_RECOVERY_LOCK=<parameter>LOCK</parameter></term>
<listitem>
<para>
Defaults to
LOCK specifies the cluster-wide mutex used to detect and
prevent a partitioned cluster (or "split brain").
</para>
<para>
No default, but the default configuration file specifies
<filename>/some/place/on/shared/storage</filename>, which
should be change to a useful value. Corresponds to
<option>--reclock</option>.

39
ctdb/server/ctdb_recover.c
View File

@ -906,11 +906,21 @@ static bool cluster_mutex_helper_args(TALLOC_CTX *mem_ctx,
const char *argstring, char ***argv)
{
int nargs, i, ret, n;
bool is_command = false;
char **args = NULL;
char *strv = NULL;
char *t = NULL;
ret = strv_split(mem_ctx, &strv, argstring, " \t");
if (argstring != NULL && argstring[0] == '!') {
/* This is actually a full command */
is_command = true;
t = discard_const(&argstring[1]);
} else {
is_command = false;
t = discard_const(argstring);
}
ret = strv_split(mem_ctx, &strv, t, " \t");
if (ret != 0) {
DEBUG(DEBUG_ERR,
("Unable to parse mutex helper string \"%s\" (%s)\n",
@ -919,7 +929,8 @@ static bool cluster_mutex_helper_args(TALLOC_CTX *mem_ctx,
}
n = strv_count(strv);
args = talloc_array(mem_ctx, char *, n + 2);
args = talloc_array(mem_ctx, char *, n + (is_command ? 1 : 2));
if (args == NULL) {
DEBUG(DEBUG_ERR,(__location__ " out of memory\n"));
return false;
@ -927,17 +938,21 @@ static bool cluster_mutex_helper_args(TALLOC_CTX *mem_ctx,
nargs = 0;
if (!ctdb_set_helper("cluster mutex helper",
cluster_mutex_helper,
sizeof(cluster_mutex_helper),
"CTDB_CLUSTER_MUTEX_HELPER",
CTDB_HELPER_BINDIR, "ctdb_mutex_fcntl_helper")) {
DEBUG(DEBUG_ERR,("ctdb exiting with error: %s\n",
__location__
" Unable to set cluster mutex helper\n"));
exit(1);
if (! is_command) {
if (!ctdb_set_helper("cluster mutex helper",
cluster_mutex_helper,
sizeof(cluster_mutex_helper),
"CTDB_CLUSTER_MUTEX_HELPER",
CTDB_HELPER_BINDIR,
"ctdb_mutex_fcntl_helper")) {
DEBUG(DEBUG_ERR,("ctdb exiting with error: %s\n",
__location__
" Unable to set cluster mutex helper\n"));
exit(1);
}
args[nargs++] = cluster_mutex_helper;
}
args[nargs++] = cluster_mutex_helper;
t = NULL;
for (i = 0; i < n; i++) {