pre/post snapshot polishing. still needs test-scripts

README.md

@@ -279,19 +279,6 @@ root@ws1:~# zfs-autobackup test --verbose
 
 This also allows you to make several snapshots during the day, but only backup the data at night when the server is not busy.
 
-## Running custom commands before and after snapshotting
-
-If you need, e.g. to quiesce a couple of mysql databases to make on-disk data consistent before snapshotting, try:
-
-```sh
-zfs-autobackup \
-    --pre-snapshot-cmd 'daemon -f jexec mysqljail1 mysql -s -e "set autocommit=0;flush logs;flush tables with read lock;\\! echo \$\$ > /tmp/mysql_lock.pid && sleep 60"' \
-    --pre-snapshot-cmd 'daemon -f jexec mysqljail2 mysql -s -e "set autocommit=0;flush logs;flush tables with read lock;\\! echo \$\$ > /tmp/mysql_lock.pid && sleep 60"' \
-    --post-snapshot-cmd 'pkill -F /jails/mysqljail1/tmp/mysql_lock.pid' \
-    --post-snapshot-cmd 'pkill -F /jails/mysqljail2/tmp/mysql_lock.pid' \
-    test
-```
-
 ## Thinning out obsolete snapshots
 
 The thinner is the thing that destroys old snapshots on the source and target.
@@ -430,6 +417,25 @@ zfs send -> send buffer -> custom send pipes -> compression -> transfer rate lim
 #### On the receiving side:
 decompression -> custom recv pipes -> buffer -> zfs recv
 
+## Running custom commands before and after snapshotting
+
+If you need, e.g. to quiesce a couple of mysql databases to make on-disk data consistent before snapshotting, you can use the `--pre-snapshot-cmd` and `--post-snapshot-cmd` options.
+
+For example:
+
+```sh
+zfs-autobackup \
+    --pre-snapshot-cmd 'daemon -f jexec mysqljail1 mysql -s -e "set autocommit=0;flush logs;flush tables with read lock;\\! echo \$\$ > /tmp/mysql_lock.pid && sleep 60"' \
+    --pre-snapshot-cmd 'daemon -f jexec mysqljail2 mysql -s -e "set autocommit=0;flush logs;flush tables with read lock;\\! echo \$\$ > /tmp/mysql_lock.pid && sleep 60"' \
+    --post-snapshot-cmd 'pkill -F /jails/mysqljail1/tmp/mysql_lock.pid' \
+    --post-snapshot-cmd 'pkill -F /jails/mysqljail2/tmp/mysql_lock.pid' \
+    backupfs1
+```
+
+The post-snapshot commands are ALWAYS executed, even if a pre-snapshot command or the actual snapshot fail.
+
+A failure of a post-snapshot command is non-fatal and will be ignored. The remaining post-snapshot commands wont be executed in that case.
+
 ## Tips
 
 * Use ```--debug``` if something goes wrong and you want to see the commands that are executed. This will also stop at the first error.

zfs_autobackup/ZfsAutobackup.py

@@ -511,8 +511,8 @@ class ZfsAutobackup:
                 self.set_title("Snapshotting")
                 source_node.consistent_snapshot(source_datasets, source_node.new_snapshotname(),
                                                 min_changed_bytes=self.args.min_change,
-                                                pre_snapshot_cmd=self.args.pre_snapshot_cmd,
+                                                pre_snapshot_cmds=self.args.pre_snapshot_cmd,
-                                                post_snapshot_cmd=self.args.post_snapshot_cmd)
+                                                post_snapshot_cmds=self.args.post_snapshot_cmd)
 
             ################# sync
             # if target is specified, we sync the datasets, otherwise we just thin the source. (e.g. snapshot mode)

zfs_autobackup/ZfsNode.py

@@ -162,7 +162,7 @@ class ZfsNode(ExecuteNode):
         """determine uniq new snapshotname"""
         return self.backup_name + "-" + time.strftime("%Y%m%d%H%M%S")
 
-    def consistent_snapshot(self, datasets, snapshot_name, min_changed_bytes, pre_snapshot_cmd=[], post_snapshot_cmd=[]):
+    def consistent_snapshot(self, datasets, snapshot_name, min_changed_bytes, pre_snapshot_cmds=[], post_snapshot_cmds=[]):
         """create a consistent (atomic) snapshot of specified datasets, per pool.
         """
 
@@ -193,7 +193,7 @@ class ZfsNode(ExecuteNode):
             return
 
         try:
-            for cmd in pre_snapshot_cmd:
+            for cmd in pre_snapshot_cmds:
                 self.verbose("Running pre-snapshot-cmd")
                 self.run(cmd=shlex.split(cmd), readonly=False)
 
@@ -207,9 +207,15 @@ class ZfsNode(ExecuteNode):
                 self.run(cmd, readonly=False)
 
         finally:
-            for cmd in post_snapshot_cmd:
+            for cmd in post_snapshot_cmds:
                 self.verbose("Running post-snapshot-cmd")
-                self.run(cmd=shlex.split(cmd), readonly=False, valid_exitcodes=[])
+                try:
+                    self.run(cmd=shlex.split(cmd), readonly=False)
+                except Exception as e:
+                    pass
+                    self.warning("Post snapshot command failed, ignoring.")
+
+
 
     def selected_datasets(self, exclude_received, exclude_paths):
         """determine filesystems that should be backed up by looking at the special autobackup-property, systemwide