[Top][All Lists]
[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]
Re: [Qemu-devel] [PATCH v4 2/2] qemu-ga: sample fsfreeze hooks
From: |
Tomoki Sekiyama |
Subject: |
Re: [Qemu-devel] [PATCH v4 2/2] qemu-ga: sample fsfreeze hooks |
Date: |
Mon, 26 Nov 2012 20:49:17 +0900 |
User-agent: |
Mozilla/5.0 (Windows NT 5.1; rv:16.0) Gecko/20121005 Thunderbird/16.0 |
On 2012/11/23 1:03, Luiz Capitulino wrote:
> On Thu, 22 Nov 2012 11:15:49 +0900
> Tomoki Sekiyama <address@hidden> wrote:
>
>> Adds sample hook scripts for --fsfreeze-hook option of qemu-ga.
>> - fsfreeze-hook : execute scripts in fsfreeze-hook.d/
>> - fsfreeze-hook.d.sample/mysql-flush.sh : quiesce MySQL before snapshot
<snip>
>> +# Iterate executables in directory "fsfreeze-hook.d" with the specified args
>> +[ ! -d "$FSFREEZE_D" ] && exit 1
>> +for file in "$FSFREEZE_D"/* ; do
>> + is_ignored_file "$file" && continue
>> + [ -x "$file" ] || continue
>> + echo "$(date): execute $file $@" >>$LOGFILE
>> + "$file" "$@" >>$LOGFILE 2>&1
>> + STATUS=$?
>> + echo "$(date): $file finished with status=$STATUS" >>$LOGFILE
>> +done
>
> execute_fsfreeze_hook() will fail the freeze process if this script fails. Two
> comments:
>
> 1. Do we want to fail the freeze process if one of the sub-scripts fails?
> If yes, then we have to exit 1 in the first failure
I originally thought the hooks are optional; even they failed, filesystem-level
consistency are still kept in the snapshot.
However, if we are going to fail fsfreeze process by one of sub-scripts'
failure, we also need to notify scripts which already succeeded to pre-freeze
to thaw (or abort) freezing, before exit 1 here.
> 2. The exit status of the script will echo's exit status. I doubt we want
> that
Do you mean $STATUS (not $status) is specialized in some shell environments?
>> diff --git a/docs/qemu-guest-agent/fsfreeze-hook.d.sample/mysql-flush.sh
>> b/docs/qemu-guest-agent/fsfreeze-hook.d.sample/mysql-flush.sh
>> new file mode 100755
>> index 0000000..e6d7998
>> --- /dev/null
>> +++ b/docs/qemu-guest-agent/fsfreeze-hook.d.sample/mysql-flush.sh
>> @@ -0,0 +1,47 @@
>> +#!/bin/sh
>> +
>> +# Flush MySQL tables to the disk before the filesystem is freezed.
>> +# At the same time, this keeps a read lock while the filesystem is freezed
>> +# in order to avoid write accesses by the other clients.
>> +
>> +MYSQL="mysql -uroot" #"-prootpassword"
>> +FIFO=/tmp/mysql-flush.fifo
>> +
>> +flush_and_wait() {
>> + printf "FLUSH TABLES WITH READ LOCK \\G\n"
>> + read < $FIFO
>> + printf "UNLOCK TABLES \\G\n"
>> +}
>> +
>> +case "$1" in
>> + freeze)
>> + mkfifo $FIFO || exit 1
>> + flush_and_wait | $MYSQL &
>
> Honest question: what happens if I don't have mysql installed?
Ah OK, availability of mysql should be checked in advance.
Thanks,
--
Tomoki Sekiyama <address@hidden>
Linux Technology Center
Hitachi, Ltd., Yokohama Research Laboratory