Re: [Qemu-devel] [PATCH v3 2/2] qemu-ga: sample fsfreeze hooks

[Tomoki Sekiyama]

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

Signed-off-by: Tomoki Sekiyama <address@hidden>
---
 docs/qemu-guest-agent/fsfreeze-hook                |   31 +++++++++++++
 .../fsfreeze-hook.d.sample/mysql-flush.sh          |   47 ++++++++++++++++++++
 2 files changed, 78 insertions(+)
 create mode 100755 docs/qemu-guest-agent/fsfreeze-hook
 create mode 100755 docs/qemu-guest-agent/fsfreeze-hook.d.sample/mysql-flush.sh

diff --git a/docs/qemu-guest-agent/fsfreeze-hook 
b/docs/qemu-guest-agent/fsfreeze-hook
new file mode 100755
index 0000000..319f68c
--- /dev/null
+++ b/docs/qemu-guest-agent/fsfreeze-hook
@@ -0,0 +1,31 @@
+#!/bin/sh
+
+# This script is executed when a guest agent receives fsfreeze-freeze and
+# fsfreeze-thaw command, if it is specified in --fsfreeze-hook (-F)
+# option of qemu-ga or placed in default path (/etc/qemu/fsfreeze-hook).
+# When the agent receives fsfreeze-freeze request, this script is issued with
+# "freeze" argument before the filesystem is freezed. And for fsfreeze-thaw
+# request, it is issued with "thaw" argument after filesystem is thawed.
+
+LOGFILE=/var/log/qga-fsfreeze-hook.log
+FSFREEZE_D=$(dirname -- "$0")/fsfreeze-hook.d
+
+# Check whether file $1 is a backup or rpm-generated file and should be ignored
+is_ignored_file() {
+    case "$1" in
+        *~ | *.bak | *.orig | *.rpmnew | *.rpmorig | *.rpmsave)
+            return 0 ;;
+    esac
+    return 1
+}
+
+# Iterate executables in directory "fsfreeze-hook.d" with the specified args
+[ ! -d "$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
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 | $MYSQL &
+        # wait until every block is flushed
+        while [ "$(echo 'SHOW STATUS LIKE "Key_blocks_not_flushed"' |\
+                 $MYSQL | tail -1 | cut -f 2)" -gt 0 ]; do
+            sleep 1
+        done
+        # for InnoDB, wait until every log is flushed
+        INNODB_STATUS=$(mktemp /tmp/mysql-flush.XXXXXX)
+        [ $? -ne 0 ] && exit 2
+        trap "rm -f $INNODB_STATUS" SIGINT
+        while :; do
+            printf "SHOW ENGINE INNODB STATUS \\G" | $MYSQL > $INNODB_STATUS
+            LOG_CURRENT=$(grep 'Log sequence number' $INNODB_STATUS |\
+                          tr -s ' ' | cut -d' ' -f4)
+            LOG_FLUSHED=$(grep 'Log flushed up to' $INNODB_STATUS |\
+                          tr -s ' ' | cut -d' ' -f5)
+            [ "$LOG_CURRENT" = "$LOG_FLUSHED" ] && break
+            sleep 1
+        done
+        rm -f $INNODB_STATUS
+        ;;
+
+    thaw)
+        [ ! -p $FIFO ] && exit 1
+        echo > $FIFO
+        rm -f $FIFO
+        ;;
+esac
+