snapshot/scheduling: A cron based scheduler for snapshot scheduling

GlusterFS volume snapshot provides point-in-time copy
of a GlusterFS volume. Currently, GlusterFS volume
snapshots can be easily scheduled by setting up 
cron jobs on one of the nodes in the GlusterFS
trusted storage pool. This has a single point failure (SPOF),
as scheduled jobs can be missed if the node running the cron
jobs dies.

The solution to the above problems is addressed in this patch.
The snap_scheduler.py helper script expects the user to install
the argparse python module before using it.

Further details for the same are available at:

http://www.gluster.org/community/documentation/index.php/Features/Scheduling_of_Snapshot

Change-Id: I2c357af5b7d3e66f270d20eef50cdeecdcbe15c7
BUG: 1198027
Signed-off-by: Avra Sengupta <asengupt@redhat.com>
Signed-off-by: Aravinda VK <avishwan@redhat.com>
Reviewed-on: http://review.gluster.org/9788
Tested-by: Gluster Build System <jenkins@build.gluster.com>
Reviewed-by: Vijay Bellur <vbellur@redhat.com>

1 files changed, 146 insertions, 0 deletions

diff --git a/extras/snap_scheduler/gcron.py b/extras/snap_scheduler/gcron.py
new file mode 100755
index 00000000000..763eb1460b8
--- /dev/null
+++ b/extras/snap_scheduler/gcron.py
@@ -0,0 +1,146 @@
+#!/usr/bin/env python
+#
+# Copyright (c) 2015 Red Hat, Inc. <http://www.redhat.com>
+# This file is part of GlusterFS.
+#
+# This file is licensed to you under your choice of the GNU Lesser
+# General Public License, version 3 or any later version (LGPLv3 or
+# later), or the GNU General Public License, version 2 (GPLv2), in all
+# cases as published by the Free Software Foundation.
+
+from __future__ import print_function
+import subprocess
+import os
+import os.path
+import sys
+import time
+import logging
+import logging.handlers
+import fcntl
+
+
+GCRON_TASKS = "/var/run/gluster/snaps/shared_storage/glusterfs_snap_cron_tasks"
+GCRON_CROND_TASK = "/etc/cron.d/glusterfs_snap_cron_tasks"
+LOCK_FILE_DIR = "/var/run/gluster/snaps/shared_storage/lock_files/"
+log = logging.getLogger("gcron-logger")
+start_time = 0.0
+
+
+def initLogger(script_name):
+    log.setLevel(logging.DEBUG)
+    logFormat = "[%(asctime)s %(filename)s:%(lineno)s %(funcName)s] "\
+        "%(levelname)s %(message)s"
+    formatter = logging.Formatter(logFormat)
+
+    sh = logging.handlers.SysLogHandler()
+    sh.setLevel(logging.ERROR)
+    sh.setFormatter(formatter)
+
+    process = subprocess.Popen(["gluster", "--print-logdir"],
+                               stdout=subprocess.PIPE)
+    out, err = process.communicate()
+    if process.returncode == 0:
+        logfile = os.path.join(out.strip(), script_name[:-3]+".log")
+
+    fh = logging.FileHandler(logfile)
+    fh.setLevel(logging.DEBUG)
+    fh.setFormatter(formatter)
+
+    log.addHandler(sh)
+    log.addHandler(fh)
+
+
+def takeSnap(volname=""):
+    success = True
+    if volname == "":
+        log.debug("No volname given")
+        return False
+
+    timeStr = time.strftime("%Y%m%d%H%M%S")
+    cli = ["gluster",
+           "snapshot",
+           "create",
+           "%s-snapshot-%s %s" % (volname, timeStr, volname)]
+    log.debug("Running command '%s'", " ".join(cli))
+
+    p = subprocess.Popen(cli, stdout=subprocess.PIPE,
+                         stderr=subprocess.PIPE)
+    out, err = p.communicate()
+    rv = p.returncode
+
+    log.debug("Command '%s' returned '%d'", " ".join(cli), rv)
+
+    if rv:
+        log.error("Snapshot of %s failed", volname)
+        log.error("Command output:")
+        log.error(err)
+        success = False
+    else:
+        log.info("Snapshot of %s successful", volname)
+
+    return success
+
+
+def doJob(name, lockFile, jobFunc, volname):
+    success = True
+    try:
+        f = os.open(lockFile, os.O_RDWR | os.O_NONBLOCK)
+        try:
+            fcntl.flock(f, fcntl.LOCK_EX | fcntl.LOCK_NB)
+            mtime = os.path.getmtime(lockFile)
+            global start_time
+            log.debug("%s last modified at %s", lockFile, time.ctime(mtime))
+            if mtime < start_time:
+                log.debug("Processing job %s", name)
+                if jobFunc(volname):
+                    log.info("Job %s succeeded", name)
+                else:
+                    log.error("Job %s failed", name)
+                    success = False
+                os.utime(lockFile, None)
+            else:
+                log.info("Job %s has been processed already", name)
+            fcntl.flock(f, fcntl.LOCK_UN)
+        except IOError as (errno, strerror):
+            log.info("Job %s is being processed by another agent", name)
+        os.close(f)
+    except IOError as (errno, strerror):
+        log.debug("Failed to open lock file %s : %s", lockFile, strerror)
+        log.error("Failed to process job %s", name)
+        success = False
+
+    return success
+
+
+def main():
+    script_name = os.path.basename(__file__)
+    initLogger(script_name)
+    global start_time
+    if sys.argv[1] == "--update":
+        if os.lstat(GCRON_TASKS).st_mtime > \
+           os.lstat(GCRON_CROND_TASK).st_mtime:
+            try:
+                process = subprocess.Popen(["touch", "-h", GCRON_CROND_TASK],
+                                           stdout=subprocess.PIPE,
+                                           stderr=subprocess.PIPE)
+                out, err = process.communicate()
+                if process.returncode != 0:
+                    log.error("Failed to touch %s. Error: %s.",
+                              GCRON_CROND_TASK, err)
+            except IOError as (errno, strerror):
+                log.error("Failed to touch %s. Error: %s.",
+                          GCRON_CROND_TASK, strerror)
+        return
+
+    volname = sys.argv[1]
+    locking_file = os.path.join(LOCK_FILE_DIR, sys.argv[2])
+    log.debug("locking_file = %s", locking_file)
+    log.debug("volname = %s", volname)
+
+    start_time = int(time.time())
+
+    doJob("Snapshot-" + volname, locking_file, takeSnap, volname)
+
+
+if __name__ == "__main__":
+    main()