pgsnap.py

#!/usr/bin/env python

import os
import sys
import time
import subprocess
import urllib2

import boto


def setup_logger():
    import logging
    from logging.handlers import SysLogHandler

    logger = logging.getLogger(LOGGER_NAME)
    handler = SysLogHandler(address='/dev/log')
    logger.setLevel(logging.DEBUG)
    logger.addHandler(handler)
    return logger


logger = setup_logger()


def who_am_i():
    """
    Return one's instance id

    This mysterious bit of code is best explained in this 2009-03-09 stackoverflow answer:
        http://stackoverflow.com/questions/625644/find-out-the-instance-id-from-within-an-ec2-machine
    """
    return urllib2.urlopen('http://169.254.169.254/latest/meta-data/instance-id', timeout=1).read().strip()


def list_ebs(conn, blacklist=None):
    """Get all ebs volumes for oneself
    
    @return [(device, ebs-id), ...]
    """
    if blacklist is None:
        blacklist = ["/dev/sda1"]
    instance_id = who_am_i()
    r = conn.get_all_instances([instance_id])[0]
    assert len(r.instances) == 1, r.instances
    i = r.instances[0]
    return [(device, volume) for device, volume in i.block_device_mapping.items() if device not in blacklist]


def snap_ebs(device, volume, conn):
    return conn.create_snapshot(volume.volume_id, device)


def freeze(mnt):
    logger.info("Calling xfs_freeze -f")
    return subprocess.call(["sudo", "xfs_freeze", "-f", mnt]) == 0


def thaw(mnt):
    logger.info("Calling xfs_freeze -u")
    return subprocess.call(["sudo", "xfs_freeze", "-u", mnt]) == 0


def main(xfs_mount_point):
    assert os.path.isdir(xfs_mount_point), "Usage: pgsnap.py xfs_mount_point"
    conn = boto.connect_ec2(os.environ["AWS_ACCESS_KEY_ID"], os.environ["AWS_SECRET_KEY_ID"])
    vols = list_ebs(conn)
    frozen = False
    start = time.time()
    try:
        frozen = freeze(xfs_mount_point)
        assert frozen, "xfs_freeze failed"
        snaps = [snap_ebs(device, volume, conn) for device, volume in vols]
        logger.info("Snapshots: {0}".format(snaps))
    finally:
        if frozen:
            thaw(xfs_mount_point)
            logger.info("XFS was frozen for {0}".format(time.time() - start))


if __name__ == '__main__':
    for arg in sys.argv[1:]:
        main(arg)