autoupdate.py

#!/usr/bin/python

import sys
import os
import time
import hashlib
import traceback

def run(cmd):
    fi = os.popen(cmd, "rb")
    output = fi.read()
    status = fi.close()
    if status is not None:
        raise IOError("command '%s' returned non zero value %d" % (cmd, status))
    return output

def exception_as_string():
    s = "Exception "+str(sys.exc_info()[0])
    info = sys.exc_info()[1]
    if info:
        s += " "+str(info)
    s += "\n"
    for l in traceback.extract_tb(sys.exc_info()[2]):
        s += "  File \"%s\", line %d, in %s\n" % (l[0],l[1],l[2])
        s += "    %s\n" % l[3]
    return s.strip()

class Server:
    def __init__(self):
        pass

    def start(self):
        try:
            self.pid = os.fork()
            if not self.pid:
                try:
                    os.execv("./mrscake-job-server", ["./mrscake-job-server"])
                finally:
                    os.abort()
        except:
            print "Error spawning server"
            self.pid = None

    def stop(self):
        if self.pid:
            os.kill(self.pid, 9)
            os.waitpid(self.pid, 0)
            self.pid = None

# distribute the load to the git server, by delaying
# instance startup by a random number of seconds
time.sleep(ord(hashlib.md5(run("hostname")).digest()[0]))

server = Server()
server.start()

while 1:
    current_revision = run("git rev-parse HEAD").strip()
    run("git fetch origin master 2>&1")
    server_revision = run("git rev-parse FETCH_HEAD").strip()

    if current_revision != server_revision:
        print "upgrading from revision %s to revision %s" % (current_revision, server_revision)
        try:
            print run("git merge FETCH_HEAD")
        except:
            print "Error merging revision %s" % server_revision
        try:
            server.stop()
            run("make mrscake-job-server")
            server.start()
        except:
            print exception_as_string()

    time.sleep(60)