#! /usr/bin/env python2.3

#
# Snakelet Server monitoring script. (Linux only)
#
# Designed to be run from a crontab.
#
# It pings the snakelet server and restarts it in daemon mode
# if it is not responding anymore. (first kills hanging pids)
#
# Dependencies: /usr/sbin/lsof, and pgrep must be available.
#

# -------------- CONFIGURE BELOW: ------------------------
SERVER_HOST = 'neptune'
SERVER_DIR = "/home/irmen/projects/Snakelets"
# -------------- CONFIGURE ENDS --------------------------


import os, socket, time, pwd
import daemon
import sys,traceback


import serv

if not os.path.isdir(SERVER_DIR):
    raise SystemExit("invalid server directory: "+SERVER_DIR)

SERVER_LOG = os.path.join(SERVER_DIR, "logs", "server.log")
SERVER_ERR_LOG = os.path.join(SERVER_DIR, "logs", "server_err.log")
SERVER_PID = os.path.join(SERVER_DIR, "logs", "server.pid")


class ServerDownError(Exception): pass


def tryConnect( host, port ):
    try:
        s=socket.socket(socket.AF_INET, socket.SOCK_STREAM)
        s.settimeout(10)        # max. 10 seconds
        s.connect( (host,port) )
        s.send("PING / HTTP/1.0\r\n\r\n") 
        reply=s.recv(15)   # just enough for "HTTP/1.1 202 OK"
        if reply.startswith("HTTP/") and (" 200 " in reply or " 202 " in reply):
            return # all is okay
        raise ServerDownError("invalid response to PING method")
    except socket.gaierror,x:
        print "HOST NAME PROBLEM",x
        raise
    except socket.error,x:
        raise ServerDownError(str(x))

def checkServer(force=False, restart=True):
    try:    
        if force:
            raise ServerDownError("(re)start or shutdown forced!")
        print "\n-----"
        print time.asctime(time.gmtime()),"GMT: checking Snakelets server."
        print "Trying to PING to %s:%d ..." %(SERVER_HOST, serv.HTTPD_PORT),
        tryConnect(SERVER_HOST, serv.HTTPD_PORT)
        print "Server is alive.\n"
    except ServerDownError,x:
        print "Server down: ",x
        print "Killing server"
        try:
            daemon.startstop(stdout=SERVER_LOG, stderr=SERVER_ERR_LOG,
                pidfile=SERVER_PID, action='stop')
        except daemon.DaemonizeError,x:
            print "Ignoring error: ",x


        checkIfPortIsFree(serv.HTTPD_PORT)

        if restart:
            print "Restarting... workdir=",SERVER_DIR

            os.chdir(SERVER_DIR)


            daemon.startstop(stdout=SERVER_LOG, stderr=SERVER_ERR_LOG,
                pidfile=SERVER_PID, action='start')
            print "%s GMT: This is the daemon." % time.asctime(time.gmtime())
            try:
                serv.main(workingdir=SERVER_DIR)
            except:
                print >>sys.stderr,"\n**** ERROR OCCURRED IN SERVER! (%s GMT) ****" % time.asctime()
                traceback.print_exc(sys.stderr)
                print >>sys.stderr,"**** END OF ERROR, EXITING! ****\n"
                print "%s GMT: an error occured, see the error log!" % time.asctime(time.gmtime())
            print "%s GMT: Daemon ends." % time.asctime(time.gmtime())

def killPids(pids):
    from signal import SIGINT,SIGTERM,SIGKILL
    for pid in pids:
        try:
            pid=int(pid)
            print "PID %d uses port!" % pid
            if pid==os.getpid():
                print "That's us.."
                continue
            try:
                while 1:
                    print "sending SIGINT to",pid
                    os.kill(pid,SIGINT)
                    time.sleep(2)
                    print "sending SIGTERM to",pid
                    os.kill(pid,SIGTERM)
                    time.sleep(2)
                    print "sending SIGKILL to",pid
                    os.kill(pid,SIGKILL)
                    time.sleep(1)
            except OSError, err:
                pass # process died, hopefully
        except ValueError:
            pass

def checkIfPortIsFree(HTTPD_PORT):
    print "Checking if port %d is in use..." % HTTPD_PORT
    import commands
    pids= commands.getoutput("/usr/sbin/lsof -i tcp@%s:%d -t" % (SERVER_HOST, HTTPD_PORT)).split('\n')

    pids=[pid for pid in pids if pid]

    killPids(pids)

    if pids:
        time.sleep(2)
        print "Port should be free now."
    else:
        print "Noone is using the port."
    print "Check if port",HTTPD_PORT,"is really available."
    s=socket.socket(socket.AF_INET, socket.SOCK_STREAM)
    try:
        try:
            s.setsockopt ( socket.SOL_SOCKET, socket.SO_REUSEADDR, 1)
            s.bind(('',HTTPD_PORT))
            s.listen(5)
            print "Port is available!"
        except socket.error:
            user=pwd.getpwuid(os.getuid())[0]    # cannot use os.getlogin() here
            print "Problem claiming port! Killing all python processes of user %s!" % user
            pids=commands.getoutput("pgrep -u %s python" % user).split('\n')
            pids=[pid for pid in pids if pid]
            killPids(pids)
            print "Port should now be available."
    finally:
        s.close()


def main(args):
    if len(args)>1:
        if args[1]=='check':
            checkServer()
        elif args[1] =='stop':
            force=False
            print "stopping server..." 
            try:
                daemon.startstop(stdout=SERVER_LOG,pidfile=SERVER_PID,action='stop')
            except daemon.DaemonizeError,x:
                print "POSSIBLE ERROR:",x
                force=True
            checkServer(force=force,restart=False)
            print "\nServer is not running anymore."
        elif args[1] =='force':
            print ">>forcing the start of another server<<"
            checkServer(force=True)
        else:
            print "Usage: %s [check|stop|force]" % args[0]
            print "(check will restart the server if it's down)"
    else:
        checkServer()
            

if __name__=="__main__":
    main(sys.argv)