simple-cluster-heartbeat Simple, pure Python implementation of a cluster singleton
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Python library service cluster singleton singleton service cluster singleton

simple-cluster-heartbeat Description

Simple, pure Python implementation of a cluster singleton simple-cluster-heartbeat is a Python script to have a singleton service running in a cluster.AbstractGoal is to have a service running on exactly one machine in a two-member cluster. I did not find something like this so I just created it. It is certainly not full-blown (only two cluster members, for example).ImplementationGenerally, the two cluster members are peers and make out the supervisor and worker roles on their own.Process detection is done via TCP connections. The script allows for the configuration of the command to run, the intervals where peers check their counterpart, and a fallback mode that pulls the command to a preferred machine.An instance of the script is started on each host. One is elected as the worker, executing a command in a loop. The other instance of the script loops and checks by connecting to a network port if the worker is still available. Once it detects that the worker is down, it assumes the worker role, starts its own network listener and executes the command in a loop.Supervisor and Worker election is based on multiple connection attempts to the peer, in random intervals.This should work on Python 2.6.3+, no other dependecies requiered. Tested on Windows, Linux, Solaris.Usage:Usage: ha_heartbeat.py commandOptions: -h, --help show this help message and exit -l LOCAL_HOST_PORT, --local=LOCAL_HOST_PORT local host and port in : format (default: localhost:22221) -r REMOTE_HOST_PORT, --remote=REMOTE_HOST_PORT remote host and port in : format (default: localhost:22222) -t INTERVAL_TEST, --interval-test=INTERVAL_TEST Maximum interval between peer checks (default: 10) --check-count=CHECK_COUNT Number of times a supervisor will check a dead peer before failing over. (default: 3) -i INTERVAL_COMMAND, --interval-commands=INTERVAL_COMMAND Interval between command executions in seconds (default: 30) -w WAIT_FOR_SERVERSOCKET, --wait-for-serversocket=WAIT_FOR_SERVERSOCKET Wait seconds for the serversocket to become available (default: 300) -m MODE, --mode=MODE Start process in WORKER or SUPERVISOR mode (default: SUPERVISOR) -f, --fallback Fallback to peer once it is up again (default: False) -v, --verbose Verbose outputExamples:Here are two usage examples: * Heartbeat command ("dir c:") executed every 30 seconds, pinned to one machine (m2), i.e., m1 takes over if m2 is down, as m2 comes back, m1 becomes supervisor again: h@m1 $ python ha_heartbeat.py -l m1:22221 -r m2:22222 -f "dir c:" h@m2 $ python ha_heartbeat.py -l m2:22222 -r m1:22221 -m WORKER "dir c:" * Heartbeat command ("ls -l") executed every 10 seconds, peer status checked every 5 seconds, no fallback once the supervisor takes over from a failed worker: h@m1 $ python ha_heartbeat.py -i 10 -t 5 -l m1:22221 -r m2:22222 "ls -l" h@m2 $ python ha_heartbeat.py -i 10 -t 5 -l m2:22222 -r m1:22221 "ls -l" Requirements: · Python

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