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Simple Pre-Forked Python JSON-RPC Server
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| import os | |
| import signal | |
| import sys | |
| import select | |
| import errno | |
| from jsonrpclib.SimpleJSONRPCServer import SimpleJSONRPCServer | |
| # BOOK-KEEPING | |
| _PIDS = [] | |
| def _kronos(signum, frame): | |
| '''As Kronos did before us, we too may have to devour our children''' | |
| for pid in _PIDS: | |
| try: | |
| os.kill(pid, signum) | |
| except OSError, e: | |
| if e.errno == errno.ESRCH: | |
| _PIDS.remove(pid) | |
| # wait on all child processes | |
| while len(_PIDS): | |
| pid, rc = os.waitpid(-1, 0) | |
| _PIDS.remove(pid) | |
| # exit non-zero to signal abnormal termination | |
| sys.exit(1) | |
| def _gogentle(signum, frame): | |
| '''Do not throw a KeyboardInterrupt Error''' | |
| os._exit(1) | |
| # API | |
| def add(x, y): | |
| '''Add x and y''' | |
| return x + y | |
| def subtract(x, y): | |
| '''Subtract y from x''' | |
| return x - y | |
| # server | |
| def main(name, *argv): | |
| global _PIDS | |
| # JSON-RPC over HTTP on INET socket localhost:8888 | |
| # under the hood, this calls `socket.bind` then `socket.listen` | |
| s = SimpleJSONRPCServer(( argv[0], int(argv[1]), )) | |
| # register our logging math functions | |
| for fn in ( add, subtract, ): | |
| s.register_function(fn) | |
| # simple pre-fork server, fork before accept | |
| for i in range(int(argv[2])): | |
| # fork our current process | |
| pid = os.fork() | |
| # if we are the child fork ... | |
| if 0 == pid: | |
| # die without unhandled exception | |
| for signum in ( signal.SIGINT, signal.SIGTERM, ): | |
| signal.signal(signum, _gogentle) | |
| # under the hood, this calls `socket.accept` | |
| s.serve_forever() | |
| os._exit(0) | |
| # if we are the papa fork | |
| else: | |
| _PIDS.append(pid) | |
| # setup signal relaying for INT and TERM | |
| for signum in ( signal.SIGINT, signal.SIGTERM, ): | |
| signal.signal(signum, _kronos) | |
| # wait on the kids | |
| while len(_PIDS): | |
| # 1s timeout here means we're checking for exiting children at most | |
| # 1x per second, prevents a busy loop | |
| reads, _, _ = select.select([sys.stdin], [], [], 1) | |
| if sys.stdin in reads: | |
| # blocking, read 1 line | |
| cmd = sys.stdin.readline() | |
| # kill ourselves ... kronos will propegate | |
| if cmd.strip() == 'exit': | |
| os.kill(os.getpid(), signal.SIGTERM) | |
| # check for exited children, non-blocking | |
| while True: | |
| pid, rc = os.waitpid(-1, os.WNOHANG) | |
| if not pid: | |
| break | |
| _PIDS.remove(pid) | |
| return 0 | |
| if __name__ == '__main__': | |
| sys.exit(main(*sys.argv)) |
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