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python-gearman之多个GearmanServer问题

时间:2015-01-26 17:24来源:www.chengxuyuans.com 点击:

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问题描述

1.开启多个GearmanServer,端口号分别为4730、4731

2.使用python-gearman开发client和worker,开启多个worker连接4730和4731两个Server

3.client发送大量任务到GearmanServer

4.多个worker中的一个或者多个在接收一个或者若干个任务后,再也不接收任务了

代码实现

注意:

在编写代码前,应该先安装python-gearman,官网链接如下:

https://pypi.python.org/pypi/gearman/

?

1.文件名:test.bash

# test.bash
for i in {0..5}; do
    python gearman_client.py
    sleep 2
done

?2.文件名:gearman_client.py

# gearman_client.py
import multiprocessing
import gearman
import traceback

def start_gearman_client(process_id):
    gm_client = gearman.GearmanClient(['127.0.0.1:4730','127.0.0.1:4731'])
    try:
        requests = []
        for gm_job_id in range(500):
            request = gm_client.submit_job(
                    task='do_task',
                    data='%d_%03d' % (process_id,gm_job_id),
                    unique='%d_%03d' % (process_id,gm_job_id),
                    background=False,wait_until_complete=False)
            requests.append(request)
        gm_client.wait_until_jobs_completed(requests)
    except:
        print traceback.format_exc()
    return 0

def main():
    child_processes = []
    for process_id in range(2):
        p = multiprocessing.Process(target=start_gearman_client, args=(process_id,))
        child_processes.append((process_id,p))
        p.start()

    for (pid,child) in child_processes:
        print 'Confirming that child number %d had died' % pid
        child.join()

if __name__ == '__main__':
    main()

?3.文件名:gearman_worker.py

# gearman_worker.py
import gearman
import multiprocessing
import time
import traceback
from functools import partial

def do_work(gearman_worker,gearman_job,worker_id):
    try:
        print 'Worker %02d processing %s from port %d: %s' % (worker_id,gearman_job.data,gearman_job.connection.gearman_port,gearman_job.unique)
        time.sleep(0.001)
    except:
        print traceback.format_exc()
    return 'Done by worker %d through port %d' % (worker_id,gearman_job.connection.gearman_port)

def start_gearman_worker(worker_id):
    gm_worker = gearman.GearmanWorker(['127.0.0.1:4730','127.0.0.1:4731'])
    gm_worker.register_task('do_task', partial(do_work,worker_id=worker_id))
    print 'Worker %d start working' % worker_id
    gm_worker.work()

if __name__ == '__main__':
    workers = []
    for pid in range(8):
        worker = multiprocessing.Process(target=start_gearman_worker,args=(pid,))
        workers.append(worker)
        worker.start()
    for worker in workers:
        worker.join()

问题复现

1.开启多个GearmanServer,端口号分别为4730、4731

2.运行命令 python gearman_worker.py

3.运行脚本 /bin/bash test.bash

4.查看worker打印输出的log,可以发现log末尾只有部分worker在接收任务并执行,有几个worker是只执行了一次任务就再也不执行了。(注意:这种状况如果没发生,多执行几次test.bash,然后观察)

这里我贴出其中一次测试结果:

测试结果 Worker 02 processing 1_467 from port 4731: 1_467
Worker 04 processing 0_484 from port 4731: 0_484
Worker 05 processing 1_468 from port 4731: 1_468
Worker 02 processing 1_469 from port 4731: 1_469
Worker 04 processing 1_470 from port 4731: 1_470
Worker 05 processing 0_486 from port 4731: 0_486
Worker 02 processing 0_487 from port 4731: 0_487
Worker 04 processing 1_474 from port 4731: 1_474
Worker 05 processing 1_473 from port 4731: 1_473
Worker 02 processing 0_490 from port 4731: 0_490
Worker 05 processing 1_476 from port 4731: 1_476
Worker 04 processing 0_491 from port 4731: 0_491
Worker 02 processing 1_478 from port 4731: 1_478
Worker 05 processing 0_492 from port 4731: 0_492
Worker 04 processing 1_479 from port 4731: 1_479
Worker 02 processing 1_484 from port 4731: 1_484
Worker 05 processing 1_485 from port 4731: 1_485
Worker 04 processing 0_497 from port 4731: 0_497
Worker 02 processing 0_498 from port 4731: 0_498
Worker 05 processing 1_489 from port 4731: 1_489
Worker 02 processing 1_492 from port 4731: 1_492
Worker 04 processing 1_493 from port 4731: 1_493
Worker 05 processing 1_495 from port 4731: 1_495
Worker 02 processing 1_498 from port 4731: 1_498
Worker 04 processing 1_499 from port 4731: 1_499

?可以看到,后面只有worker2、4、5在执行任务,其他的worker都不工作了。

问题分析与解决

在开始问题分析之前,先了解一下GearmanServer与client、worker之间大概的工作流程。



1.client提交一个Job到GearmanServer

2.GearmanServer找出所有Sleeping的worker

3.GearmanServer向这些Sleeping的worker发送'noop'命令,唤醒worker

4.worker向GearmanServer发送Grab_Job的命令获取Job

?

根据上面的流程,我们可以知道,worker要获取Job,首先必须受到GearmanServer发送的“NOOP”命令。那么,worker不执行任务了,不外乎以下几种情况:

1. worker同GearmanServer断开了连接

2. GearmanServer之中因为某些原因,没有向所有worker发送“NOOP”

这两点也是可以通过代码来验证的,我当时在python-gearman中加了一些打印输出,可以确定worker同GearmanServer的连接并没有断开。那么,原因只能是GearmanServer没有向所有的worker发送NOOP。

这样的话,有以下两种方案来解决:

1.查阅GearmanServer(C实现),修改源码,对所有worker发送NOOP

2.修改python-gearman的代码,使得所有worker能够主动从GearmanServer获取Job

对于第一种方案,显然成本很高,而且风险极大,可能会引发更大的BUG,显然不可取。所以我们选择第二种方案,让worker主动去GearmanServer拉取Job,而不是死等“NOOP”。

第二种方案怎么实现呢?这里我就不详细介绍了,一切尽在代码中,以下是我在github发布的源码,是基于python-gearman的官方版本修改出来的,链接如下:

https://github.com/yunjianfei/python-gearman

主要特性有:

1.加入了TCP keepalive特性

2.采用epoll,效率更高

3.worker加入主动抓取任务的功能,保证能从多个server获取任务

希望大家踊跃使用,如果发现bug,请联系我,谢谢

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