使用Python检查dev_appserver是否在本地运行

Question

我有一个脚本，用来连接到localhost:8080，以便在dev_appserver实例上运行一些命令。我使用了remote_api_stub和httplib.HTTPConnection这两种工具。在我调用这两个工具之前，我想先确认一下服务器是否真的在运行。

在Python中，判断以下两点的“最佳做法”是什么呢：

1. 如何确认localhost:8080上是否有任何网页服务器在运行？
2. 如何确认dev_appserver是否在localhost:8080上运行？

Answer 1

我有一个用来构建项目的脚本，它通过远程接口来执行一些操作。为了确认服务器是否在运行，我只需要用curl这个工具，确保它没有返回错误信息。

  <target name="-local-server-up">
    <!-- make sure local server is running -->
    <exec executable="curl" failonerror="true">
      <arg value="-s"/>
      <arg value="${local.host}${remote.api}"/>
    </exec>
    <echo>local server running</echo>
  </target>

你也可以在Python中用call来做到同样的事情（前提是你的电脑上安装了curl）。

Answer 2

我会选择类似这样的东西：

import httplib

GAE_DEVSERVER_HEADER = "Development/1.0"

def is_HTTP_server_running(host, port, just_GAE_devserver = False):
   conn= httplib.HTTPConnection(host, port)
   try:
       conn.request('HEAD','/')
       return not just_GAE_devserver or \
             conn.getresponse().getheader('server') == GAE_DEVSERVER_HEADER   
   except (httplib.socket.error, httplib.HTTPException):
       return False
   finally:
       conn.close()  

测试过：

assert is_HTTP_server_running('yahoo.com','80') == True
assert is_HTTP_server_running('yahoo.com','80', just_GAE_devserver = True) == False
assert is_HTTP_server_running('localhost','8088') == True
assert is_HTTP_server_running('localhost','8088', just_GAE_devserver = True) == True
assert is_HTTP_server_running('foo','8088') == False
assert is_HTTP_server_running('foo','8088', just_GAE_devserver = True) == False

Answer 3

这样做就可以了：

import httplib

NO_WEB_SERVER = 0
WEB_SERVER = 1
GAE_DEV_SERVER_1_0 = 2
def checkServer(host, port, try_only_ssl = False):
    hh = None
    connectionType = httplib.HTTPSConnection if try_only_ssl \
                                             else httplib.HTTPConnection
    try:
        hh = connectionType(host, port)
        hh.request('GET', '/_ah/admin')
        resp = hh.getresponse()
        headers = resp.getheaders()
        if headers:
            if (('server', 'Development/1.0') in headers):
                return GAE_DEV_SERVER_1_0|WEB_SERVER
            return WEB_SERVER
    except httplib.socket.error:
        return NO_WEB_SERVER
    except httplib.BadStatusLine:
        if not try_only_ssl:
            # retry with SSL
            return checkServer(host, port, True)
    finally:
        if hh:
            hh.close()
    return NO_WEB_SERVER

print checkServer('scorpio', 22)   # will print 0 an  ssh server
print checkServer('skiathos', 80)  # will print 1 for an apache web server
print checkServer('skiathos', 8080) # will print 3, a GAE Dev Web server
print checkServer('no-server', 80) # will print 0, no server
print checkServer('www.google.com', 80) # will print 1
print checkServer('www.google.com', 443) # will print 1