Extend wait_for module to support draining of active tcp connections

utilities/wait_for

@@ -23,6 +23,15 @@ import datetime
 import time
 import sys
 import re
+import binascii
+
+HAS_PSUTIL = False
+try:
+    import psutil
+    HAS_PSUTIL = True
+    # just because we can import it on Linux doesn't mean we will use it
+except ImportError:
+    pass
 
 DOCUMENTATION = '''
 ---
@@ -38,6 +47,9 @@ description:
      - In 1.6 and later, this module can 
        also be used to wait for a file to be available or absent on the 
        filesystem.
+     - In X and later, this module can also be used to wait for active
+       connections to be closed before continuing, useful if a node
+       is being rotated out of a load balancer pool.
 version_added: "0.7"
 options:
   host:
@@ -62,10 +74,10 @@ options:
     required: false
   state:
     description:
-      - either C(present), C(started), or C(stopped), C(absent)
+      - either C(present), C(started), or C(stopped), C(absent), or C(drained)
-      - When checking a port C(started) will ensure the port is open, C(stopped) will check that it is closed
+      - When checking a port C(started) will ensure the port is open, C(stopped) will check that it is closed, C(drained) will check for active connections
       - When checking for a file or a search string C(present) or C(started) will ensure that the file or string is present before continuing, C(absent) will check that file is absent or removed
-    choices: [ "present", "started", "stopped", "absent" ]
+    choices: [ "present", "started", "stopped", "absent", "drained" ]
     default: "started"
   path:
     version_added: "1.4"
@@ -77,6 +89,11 @@ options:
     required: false
     description:
       - Can be used to match a string in either a file or a socket connection. Defaults to a multiline regex.
+  exclude_hosts:
+    version_added: "1.x"
+    required: false
+    description:
+      - list of hosts or IPs to ignore when looking for active TCP connections for C(drained) state
 notes:
   - The ability to use search_regex with a port connection was added in 1.7.
 requirements: []
@@ -88,6 +105,12 @@ EXAMPLES = '''
 # wait 300 seconds for port 8000 to become open on the host, don't start checking for 10 seconds
 - wait_for: port=8000 delay=10
 
+# wait 300 seconds for port 8000 of any IP to close active connections, don't start checking for 10 seconds
+- wait_for: host=0.0.0.0 port=8000 delay=10 state=drained
+
+# wait 300 seconds for port 8000 of any IP to close active connections, ignoring connections for specified hosts
+- wait_for: host=0.0.0.0 port=8000 state=drained exclude_hosts=10.2.1.2,10.2.1.3
+
 # wait until the file /tmp/foo is present before continuing
 - wait_for: path=/tmp/foo
 
@@ -105,6 +128,173 @@ EXAMPLES = '''
 
 '''
 
+class TCPConnectionInfo(object):
+    """
+    This is a generic TCP Connection Info strategy class that relies
+    on the psutil module, which is not ideal for targets, but necessary
+    for cross platform support.
+
+    A subclass may wish to override some or all of these methods.
+      - _get_exclude_ips()
+      - get_active_connections()
+
+    All subclasses MUST define platform and distribution (which may be None).
+    """
+    platform = 'Generic'
+    distribution = None
+
+    match_all_ips = {
+        socket.AF_INET: '0.0.0.0',
+        socket.AF_INET6: '::',
+    }
+    connection_states = {
+        '01': 'ESTABLISHED',
+        '02': 'SYN_SENT',
+        '03': 'SYN_RECV',
+        '04': 'FIN_WAIT1',
+        '05': 'FIN_WAIT2',
+        '06': 'TIME_WAIT',
+    }
+
+    def __new__(cls, *args, **kwargs):
+        return load_platform_subclass(TCPConnectionInfo, args, kwargs)
+
+    def __init__(self, module):
+        self.module = module
+        self.name = module.params['name']
+        (self.family, self.ip) = _convert_host_to_ip(self.module.params['host'])
+        self.port = int(self.module.params['port'])
+        self.exclude_ips = self._get_exclude_ips()
+        if not HAS_PSUTIL:
+            module.fail_json(msg="psutil module required for wait_for")
+
+    def _get_exclude_ips(self):
+        if self.module.params['exclude_hosts'] is None:
+            return []
+        exclude_hosts = self.module.params['exclude_hosts'].split(',')
+        return [ _convert_host_to_hex(h)[1] for h in exclude_hosts ]
+
+    def get_active_connections_count(self):
+        active_connections = 0
+        for p in psutil.process_iter():
+            connections = p.get_connections(kind='inet')
+            for conn in connections:
+                if conn.status not in self.connection_states.values():
+                    continue
+                (local_ip, local_port) = conn.local_address
+                if self.port == local_port and self.ip in [self.match_all_ips[self.family], local_ip]:
+                     (remote_ip, remote_port) = conn.remote_address
+                     if remote_ip not in self.exclude_ips:
+                         active_connections += 1
+        return active_connections
+
+
+# ===========================================
+# Subclass: Linux
+
+class LinuxTCPConnectionInfo(TCPConnectionInfo):
+    """
+    This is a TCP Connection Info evaluation strategy class
+    that utilizes information from Linux's procfs. While less universal,
+    does allow Linux targets to not require an additional library.
+    """
+    platform = 'Linux'
+    distribution = None
+
+    source_file = {
+        socket.AF_INET: '/proc/net/tcp',
+        socket.AF_INET6: '/proc/net/tcp6'
+    }
+    match_all_ips = {
+        socket.AF_INET: '00000000',
+        socket.AF_INET6: '00000000000000000000000000000000',
+    }
+    local_address_field = 1
+    remote_address_field = 2
+    connection_state_field = 3
+
+    def __init__(self, module):
+        self.module = module
+        self.name = module.params['name']
+        (self.family, self.ip) = _convert_host_to_hex(module.params['host'])
+        self.port = "%0.4X" % int(module.params['port'])
+        self.exclude_ips = self._get_exclude_ips()
+
+    def _get_exclude_ips(self):
+        if self.module.params['exclude_hosts'] is None:
+            return []
+        exclude_hosts = self.module.params['exclude_hosts'].split(',')
+        return [ _convert_host_to_hex(h) for h in exclude_hosts ]
+
+    def get_active_connections_count(self):
+        active_connections = 0
+        f = open(self.source_file[self.family])
+        for tcp_connection in f.readlines():
+            tcp_connection = tcp_connection.strip().split(' ')
+            if tcp_connection[self.local_address_field] == 'local_address':
+                continue
+            if tcp_connection[self.connection_state_field] not in self.connection_states:
+                continue
+            (local_ip, local_port) = tcp_connection[self.local_address_field].split(':')
+            if self.port == local_port and self.ip in [self.match_all_ips[self.family], local_ip]:
+                 (remote_ip, remote_port) = tcp_connection[self.remote_address_field].split(':')
+                 if remote_ip not in self.exclude_ips:
+                     active_connections += 1
+        f.close()
+        return active_connections
+
+
+def _convert_host_to_ip(host):
+    """
+    Perform forward DNS resolution on host, IP will give the same IP
+
+    Args:
+        host: String with either hostname, IPv4, or IPv6 address
+
+    Returns:
+        Tuple containing address family and IP
+    """
+    addrinfo = socket.getaddrinfo(host, 80, 0, 0, socket.SOL_TCP)[0]
+    return (addrinfo[0], addrinfo[4][0])
+
+def _convert_host_to_hex(host):
+    """
+    Convert the provided host to the format in /proc/net/tcp*
+
+    /proc/net/tcp uses little-endian four byte hex for ipv4
+    /proc/net/tcp6 uses little-endian per 4B word for ipv6
+
+    Args:
+        host: String with either hostname, IPv4, or IPv6 address
+
+    Returns:
+        Tuple containing address family and the little-endian converted host
+    """
+    (family, ip) = _convert_host_to_ip(host)
+    hexed = binascii.hexlify(socket.inet_pton(family, ip)).upper()
+    if family == socket.AF_INET:
+        hexed = _little_endian_convert_32bit(hexed)
+    elif family == socket.AF_INET6:
+        # xrange loops through each 8 character (4B) set in the 128bit total
+        hexed = "".join([ _little_endian_convert_32bit(hexed[x:x+8]) for x in xrange(0, 32, 8) ])
+    return (family, hexed)
+
+def _little_endian_convert_32bit(block):
+    """
+    Convert to little-endian, effectively transposing
+    the order of the four byte word
+    12345678 -> 78563412
+
+    Args:
+        block: String containing a 4 byte hex representation
+
+    Returns:
+        String containing the little-endian converted block
+    """
+    # xrange starts at 6, and increments by -2 until it reaches -2
+    # which lets us start at the end of the string block and work to the begining
+    return "".join([ block[x:x+2] for x in xrange(6, -2, -2) ])
+
 def main():
 
     module = AnsibleModule(
@@ -116,7 +306,8 @@ def main():
             port=dict(default=None),
             path=dict(default=None),
             search_regex=dict(default=None),
-            state=dict(default='started', choices=['started', 'stopped', 'present', 'absent']),
+            state=dict(default='started', choices=['started', 'stopped', 'present', 'absent', 'drained']),
+            exclude_hosts=dict(default=None, type='list')
         ),
     )
 
@@ -133,11 +324,19 @@ def main():
     state = params['state']
     path = params['path']
     search_regex = params['search_regex']
+    if params['exclude_hosts']:
+        exclude_hosts = params['exclude_hosts'].split(',')
+    else:
+        exclude_hosts = []
     
     if port and path:
         module.fail_json(msg="port and path parameter can not both be passed to wait_for")
     if path and state == 'stopped':
         module.fail_json(msg="state=stopped should only be used for checking a port in the wait_for module")
+    if path and state == 'drained':
+        module.fail_json(msg="state=drained should only be used for checking a port in the wait_for module")
+    if exclude_hosts and state != 'drained':
+        module.fail_json(msg="exclude_hosts should only be with state=drained")
         
     start = datetime.datetime.now()
 
@@ -242,6 +441,20 @@ def main():
                 else:
                     module.fail_json(msg="Timeout when waiting for file %s" % (path), elapsed=elapsed.seconds)
 
+    elif state == 'drained':
+        ### wait until all active connections are gone
+        end = start + datetime.timedelta(seconds=timeout)
+        tcpconns = TCPConnectionInfo(module)
+        while datetime.datetime.now() < end:
+            try:
+                if tcpconns.get_active_connections_count() == 0:
+                    break
+            except IOError:
+                pass
+            time.sleep(1)
+        else:
+            elapsed = datetime.datetime.now() - start
+            module.fail_json(msg="Timeout when waiting for %s:%s to drain" % (host, port), elapsed=elapsed.seconds)
 
     elapsed = datetime.datetime.now() - start
     module.exit_json(state=state, port=port, search_regex=search_regex, path=path, elapsed=elapsed.seconds)