From b6ff5e4650acd02edaece23025ad8b0b76a1252e Mon Sep 17 00:00:00 2001
From: JDierkse <j.dierkse@madeo.nl>
Date: Tue, 9 Feb 2021 16:02:01 +0100
Subject: [PATCH] Only initialize Docker Client when necessary

---
 net-dhcp/network.py | 42 +++++++++++++++++++++++++++++-------------
 1 file changed, 29 insertions(+), 13 deletions(-)

diff --git a/net-dhcp/network.py b/net-dhcp/network.py
index ea11af0..ddaa794 100644
--- a/net-dhcp/network.py
+++ b/net-dhcp/network.py
@@ -25,10 +25,19 @@ logger = logging.getLogger('net-dhcp')
 
 interface.InitializeLibrary(LIBRARY)
 
-client = docker.from_env()
+dockerClient = None
+
+def get_docker_client():
+    global dockerClient
+    if dockerClient is None:
+        dockerClient = docker.from_env()
+
 @atexit.register
-def close_docker():
-    client.close()
+def close_docker_client():
+    global dockerClient
+    if dockerClient is not None:
+        dockerClient.close()
+        dockerClient = None
 
 gateway_hints = {}
 container_dhcp_clients = {}
@@ -43,28 +52,34 @@ def veth_pair(e):
 
 def iface_addrs(iface):
     return list(map(lambda a: ipaddress.ip_interface((a['address'], a['prefixlen'])), iface.ipaddr))
+
 def iface_nets(iface):
     return list(map(lambda n: n.network, iface_addrs(iface)))
 
 def get_bridges():
+    get_docker_client()
     reserved_nets = set(map(ipaddress.ip_network, map(lambda c: c['Subnet'], \
         itertools.chain.from_iterable(map(lambda i: i['Config'], filter(lambda i: i['Driver'] != 'net-dhcp', \
-            map(lambda n: n.attrs['IPAM'], client.networks.list())))))))
+            map(lambda n: n.attrs['IPAM'], dockerClient.networks.list())))))))
 
     return dict(map(lambda i: (i['ifname'], i), filter(lambda i: i['kind'] == 'bridge' and not \
         set(iface_nets(i)).intersection(reserved_nets), map(lambda i: interface.GetInterface(LIBRARY, i['ifname']), \
             interface.GetInterfaces(LIBRARY)))))
 
 def net_bridge(n):
-    return interface.GetInterface(LIBRARY, client.networks.get(n).attrs['Options'][OPT_BRIDGE])
+    get_docker_client()
+    return interface.GetInterface(LIBRARY, dockerClient.networks.get(n).attrs['Options'][OPT_BRIDGE])
+
 def ipv6_enabled(n):
-    options = client.networks.get(n).attrs['Options']
+    get_docker_client()
+    options = dockerClient.networks.get(n).attrs['Options']
     return OPT_IPV6 in options and options[OPT_IPV6] == 'true'
 
 def endpoint_container_iface(n, e):
-    for cid, info in client.networks.get(n).attrs['Containers'].items():
+    get_docker_client()
+    for cid, info in dockerClient.networks.get(n).attrs['Containers'].items():
         if info['EndpointID'] == e:
-            container = client.containers.get(cid)
+            container = dockerClient.containers.get(cid)
             netns = f'/proc/{container.attrs["State"]["Pid"]}/ns/net'
 
             with pyroute2.NetNS(netns) as rtnl:
@@ -91,9 +106,10 @@ def await_endpoint_container_iface(n, e, timeout=5):
     return iface
 
 def endpoint_container_hostname(n, e):
-    for cid, info in client.networks.get(n).attrs['Containers'].items():
+    get_docker_client()
+    for cid, info in dockerClient.networks.get(n).attrs['Containers'].items():
         if info['EndpointID'] == e:
-            return client.containers.get(cid).attrs['Config']['Hostname']
+            return dockerClient.containers.get(cid).attrs['Config']['Hostname']
     return None
 
 @app.route('/NetworkDriver.GetCapabilities', methods=['POST'])
@@ -378,6 +394,6 @@ class ContainerDHCPManager:
                 self._thread.join()
 
                 # we have to do this since the docker client leaks sockets...
-                global client
-                client.close()
-                client = docker.from_env()
+                close_docker_client()
+                get_docker_client()
+