improve host detection

Author: tuvshuud

testcontainers/core/container.py

@@ -78,30 +78,33 @@ def __del__(self):
                 pass
 
     def get_container_host_ip(self) -> str:
-        # https://github.com/testcontainers/testcontainers-go/blob/dd76d1e39c654433a3d80429690d07abcec04424/docker.go#L644
-        # if os env TC_HOST is set, use it
-        host = os.environ.get('TC_HOST')
-        if host:
-            return host
-
         # infer from docker host
-        url = self.get_docker_client().host()
-
-        if 'http' in url.scheme or 'tcp' in url.scheme:
-            return url.hostname
-        if 'unix' in url.scheme or 'npipe' in url.scheme:
-            # if testcontainers itself runs in docker, get the newly spawned
-            # container's IP address from the dockder "bridge" network
-            if inside_container():
+        host = self.get_docker_client().host()
+        if not host:
+            return "localhost"
+
+        # check testcontainers itself runs inside docker container
+        if inside_container():
+            # If newly spawned container's gateway IP address from the docker
+            # "bridge" network is equal to detected host address, we should use
+            # container IP address, otherwise fall back to detected host
+            # address. Even it's inside container, we need to double check,
+            # because docker host might be set to docker:dind, usually in CI/CD environment
+            gateway_ip = self.get_docker_client().gateway_ip(self._container.id)
+
+            if gateway_ip == host:
                 return self.get_docker_client().bridge_ip(self._container.id)
-        return "localhost"
+        return host
 
     def get_exposed_port(self, port) -> str:
-        url = self.get_docker_client().host()
-        if 'unix' in url.scheme or 'npipe' in url.scheme:
-            if inside_container():
+        mapped_port = self.get_docker_client().port(self._container.id, port)
+        if inside_container():
+            gateway_ip = self.get_docker_client().gateway_ip(self._container.id)
+            host = self.get_docker_client().host()
+
+            if gateway_ip == host:
                 return port
-        return self.get_docker_client().port(self._container.id, port)
+        return mapped_port
 
     def with_command(self, command: str) -> 'DockerContainer':
         self._command = command

testcontainers/core/docker_client.py

@@ -10,9 +10,12 @@
 #    WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
 #    License for the specific language governing permissions and limitations
 #    under the License.
+import os
 import urllib
 import docker
 from docker.models.containers import Container
+from testcontainers.core.utils import inside_container
+from testcontainers.core.utils import default_gateway_ip
 
 
 class DockerClient(object):
@@ -44,8 +47,26 @@ def bridge_ip(self, container_id):
         container = self.client.api.containers(filters={'id': container_id})[0]
         return container['NetworkSettings']['Networks']['bridge']['IPAddress']
 
+    def gateway_ip(self, container_id):
+        container = self.client.api.containers(filters={'id': container_id})[0]
+        return container['NetworkSettings']['Networks']['bridge']['Gateway']
+
     def host(self):
+        # https://github.com/testcontainers/testcontainers-go/blob/dd76d1e39c654433a3d80429690d07abcec04424/docker.go#L644
+        # if os env TC_HOST is set, use it
+        host = os.environ.get('TC_HOST')
+        if host:
+            return host
         try:
-            return urllib.parse.urlparse(self.client.api.base_url)
+            url = urllib.parse.urlparse(self.client.api.base_url)
+
         except ValueError:
             return None
+        if 'http' in url.scheme or 'tcp' in url.scheme:
+            return url.hostname
+        if 'unix' in url.scheme or 'npipe' in url.scheme:
+            if inside_container():
+                ip_address = default_gateway_ip()
+                if ip_address:
+                    return ip_address
+        return "localhost"

testcontainers/core/utils.py

@@ -1,5 +1,6 @@
 import os
 import sys
+import subprocess
 
 LINUX = "linux"
 MAC = "mac"
@@ -35,3 +36,21 @@ def inside_container():
     https://github.com/docker/docker/blob/a9fa38b1edf30b23cae3eade0be48b3d4b1de14b/daemon/initlayer/setup_unix.go#L25
     """
     return os.path.exists('/.dockerenv')
+
+
+def default_gateway_ip():
+    """
+    Returns gateway IP address of the host that testcontainer process is
+    running on
+
+    https://github.com/testcontainers/testcontainers-java/blob/3ad8d80e2484864e554744a4800a81f6b7982168/core/src/main/java/org/testcontainers/dockerclient/DockerClientConfigUtils.java#L27
+    """
+    cmd = ["sh", "-c", "ip route|awk '/default/ { print $3 }'"]
+    try:
+        process = subprocess.Popen(cmd, stdout=subprocess.PIPE,
+                                   stderr=subprocess.PIPE)
+        ip_address = process.communicate()[0]
+        if ip_address and process.returncode == 0:
+            return ip_address.decode('utf-8').strip().strip('\n')
+    except subprocess.SubprocessError:
+        return None