Use /proc/1/sched

pre_commit/languages/docker.py

@@ -19,7 +19,7 @@ get_default_version = helpers.basic_get_default_version
 healthy = helpers.basic_healthy
 
 
-def _is_in_docker() -> bool:
+def _is_in_docker_cgroup() -> bool:
     try:
         with open('/proc/1/cgroup', 'rb') as f:
             for line in f.readlines():
@@ -37,7 +37,27 @@ def _is_in_docker() -> bool:
         return False
 
 
-def _get_container_id() -> str:
+def _is_in_docker_sched() -> bool:
+    try:
+        with open('/proc/1/sched', 'rb') as f:
+            line = f.readline()
+
+            if line.startswith(b'systemd ') or line.startswith(b'init '):
+                return False
+
+            return True
+    except FileNotFoundError:
+        return False
+
+
+def _is_in_docker() -> bool:
+    if _is_in_docker_cgroup() or _is_in_docker_sched():
+        return True
+
+    return False
+
+
+def _get_container_id_cgroup() -> str:
     # It's assumed that we already check /proc/1/cgroup in _is_in_docker. The
     # cpuset cgroup controller existed since cgroups were introduced so this
     # way of getting the container ID is pretty reliable.
@@ -45,7 +65,90 @@ def _get_container_id() -> str:
         for line in f.readlines():
             if line.split(b':')[1] == b'cpuset':
                 return os.path.basename(line.split(b':')[2]).strip().decode()
-    raise RuntimeError('Failed to find the container ID in /proc/1/cgroup.')
+
+    return ''
+
+
+def _get_container_id_sched() -> str:
+    # The idea here is to try to match the the workdir option found in the
+    # overlay mount with the GraphDriver.Data.WorkDir from the docker describe.
+
+    # Get details for the overlay mount type
+    try:
+        _, out, _ = cmd_output_b('mount', '-t', 'overlay')
+    except CalledProcessError:
+        # No mount command available or the -t option is not supported
+        return ''
+
+    lines = out.decode().strip().split('\n')
+
+    # There is always only one overlay mount inside the container
+    if len(lines) > 1 or lines[0] == '' or '(' not in lines[0]:
+        return ''
+
+    _, all_opts = lines[0].strip(')').split('(')
+    opts = all_opts.split(',')
+
+    # Search for workdir option
+    for opt in opts:
+        if '=' in opt:
+            k, v = opt.split('=')
+
+            if k == 'workdir':
+                # We have found workdir
+                workdir = v
+
+                break
+    else:
+        # No workdir was found
+        return ''
+
+    # Get list IDs for all running containers
+    try:
+        _, out, _ = cmd_output_b('docker', 'ps', '--format', '{{ .ID }}')
+    except CalledProcessError:
+        # There is probably no docker command
+        return ''
+
+    container_ids = out.decode().strip().split('\n')
+
+    # Check if there are any container IDs
+    if len(container_ids) == 1 and container_ids[0] == '':
+        return ''
+
+    # Search for a container that has the workdir we got from the mount command
+    for container_id in container_ids:
+        try:
+            _, out, _ = cmd_output_b('docker', 'inspect', container_id)
+        except CalledProcessError:
+            # Container probably doesn't exist anymore
+            return ''
+
+        container, = json.loads(out)
+
+        if (
+                'GraphDriver' in container and
+                'Data' in container['GraphDriver'] and
+                'WorkDir' in container['GraphDriver']['Data'] and
+                container['GraphDriver']['Data']['WorkDir'] == workdir
+        ):
+            # We have found matching container!
+            return container_id
+    else:
+        # No matching container found
+        return ''
+
+
+def _get_container_id() -> str:
+    container_id = _get_container_id_cgroup()
+
+    if container_id == '':
+        container_id = _get_container_id_sched()
+
+        if container_id == '':
+            raise RuntimeError('Failed to find the container ID.')
+
+    return container_id
 
 
 def _get_docker_path(path: str) -> str: