From d8f8b6ec700fe9c7446eba99ed97b94a6685ad0f Mon Sep 17 00:00:00 2001
From: YueGuobin <yueguobin@outlook.com>
Date: Fri, 27 Feb 2026 16:35:11 +0100
Subject: [PATCH] fix(docker): handle container name conflict automatically

   When a Docker container with the same name already exists (e.g., from a
   previous crashed GNS3 session), Docker returns a 409 Conflict error
   when trying to create a new container with that name. This causes the
   project open operation to fail.

   This fix adds automatic cleanup of stale containers when encountering
   a name conflict:
   - Added DockerHttp409Error exception class
   - Updated http_query to detect 409 status codes
   - Modified create() to remove conflicting containers and retry

   Fixes the issue where opening a project fails with:
   "Docker has returned an error: 409 Conflict. The container name
   '/GNS3.xxx' is already in use by container 'xxx'"
---
 gns3server/compute/docker/__init__.py     |  4 ++-
 gns3server/compute/docker/docker_error.py |  4 +++
 gns3server/compute/docker/docker_vm.py    | 36 +++++++++++++++++++----
 3 files changed, 38 insertions(+), 6 deletions(-)

diff --git a/gns3server/compute/docker/__init__.py b/gns3server/compute/docker/__init__.py
index a441af830..4c12314d5 100644
--- a/gns3server/compute/docker/__init__.py
+++ b/gns3server/compute/docker/__init__.py
@@ -33,7 +33,7 @@ from gns3server.config import Config
 from gns3server.utils.asyncio import locking
 from gns3server.compute.base_manager import BaseManager
 from gns3server.compute.docker.docker_vm import DockerVM
-from gns3server.compute.docker.docker_error import DockerError, DockerHttp304Error, DockerHttp404Error
+from gns3server.compute.docker.docker_error import DockerError, DockerHttp304Error, DockerHttp404Error, DockerHttp409Error
 
 log = logging.getLogger(__name__)
 
@@ -236,6 +236,8 @@ class Docker(BaseManager):
                 raise DockerHttp304Error("Docker has returned an error: {} {}".format(response.status, body))
             elif response.status == 404:
                 raise DockerHttp404Error("Docker has returned an error: {} {}".format(response.status, body))
+            elif response.status == 409:
+                raise DockerHttp409Error("Docker has returned an error: {} {}".format(response.status, body))
             else:
                 raise DockerError("Docker has returned an error: {} {}".format(response.status, body))
         return response
diff --git a/gns3server/compute/docker/docker_error.py b/gns3server/compute/docker/docker_error.py
index 5d2b9b1d8..17d45ebbe 100644
--- a/gns3server/compute/docker/docker_error.py
+++ b/gns3server/compute/docker/docker_error.py
@@ -32,3 +32,7 @@ class DockerHttp304Error(DockerError):
 
 class DockerHttp404Error(DockerError):
     pass
+
+
+class DockerHttp409Error(DockerError):
+    pass
diff --git a/gns3server/compute/docker/docker_vm.py b/gns3server/compute/docker/docker_vm.py
index 79b5f640b..7b58305c6 100644
--- a/gns3server/compute/docker/docker_vm.py
+++ b/gns3server/compute/docker/docker_vm.py
@@ -43,7 +43,8 @@ from ..nios.nio_udp import NIOUDP
 from .docker_error import (
     DockerError,
     DockerHttp304Error,
-    DockerHttp404Error
+    DockerHttp404Error,
+    DockerHttp409Error
 )
 
 import logging
@@ -459,10 +460,35 @@ class DockerVM(BaseNode):
             if extra_hosts:
                 params["Env"].append("GNS3_EXTRA_HOSTS={}".format(extra_hosts))
 
-        # Support name in Doker: [a-zA-Z0-9][a-zA-Z0-9_.-]
-        result = await self.manager.query("POST", "containers/create?name={}".format(self.docker_name), data=params)
-        self._cid = result['Id']
-        log.info("Docker container '{name}' [{id}] created".format(name=self._name, id=self._id))
+        try:
+            # Supported names in Docker: [a-zA-Z0-9][a-zA-Z0-9_.-]
+            result = await self.manager.query("POST", f"containers/create?name={self.docker_name}", data=params)
+        except DockerHttp409Error:
+            # Container name already exists. This can happen when the server crashes
+            # and leaves containers behind. Try to remove the conflicting container.
+            log.warning(f"Container name '{self.docker_name}' is already in use, attempting to clean up the stale container...")
+            try:
+                # Try to get and remove the conflicting container
+                try:
+                    container_info = await self.manager.query("GET", f"containers/{self.docker_name}/json")
+                    container_id = container_info["Id"]
+                    # Force remove the container
+                    await self.manager.query("DELETE", f"containers/{container_id}", params={"force": 1, "v": 1})
+                    log.info(f"Removed stale container '{self.docker_name}' ({container_id})")
+                except DockerHttp404Error:
+                    # Container doesn't exist anymore, race condition - just continue
+                    pass
+                # Retry creating the container
+                result = await self.manager.query("POST", f"containers/create?name={self.docker_name}", data=params)
+            except DockerError as e:
+                log.error(f"Failed to clean up conflicting container '{self.docker_name}': {e}")
+                raise
+        self._cid = result["Id"]
+        log.info(f"Docker container '{self._name}' [{self._id}] created")
+        if self._cpus > 0:
+            log.info(f"CPU limit set to {self._cpus} CPUs")
+        if self._memory > 0:
+            log.info(f"Memory limit set to {self._memory} MB")
         return True
 
     def _format_env(self, variables, env):