Fix missing /fleets/apply for old servers (#2582)

Author: r4victor

src/dstack/_internal/cli/services/configurators/fleet.py

@@ -20,6 +20,7 @@
 from dstack._internal.core.errors import (
     CLIError,
     ConfigurationError,
+    MethodNotAllowedError,
     ResourceNotExistsError,
     ServerClientError,
     URLNotFoundError,
@@ -367,7 +368,7 @@ def _apply_plan(api: Client, plan: FleetPlan) -> Fleet:
             project_name=api.project,
             plan=plan,
         )
-    except URLNotFoundError:
+    except (URLNotFoundError, MethodNotAllowedError):
         # TODO: Remove in 0.20
         return api.client.fleets.create(
             project_name=api.project,

src/dstack/_internal/core/errors.py

@@ -22,6 +22,10 @@ class URLNotFoundError(ClientError):
     pass
 
 
+class MethodNotAllowedError(ClientError):
+    pass
+
+
 class ServerClientErrorCode(str, enum.Enum):
     UNSPECIFIED_ERROR = "error"
     RESOURCE_EXISTS = "resource_exists"

src/dstack/api/server/__init__.py

@@ -6,7 +6,12 @@
 import requests
 
 from dstack import version
-from dstack._internal.core.errors import ClientError, ServerClientError, URLNotFoundError
+from dstack._internal.core.errors import (
+    ClientError,
+    MethodNotAllowedError,
+    ServerClientError,
+    URLNotFoundError,
+)
 from dstack._internal.utils.logging import get_logger
 from dstack.api.server._backends import BackendsAPIClient
 from dstack.api.server._fleets import FleetsAPIClient
@@ -156,6 +161,8 @@ def _request(
                 )
             if resp.status_code == 404:
                 raise URLNotFoundError(f"Status code 404 when requesting {resp.request.url}")
+            if resp.status_code == 405:
+                raise MethodNotAllowedError(f"Status code 405 when requesting {resp.request.url}")
             if 400 <= resp.status_code < 600:
                 raise ClientError(
                     f"Unexpected error: status code {resp.status_code}"