Improve legacy artifact remote handling

This creates a new ArtifactRemote class, derived from CASRemote that
extends initialisation to check for an artifact service. This drops the
remote early rather than raising an error on method not found each time
it tries to use it.

Fixes #1025

1 files changed, 8 insertions, 6 deletions

diff --git a/src/buildstream/_basecache.py b/src/buildstream/_basecache.py
index 68654b2a0..ef9414787 100644
--- a/src/buildstream/_basecache.py
+++ b/src/buildstream/_basecache.py
@@ -37,6 +37,7 @@ class BaseCache():
     spec_name = None
     spec_error = None
     config_node_name = None
+    remote_class = CASRemote
 
     def __init__(self, context):
         self.context = context
@@ -163,18 +164,19 @@ class BaseCache():
         q = multiprocessing.Queue()
         for remote_spec in remote_specs:
 
-            error = CASRemote.check_remote(remote_spec, q)
+            error = self.remote_class.check_remote(remote_spec, q)
 
             if error and on_failure:
                 on_failure(remote_spec.url, error)
+                continue
             elif error:
                 raise self.spec_error(error)  # pylint: disable=not-callable
-            else:
-                self._has_fetch_remotes = True
-                if remote_spec.push:
-                    self._has_push_remotes = True
 
-                remotes[remote_spec.url] = CASRemote(remote_spec)
+            self._has_fetch_remotes = True
+            if remote_spec.push:
+                self._has_push_remotes = True
+
+            remotes[remote_spec.url] = self.remote_class(remote_spec)
 
         for project in self.context.get_projects():
             remote_specs = self.global_remote_specs