Improve robustness when fetching artifacts from remote artifact cache

Previously Morph would check if an artifact is present in the remote
artifact cache, then fetch the necessary files. If an error occured
during fetching, it would raise an error and abort.

Instead, we should just try and fetch the files and if anything fails,
move on to building locally. This avoids the situation where an error in
the remote cache makes local building impossible, which we experienced
recently.

2 files changed, 18 insertions, 30 deletions

diff --git a/morphlib/buildcommand.py b/morphlib/buildcommand.py
index 7ad7909d..5e080a41 100644
--- a/morphlib/buildcommand.py
+++ b/morphlib/buildcommand.py
@@ -274,31 +274,25 @@ class BuildCommand(object):
                     'name': a.name,
                 })
 
-            self.app.status(msg='Checking if %(kind)s needs '
-                                'building %(sha1)s',
-                            kind=a.source.morphology['kind'],
-                            sha1=a.source.sha1[:7])
-
-            if self.is_built(a):
-                self.cache_artifacts_locally([a])
-                self.app.status(
-                    msg='The %(kind)s is cached at %(cache)s',
-                    kind=a.source.morphology['kind'],
-                    cache=os.path.basename(self.lac.artifact_filename(a))[:7])
-            else:
-                self.app.status(msg='Building %(kind)s %(name)s',
-                                name=a.name, kind=a.source.morphology['kind'])
-                self.build_artifact(a, build_env)
+            self.cache_or_build_artifact(a, build_env)
 
             self.app.status(msg='%(kind)s %(name)s is cached at %(cachepath)s',
                             kind=a.source.morphology['kind'], name=a.name,
                             cachepath=self.lac.artifact_filename(a),
                             chatty=(a.source.morphology['kind'] != "system"))
+
         self.app.status_prefix = old_prefix
 
-    def is_built(self, artifact):
-        '''Does either cache already have the artifact?'''
-        return self.lac.has(artifact) or (self.rac and self.rac.has(artifact))
+    def cache_or_build_artifact(self, artifact, build_env):
+        if self.rac is not None:
+            try:
+                self.cache_artifacts_locally([artifact])
+            except morphlib.remoteartifactcache.GetError:
+                # Error is logged by the RemoteArtifactCache object.
+                pass
+
+        if not self.lac.has(artifact):
+            self.build_artifact(artifact, build_env)
 
     def build_artifact(self, artifact, build_env):
         '''Build one artifact.
@@ -307,6 +301,10 @@ class BuildCommand(object):
         in either the local or remote cache already.
 
         '''
+        self.app.status(msg='Building %(kind)s %(name)s',
+                        name=artifact.name,
+                        kind=artifact.source.morphology['kind'])
+
         self.get_sources(artifact)
         deps = self.get_recursive_deps(artifact)
         self.cache_artifacts_locally(deps)
diff --git a/morphlib/plugins/cross-bootstrap_plugin.py b/morphlib/plugins/cross-bootstrap_plugin.py
index ec0cfbcb..bfd0d047 100644
--- a/morphlib/plugins/cross-bootstrap_plugin.py
+++ b/morphlib/plugins/cross-bootstrap_plugin.py
@@ -1,4 +1,4 @@
-# Copyright (C) 2013  Codethink Limited
+# Copyright (C) 2013-2014  Codethink Limited
 #
 # This program is free software; you can redistribute it and/or modify
 # it under the terms of the GNU General Public License as published by
@@ -299,18 +299,8 @@ class CrossBootstrapPlugin(cliapp.Plugin):
                 'Nothing to cross-compile. Only chunks built in \'bootstrap\' '
                 'mode can be cross-compiled.')
 
-        # FIXME: merge with build-command's code
         for i, a in enumerate(cross_chunks):
-            if build_command.is_built(a):
-                self.app.status(msg='The %(kind)s %(name)s is already built',
-                                kind=a.source.morphology['kind'],
-                                name=a.name)
-                build_command.cache_artifacts_locally([a])
-            else:
-                self.app.status(msg='Cross-building %(kind)s %(name)s',
-                                kind=a.source.morphology['kind'],
-                                name=a.name)
-                build_command.build_artifact(a, build_env)
+            build_command.cache_or_build_artifact(a, build_env)
 
         for i, a in enumerate(native_chunks):
             build_command.get_sources(a)