Move the chunk cache logic into buildcommand

This avoids needing to pass the cache to the staging area since
lac.get returns a path to a directory tree rather than a file
handle now, so we also don't need to do any unpacking.

1 files changed, 21 insertions, 2 deletions

diff --git a/morphlib/buildcommand.py b/morphlib/buildcommand.py
index fd5acdf5..d7c445df 100644
--- a/morphlib/buildcommand.py
+++ b/morphlib/buildcommand.py
@@ -497,8 +497,27 @@ class BuildCommand(object):
                 chunk_name=artifact.name,
                 cache=artifact.source.cache_key[:7],
                 chatty=True)
-            handle = self.lac.get(artifact)
-            staging_area.install_artifact(handle)
+            chunk_cache_dir = os.path.join(self.app.settings['tempdir'],
+                                           'chunks')
+            artifact_checkout = os.path.join(
+                chunk_cache_dir, os.path.basename(artifact.basename()) + '.d')
+            if not os.path.exists(artifact_checkout):
+                self.app.status(
+                    msg='Checking out %(chunk)s from cache.',
+                    chunk=artifact.name
+                    )
+                temp_checkout = os.path.join(self.app.settings['tempdir'],
+                                             artifact.basename())
+                try:
+                    self.lac.get(artifact, temp_checkout)
+                except BaseException:
+                    shutil.rmtree(temp_checkout)
+                    raise
+                # TODO: This rename is not concurrency safe if two builds are
+                #       extracting the same chunk, one build will fail because
+                #       the other renamed its tempdir here first.
+                os.rename(temp_checkout, artifact_checkout)
+            staging_area.install_artifact(artifact, artifact_checkout)
 
         if target_source.build_mode == 'staging':
             morphlib.builder.ldconfig(self.app.runcmd, staging_area.dirname)