Add an LRU cache for detected build-systems

This will speed up builds of chunks which don't have a chunk
morph. It won't have much (if any) effect on the speed of the
first build, but subsequent builds will be much faster as we
won't have to query the git cache.

1 files changed, 101 insertions, 19 deletions

diff --git a/morphlib/sourceresolver.py b/morphlib/sourceresolver.py
index 6ffff444..ec264360 100644
--- a/morphlib/sourceresolver.py
+++ b/morphlib/sourceresolver.py
@@ -26,6 +26,8 @@ import morphlib
 
 tree_cache_size = 10000
 tree_cache_filename = 'trees.cache.pickle'
+buildsystem_cache_size = 10000
+buildsystem_cache_filename = 'detected-chunk-buildsystems.cache.pickle'
 
 
 class PickleCacheManager(object):
@@ -135,16 +137,19 @@ class SourceResolver(object):
     '''
 
     def __init__(self, local_repo_cache, remote_repo_cache,
-                 tree_cache_manager, update_repos, status_cb=None):
+                 tree_cache_manager, buildsystem_cache_manager, update_repos,
+                 status_cb=None):
         self.lrc = local_repo_cache
         self.rrc = remote_repo_cache
         self.tree_cache_manager = tree_cache_manager
+        self.buildsystem_cache_manager = buildsystem_cache_manager
 
         self.update = update_repos
         self.status = status_cb
 
         self._resolved_trees = {}
         self._resolved_morphologies = {}
+        self._resolved_buildsystems = {}
 
     def _resolve_ref(self, reponame, ref):
         '''Resolves commit and tree sha1s of the ref in a repo and returns it.
@@ -206,12 +211,15 @@ class SourceResolver(object):
         return absref, tree
 
     def _get_morphology(self, reponame, sha1, filename):
-        '''Read the morphology at the specified location.'''
+        '''Read the morphology at the specified location.
+
+        Returns None if the file does not exist in the specified commit.
+
+        '''
         key = (reponame, sha1, filename)
         if key in self._resolved_morphologies:
             return self._resolved_morphologies[key]
 
-        morph_name = os.path.splitext(os.path.basename(filename))[0]
         loader = morphlib.morphloader.MorphologyLoader()
         if self.lrc.has_repo(reponame):
             self.status(msg="Looking for %(reponame)s:%(filename)s in the "
@@ -233,23 +241,62 @@ class SourceResolver(object):
                 morph = loader.load_from_string(text)
             except morphlib.remoterepocache.CatFileError:
                 morph = None
-                file_list = self._rrc.ls_tree(reponame, sha1)
         else:
+            # We assume that _resolve_ref() must have already been called and
+            # so the repo in question would have been made available already
+            # if it had been possible.
             raise NotcachedError(reponame)
 
         if morph is None:
-            self.status(msg="File %s doesn't exist: attempting to infer "
-                            "chunk morph from repo's build system"
-                        % filename, chatty=True)
-            bs = morphlib.buildsystem.detect_build_system(file_list)
-            if bs is None:
-                raise MorphologyNotFoundError(filename)
-            morph = bs.get_morphology(morph_name)
+            return None
+        else:
             loader.validate(morph)
             loader.set_commands(morph)
             loader.set_defaults(morph)
+            self._resolved_morphologies[key] = morph
+            return morph
+
+    def _detect_build_system(self, reponame, sha1, expected_filename):
+        '''Attempt to detect buildsystem of the given commit.
+
+        Returns None if no known build system was detected.
+
+        '''
+        self.status(msg="File %s doesn't exist: attempting to infer "
+                        "chunk morph from repo's build system" %
+                    expected_filename, chatty=True)
+
+        if self.lrc.has_repo(reponame):
+            repo = self.lrc.get_repo(reponame)
+            file_list = repo.list_files(ref=sha1, recurse=False)
+        elif self.rrc is not None:
+            file_list = self.rrc.ls_tree(reponame, sha1)
+        else:
+            # We assume that _resolve_ref() must have already been called and
+            # so the repo in question would have been made available already
+            # if it had been possible.
+            raise NotcachedError(reponame)
 
-        self._resolved_morphologies[morph] = morph
+        buildsystem = morphlib.buildsystem.detect_build_system(file_list)
+
+        if buildsystem is None:
+            # It might surprise you to discover that if we can't autodetect a
+            # build system, we raise MorphologyNotFoundError. Users are
+            # required to provide a morphology for any chunk where Morph can't
+            # infer the build instructions automatically, so this is the right
+            # error.
+            raise MorphologyNotFoundError(expected_filename)
+
+        return buildsystem.name
+
+    def _create_morphology_for_build_system(self, buildsystem_name,
+                                            morph_name):
+        bs = morphlib.buildsystem.lookup_build_system(buildsystem_name)
+        loader = morphlib.morphloader.MorphologyLoader()
+        morph = bs.get_morphology(morph_name)
+        loader.validate(morph)
+        loader.set_commands(morph)
+        loader.set_defaults(morph)
         return morph
 
     def traverse_morphs(self, definitions_repo, definitions_ref,
@@ -260,9 +307,9 @@ class SourceResolver(object):
         chunk_in_definitions_repo_queue = []
         chunk_in_source_repo_queue = []
 
-        resolved_commits = {}
-
         self._resolved_trees = self.tree_cache_manager.load_cache()
+        self._resolved_buildsystems = \
+            self.buildsystem_cache_manager.load_cache()
 
         resolved_morphologies = {}
 
@@ -314,19 +361,48 @@ class SourceResolver(object):
 
         def process_chunk(repo, ref, filename):
             absref, tree = self._resolve_ref(repo, ref)
-            key = (definitions_repo, definitions_absref, filename)
-            morphology = self._get_morphology(*key)
+
+            key = (repo, ref, filename)
+            morph_name = os.path.splitext(os.path.basename(filename))[0]
+
+            morphology = None
+            buildsystem = None
+
+            if key in self._resolved_buildsystems:
+                buildsystem = self._resolved_buildsystems[key]
+
+            if buildsystem is None:
+                # The morphologies aren't locally cached, so a morphology
+                # for a chunk kept in the chunk repo will be read every time.
+                # So, always keep your chunk morphs in your definitions repo.
+                morphology = self._get_morphology(*key)
+
+            if morphology is None:
+                if buildsystem is None:
+                    buildsystem = self._detect_build_system(*key)
+                if buildsystem is None:
+                    raise MorphologyNotFoundError(filename)
+                else:
+                    morphology = self._create_morphology_for_build_system(
+                        buildsystem, morph_name)
+                    self._resolved_morphologies[key] = morphology
+
             visit(repo, ref, filename, absref, tree, morphology)
 
         for repo, ref, filename in chunk_in_definitions_repo_queue:
-            process_chunk_repo(repo, ref, filename)
+            process_chunk(repo, ref, filename)
 
         for repo, ref, filename in chunk_in_source_repo_queue:
-            process_chunk_repo(repo, ref, filename)
+            process_chunk(repo, ref, filename)
 
         logging.debug('Saving contents of resolved tree cache')
         self.tree_cache_manager.save_cache(self._resolved_trees)
 
+        logging.debug('Saving contents of build systems cache')
+        self.buildsystem_cache_manager.save_cache(
+            self._resolved_buildsystems)
+
+
 
 def create_source_pool(lrc, rrc, repo, ref, filename, cachedir,
                        original_ref=None, update_repos=True,
@@ -357,7 +433,13 @@ def create_source_pool(lrc, rrc, repo, ref, filename, cachedir,
     tree_cache_manager = PickleCacheManager(
         os.path.join(cachedir, tree_cache_filename), tree_cache_size)
 
-    resolver = SourceResolver(lrc, rrc, tree_cache_manager, update_repos, status_cb)
+    buildsystem_cache_manager = PickleCacheManager(
+        os.path.join(cachedir, buildsystem_cache_filename),
+        buildsystem_cache_size)
+
+    resolver = SourceResolver(lrc, rrc, tree_cache_manager,
+                              buildsystem_cache_manager, update_repos,
+                              status_cb)
     resolver.traverse_morphs(repo, ref, [filename],
                              visit=add_to_pool,
                              definitions_original_ref=original_ref)