Add RemoteRepoCache and integrate it into _create_source_pool().

This adds a new setting called 'cache-server' to morph. It is None
by default and should be set to the HTTP URL of a morph cache server
to be used.

The RemoteRepoCache object provides two methods: resolve_ref() and
cat_file(), both of which wrap the communication with the cache
server and return a SHA1 string and file contents, respectively.

The _create_source_pool() method now takes a local and an optional
remote repo cache and tries to do whatever is best to resolve
refs and load morphologies for the Source objects it creates.

1 files changed, 84 insertions, 0 deletions

diff --git a/morphlib/remoterepocache.py b/morphlib/remoterepocache.py
new file mode 100644
index 00000000..fd843682
--- /dev/null
+++ b/morphlib/remoterepocache.py
@@ -0,0 +1,84 @@
+# Copyright (C) 2012  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
+# the Free Software Foundation; version 2 of the License.
+# 
+# This program is distributed in the hope that it will be useful,
+# but WITHOUT ANY WARRANTY; without even the implied warranty of
+# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+# GNU General Public License for more details.
+# 
+# You should have received a copy of the GNU General Public License along
+# with this program; if not, write to the Free Software Foundation, Inc.,
+# 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
+
+
+import cliapp
+import json
+import urllib2
+import urlparse
+
+
+class ResolveRefError(cliapp.AppException):
+
+    def __init__(self, repo_name, ref):
+        cliapp.AppException.__init__(
+                self, 'Failed to resolve ref %s for repo %s' %
+                (ref, repo_name))
+
+
+class CatFileError(cliapp.AppException):
+
+    def __init__(self, repo_name, ref, filename):
+        cliapp.AppException.__init__(
+                self, 'Failed to cat file %s in ref %s of repo %s' %
+                (filename, ref, repo_name))
+
+
+class RemoteRepoCache(object):
+
+    def __init__(self, server_url, base_urls):
+        self.server_url = server_url
+        self._base_urls = base_urls
+
+    def _base_iterate(self, repo_name):
+        for base_url in self._base_urls:
+            if not base_url.endswith('/'):
+                base_url += '/'
+            repo_url = urlparse.urljoin(base_url, repo_name)
+            yield repo_url
+
+    def resolve_ref(self, repo_name, ref):
+        for repo_url in self._base_iterate(repo_name):
+            try:
+                return self._resolve_ref_for_repo_url(repo_url, ref)
+            except:
+                pass
+        raise ResolveRefError(repo_name, ref)
+
+    def cat_file(self, repo_name, ref, filename):
+        for repo_url in self._base_iterate(repo_name):
+            try:
+                return self._cat_file_for_repo_url(repo_url, ref, filename)
+            except:
+                pass
+        raise CatFileError(repo_name, ref, filename)
+
+    def _resolve_ref_for_repo_url(self, repo_url, ref): # pragma: no cover
+        data = self._make_request('sha1s?repo=%s&ref=%s' % (repo_url, ref))
+        info = json.loads(data)
+        return info['sha1']
+
+    def _cat_file_for_repo_url(self, repo_url, ref,
+                               filename): # pragma: no cover
+        return self._make_request(
+                'files?repo=%s&ref=%s&filename=%s' % (repo_url, ref, filename))
+
+    def _make_request(self, path):
+        server_url = self.server_url
+        if not server_url.endswith('/'):
+            server_url += '/'
+        url = urlparse.urljoin(server_url, '/1.0/%s' % path)
+        handle = urllib2.urlopen(url)
+        return handle.read()