Implement server-side caching.

For the beginning, let's place server package cache into
muranorepository/api dir (this path can be easily got with
v1_api.root_path).

Change-Id: I7acbb174491f153eb340efb92ed3b0ce4c5f840f
Implements-feature: MRN-1149

muranorepository/api/v1.py

@@ -16,6 +16,7 @@ import os
 
 from flask import Blueprint, send_file
 from flask import jsonify, request, abort
+from flask import make_response
 from werkzeug import secure_filename
 
 from muranorepository.utils.parser import ManifestParser
@@ -25,20 +26,23 @@ from oslo.config import cfg
 CONF = cfg.CONF
 
 v1_api = Blueprint('v1', __name__)
+CACHE_DIR = os.path.join(v1_api.root_path, 'cache')
+
+if not os.path.exists(CACHE_DIR):
+    os.mkdir(CACHE_DIR)
 
 
-def _get_archive(client):
+def _get_archive(client, hash_sum):
     parser = ManifestParser(CONF.manifests)
     manifests = parser.parse()
+    types = None
     if client == 'conductor':
-        return Archiver().create(manifests,
-                                 'heat',
-                                 'agent',
-                                 'scripts')
+        types = ('heat', 'agent', 'scripts')
     elif client == 'ui':
-        return Archiver().create(manifests, client)
+        types = ('ui',)
     else:
         abort(404)
+    return Archiver().create(client, CACHE_DIR, manifests, hash_sum, types)
 
 
 def _get_locations(data_type, result_path):
@@ -83,8 +87,11 @@ def _check_data_type(data_type):
 
 @v1_api.route('/client/<path:type>')
 def get_archive_data(type):
-    return send_file(_get_archive(type),
-                     mimetype='application/octet-stream')
+    path = _get_archive(type, request.args.get('hash'))
+    if path:
+        return send_file(path, mimetype='application/octet-stream')
+    else:
+        return make_response(('Not modified', 304))
 
 
 @v1_api.route('/admin/<data_type>')

muranorepository/utils/archiver.py

@@ -15,11 +15,15 @@ import os
 import tarfile
 import tempfile
 import shutil
+import hashlib
 import logging as log
 from oslo.config import cfg
 from muranorepository.consts import DATA_TYPES
 CONF = cfg.CONF
 
+ARCHIVE_PKG_NAME = 'data.tar.gz'
+CHUNK_SIZE = 1 << 20  # 1MB
+
 
 class Archiver(object):
     def _copy_data(self, file_lists, src, dst):
@@ -39,18 +43,70 @@ class Archiver(object):
                 log.error("Unable to copy file "
                           "{0}".format(file))
 
-    def _compose_archive(self, path):
-        target_archive = "data.tar.gz"
-        with tarfile.open(target_archive, "w:gz") as tar:
+    def _get_hash(self, archive_path):
+        """Calculate SHA1-hash of archive file.
+
+        SHA-1 take a bit more time than MD5
+        (see http://tinyurl.com/kpj5jy7), but is more secure.
+        """
+        # Copy-pasted from muranodashboard/panel/services/metadata.py
+        if os.path.exists(archive_path):
+            sha1 = hashlib.sha1()
+            with open(archive_path) as f:
+                buf = f.read(CHUNK_SIZE)
+                while buf:
+                    sha1.update(buf)
+                    buf = f.read(CHUNK_SIZE)
+            hsum = sha1.hexdigest()
+            log.debug("Archive '{0}' has hash-sum {1}".format(
+                archive_path, hsum))
+            return hsum
+        else:
+            log.info(
+                "Archive '{0}' doesn't exist, no hash to calculate".format(
+                    archive_path))
+            return None
+
+    def _compose_archive(self, path, cache_dir):
+        with tarfile.open(ARCHIVE_PKG_NAME, "w:gz") as tar:
             for item in os.listdir(path):
                 tar.add(os.path.join(path, item), item)
         try:
             shutil.rmtree(path, ignore_errors=True)
         except Exception as e:
             log.error("Unable to delete temp directory: {0}".format(e))
-        return os.path.abspath(target_archive)
+        hash_sum = self._get_hash(ARCHIVE_PKG_NAME)
+        pkg_dir = os.path.join(cache_dir, hash_sum)
+        os.mkdir(pkg_dir)
+        shutil.move(ARCHIVE_PKG_NAME, os.path.join(pkg_dir, ARCHIVE_PKG_NAME))
+        return os.path.abspath(os.path.join(pkg_dir, ARCHIVE_PKG_NAME))
 
-    def create(self, manifests, *types):
+    def _is_data_cached(self, cache_dir, hash_sum):
+        existing_caches = os.listdir(cache_dir)
+        if len(existing_caches) == 1:
+            if existing_caches[0] == hash_sum:
+                path = os.path.join(cache_dir, hash_sum, ARCHIVE_PKG_NAME)
+                if not os.path.exists(path):
+                    raise RuntimeError(
+                        'Archive package is missing at dir {0}'.format(
+                            os.path.join(cache_dir, hash_sum)))
+                log.debug('Archive package already exists at {0} and it ' +
+                          'matches hash-sum {1}.'.format(path, hash_sum))
+                return True
+            else:
+                path = os.path.join(cache_dir, hash_sum)
+                log.info('Archive package already exists at {0}, but it '
+                         "doesn't match requested hash-sum {1}. "
+                         'Deleting it.'.format(path))
+                shutil.rmtree(path)
+                return False
+        elif len(existing_caches) == 0:
+            return False
+        else:
+            raise RuntimeError('Too many cached archives at {0}'.format(
+                cache_dir))
+
+    def create(self, client_type, cache_root, manifests, hash_sum, types):
         """
         manifests -- list of Manifest objects
         *types - desired data types to be added to archive
@@ -62,6 +118,14 @@ class Archiver(object):
             temp_dir = tempfile.mkdtemp()
         except:
             temp_dir = '/tmp'
+
+        cache_dir = os.path.join(cache_root, client_type)
+        if not os.path.exists(cache_dir):
+            os.mkdir(cache_dir)
+
+        if self._is_data_cached(cache_dir, hash_sum):
+            return None
+
         for data_type in types:
             if data_type not in DATA_TYPES:
                 raise Exception("Please, specify one of the supported data "
@@ -84,4 +148,4 @@ class Archiver(object):
                         "Manifest for {0} service has no file definitions for "
                         "{1}".format(manifest.service_display_name, data_type))
 
-        return self._compose_archive(temp_dir)
+        return self._compose_archive(temp_dir, cache_dir)