From 8bff41ddef78fa851b09d141c93bdf387abc1dee Mon Sep 17 00:00:00 2001
From: Michael Vrable <mvrable@cs.ucsd.edu>
Date: Wed, 6 Aug 2008 12:11:22 -0700
Subject: [PATCH] Begin new storage-abstraction layer.

Begin work on new Python code for providing uniform access to both local
filesystem and remote S3 storage.  Convert the existing Python module to
use the new interface.
---
 cumulus-util                         |  5 +++-
 lbs.py => python/cumulus/__init__.py | 36 +++++++++++++-------------
 python/cumulus/store/__init__.py     | 22 ++++++++++++++++
 python/cumulus/store/s3.py           | 38 ++++++++++++++++++++++++++++
 4 files changed, 82 insertions(+), 19 deletions(-)
 rename lbs.py => python/cumulus/__init__.py (97%)
 create mode 100644 python/cumulus/store/__init__.py
 create mode 100644 python/cumulus/store/s3.py

diff --git a/cumulus-util b/cumulus-util
index 59c5fc7..f5d5fa3 100755
--- a/cumulus-util
+++ b/cumulus-util
@@ -4,7 +4,10 @@
 
 import getpass, os, stat, sys, time
 from optparse import OptionParser
-import lbs
+import cumulus
+
+# Compatibility
+lbs = cumulus
 
 # We support up to "LBS Snapshot v0.8" formats, but are also limited by the lbs
 # module.
diff --git a/lbs.py b/python/cumulus/__init__.py
similarity index 97%
rename from lbs.py
rename to python/cumulus/__init__.py
index b8de982..602e70e 100644
--- a/lbs.py
+++ b/python/cumulus/__init__.py
@@ -12,6 +12,8 @@ from __future__ import division
 import os, re, sha, tarfile, tempfile, thread
 from pysqlite2 import dbapi2 as sqlite3
 
+import cumulus.store, cumulus.store.file
+
 # The largest supported snapshot format that can be understood.
 FORMAT_VERSION = (0, 8)         # LBS Snapshot v0.8
 
@@ -82,19 +84,19 @@ class LowlevelDataStore:
     """
 
     def __init__(self, path):
-        self.path = path
-
-    # Low-level filesystem access.  These methods could be overwritten to
-    # provide access to remote data stores.
-    def lowlevel_list(self):
-        """Get a listing of files stored."""
+        self.store = cumulus.store.file.FileStore(path)
 
-        return os.listdir(self.path)
+    def _classify(self, filename):
+        for (t, r) in cumulus.store.type_patterns.items():
+            if r.match(filename):
+                return (t, filename)
+        return (None, filename)
 
     def lowlevel_open(self, filename):
         """Return a file-like object for reading data from the given file."""
 
-        return open(os.path.join(self.path, filename), 'rb')
+        (type, filename) = self._classify(filename)
+        return self.store.get(type, filename)
 
     def lowlevel_stat(self, filename):
         """Return a dictionary of information about the given file.
@@ -103,21 +105,19 @@ class LowlevelDataStore:
         file in bytes.
         """
 
-        stat = os.stat(os.path.join(self.path, filename))
-        return {'size': stat.st_size}
+        (type, filename) = self._classify(filename)
+        return self.store.stat(type, filename)
 
     # Slightly higher-level list methods.
     def list_snapshots(self):
-        for f in self.lowlevel_list():
-            m = re.match(r"^snapshot-(.*)\.lbs$", f)
-            if m:
-                yield m.group(1)
+        for f in self.store.list('snapshots'):
+            m = cumulus.store.type_patterns['snapshots'].match(f)
+            if m: yield m.group(1)
 
     def list_segments(self):
-        for f in self.lowlevel_list():
-            m = re.match(r"^([0-9a-f]{8}-[0-9a-f]{4}-[0-9a-f]{4}-[0-9a-f]{4}-[0-9a-f]{12})(\.\S+)?$", f)
-            if m:
-                yield m.group(1)
+        for f in self.store.list('segments'):
+            m = cumulus.store.type_patterns['segments'].match(f)
+            if m: yield m.group(1)
 
 class ObjectStore:
     def __init__(self, data_store):
diff --git a/python/cumulus/store/__init__.py b/python/cumulus/store/__init__.py
new file mode 100644
index 0000000..5ebf0d7
--- /dev/null
+++ b/python/cumulus/store/__init__.py
@@ -0,0 +1,22 @@
+import re
+
+type_patterns = {
+    'checksums': re.compile(r"^snapshot-(.*)\.(\w+)sums$"),
+    'segments': re.compile(r"^([0-9a-f]{8}-[0-9a-f]{4}-[0-9a-f]{4}-[0-9a-f]{4}-[0-9a-f]{12})(\.\S+)?$"),
+    'snapshots': re.compile(r"^snapshot-(.*)\.lbs$")
+}
+
+class Store:
+    """Base class for all cumulus storage backends."""
+
+    def list(self, type):
+        raise NotImplementedException
+
+    def get(self, type, name):
+        raise NotImplementedException
+
+    def put(self, type, name, fp):
+        raise NotImplementedException
+
+    def delete(self, type, name):
+        raise NotImplementedException
diff --git a/python/cumulus/store/s3.py b/python/cumulus/store/s3.py
new file mode 100644
index 0000000..0453c21
--- /dev/null
+++ b/python/cumulus/store/s3.py
@@ -0,0 +1,38 @@
+import os, sys, tempfile
+import boto
+from boto.s3.bucket import Bucket
+from boto.s3.key import Key
+
+import cumulus.store
+
+class S3Store(cumulus.store.Store):
+    def __init__(self, bucket, prefix):
+        self.conn = boto.connect_s3(is_secure=False)
+        self.bucket = self.conn.create_bucket(bucket)
+        while prefix.endswith("/"): prefix = prefix[:-1]
+        self.prefix = prefix
+
+    def _get_key(self, type, name):
+        k = Key(self.bucket)
+        k.key = "%s/%s/%s" % (self.prefix, type, name)
+        return k
+
+    def list(self, type):
+        prefix = "%s/%s/" % (self.prefix, type)
+        for i in self.bucket.list(prefix):
+            assert i.key.startswith(prefix)
+            yield i.key[len(prefix):]
+
+    def get(self, type, name):
+        fp = tempfile.TemporaryFile()
+        k = self._get_key(type, name)
+        k.get_file(fp)
+        fp.seek(0)
+        return fp
+
+    def put(self, type, name, fp):
+        k = self._get_key(type, name)
+        k.send_file(fp)
+
+    def delete(self, type, name):
+        self.bucket.delete_key("%s/%s/%s" % (self.prefix, type, name))
-- 
2.20.1