version support with peek-ahead functionality
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Sandy Walsh
parent
be6dee825c
commit
8b0f265a9e
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@ -17,16 +17,37 @@ def handle_datetime(obj):
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def InvalidVersion(Exception):
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pass
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def OutOfSync(Exception):
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pass
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BOR_MAGIC_NUMBER = 0x69867884
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class Version1(object):
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# Version 1 SCHEMA
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# ----------------
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class Version0(object):
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# Preamble ... same for all versions.
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# i = 0x69867884 (EVNT)
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# h = version
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def __init__(self):
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self.preamble_schema = "ih"
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self.preamble_size = struct.calcsize(self.preamble_schema)
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def make_preamble(self, version):
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return struct.pack(self.preamble_schema, BOR_MAGIC_NUMBER, version)
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def load_preamble(self, file_handle):
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raw = file_handle.read(self.preamble_size)
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header = struct.unpack(self.preamble_schema, raw)
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if header[0] != BOR_MAGIC_NUMBER:
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raise OutOfSync()
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return header[1]
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class Version1(Version0):
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# Version 1 SCHEMA
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# ----------------
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# i = metadata block length
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# i = raw notification block length
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# i = 0x00000000 EOR
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@ -44,7 +65,7 @@ class Version1(object):
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#--------
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# With above Event and Metadata
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#
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# Header schema: "ihiii"
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# Header schema: "iii"
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# Metadata length: 119
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# Raw notification length: 201
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# Metadata = 6 strings (3 key-value pairs)
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@ -59,7 +80,8 @@ class Version1(object):
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# - 197
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def __init__(self):
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self.header_schema = "ihiii"
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super(Version1, self).__init__()
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self.header_schema = "iii"
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self.header_size = struct.calcsize(self.header_schema)
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def pack(self, notification, metadata):
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@ -84,22 +106,21 @@ class Version1(object):
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metadata = struct.pack(metadata_schema, *metadata_values)
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header = struct.pack(self.header_schema, BOR_MAGIC_NUMBER, 1,
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header = struct.pack(self.header_schema,
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struct.calcsize(metadata_schema),
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struct.calcsize(raw_block_schema), 0)
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return (header, metadata, raw_block)
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preamble = self.make_preamble(1)
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return (preamble, header, metadata, raw_block)
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def unpack(self, file_handle):
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header_bytes = file_handle.read(self.header_size)
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header = struct.unpack(self.header_schema, header_bytes)
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if header[0] != BOR_MAGIC_NUMBER:
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raise OutOfSync()
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if header[1] != 1:
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raise InvalidVersion("Expected V1, got V%d" % header[1])
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if header[2] != 0:
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raise OutOfSync("Didn't find 0 EOR marker.")
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metadata_bytes = file_handle.read(header[2])
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metadata_bytes = file_handle.read(header[0])
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num_strings = struct.unpack_from("i", metadata_bytes)
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offset = struct.calcsize("i")
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lengths = num_strings[0] / 2
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@ -114,7 +135,7 @@ class Version1(object):
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metadata = dict((key_values[n], key_values[n+1])
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for n in range(len(key_values))[::2])
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raw = file_handle.read(header[3])
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raw = file_handle.read(header[1])
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raw_len = struct.unpack_from("i", raw)
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offset = struct.calcsize("i")
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raw_json = struct.unpack_from("%ds" % raw_len[0], raw, offset=offset)
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@ -140,35 +161,38 @@ def pack_notification(notification, metadata, version=CURRENT_VERSION):
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return version_handler.pack(notification, metadata)
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def unpack_notification(file_handle, version=CURRENT_VERSION):
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def unpack_notification(file_handle):
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v0 = Version0()
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version = v0.load_preamble(file_handle)
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version_handler = get_version_handler(version)
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return version_handler.unpack(file_handle)
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event = {"event_type": "nova.compute.run_instance.start",
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"generated": datetime.datetime.utcnow(),
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"request_id": "req-1234abcd5678efgh",
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"source": "n-compute-1973",
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"payload": {
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"foo": 123,
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"blah": "abc",
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"zoo": False
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}
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}
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json_event = json.dumps(event, default=handle_datetime)
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metadata = {'request_id': event['request_id'],
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'event_type': event['event_type'],
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'source': event['source'],
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}
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if __name__ == "__main__":
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event = {"event_type": "nova.compute.run_instance.start",
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"generated": datetime.datetime.utcnow(),
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"request_id": "req-1234abcd5678efgh",
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"source": "n-compute-1973",
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"payload": {
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"foo": 123,
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"blah": "abc",
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"zoo": False
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}
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}
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json_event = json.dumps(event, default=handle_datetime)
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metadata = {'request_id': event['request_id'],
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'event_type': event['event_type'],
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'source': event['source'],
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}
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binary = pack_notification(json_event, metadata)
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binary = pack_notification(json_event, metadata)
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with open("test.dat", "wb") as f:
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for block in binary:
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f.write(block)
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with open("test.dat", "wb") as f:
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for block in binary:
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f.write(block)
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with open("test.dat", "rb") as f:
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metadata, notification = unpack_notification(f)
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print "Metadata:", metadata
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print "Notification:", notification
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with open("test.dat", "rb") as f:
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metadata, notification = unpack_notification(f)
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print "Metadata:", metadata
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print "Notification:", notification
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