On 23/06/2021 19:42, Larry Martell wrote:
When an AWS cloudwatch event is passed to a consumer it looks like this:
{
"awslogs": {
"data": "ewogICAgIm1l..."
}
}
To get the actual message I do this:
def _decode(data):
compressed_payload = b64decode(data)
json_payload = zlib.decompress(compressed_payload, 16+zlib.MAX_WBITS)
return json.loads(json_payload)
message = _decode(json.dumps(event['awslogs']['data']))
This returns the log message as a string.
For my unit tests I need to reverse this - given a message as a string
I want to generate the compressed, encoded event structure.
I have not been able to get this to work. I have this:
message = b'test message'
compressed= zlib.compress(message)
event['awslogs']['data'] = str(compressed)
message = _decode(json.dumps(event['awslogs']['data']))
Traceback (most recent call last):
File "<stdin>", line 1, in <module>
File "<stdin>", line 3, in _decode
zlib.error: Error -3 while decompressing data: incorrect header check
Anyone see how to make this work?
The json/bas64 parts are not involved in the problem:
>>> zlib.decompress(zlib.compress(b"foo"), 16 + zlib.MAX_WBITS)
Traceback (most recent call last):
File "<pyshell#4>", line 1, in <module>
zlib.decompress(zlib.compress(b"foo"), 16 + zlib.MAX_WBITS)
zlib.error: Error -3 while decompressing data: incorrect header check
whereas:
>>> zlib.decompress(zlib.compress(b"foo"))
b'foo'
Unfortunately compress() doesn't accept the flags you seem to require.
However, reading around a bit in the zlib docs turns up the compressobj
which does. So
>>> def mycompress(data):
obj = zlib.compressobj(wbits=16 + zlib.MAX_WBITS)
result = obj.compress(data)
result += obj.flush()
return result
>>> zlib.decompress(mycompress(b"foo"), 16 + zlib.MAX_WBITS)
b'foo'
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