AWS Lambda function that processes cloudwatch logs and invokes a slack function

cloudwatch_logs.py

import boto3
import datetime
import json
import urllib2
import base64
import gzip
from StringIO import StringIO

print('Loading function')

class SlackWrapper:
    #slack
    __channel = '#test'
    __icon_url = 'https://raw.githubusercontent.com/donnemartin/dev-setup-resources/master/res/aws_lambda.png'
    __username = 'lambda'

    def __init__(self, username = __username):
        self.username = username
        self.client = boto3.client('lambda', region_name='ap-northeast-1')

    def post(self, posttext):
        params = {
                  'channel': self.__channel ,
                  'text':posttext,
                  'icon_url': self.__icon_url,
                  'username':self.username
                  }
        print params
        self.client.invoke(FunctionName='slack', InvocationType='Event', Payload=json.dumps(params))


class JST(datetime.tzinfo):
    def utcoffset(self, dt):
        return datetime.timedelta(hours=9)
    def dst(self, dt):
        return datetime.timedelta(0)
    def tzname(self, dt):
        return "JST"

def get_events(record):
    decoded_data = record.decode('base64')
    unzipped_data = gzip.GzipFile(fileobj=StringIO(decoded_data)).read()
    json_data = json.loads(unzipped_data)
    first_time = json_data['logEvents'][0]['timestamp']/1000.0
    events= "`" + datetime.datetime.fromtimestamp(first_time, tz=JST()).strftime('%Y-%m-%d %H:%M:%S%z') + "`\n"
    for data in json_data['logEvents']:
        events += data['message']
    return events, json_data['logGroup']

def lambda_handler(event, context):
    print("Received event: " + json.dumps(event, indent=2))

    if ("awslogs" in event):
        message, log_group = get_events(event['awslogs']['data'])
        slack = SlackWrapper(log_group)
        return slack.post(message)
    else:
        raise Exception('ERROR: not a cloudwatch logs event')