Python/Boto - Writing to AWS CloudWatch Logs without sequence token

Question

I am trying to send logs to AWS CloudWatch Logs using Python and Boto framework. I am doing this:

res=logs.put_log_events("FOO", "BAR",
     [{'timestamp':int(round(time.time() * 1000)),
       'message':time.strftime("%m/%d/%Y %H:%M:%S")+' Scheduled  monitoring check' }], 
     sequence_token=None)

I get an error each time I run:

boto.logs.exceptions.InvalidSequenceTokenException: InvalidSequenceTokenException: 400 Bad Request
{u'message': u'The given sequenceToken is invalid. The next expected sequenceToken is: 49540113336360065754596906019042392283494234157161146226', u'expectedSequenceToken': u'49540113336360065754596906019042392283494234157161146226', u'__type': u'InvalidSequenceTokenException'}

It is somewhat impractical for me to store that token. It makes no sense, why can't I just append to the log stream ?

How can I get around this ?

Answer 1

AWS Cloud Watch Putlogevent code

import boto3
import time


client = boto3.client('logs')

LOG_GROUP='cloudwatch_customlog'
LOG_STREAM='{}-{}'.format(time.strftime('%Y-%m-%d'),'logstream')

try:
   client.create_log_group(logGroupName=LOG_GROUP)
except client.exceptions.ResourceAlreadyExistsException:
   pass

try:
   client.create_log_stream(logGroupName=LOG_GROUP, logStreamName=LOG_STREAM)
except client.exceptions.ResourceAlreadyExistsException:
   pass

response = client.describe_log_streams(
   logGroupName=LOG_GROUP,
   logStreamNamePrefix=LOG_STREAM
)

event_log = {
   'logGroupName': LOG_GROUP,
   'logStreamName': LOG_STREAM,
   'logEvents': [
       {
           'timestamp': int(round(time.time() * 1000)),
           'message': time.strftime('%Y-%m-%d %H:%M:%S')+'\t Your custom log messages'
       }
   ],
}

if 'uploadSequenceToken' in response['logStreams'][0]:
   event_log.update({'sequenceToken': response['logStreams'][0] ['uploadSequenceToken']})

response = client.put_log_events(**event_log)
print(response)

Answer 2

Though most answers here work, BUT.. If you have multiple processes that write to the same stream really fast, they'll get the exception all the time, and if you put it in a loop, the same race condition applies. Everyone should be aware of that!