def increment_counter()

in amazon_polly_async_batch/dynamo.py [0:0]

• 23 lines of code
• 7 McCabe index (conditional complexity)

    def increment_counter(self, set_name, field):
        """
        Increments the `field` counter by 1 for the `set_name`. Because this method can be executing
        in multiple Lambdas concurrently, use a conditional update so we don't lose counters.
        :param set_name: the name of the set
        :param field: the field to increment (successes or failures)
        """
        success, attempts = False, 0
        while attempts <= 10 and not success:
            try:
                attempts = attempts + 1
                # Load up the existing record
                existing = self.get_set(set_name)
                # Add one to the correct field, so long as no one updated in the meantime
                results = dynamodb.update_item(
                    TableName=self.table_name,
                    Key={'setName': {'S': set_name}},
                    UpdateExpression='ADD {} :num SET updatedTime = :when'.format(field),
                    ConditionExpression='{} = :existing'.format(field),
                    ExpressionAttributeValues={':num': {'N': '1'},
                                               ':existing': {'N': '{}'.format(existing[field]['N'])},
                                               ':when': {'S': datetime.datetime.now().isoformat()}}
                )
                # Got this far? Then success!
                success = True
            except ClientError as e:
                if e.response['Error']['Code'] == 'ConditionalCheckFailedException': 
                    # Another Lambda updated the value under our feet; sleep a teeny bit and try again
                    time.sleep(0.1)
                else:
                    raise
        if not success:
            logger.error('Failed to increment {} for set {}'.format(set_name, field))