message_wrapper.py

# Copyright Amazon.com, Inc. or its affiliates. All Rights Reserved.
# SPDX-License-Identifier: Apache-2.0

"""
Purpose

Demonstrate basic message operations in Amazon Simple Queue Service (Amazon SQS).
"""

# snippet-start:[python.example_code.sqs.message_wrapper_imports]
import logging
import sys

import boto3
from botocore.exceptions import ClientError
import queue_wrapper
from os import environ
logger = logging.getLogger(__name__)
sqs = boto3.resource('sqs',aws_access_key_id=environ['SQS_AWS_ACCESS_KEY_ID'],
        aws_secret_access_key=environ['SQS_AWS_SECRET_ACCESS_KEY'],
        region_name=environ['SQS_REGION'])
# snippet-end:[python.example_code.sqs.message_wrapper_imports]


# snippet-start:[python.example_code.sqs.SendMessage]
def send_message(queue, message_body, message_attributes=None):
    """
    Send a message to an Amazon SQS queue.

    :param queue: The queue that receives the message.
    :param message_body: The body text of the message.
    :param message_attributes: Custom attributes of the message. These are key-value
                               pairs that can be whatever you want.
    :return: The response from SQS that contains the assigned message ID.
    """
    if not message_attributes:
        message_attributes = {}

    try:
        response = queue.send_message(
            MessageBody=message_body,
            MessageAttributes=message_attributes
        )
    except ClientError as error:
        logger.exception("Send message failed: %s", message_body)
        raise error
    else:
        return response
# snippet-end:[python.example_code.sqs.SendMessage]


# snippet-start:[python.example_code.sqs.SendMessageBatch]
def send_messages(queue, messages):
    """
    Send a batch of messages in a single request to an SQS queue.
    This request may return overall success even when some messages were not sent.
    The caller must inspect the Successful and Failed lists in the response and
    resend any failed messages.

    :param queue: The queue to receive the messages.
    :param messages: The messages to send to the queue. These are simplified to
                     contain only the message body and attributes.
    :return: The response from SQS that contains the list of successful and failed
             messages.
    """
    try:
        entries = [{
            'Id': str(ind),
            'MessageBody': msg['body'],
            'MessageAttributes': msg['attributes']
        } for ind, msg in enumerate(messages)]
        response = queue.send_messages(Entries=entries)
        if 'Successful' in response:
            for msg_meta in response['Successful']:
                logger.info(
                    "Message sent: %s: %s",
                    msg_meta['MessageId'],
                    messages[int(msg_meta['Id'])]['body']
                )
        if 'Failed' in response:
            for msg_meta in response['Failed']:
                logger.warning(
                    "Failed to send: %s: %s",
                    msg_meta['MessageId'],
                    messages[int(msg_meta['Id'])]['body']
                )
    except ClientError as error:
        logger.exception("Send messages failed to queue: %s", queue)
        raise error
    else:
        return response
# snippet-end:[python.example_code.sqs.SendMessageBatch]


# snippet-start:[python.example_code.sqs.ReceiveMessage]
def receive_messages(queue, max_number, wait_time):
    """
    Receive a batch of messages in a single request from an SQS queue.

    :param queue: The queue from which to receive messages.
    :param max_number: The maximum number of messages to receive. The actual number
                       of messages received might be less.
    :param wait_time: The maximum time to wait (in seconds) before returning. When
                      this number is greater than zero, long polling is used. This
                      can result in reduced costs and fewer false empty responses.
    :return: The list of Message objects received. These each contain the body
             of the message and metadata and custom attributes.
    """
    try:
        messages = queue.receive_messages(
            MessageAttributeNames=['All'],
            MaxNumberOfMessages=max_number,
            WaitTimeSeconds=wait_time
        )
        for msg in messages:
            logger.info("Received message: %s: %s", msg.message_id, msg.body)
    except ClientError as error:
        logger.exception("Couldn't receive messages from queue: %s", queue)
        raise error
    else:
        return messages
# snippet-end:[python.example_code.sqs.ReceiveMessage]


# snippet-start:[python.example_code.sqs.DeleteMessage]
def delete_message(message):
    """
    Delete a message from a queue. Clients must delete messages after they
    are received and processed to remove them from the queue.

    :param message: The message to delete. The message's queue URL is contained in
                    the message's metadata.
    :return: None
    """
    try:
        message.delete()
        logger.info("Deleted message: %s", message.message_id)
    except ClientError as error:
        logger.exception("Couldn't delete message: %s", message.message_id)
        raise error
# snippet-end:[python.example_code.sqs.DeleteMessage]


# snippet-start:[python.example_code.sqs.DeleteMessageBatch]
def delete_messages(queue, messages):
    """
    Delete a batch of messages from a queue in a single request.

    :param queue: The queue from which to delete the messages.
    :param messages: The list of messages to delete.
    :return: The response from SQS that contains the list of successful and failed
             message deletions.
    """
    try:
        entries = [{
            'Id': str(ind),
            'ReceiptHandle': msg.receipt_handle
        } for ind, msg in enumerate(messages)]
        response = queue.delete_messages(Entries=entries)
        if 'Successful' in response:
            for msg_meta in response['Successful']:
                logger.info("Deleted %s", messages[int(msg_meta['Id'])].receipt_handle)
        if 'Failed' in response:
            for msg_meta in response['Failed']:
                logger.warning(
                    "Could not delete %s",
                    messages[int(msg_meta['Id'])].receipt_handle
                )
    except ClientError:
        logger.exception("Couldn't delete messages from queue %s", queue)
    else:
        return response
# snippet-end:[python.example_code.sqs.DeleteMessageBatch]


# snippet-start:[python.example_code.sqs.Scenario_SendReceiveBatch]
def usage_demo():
    """
    Shows how to:
    * Read the lines from this Python file and send the lines in
      batches of 10 as messages to a queue.
    * Receive the messages in batches until the queue is empty.
    * Reassemble the lines of the file and verify they match the original file.
    """
    def pack_message(msg_path, msg_body, msg_line):
        return {
            'body': msg_body,
            'attributes': {
                'path': {'StringValue': msg_path, 'DataType': 'String'},
                'line': {'StringValue': str(msg_line), 'DataType': 'String'}
            }
        }

    def unpack_message(msg):
        return (msg.message_attributes['path']['StringValue'],
                msg.body,
                int(msg.message_attributes['line']['StringValue']))

    print('-'*88)
    print("Welcome to the Amazon Simple Queue Service (Amazon SQS) demo!")
    print('-'*88)

    queue = queue_wrapper.create_queue('sqs-usage-demo-message-wrapper')

    with open(__file__) as file:
        lines = file.readlines()

    line = 0
    batch_size = 10
    received_lines = [None]*len(lines)
    print(f"Sending file lines in batches of {batch_size} as messages.")
    while line < len(lines):
        messages = [pack_message(__file__, lines[index], index)
                    for index in range(line, min(line + batch_size, len(lines)))]
        line = line + batch_size
        send_messages(queue, messages)
        print('.', end='')
        sys.stdout.flush()
    print(f"Done. Sent {len(lines) - 1} messages.")

    print(f"Receiving, handling, and deleting messages in batches of {batch_size}.")
    more_messages = True
    while more_messages:
        received_messages = receive_messages(queue, batch_size, 2)
        print('.', end='')
        sys.stdout.flush()
        for message in received_messages:
            path, body, line = unpack_message(message)
            received_lines[line] = body
        if received_messages:
            delete_messages(queue, received_messages)
        else:
            more_messages = False
    print('Done.')

    if all([lines[index] == received_lines[index] for index in range(len(lines))]):
        print(f"Successfully reassembled all file lines!")
    else:
        print(f"Uh oh, some lines were missed!")

    queue.delete()

    print("Thanks for watching!")
    print('-'*88)
# snippet-end:[python.example_code.sqs.Scenario_SendReceiveBatch]


if __name__ == '__main__':
    usage_demo()