receiveMessage method

Future<ReceiveMessageResult> receiveMessage({
  1. required String queueUrl,
  2. List<QueueAttributeName>? attributeNames,
  3. int? maxNumberOfMessages,
  4. List<String>? messageAttributeNames,
  5. String? receiveRequestAttemptId,
  6. int? visibilityTimeout,
  7. int? waitTimeSeconds,
})

Retrieves one or more messages (up to 10), from the specified queue. Using the WaitTimeSeconds parameter enables long-poll support. For more information, see Amazon SQS Long Polling in the Amazon Simple Queue Service Developer Guide.

Short poll is the default behavior where a weighted random set of machines is sampled on a ReceiveMessage call. Thus, only the messages on the sampled machines are returned. If the number of messages in the queue is small (fewer than 1,000), you most likely get fewer messages than you requested per ReceiveMessage call. If the number of messages in the queue is extremely small, you might not receive any messages in a particular ReceiveMessage response. If this happens, repeat the request.

For each message returned, the response includes the following:

  • The message body.
  • An MD5 digest of the message body. For information about MD5, see RFC1321.
  • The MessageId you received when you sent the message to the queue.
  • The receipt handle.
  • The message attributes.
  • An MD5 digest of the message attributes.
The receipt handle is the identifier you must provide when deleting the message. For more information, see Queue and Message Identifiers in the Amazon Simple Queue Service Developer Guide.

You can provide the VisibilityTimeout parameter in your request. The parameter is applied to the messages that Amazon SQS returns in the response. If you don't include the parameter, the overall visibility timeout for the queue is used for the returned messages. For more information, see Visibility Timeout in the Amazon Simple Queue Service Developer Guide.

A message that isn't deleted or a message whose visibility isn't extended before the visibility timeout expires counts as a failed receive. Depending on the configuration of the queue, the message might be sent to the dead-letter queue.

May throw OverLimit.

Parameter queueUrl : The URL of the Amazon SQS queue from which messages are received.

Queue URLs and names are case-sensitive.

Parameter attributeNames : A list of attributes that need to be returned along with each message. These attributes include:

  • All – Returns all values.
  • ApproximateFirstReceiveTimestamp – Returns the time the message was first received from the queue (epoch time in milliseconds).
  • ApproximateReceiveCount – Returns the number of times a message has been received across all queues but not deleted.
  • AWSTraceHeader – Returns the AWS X-Ray trace header string.
  • SenderId
    • For an IAM user, returns the IAM user ID, for example ABCDEFGHI1JKLMNOPQ23R.
    • For an IAM role, returns the IAM role ID, for example ABCDE1F2GH3I4JK5LMNOP:i-a123b456.
  • SentTimestamp – Returns the time the message was sent to the queue (epoch time in milliseconds).
  • MessageDeduplicationId – Returns the value provided by the producer that calls the SendMessage action.
  • MessageGroupId – Returns the value provided by the producer that calls the SendMessage action. Messages with the same MessageGroupId are returned in sequence.
  • SequenceNumber – Returns the value provided by Amazon SQS.

Parameter maxNumberOfMessages : The maximum number of messages to return. Amazon SQS never returns more messages than this value (however, fewer messages might be returned). Valid values: 1 to 10. Default: 1.

Parameter messageAttributeNames : The name of the message attribute, where N is the index.

  • The name can contain alphanumeric characters and the underscore (_), hyphen (-), and period (.).
  • The name is case-sensitive and must be unique among all attribute names for the message.
  • The name must not start with AWS-reserved prefixes such as AWS. or Amazon. (or any casing variants).
  • The name must not start or end with a period (.), and it should not have periods in succession (..).
  • The name can be up to 256 characters long.
When using ReceiveMessage, you can send a list of attribute names to receive, or you can return all of the attributes by specifying All or .* in your request. You can also use all message attributes starting with a prefix, for example bar.*.

Parameter receiveRequestAttemptId : This parameter applies only to FIFO (first-in-first-out) queues.

The token used for deduplication of ReceiveMessage calls. If a networking issue occurs after a ReceiveMessage action, and instead of a response you receive a generic error, it is possible to retry the same action with an identical ReceiveRequestAttemptId to retrieve the same set of messages, even if their visibility timeout has not yet expired.

  • You can use ReceiveRequestAttemptId only for 5 minutes after a ReceiveMessage action.
  • When you set FifoQueue, a caller of the ReceiveMessage action can provide a ReceiveRequestAttemptId explicitly.
  • If a caller of the ReceiveMessage action doesn't provide a ReceiveRequestAttemptId, Amazon SQS generates a ReceiveRequestAttemptId.
  • It is possible to retry the ReceiveMessage action with the same ReceiveRequestAttemptId if none of the messages have been modified (deleted or had their visibility changes).
  • During a visibility timeout, subsequent calls with the same ReceiveRequestAttemptId return the same messages and receipt handles. If a retry occurs within the deduplication interval, it resets the visibility timeout. For more information, see Visibility Timeout in the Amazon Simple Queue Service Developer Guide.

  • While messages with a particular MessageGroupId are invisible, no more messages belonging to the same MessageGroupId are returned until the visibility timeout expires. You can still receive messages with another MessageGroupId as long as it is also visible.
  • If a caller of ReceiveMessage can't track the ReceiveRequestAttemptId, no retries work until the original visibility timeout expires. As a result, delays might occur but the messages in the queue remain in a strict order.
The maximum length of ReceiveRequestAttemptId is 128 characters. ReceiveRequestAttemptId can contain alphanumeric characters (a-z, A-Z, 0-9) and punctuation (!"#$%&'()*+,-./:;<=>?@[\]^_`{|}~).

For best practices of using ReceiveRequestAttemptId, see Using the ReceiveRequestAttemptId Request Parameter in the Amazon Simple Queue Service Developer Guide.

Parameter visibilityTimeout : The duration (in seconds) that the received messages are hidden from subsequent retrieve requests after being retrieved by a ReceiveMessage request.

Parameter waitTimeSeconds : The duration (in seconds) for which the call waits for a message to arrive in the queue before returning. If a message is available, the call returns sooner than WaitTimeSeconds. If no messages are available and the wait time expires, the call returns successfully with an empty list of messages.

Implementation

Future<ReceiveMessageResult> receiveMessage({
  required String queueUrl,
  List<QueueAttributeName>? attributeNames,
  int? maxNumberOfMessages,
  List<String>? messageAttributeNames,
  String? receiveRequestAttemptId,
  int? visibilityTimeout,
  int? waitTimeSeconds,
}) async {
  ArgumentError.checkNotNull(queueUrl, 'queueUrl');
  final $request = <String, dynamic>{};
  $request['QueueUrl'] = queueUrl;
  attributeNames?.also((arg) =>
      $request['AttributeNames'] = arg.map((e) => e.toValue()).toList());
  maxNumberOfMessages?.also((arg) => $request['MaxNumberOfMessages'] = arg);
  messageAttributeNames
      ?.also((arg) => $request['MessageAttributeNames'] = arg);
  receiveRequestAttemptId
      ?.also((arg) => $request['ReceiveRequestAttemptId'] = arg);
  visibilityTimeout?.also((arg) => $request['VisibilityTimeout'] = arg);
  waitTimeSeconds?.also((arg) => $request['WaitTimeSeconds'] = arg);
  final $result = await _protocol.send(
    $request,
    action: 'ReceiveMessage',
    version: '2012-11-05',
    method: 'POST',
    requestUri: '/',
    exceptionFnMap: _exceptionFns,
    shape: shapes['ReceiveMessageRequest'],
    shapes: shapes,
    resultWrapper: 'ReceiveMessageResult',
  );
  return ReceiveMessageResult.fromXml($result);
}