Enabling Long Polling in Amazon SQS

Long polling helps lower your cost of using Amazon SQS by reducing the number of empty responses and eliminating false empty responses. For more information about long polling, see Amazon SQS Long Polling.

In this example, you use the AWS SDK for Ruby with Amazon SQS to:

Prerequisites

Before running the example code, you need to install and configure the AWS SDK for Ruby, as described in:

You also need to create the queues existing-queue and receive-queue, which you can do in the Amazon SQS console.

Example

# Copyright 2010-2019 Amazon.com, Inc. or its affiliates. All Rights Reserved.
#
# This file is licensed under the Apache License, Version 2.0 (the "License").
# You may not use this file except in compliance with the License. A copy of the
# License is located at
#
# http://aws.amazon.com/apache2.0/
#
# This file is distributed on an "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS
# OF ANY KIND, either express or implied. See the License for the specific
# language governing permissions and limitations under the License.

# Demonstrates how to:
# 1. Create a queue and set it for long polling.
# 2. Set long polling for an existing queue.
# 3. Set long polling when receiving messages for a queue.

require 'aws-sdk-sqs'  # v2: require 'aws-sdk'

sqs = Aws::SQS::Client.new(region: 'us-east-1')

# Create a queue and set it for long polling.
new_queue_name = "new-queue"

create_queue_result = sqs.create_queue({
  queue_name: new_queue_name,
  attributes: {
    "ReceiveMessageWaitTimeSeconds" => "20" # Wait 20 seconds to receive messages.
  },
})
  
puts create_queue_result.queue_url

# Set long polling for an existing queue.
begin
  existing_queue_name = "existing-queue"
  existing_queue_url = sqs.get_queue_url(queue_name: existing_queue_name).queue_url

  sqs.set_queue_attributes({
    queue_url: existing_queue_url,
    attributes: { 
      "ReceiveMessageWaitTimeSeconds" => "20" # Wait 20 seconds to receive messages.
    },
  })
rescue Aws::SQS::Errors::NonExistentQueue
  puts "Cannot set long polling for a queue named '#{existing_queue_name}', as it does not exist."
end

# Set long polling when receiving messages for a queue.

# 1. Using receive_message.
begin
  receive_queue_name = "receive-queue"
  receive_queue_url = sqs.get_queue_url(queue_name: receive_queue_name).queue_url

  puts "Begin receipt of any messages using receive_message..."
  receive_message_result = sqs.receive_message({
    queue_url: receive_queue_url,
    attribute_names: ["All"], # Receive all available built-in message attributes.
    message_attribute_names: ["All"], # Receive any custom message attributes.
    max_number_of_messages: 10 # Receive up to 10 messages, if there are that many.
  })

  puts "Received #{receive_message_result.messages.count} message(s)."
rescue Aws::SQS::Errors::NonExistentQueue
  puts "Cannot receive messages using receive_message for a queue named '#{receive_queue_name}', as it does not exist."
end 

# 2. Using Aws::SQS::QueuePoller.
begin
  puts "Begin receipt of any messages using Aws::SQS::QueuePoller..."
  puts "(Will keep polling until no more messages available for at least 60 seconds.)"
  poller = Aws::SQS::QueuePoller.new(receive_queue_url)

  poller_stats = poller.poll({
    max_number_of_messages: 10,
    idle_timeout: 60 # Stop polling after 60 seconds of no more messages available (polls indefinitely by default).
  }) do |messages|
    messages.each do |message|
      puts "Message body: #{message.body}"
    end
  end
  # Note: If poller.poll is successful, all received messages are automatically deleted from the queue.

  puts "Poller stats:"
  puts "  Polling started at: #{poller_stats.polling_started_at}"
  puts "  Polling stopped at: #{poller_stats.polling_stopped_at}"
  puts "  Last message received at: #{poller_stats.last_message_received_at}"
  puts "  Number of polling requests: #{poller_stats.request_count}"
  puts "  Number of received messages: #{poller_stats.received_message_count}"
rescue Aws::SQS::Errors::NonExistentQueue
  puts "Cannot receive messages using Aws::SQS::QueuePoller for a queue named '#{receive_queue_name}', as it does not exist."
end