在 Amazon SQS 中使用死信队列 - Amazon 适用于 Ruby 的 SDK
先决条件示例
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在 Amazon SQS 中使用死信队列

Amazon SQS 可为死信队列提供支持。死信队列是其他（源）队列可将其作为无法成功处理的消息的目标的队列。您可以搁置和隔离死信队列中的这些消息以确定其处理失败的原因。有关死信队列的更多信息，请参阅使用 Amazon SQS 死信队列。

在此示例中，您结合使用适用于 Ruby 的 Amazon SDK 和 Amazon SQS 以实现如下用途：

  1. 通过使用 Aws::SQS::Client#create_queue 来创建表示死信队列的队列。

  2. 通过使用 Aws::SQS::Client#set_queue_attributes 来将死信队列与现有队列相关联。

  3. 通过使用 Aws::SQS::Client#send_message 来向现有队列发送消息。

  4. 通过使用 Aws::SQS::QueuePoller 来轮询队列。

  5. 通过使用 Aws::SQS::Client#receive_message 来接收死信队列中的消息。

先决条件

在运行示例代码之前，您需要安装并配置适用于 Ruby 的 Amazon SDK，如以下文档所述：

您还需要使用 Amazon Web Services Management Console创建现有队列 my-queue。

注意

为简单起见，此示例代码没有演示 Aws::SQS::Client#add_permission。在真实场景中，您应始终限制对 SendMessage、ReceiveMessage、DeleteMessage 和 DeleteQueue 之类的操作的访问。不这样做可能会导致信息泄露、拒绝服务或将消息注入您的队列中。

示例

# 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 representing a dead letter queue.
# 2. Associate the dead letter queue with an existing queue.

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

# Uncomment for Windows.
# Aws.use_bundled_cert!

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

# Create a queue representing a dead letter queue.
dead_letter_queue_name = "dead-letter-queue"

sqs.create_queue({
  queue_name: dead_letter_queue_name
})

# Get the dead letter queue's URL and ARN, so that you can associate it with an existing queue.
dead_letter_queue_url = sqs.get_queue_url(queue_name: dead_letter_queue_name).queue_url

dead_letter_queue_arn = sqs.get_queue_attributes({
  queue_url: dead_letter_queue_url,
  attribute_names: ["QueueArn"]
}).attributes["QueueArn"]

# Associate the dead letter queue with an existing queue.
begin
  queue_name = "my-queue"
  queue_url = sqs.get_queue_url(queue_name: queue_name).queue_url

  # Use a redrive policy to specify the dead letter queue and its behavior.
  redrive_policy = {
    "maxReceiveCount" => "5", # After the queue receives the same message 5 times, send that message to the dead letter queue.
    "deadLetterTargetArn" => dead_letter_queue_arn
  }.to_json

  sqs.set_queue_attributes({
    queue_url: queue_url,
    attributes: {
      "RedrivePolicy" => redrive_policy
    }
  })

rescue Aws::SQS::Errors::NonExistentQueue
  puts "A queue named '#{queue_name}' does not exist."
  exit(false)
end

# Send a message to the queue.
puts "Sending a message..."

sqs.send_message({
  queue_url: queue_url,
  message_body: "I hope I get moved to the dead letter queue."
})

30.downto(0) do |i|
  print "\rWaiting #{i} second(s) for sent message to be receivable..."
  sleep(1)
end

puts "\n"

poller = Aws::SQS::QueuePoller.new(queue_url)
# Receive 5 messages max and stop polling after 20 seconds of no received messages.
poller.poll(max_number_of_messages:5, idle_timeout: 20) do |messages|
  messages.each do |msg|
    puts "Received message ID: #{msg.message_id}"
  end
end

# Check to see if Amazon SQS moved the message to the dead letter queue.
receive_message_result = sqs.receive_message({
  queue_url: dead_letter_queue_url,
  max_number_of_messages: 1
})

if receive_message_result.messages.count > 0
  puts "\n#{receive_message_result.messages[0].body}"
else
  puts "\nNo messages received."
end