SQS (Simple Queue Service)

Overview

DevCloud SQS provides in-memory message queues. Queues are stored in memory with thread-safe access (sync.RWMutex). Data is not persisted — all queues and messages are lost on server restart.

SQS supports dual protocol: legacy Query protocol (form-encoded with XML responses) and modern JSON 1.0 protocol (used by boto3 1.42+). The protocol is auto-detected based on the Content-Type header.

Supported APIs

All 23 SQS operations are handled over the JSON 1.0 protocol.

Operation	Description
CreateQueue	Create a new queue (returns existing if name matches); supports FIFO + attributes
ListQueues	List queues with optional name prefix filter
GetQueueUrl	Resolve queue name to its URL
DeleteQueue	Delete a queue and all its messages
PurgeQueue	Remove all messages from a queue
SendMessage / SendMessageBatch	Send one or many messages (computes MD5 hash)
ReceiveMessage	Receive messages with visibility timeout and MaxNumberOfMessages
DeleteMessage / DeleteMessageBatch	Delete one or many messages by receipt handle
ChangeMessageVisibility / ChangeMessageVisibilityBatch	Adjust message visibility timeout
GetQueueAttributes / SetQueueAttributes	Read/write queue attributes (incl. RedrivePolicy)
TagQueue / UntagQueue / ListQueueTags	Manage queue tags
ListDeadLetterSourceQueues	List queues that use a queue as their dead-letter target
StartMessageMoveTask / ListMessageMoveTasks / CancelMessageMoveTask	Redrive messages out of a dead-letter queue
AddPermission / RemovePermission	Accepted (no-op — permissions are not enforced)

boto3 Examples

Send and receive messages

import boto3

sqs = boto3.client(
    "sqs",
    endpoint_url="http://localhost:4747",
    aws_access_key_id="test",
    aws_secret_access_key="test",
    region_name="us-east-1",
)

# Create queue
response = sqs.create_queue(QueueName="my-queue")
queue_url = response["QueueUrl"]

# Send message
sqs.send_message(QueueUrl=queue_url, MessageBody="Hello from DevCloud!")

# Receive messages
messages = sqs.receive_message(QueueUrl=queue_url, MaxNumberOfMessages=10)
for msg in messages.get("Messages", []):
    print(msg["Body"])
    sqs.delete_message(QueueUrl=queue_url, ReceiptHandle=msg["ReceiptHandle"])

List queues

response = sqs.list_queues()
for url in response.get("QueueUrls", []):
    print(url)

AWS CLI Examples

# Create queue
aws --endpoint-url http://localhost:4747 sqs create-queue --queue-name my-queue

# Send message
aws --endpoint-url http://localhost:4747 sqs send-message \
  --queue-url http://localhost:4747/000000000000/my-queue \
  --message-body "hello"

# Receive messages
aws --endpoint-url http://localhost:4747 sqs receive-message \
  --queue-url http://localhost:4747/000000000000/my-queue

Known Limitations

In-memory only — no persistence across restarts
Dead-letter redrive (message move tasks) runs synchronously: tasks complete immediately, so there is no RUNNING status and MaxNumberOfMessagesPerSecond is not throttled
AddPermission/RemovePermission are accepted but not enforced (no access-policy checks)
Queue-level DelaySeconds and VisibilityTimeout attributes are stored and echoed back by SetQueueAttributes/GetQueueAttributes but not enforced: SendMessage ignores DelaySeconds and ReceiveMessage honors only its per-request VisibilityTimeout (default 30s)
No message retention/expiry enforcement
No long polling (WaitTimeSeconds is not honored — receives return immediately)