AMQP 0.9.1 Support Status

This page tracks OtterMQ’s support for AMQP 0.9.1 classes and methods. It is intended to help users understand current capabilities and to guide contributors.

Status levels:

• Implemented ✅: Feature is available and tested
• Partial ⚠️: Some behavior is missing or differs from spec
• Planned ❌: Not yet implemented but on the roadmap
• Not Supported ‼️: Out of scope or no plans yet

Summary by Class

Class	Status	Notes
connection	100%	All methods fully implemented
channel	100%	All methods fully implemented including flow control
exchange	100%	All exchange types fully implemented
queue	100%	All methods fully implemented including priority queues
basic	100%	All methods fully implemented including priority delivery
tx	100%	All transaction methods fully implemented

connection

Method	Status	Notes
connection.start	✅
connection.start-ok	✅
connection.tune	✅
connection.tune-ok	✅
connection.open	✅
connection.open-ok	✅
connection.close	✅
connection.close-ok	✅

channel

Method	Status	Notes
channel.open	✅
channel.open-ok	✅
channel.flow	✅	Client-initiated flow control; server-initiated flow supported
channel.flow-ok	✅
channel.close	✅
channel.close-ok	✅

Flow Control Features:

• ✅ Client-initiated flow control (client pauses message delivery)
• ✅ Server-initiated flow control (server pauses client publishing)
• ✅ Per-channel flow state (independent control per channel)
• ✅ Integration with QoS throttling
• ✅ basic.get unaffected by flow (synchronous pull always works)
• ✅ basic.consume respects flow state (async delivery can be paused)
• ✅ Thread-safe flow state management

QoS and Consumer Management:

• ✅ Per-consumer prefetch limits (O(1) counting)
• ✅ Channel-level global prefetch limits
• ✅ Automatic requeue on consumer cancel (AMQP spec compliant)
• ✅ Redelivered flag set correctly on requeued messages
• ✅ O(1) consumer cancel performance (dual-index tracking)
• ✅ Multiple consumers per channel with independent unacked tracking

exchange

Method	Status	Notes
exchange.declare	✅	Supports direct, fanout, and topic exchange types
exchange.declare-ok	✅
exchange.delete	✅
exchange.delete-ok	✅

Topic Exchange Features:

• ✅ Wildcard pattern matching with * (matches exactly one word)
• ✅ Wildcard pattern matching with # (matches zero or more words)
• ✅ Dot-separated routing key matching
• ✅ Multiple binding patterns per queue
• ✅ Complex pattern combinations (e.g., *.error.#, log.*.database)
• ✅ Malformed input validation (empty words, invalid patterns)

queue

Method	Status	Notes
queue.declare	✅	Supports x-max-priority argument (1-255, configurable limit)
queue.declare-ok	✅
queue.bind	✅
queue.bind-ok	✅
queue.unbind	✅
queue.unbind-ok	✅
queue.purge	✅	Works with priority queues
queue.purge-ok	✅
queue.delete	✅
queue.delete-ok	✅

Priority Queue Features:

• ✅ Queue-level priority configuration via x-max-priority argument
• ✅ Priority range: 0-255 (configurable max, default: 10)
• ✅ Higher priority messages delivered first
• ✅ FIFO ordering within same priority level
• ✅ Messages without priority default to 0 (lowest)
• ✅ Priority clamped to queue’s max-priority setting
• ✅ Lazy channel allocation (memory efficient)
• ✅ Backward compatible (queues without x-max-priority remain FIFO)
• ✅ Integration with DLX, TTL, and QLL extensions

basic

Method	Status	Notes
basic.qos	✅	Per-consumer and channel-level prefetch supported
basic.qos-ok	✅
basic.consume	✅	‼️noLocal not supported (same as RabbitMQ)
basic.consume-ok	✅
basic.cancel	✅	Automatically requeues unacked messages per AMQP spec
basic.cancel-ok	✅
basic.publish	✅
basic.return	✅	‼️immediate flag is deprecated and will not be implemented
basic.deliver	✅	Respects message priority for delivery order
basic.get	✅	Returns highest priority message first
basic.get-ok	✅
basic.get-empty	✅
basic.ack	✅
basic.reject	✅	Requeue works; dead-lettering implemented
basic.recover-async	✅
basic.recover	✅
basic.recover-ok	✅
basic.nack	✅	*not part of amqp 0-9-1 specs

tx (Transactions)

Method	Status	Notes
tx.select	✅	Enter transaction mode (idempotent)
tx.select-ok	✅
tx.commit	✅	Atomically commit buffered operations
tx.commit-ok	✅
tx.rollback	✅	Discard buffered operations
tx.rollback-ok	✅

Transaction Features:

• ✅ Transactional publishing with buffering
• ✅ Transactional acknowledgments (ACK/NACK/REJECT)
• ✅ Multiple commits per transaction mode
• ✅ Channel close implicit rollback
• ✅ Mandatory message handling in transactions
• ✅ Mixed operations (publish + ack) in single transaction

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RabbitMQ Extensions

Beyond core AMQP 0.9.1, OtterMQ implements popular RabbitMQ extensions:

Extension	Status	Configuration	Documentation
Dead Letter Exchange (DLX)	✅ Full	OTTERMQ_ENABLE_DLX=true	DLX Guide
Message TTL	✅ Full	OTTERMQ_ENABLE_TTL=true	TTL Guide

Extension Details

Dead Letter Exchange (DLX)

• Queue arguments: x-dead-letter-exchange, x-dead-letter-routing-key
• Death reasons: rejected, expired, maxlen (future)
• Full x-death header tracking with count, time, reason, original queue/exchange
• Compatible with all RabbitMQ clients

Message TTL and Expiration

• Per-message TTL: Expiration property (milliseconds as string)
• Per-queue TTL: x-message-ttl queue argument
• Precedence: Per-message TTL takes priority over per-queue TTL
• Lazy expiration: Checked at retrieval time (delivery, basic.get, requeue)
• DLX integration: Expired messages routed to DLX with reason "expired"
• Compatible with RabbitMQ TTL semantics

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Notes:

• Keep this table in sync with the implementation in internal/core/amqp/* and internal/core/broker/*.
• When adding or changing behavior, update the status and add notes on limitations or differences from RabbitMQ behavior.
• “Partial” (⚠️) means one or more optional behaviors/properties are not yet implemented.