Terminology Guide

This document explains the terminology used in amqp-contract and how it maps to standard AMQP/RabbitMQ terms.

Core Terms

Client vs Publisher

In amqp-contract, we use the term "client" where AMQP documentation typically uses "publisher":

• TypedAmqpClient = Type-safe message publisher
• client.publish() = Publish a message to an exchange

Why "client"?

• Conveys the concept of an application that initiates communication
• Clear and intuitive for developers from various backgrounds
• Distinguishes this implementation from generic AMQP publishers

Standard AMQP terminology:

• Publisher/Producer = Application that sends messages
• Publishing = Sending messages to an exchange

Worker vs Consumer

In amqp-contract, we use the term "worker" where AMQP documentation typically uses "consumer":

• TypedAmqpWorker = Type-safe message consumer
• handlers = Message processing functions for each consumer

Why "worker"?

• Emphasizes the processing/handling aspect
• Familiar to developers from job queue systems (Bull, BullMQ, etc.)
• Conveys background processing behavior
• Implies an active processor rather than passive receiver

Standard AMQP terminology:

• Consumer/Subscriber = Application that receives messages
• Consuming = Receiving messages from a queue

Terminology Mapping

amqp-contract	AMQP Standard	Description
Client	Publisher / Producer	Sends messages
Worker	Consumer / Subscriber	Receives and processes messages
Contract	Schema / Specification	Defines exchanges, queues, and messages
Publisher (in contract)	Publishing endpoint	Named message publisher in contract
Consumer (in contract)	Consuming endpoint	Named message consumer in contract

Important: Contract vs Runtime Terminology

It's important to distinguish between contract-level and runtime-level terminology:

Contract Level

When defining a contract, we use standard AMQP terms:

const contract = defineContract({
  publishers: {
    // ← "publisher" in contract
    orderCreated: definePublisher(exchange, schema, options),
  },
  consumers: {
    // ← "consumer" in contract
    processOrder: defineConsumer(queue, schema),
  },
});

These terms (publishers, consumers) describe the messaging patterns in your contract.

Runtime Level

When implementing the contract, we use our terms:

// Client = runtime publisher
const client = await TypedAmqpClient.create({ contract, urls }).resultToPromise();

await client.publish("orderCreated", message).resultToPromise();

// Worker = runtime consumer
const worker = await TypedAmqpWorker.create({
  contract,
  handlers: {
    processOrder: async (message) => {
      // Handle message
    },
  },
  urls,
}).resultToPromise();

These terms (TypedAmqpClient, TypedAmqpWorker) describe the runtime components that implement the contract.

Why We Made This Choice

1. Clarity of Intent

The terms "client" and "worker" make the role of each component immediately clear:

• Client: Initiates communication (sends messages)
• Worker: Performs work (processes messages)

2. Familiarity

Many developers are familiar with these concepts from:

• Job queues: Bull, BullMQ, Sidekiq use "worker"
• HTTP: "client" is widely understood
• Distributed systems: Client/worker is a common pattern

3. Avoiding Ambiguity

The term "consumer" can be ambiguous:

• RabbitMQ consumer (technical)
• Business consumer (user of a service)
• Event consumer (event-driven architecture)

"Worker" is more specific to processing/handling behavior.

4. TypeScript Type Names

Our class names become:

• TypedAmqpClient (clear and concise)
• TypedAmqpWorker (clear and concise)

Compare with alternatives:

• TypedAmqpPublisher (more technical)
• TypedAmqpConsumer (ambiguous)

For AMQP Veterans

If you're coming from RabbitMQ or other AMQP libraries, here's a quick mental mapping:

// Other AMQP libraries might use:
const publisher = await createPublisher(config);
await publisher.publish(exchange, routingKey, message);

const consumer = await createConsumer(queue, handler);

// amqp-contract uses:
const client = await TypedAmqpClient.create({ contract, urls }).resultToPromise();

await client.publish("orderCreated", message).resultToPromise();

const worker = await TypedAmqpWorker.create({
  contract,
  handlers: { processOrder: handler },
  urls,
}).resultToPromise();

The functionality is identical; only the naming differs.

Future Considerations

We're committed to listening to the community. If there's strong feedback that the standard AMQP terms would be clearer, we may consider:

1. Type Aliases (backward compatible)

   export { TypedAmqpClient as TypedAmqpPublisher };
   export { TypedAmqpWorker as TypedAmqpConsumer };

2. Gradual Migration (deprecation period)

   • Introduce new names with deprecation warnings
   • Provide migration guide
   • Remove old names in v2.0

3. Documentation Enhancements

   • More prominent mapping explanations
   • Quick reference guide
   • Migration guide for RabbitMQ users

Providing Feedback

If you have opinions about our terminology choices, we'd love to hear from you:

• GitHub Discussions: Share your thoughts and vote on terminology
• GitHub Issues: Report terminology-related confusion
• Community Survey: Participate in our annual developer survey

Your feedback helps us improve the developer experience for everyone!

Summary

Quick Reference:

• Use TypedAmqpClient when you need to publish messages
• Use TypedAmqpWorker when you need to consume messages
• Remember: client = publisher, worker = consumer
• Contract definitions use standard terms: publishers and consumers
• Runtime components use our terms: TypedAmqpClient and TypedAmqpWorker

When reading RabbitMQ or AMQP documentation:

• Replace "publisher" with "client" mentally
• Replace "consumer" with "worker" mentally
• The concepts and patterns are identical

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This terminology was chosen to provide the clearest possible developer experience while maintaining full compatibility with AMQP semantics.