watermill

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Published: Feb 19, 2020 License: MIT Imports: 12 Imported by: 205

README

Watermill

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Watermill is a Go library for working efficiently with message streams. It is intended for building event driven applications, enabling event sourcing, RPC over messages, sagas and basically whatever else comes to your mind. You can use conventional pub/sub implementations like Kafka or RabbitMQ, but also HTTP or MySQL binlog if that fits your use case.

Goals

  • Easy to understand.
  • Universal - event-driven architecture, messaging, stream processing, CQRS - use it for whatever you need.
  • Fast (see Benchmarks).
  • Flexible with middlewares, plugins and Pub/Sub configurations.
  • Resilient - using proven technologies and passing stress tests (see Stability).

Getting Started

Pick what you like the best or see in order:

  1. Follow the Getting Started guide.
  2. See examples below.
  3. Read the full documentation: https://watermill.io/

Examples

Background

Building distributed and scalable services is rarely as easy as some may suggest. There is a lot of hidden knowledge that comes with writing such systems. Just like you don't need to know the whole TCP stack to create a HTTP REST server, you shouldn't need to study all of this knowledge to start with building message-driven applications.

Watermill's goal is to make communication with messages as easy to use as HTTP routers. It provides the tools needed to begin working with event-driven architecture and allows you to learn the details on the go.

At the heart of Watermill there is one simple interface:

func(*Message) ([]*Message, error)

Your handler receives a message and decides whether to publish new message(s) or return an error. What happens next is up to the middlewares you've chosen.

You can find more about our motivations in our Introducing Watermill blog post.

Pub/Subs

All publishers and subscribers have to implement an interface:

type Publisher interface {
	Publish(topic string, messages ...*Message) error
	Close() error
}

type Subscriber interface {
	Subscribe(ctx context.Context, topic string) (<-chan *Message, error)
	Close() error
}

Supported Pub/Subs:

All Pub/Subs implementation documentation can be found in the documentation.

Contributing

Please check our contributing guide.

Stability

Watermill v1.0.0 has been released and is production-ready. The public API is stable and will not change without changing the major version.

To ensure that all Pub/Subs are stable and safe to use in production, we created a set of tests that need to pass for each of the implementations before merging to master. All tests are also executed in stress mode - that means that we are running all the tests 20x in parallel.

All tests are run with the race condition detector enabled (-race flag in tests).

Benchmarks

Initial tools for benchmarking Pub/Subs can be found in watermill-benchmark.

All benchmarks are being done on a single 16 CPU VM instance, running one binary and dependencies in Docker Compose.

These numbers are meant to serve as a rough estimate of how fast messages can be processed by different Pub/Subs. Keep in mind that the results can be vastly different, depending on the setup and configuration (both much lower and higher).

Here's the short version for message size of 16 bytes.

Pub/Sub Publish (messages / s) Subscribe (messages / s)
Kafka (one node) 63,506 110,811
Kafka (5 nodes) 70,252 117,529
NATS 76,208 38,169
SQL (MySQL) 7,299 154
SQL (PostgreSQL) 4,142 98
Google Cloud Pub/Sub 7,416 39,591
AMQP 2,408 10,608
GoChannel 272,938 101,371

Support

If you didn't find the answer to your question in the documentation, feel free to ask us directly!

Please join us on the #watermill channel on the Gophers slack: You can get an invite here.

Every bit of feedback is very welcome and appreciated. Please submit it using the survey.

Why the name?

It processes streams!

License

MIT License

Documentation

Overview

Watermill is a Golang library for working efficiently with message streams.

It is intended for building event driven applications, enabling event sourcing, RPC over messages, sagas and basically whatever else comes to your mind.

You can use conventional pub/sub implementations like Kafka or RabbitMQ, but also HTTP or MySQL binlog if that fits your use case.

Website with detailed documentation: https://watermill.io/

Getting started guide: https://watermill.io/docs/getting-started/

Index

Constants

This section is empty.

Variables

This section is empty.

Functions

func NewShortUUID added in v0.3.0

func NewShortUUID() string

func NewULID added in v0.3.0

func NewULID() string

func NewUUID added in v0.3.0

func NewUUID() string

Types

type CaptureLoggerAdapter added in v0.3.0

type CaptureLoggerAdapter struct {
	// contains filtered or unexported fields
}

CaptureLoggerAdapter is a logger which captures all logs. This logger is mostly useful for testing logging.

func NewCaptureLogger added in v0.3.0

func NewCaptureLogger() *CaptureLoggerAdapter

func (*CaptureLoggerAdapter) Captured added in v0.3.0

func (c *CaptureLoggerAdapter) Captured() map[LogLevel][]CapturedMessage

func (*CaptureLoggerAdapter) Debug added in v0.3.0

func (c *CaptureLoggerAdapter) Debug(msg string, fields LogFields)

func (*CaptureLoggerAdapter) Error added in v0.3.0

func (c *CaptureLoggerAdapter) Error(msg string, err error, fields LogFields)

func (*CaptureLoggerAdapter) Has added in v0.3.0

func (*CaptureLoggerAdapter) HasError added in v0.3.0

func (c *CaptureLoggerAdapter) HasError(err error) bool

func (*CaptureLoggerAdapter) Info added in v0.3.0

func (c *CaptureLoggerAdapter) Info(msg string, fields LogFields)

func (*CaptureLoggerAdapter) Trace added in v0.3.0

func (c *CaptureLoggerAdapter) Trace(msg string, fields LogFields)

func (*CaptureLoggerAdapter) With added in v0.3.0

type CapturedMessage added in v0.3.0

type CapturedMessage struct {
	Level  LogLevel
	Fields LogFields
	Msg    string
	Err    error
}

type LogFields

type LogFields map[string]interface{}

func (LogFields) Add

func (l LogFields) Add(newFields LogFields) LogFields

func (LogFields) Copy added in v0.3.0

func (l LogFields) Copy() LogFields

type LogLevel added in v0.3.0

type LogLevel uint
const (
	TraceLogLevel LogLevel = iota + 1
	DebugLogLevel
	InfoLogLevel
	ErrorLogLevel
)

type LoggerAdapter

type LoggerAdapter interface {
	Error(msg string, err error, fields LogFields)
	Info(msg string, fields LogFields)
	Debug(msg string, fields LogFields)
	Trace(msg string, fields LogFields)
	With(fields LogFields) LoggerAdapter
}

LoggerAdapter is an interface, that you need to implement to support Watermill logging. You can use StdLoggerAdapter as a reference implementation.

func NewStdLogger

func NewStdLogger(debug, trace bool) LoggerAdapter

NewStdLogger creates StdLoggerAdapter which sends al logs to stderr.

func NewStdLoggerWithOut added in v0.3.0

func NewStdLoggerWithOut(out io.Writer, debug bool, trace bool) LoggerAdapter

NewStdLoggerWithOut creates StdLoggerAdapter which sends all logs to provided io.Writer.

type NopLogger

type NopLogger struct{}

NopLogger is a logger which discards all logs.

func (NopLogger) Debug

func (NopLogger) Debug(msg string, fields LogFields)

func (NopLogger) Error

func (NopLogger) Error(msg string, err error, fields LogFields)

func (NopLogger) Info

func (NopLogger) Info(msg string, fields LogFields)

func (NopLogger) Trace

func (NopLogger) Trace(msg string, fields LogFields)

func (NopLogger) With added in v0.3.0

func (l NopLogger) With(fields LogFields) LoggerAdapter

type StdLoggerAdapter

type StdLoggerAdapter struct {
	ErrorLogger *log.Logger
	InfoLogger  *log.Logger
	DebugLogger *log.Logger
	TraceLogger *log.Logger
	// contains filtered or unexported fields
}

StdLoggerAdapter is a logger implementation, which sends al logs to provided standard output.

func (*StdLoggerAdapter) Debug

func (l *StdLoggerAdapter) Debug(msg string, fields LogFields)

func (*StdLoggerAdapter) Error

func (l *StdLoggerAdapter) Error(msg string, err error, fields LogFields)

func (*StdLoggerAdapter) Info

func (l *StdLoggerAdapter) Info(msg string, fields LogFields)

func (*StdLoggerAdapter) Trace

func (l *StdLoggerAdapter) Trace(msg string, fields LogFields)

func (*StdLoggerAdapter) With added in v0.3.0

func (l *StdLoggerAdapter) With(fields LogFields) LoggerAdapter

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