Emque

Emque is an in-memory message broker

Features

• In-memory message broker
• HTTP or gRPC transport
• Clustering
• Sharding
• Proxying
• Discovery
• Auto retries
• TLS support
• Command line interface
• Interactive prompt
• Go client library

Emque generates a self signed certificate by default if no TLS config is specified

API

Publish

/pub?topic=string	publish payload as body

Subscribe

/sub?topic=string	subscribe as websocket

Architecture

• Emque servers are standalone servers with in-memory queues and provide a HTTP API
• Emque clients shard or cluster Emque servers by publish/subscribing to one or all servers
• Emque proxies use the go client to cluster Emque servers and provide a unified HTTP API

Because of this simplistic architecture, proxies and servers can be chained to build message pipelines

Usage

Install

go get github.com/asim/emque

Run Server

Listens on *:8081

emque

Set server address

emque --address=localhost:9091

Enable TLS

emque --cert_file=cert.pem --key_file=key.pem

Persist to file per topic

emque --persist

Use gRPC transport

emque --transport=grpc

Run Proxy

Emque can be run as a proxy which includes clustering, sharding and auto retry features.

Clustering: Publish and subscribe to all Emque servers

emque --proxy --servers=10.0.0.1:8081,10.0.0.1:8082,10.0.0.1:8083

Sharding: Requests are sent to a single server based on topic

emque --proxy --servers=10.0.0.1:8081,10.0.0.1:8082,10.0.0.1:8083 --select=shard

Resolver: Use a name resolver rather than specifying server ips

emque --proxy --resolver=dns --servers=emque.proxy.dev

Run Client

Publish

echo "A completely arbitrary message" | emque --client --topic=foo --publish --servers=localhost:8081

Subscribe

emque --client --topic=foo --subscribe --servers=localhost:8081

Interactive mode

emque -i --topic=foo

Publish

Publish via HTTP

curl -k -d "A completely arbitrary message" "https://localhost:8081/pub?topic=foo"

Subscribe

Subscribe via websockets

curl -k -i -N -H "Connection: Upgrade" \
	-H "Upgrade: websocket" \
	-H "Host: localhost:8081" \
	-H "Origin:http://localhost:8081" \
	-H "Sec-Websocket-Version: 13" \
	-H "Sec-Websocket-Key: Emque" \
	"https://localhost:8081/sub?topic=foo"

Go Client

Emque provides a simple go client

import "github.com/asim/emque/client"

Publish

// publish to topic foo
err := client.Publish("foo", []byte(`bar`))

Subscribe

// subscribe to topic foo
ch, err := client.Subscribe("foo")
if err != nil {
	return
}

data := <-ch

New Client

// defaults to Emque server localhost:8081
c := client.New()

gRPC client

import "github.com/asim/emque/client/grpc"

c := grpc.New()

Clustering

Clustering is supported on the client side. Publish/Subscribe operations are performed against all servers.

c := client.New(
	client.WithServers("10.0.0.1:8081", "10.0.0.1:8082", "10.0.0.1:8083"),
)

Sharding

Sharding is supported via client much like gomemcache. Publish/Subscribe operations are performed against a single server.

import "github.com/asim/emque/client/selector"

c := client.New(
	client.WithServers("10.0.0.1:8081", "10.0.0.1:8082", "10.0.0.1:8083"),
	client.WithSelector(new(selector.Shard)),
)

Resolver

A name resolver can be used to discover the ip addresses of Emque servers

import "github.com/asim/emque/client/resolver"

c := client.New(
	// use the DNS resolver
	client.WithResolver(new(resolver.DNS)),
	// specify DNS name as server
	client.WithServers("emque.proxy.local"),
)