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https://github.com/hashicorp/serf

Service orchestration and management tool.
https://github.com/hashicorp/serf

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Service orchestration and management tool.

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# Serf [![Build Status](https://github.com/hashicorp/serf/workflows/Checks/badge.svg)](https://github.com/hashicorp/serf/actions) [![Join the chat at https://gitter.im/hashicorp-serf/Lobby](https://badges.gitter.im/hashicorp-serf/Lobby.svg)](https://gitter.im/hashicorp-serf/Lobby?utm_source=badge&utm_medium=badge&utm_campaign=pr-badge&utm_content=badge)



* Website: https://www.serf.io

* Chat: [Gitter](https://gitter.im/hashicorp-serf/Lobby)

* Mailing list: [Google Groups](https://groups.google.com/group/serfdom/)



Serf is a decentralized solution for service discovery and orchestration

that is lightweight, highly available, and fault tolerant.



Serf runs on Linux, Mac OS X, and Windows. An efficient and lightweight gossip

protocol is used to communicate with other nodes. Serf can detect node failures

and notify the rest of the cluster. An event system is built on top of

Serf, letting you use Serf's gossip protocol to propagate events such

as deploys, configuration changes, etc. Serf is completely masterless

with no single point of failure.



Here are some example use cases of Serf, though there are many others:



* Discovering web servers and automatically adding them to a load balancer

* Organizing many memcached or redis nodes into a cluster, perhaps with

  something like [twemproxy](https://github.com/twitter/twemproxy) or

  maybe just configuring an application with the address of all the

  nodes

* Triggering web deploys using the event system built on top of Serf

* Propagating changes to configuration to relevant nodes.

* Updating DNS records to reflect cluster changes as they occur.

* Much, much more.



## Quick Start



First, [download a pre-built Serf binary](https://www.serf.io/downloads.html)

for your operating system, [compile Serf yourself](#developing-serf), or install

using `go get -u github.com/hashicorp/serf/cmd/serf`.



Next, let's start a couple Serf agents. Agents run until they're told to quit

and handle the communication of maintenance tasks of Serf. In a real Serf

setup, each node in your system will run one or more Serf agents (it can

run multiple agents if you're running multiple cluster types. e.g. web

servers vs. memcached servers).



Start each Serf agent in a separate terminal session so that we can see

the output of each. Start the first agent:



```

$ serf agent -node=foo -bind=127.0.0.1:5000 -rpc-addr=127.0.0.1:7373

...

```



Start the second agent in another terminal session (while the first is still

running):



```

$ serf agent -node=bar -bind=127.0.0.1:5001 -rpc-addr=127.0.0.1:7374

...

```



At this point two Serf agents are running independently but are still

unaware of each other. Let's now tell the first agent to join an existing

cluster (the second agent). When starting a Serf agent, you must join an

existing cluster by specifying at least one existing member. After this,

Serf gossips and the remainder of the cluster becomes aware of the join.

Run the following commands in a third terminal session.



```

$ serf join 127.0.0.1:5001

...

```



If you're watching your terminals, you should see both Serf agents

become aware of the join. You can prove it by running `serf members`

to see the members of the Serf cluster:



```

$ serf members

foo    127.0.0.1:5000    alive

bar    127.0.0.1:5001    alive

...

```



At this point, you can ctrl-C or force kill either Serf agent, and they'll

update their membership lists appropriately. If you ctrl-C a Serf agent,

it will gracefully leave by notifying the cluster of its intent to leave.

If you force kill an agent, it will eventually (usually within seconds)

be detected by another member of the cluster which will notify the

cluster of the node failure.



## Documentation



Full, comprehensive documentation is viewable on the Serf website:



https://www.serf.io/docs



## Developing Serf



If you wish to work on Serf itself, you'll first need [Go](https://golang.org)

installed (version 1.10+ is _required_). Make sure you have Go properly

[installed](https://golang.org/doc/install),

including setting up your [GOPATH](https://golang.org/doc/code.html#GOPATH).



Next, clone this repository into `$GOPATH/src/github.com/hashicorp/serf` and

then just type `make`. In a few moments, you'll have a working `serf` executable:



```

$ make

...

$ bin/serf

...

```



*NOTE: `make` will also place a copy of the executable under `$GOPATH/bin/`*



Serf is first and foremost a library with a command-line interface, `serf`. The

Serf library is independent of the command line agent, `serf`.  The `serf`

binary is located under `cmd/serf` and can be installed stand alone by issuing

the command `go get -u github.com/hashicorp/serf/cmd/serf`.  Applications using

the Serf library should only need to include `github.com/hashicorp/serf`.



Tests can be run by typing `make test`.



If you make any changes to the code, run `make format` in order to automatically

format the code according to Go [standards](https://golang.org/doc/effective_go.html#formatting).