PlanB: a distributed HTTP and websocket proxy

What Is It?

PlanB is a HTTP and websocket proxy backed by Redis and inspired by Hipache.

It aims to be fully compatible with Hipache when Redis is used as a backend. The same format is used for all keys stored in Redis so migrating from Hipache to PlanB should be completely seamless. The process should be as simple as replacing Hipache's executable for PlanB.

Start-up flags

The following flags are available for configuring PlanB on start-up:

• --listen/-l: the address to which PlanB will bind. Default value is 0.0.0.0:8989.
• --read-redis-host: Redis host of the server which contains application addresses. Default value is localhost.
• --read-redis-port: Redis port of the server which contains application addresses. Default value is 6379.
• --write-redis-host: Redis host of the server which PlanB will use for publishing dead backends. Default value is localhost.
• --write-redis-port: Redis port of the server which which PlanB will use for publishing dead backends. Default value is 6379.
• --access-log: File path where access log will be written. If value equals syslog log will be sent to local syslog. If value equals stdout log will be sent to stdout. Default value is ./access.log.
• --request-timeout: Total backend request timeout in seconds. Default value is 30.
• --dial-timeout: Dial backend request timeout in seconds. Default value is 10.
• --dead-backend-time: Time in seconds a backend will remain disabled after a network failure. Default value is 30.
• --flush-interval: Time in milliseconds to flush the proxied request. Default value is 10.
• --request-id-header: Enables PlanB to set a header with an unique ID to the requests, facilitating the process of tracing requests.

Features

• Load-Balancing
• Dead Backend Detection
• Dynamic Configuration
• WebSocket

Install

The easiest way to install PlanB is to pull the trusted build from the hub.docker.com and launch it in the container:

# run Redis
docker run -d -p 6379:6379 redis

# run PlanB
docker run -d --net=host tsuru/planb:v1 --listen ":80"

VHOST Configuration

The configuration is managed by Redis that makes possible to update the configuration dynamically and gracefully while the server is running, and have that state shared across workers and even across instances.

Let's take an example to proxify requests to 2 backends for the hostname www.tsuru.io. The 2 backends IP are 192.168.0.42 and 192.168.0.43 and they serve the HTTP traffic on the port 80.

redis-cli is the standard client tool to talk to Redis from the terminal.

Follow these steps:

Create the frontend:

$ redis-cli rpush frontend:www.tsuru.io mywebsite
(integer) 1

The frontend identifer is mywebsite, it could be anything.

Add the 2 backends:

$ redis-cli rpush frontend:www.tsuru.io http://192.168.0.42:80
(integer) 2
$ redis-cli rpush frontend:www.tsuru.io http://192.168.0.43:80
(integer) 3

Review the configuration:

$ redis-cli lrange frontend:www.tsuru.io 0 -1
1) "mywebsite"
2) "http://192.168.0.42:80"
3) "http://192.168.0.43:80"

While the server is running, any of these steps can be re-run without messing up with the traffic.

Debbugging and Troubleshooting

One way to debug/toubleshoot planb is by analyzing the running goroutines.

Planb is able to handle the USR1 signal to dump goroutines in its execution screen:

$ kill -s USR1 <planb-PID>

Links

• Repository & Issue Tracker: https://github.com/tsuru/planb
• Talk to us on Gitter: https://gitter.im/tsuru/tsuru