Marathoner

Marathoner is a service discovery for marathon. It publishes service ports from marathon on desired interface so you always talk to 127.0.0.1 and known port. It manages haproxy and ensures that configuration is updated as soon as there are changes in running marathon tasks.

Marathoner consists of two parts:

• Listeners listen for updates and handles config update and haproxy reload.
• Updaters keep track of running and healthy apps and pushes changes to listeners.

You would probably want to run 3-5 updaters (one per marathon server) and listeners on each node for high availability.

You can also run optional logger to log every state change that happens.

Ascii view

        +---------+   +---------+   +---------+
        |marathon1|   |marathon2|   |marathon3|
        +----^----+   +----^----+   +----^----+
             |             |             |
             |             |             |
             ^-------------^-------------^  polling random alive marathon
             |             |             |
         +---+---+     +---+---+     +---+---+
         |updater|     |updater|     |updater|
         +---+---+     +---+---+     +---+---+
             |             |             |
             |             |             |  pushing to every connected client
             |             |             |
       +-----v------+------v------+------v------+
       |            |             |             |
       |            |             |             |
  +----v----+  +----v----+   +----v----+   +----v----+
  |listener1|  |listener1|   |listener1|   |listener1|
  +----+----+  +----+----+   +----+----+   +----+----+
       |            |             |             |
       |            |             |             |  reloading local haproxy
       |            |             |             |
   +---v---+    +---v---+     +---v---+     +---v---+
   |haproxy|    |haproxy|     |haproxy|     |haproxy|
   +---^---+    +---^---+     +---^---+     +---^---+
       |            |             |             |
       |            |             |             |  apps talk to local haproxy
       |            |             |             |
     +-+-+        +-+-+         +-+-+         +-+-+
     |app|        |app|         |app|         |app|
     +---+        +---+         +---+         +---+

Features

• Nearly zero configuration, everything needed is in marathon.
• Both components are independent and share nothing for high availability.
• Marathon api is only used by updaters, thus reducing load on marathon.
• Health check awareness, only healthy tasks are added to haproxy.
• Nothing breaks if marathon goes down for some reason.
• Listeners do nothing if no changes happen in marathon, no polling involved.
• Graceful restarts and config checking for haproxy to avoid downtime.
• Services available externally and internally without any app code changes.

Usage

Marathoner is designed to run in docker containers.

Updater

The following command runs marathoner updater with update interval of 1 second and two marathon hosts. Updater is reachable at port 7676.

docker run -d -p 7676:7676 bobrik/marathoner-updater:1.10 \
  -m http://marathon1:8080,http://marathon2:8080 -i 1

Listener

The following command runs marathoner listener with two updaters and publishes apps on 127.0.0.1. Notice that you need to run listener with --net=host.

docker run -d --net=host bobrik/marathoner-listener:1.10 \
  -u marathoner-updater1:7676,marathoner-updater2:7676 -b 127.0.0.1

Logger

The following command runs marathoner logger with specified updater and logs state changes to stdout:

docker run --rm bobrik/marathoner-logger:1.10 -u marathoner-updater1:7676

Exposing apps

Marathon apps that needs to be exported should have label marathoner_haproxy_enabled set to true.

Building

If you made some changes and wish to check how they work, ./containers/make.sh could help you with building containers. Just run:

# build listener image with the name my-listener
./containers/make.sh listener my-listener

# build updater image with the name my-updater
./containers/make.sh updater my-updater

# build logger image with the name my-logger
./containers/make.sh updater my-logger

Version history

• 1.10
  • Updater: only asking for apps with marathoner enabled
• 1.9
  • Updater: 20 second timeout for getting state from marathon
• 1.8
  • Listener: Configuring timeout to kill previous haproxy instances
• 1.7
  • Listener: Fixed backports repo for haproxy
  • Listener: Haproxy is launched and managed entirely from listener
  • Listener: Constant retry in listener loop
  • Listener: Externalized haproxy template
  • Listener: Added labels to HaproxyApp structure
  • Listener: Only apps with marathoner_haproxy_enabled label set to true appear in haproxy
• 1.6
  • Higher timeouts for idle connections, more connections (only listener)
• 1.5
  • Removed port range support since it required coordination
  • Logging current updater endpoint in listener and logger
  • Worakround for d2iq-archive/marathon#1106
• 1.4
  • Added labels for apps
  • Using /v2/apps?embed=apps.tasks instead of /v2/tasks
  • Using startedAt from marathon
  • Depends on unreleased yet marathon 0.8.0
  • Port range support
  • golint fixes
• 1.3
  • seeding random generator for better load distribution
• 1.2
  • added logger container
• 1.1
  • updater: avoid adding tasks that are not started
• 1.0
  • first public version

TODO

• tagged automated builds with godep maybe
• exit trap in listener for faster exit