README
dowding
Docker cluster scheduler
The name is a tribute to the real master planner
install
$ npm install dowding
usage
var dowding = require('dowding')
var scheduler = dowding({
// pass a function that will list our inventory
inventory:function(done){
// the inventory is an array of objects
// each object has 'hostname' and 'docker' properties
// servers can also have arbitrary meta data
var servers = [{
hostname:'host1',
docker:'192.168.8.120:2375',
tags:'apple,peach'
},{
hostname:'host2',
docker:'192.168.8.121:2375',
tags:'orange'
}]
done(null, servers)
},
leastBusy:function(servers, done){
// this is a naive function that always returns the first server
// you can have any logic you want here
done(null, servers[0])
}
})
To allocate a new container:
scheduler.allocate({
name:'myjob'
}, function(err, server){
// server is an entry from our inventory
})
Allocate a server that does not run another 'myjob' container (mutual exclusion):
scheduler.allocate({
name:'myjob.2'
}, function(err, server){
// server will not be where myjob.1 is running
})
Allocate the server that is running the basevolume
container:
scheduler.allocate({
name:'mydatabase',
parent:'basevolume'
}, function(err, server){
// server will be the same as where basevolume is running
// it will pass an error if basevolume is not found
})
mutual exclusion
If a container has a name of the following format:
<jobname>.<pid>
For example:
auth.abc
and
auth.xyz
These 2 auth containers will not be allocated onto the same server.
Here is an example of running the allocation:
scheduler.allocate({
name:'auth.abc'
}, function(err, server){
// server is one object from the inventory
})
If you just want a server you can omit the filter information:
scheduler.allocate(function(err, server){
// server is one object from the inventory
})
parent
You can instruct dowding to allocate a container onto a server that another container is running.
This is useful in scenarios like --volumes-from
where one container has a local dependency on another.
least-busy
When there are multiple servers that could be choosen - the default behaviour is to pick the least busy
server.
Least busy is determined by the number of containers running on each host.
You can pass a function to override this decision.
The function will be passed an object where the keys are the server hostname and the values are objects with the following properties:
- hostname
- docker
- jobs
You can use this information to decide which server should be allocated.
api
var scheduler = dowding(opts)
Create a new scheduler passing the following options:
- inventory - a function that will return a list of servers on our network
- leastBusy - a function that defines the logic for picking the least busy of our servers
scheduler.allocate([opts], function(err, server){})
Allocate a docker server for a job
Opts is an optional object used to filter the allocation - it has these keys:
- name - the name of the container, possibly in
. format for mutual exclusion - parent - the name of a parent container - the job will be routed to the server it is running on
scheduler.find(name, function(err, server){})
Find which server that a container is running - server can be null if the container is not found.
license
MIT