Getting started
Introduction
Dkron nodes can work in two modes, agents or servers.
A Dkron agent is a cluster member that can handle job executions, run your scripts and return the resulting output to the server.
A Dkron server is also a cluster member that send job execution queries to agents or other servers, so servers can execute jobs too.
The main distinction is that servers order job executions, can be used to schedule jobs, handles data storage and participate on leader election.
Dkron clusters have a leader, the leader is responsible of starting job execution queries in the cluster.
Any Dkron agent or server acts as a cluster member and it's available to run scheduled jobs.
You can choose whether a job is run on a node or nodes by specifying tags and a count of target nodes having this tag do you want a job to run. This gives an unprecedented level of flexibility in runnig jobs across a cluster of any size and with any combination of machines you need.
All the execution responses will be gathered by the scheduler and stored in the database.
Backend stores
Dkron relies on the key-value store for data storage, an instance of the distributed store can be run in the same machines as Dkron or connect it to an already existing cluster.
By default dkron will start with a file based, embedded KV store called BoltDB, it is functional for a single node demo but does not offers clustering or HA.
It is compatible with etcd, Consul, Zookeeper, Redis, DynamoDB and BoltDB. For instructions on how to install and configure any one of these systems refer to their official sites:
Installation
See the installation.
Configuration
See the configuration.
Usage
By default Dkron uses the following ports:
8946for communicating between agents8080for HTTP for the API and Dashboard6868for RPC comunication between agents.
Be sure you have opened this ports (or the ones that you configured) in your firewall or AWS security groups.
By default dkron will use the embedded BoltDB KV store. A different store can be specified setting backend and backend-machines flag in the config file, env variables or as a command line flag.
To start a Dkron server instance:
dkron agent --server
Time to add the first job:
This job will only run in just one dkron_server node due to the node count in the tag. Refer to the target node spec for details.
curl localhost:8080/v1/jobs -XPOST -d '{
"name": "job1",
"schedule": "@every 10s",
"timezone": "Europe/Berlin",
"owner": "Platform Team",
"owner_email": "[email protected]",
"disabled": false,
"tags": {
"dkron_server": "true:1"
},
"concurrency": "allow",
"executor": "shell",
"executor_config": {
"command": "date"
}
}`
That's it!