Getting Started¶

Understanding the configuration file¶

The configuration file for Kairosdb 1.3 and later uses Hocon (https://github.com/lightbend/config/blob/main/HOCON.md) The configuration is hierarchical and looks like json with kairosdb at the root. Configurations with periods represent each level of the configuration tree.

Changing File Handle Limit on Linux¶

If you have a lot of clients pushing metrics, you may run out of file handles. We recommend increasing the number of file handles. Here is an example of [http://tech-torch.blogspot.com/2009/07/linux-ubuntu-tomcat-too-many-open-files.html changing file handles on CentOS].

Changing Datastore¶

KairosDB can be configured to use one of two backends for storing data. By default KairosDB is configured to use an in memory H2 database to store datapoints. To change the datastore that is used change the kairosdb.service.datastore property in the kairosdb.conf file. The property kairosdb.services.datastore could be located

kairosdb: {
    service: {
        datastore: "<config value>"
    }
}

Using with H2¶

kairosdb.service.datastore: "org.kairosdb.datastore.h2.H2Module"

By default KairosDB is configured to run using the H2 database. This lets you do development work without setting up and running Cassandra.

Using with Cassandra¶

kairosdb.service.datastore: "org.kairosdb.datastore.cassandra.CassandraModule"

The default configuration for Cassandra is to use wide rows. Each row is set to contain 3 weeks of data. The reason behind setting it to 3 weeks is if you wrote a metric every millisecond for 3 weeks it would be just over 1 billion columns. Cassandra has a 2 billion column limit.

The row size has been a point of some confusion. Basically it comes down to this: The more data you can fit into a single row the better the system will perform when querying the data. This does not mean that Cassandra only holds 3 weeks worth of data, it means data is written to the same row for 3 weeks before going to a new row. See the Broken:[CassandraSchema cassandra schema for more details].

Changing the read_repair_chance: This value tells cassandra how often to perform a read repair. The read repair chance will default to 1 (100% chance). The recommended value is 0.1 (10% chance). To change this log into the cassandra-cli client and run the following commands

> use kairosdb;
> update column family data_points with read_repair_chance = 0.1;
> update column family row_key_index with read_repair_chance = 0.1;
> update column family string_index with read_repair_chance = 0.1;

Note: If you are using the newer cqlsh command, you will need to use the alter syntax

> use kairosdb;
> ALTER TABLE data_points WITH read_repair_chance = 0.1;
> ALTER TABLE row_key_index WITH read_repair_chance = 0.1;
> ALTER TABLE string_index WITH read_repair_chance = 0.1;

Using as a Remote Datastore¶

The remote datastore functionality was moved into its own plugin https://github.com/kairosdb/kairos-remote