hosted-metrics-api Configurations

Configurations

There are mainly three relevant places where HM-API and its instances get configured:

• HM-API cli arguments
• HM-API ConfigMap
  • Deployment Plans
  • Config Defaults
• Instance ConfigMap

HM-API Cli arguments

This lists the cli parameters which HM-API knows, together with an explanation what each of them does.

HM-API ConfigMap

By default the name of this ConfigMap is hm-api-config, unless specified otherwise with the -config-map argument. It contains various settings which are regularly read and used by HM-API. If an HM-API default setting is not present, or the whole ConfigMap doesn’t exist, then HM-API will add it on startup. This means it is possible that this ConfigMap gets modified when an HM-API version update is deployed which introduces new defaults.

Deployment Plans

A plan defines what sizes of instances are known to HM-API. When a plan has been selected for an instance, it is still possible to override certain limits with specific overrides, but the plan gives a basic template of sizes which should be deployed.

The plans exist under the key plans.json and the default plans look like this:

    {
      "large": {
        "Name": "Large",
        "Partitions": 128,
        "CPU": 100,
        "Mem": 1000
      },
      "medium": {
        "Name": "Medium",
        "Partitions": 32,
        "CPU": 100,
        "Mem": 1000
      },
      "small": {
        "Name": "Small",
        "Partitions": 8,
        "CPU": 50,
        "Mem": 500
      }
    }

When a new instance gets deployed, one of the configured plans must be selected. It will determine the resource requests & limits, the number of partitions in Kafka, and, based on the partitioning policy, the number of Metrictanks that will get deployed.

Using the default partitioning policy (ConstantWithNoOverlap) with its default values (partitionsPerReader/partitionsPerWriter set to 8). The number of Metrictanks read deployments (and write deployments) is then <number of partitions> / 8, so a medium instance with 32 partitions results in 4 shards. Each read deployment gets 2 Metrictank pods, and each write deployment 1 Metrictank pod.

The plan definitions may be modified by editing the config map with kubectl -n metrictank edit configmap hm-api-config.

Config Defaults

The config defaults are a long list of parameters, some of which affect the behavior of HM-API itself, but most are configuring the instances managed by HM-API. These parameters exist in a map under the key config-defaults.json. All of them can also be overridden in the instance specific configuration which is described here.

The parameters which configure one of the following services are prefixed by one string for each service:

For example to configure the Metrictank setting -warm-up-period the accoding entry in config-defaults.json would look like MT_WARM_UP_PERIOD. A few service-specific settings get added to config-defaults.json by default, others can freely be added by using the same string format.

To get a detailed explanation for each of the settings for Tsdb-Gw, Metrictank, the importer tool and Graphite, please refer to their according documentation. This is an overview of all settings, with an explanation, which are not specific to one of those three services:

Instance ConfigMap

Each instance has a configmap which stores the settings from which the instance resources are generated. The name format of that configmap looks like instance-config-<org>-<name>, so for example the name of the configmap for an instance of the org 22 with the name myinstance would look like instance-config-22-myinstance.

This configmap contains 5 keys, but only the value of deployment-config.json is relevant for configuring the instance. The values of the other 4 keys of that configmap are generated from the value of deployment-config.json. So editing them is not recommended, because they will get overwritten again.

For an explanation of the contents of the Metrictank and Tsdb-Gw configuration files, please refer to the documentation of the according service.

This is a list of the other configurations in deployment-config.json, together with an explanation for each of them:

Overrides

The overrides, overridesA and overridesB can contain parameters to override default values.