How to Use Configuration Entries

Configuration entries can be created to provide cluster-wide defaults for various aspects of Consul.

Outside of Kubernetes, configuration entries can be specified in HCL or JSON using either snake_case or CamelCase for key names. On Kubernetes, configuration entries can be managed by custom resources in YAML.

Outside of Kubernetes, every configuration entry specified in HCL or JSON has at least two fields: Kind and Name. Those two fields are used to uniquely identify a configuration entry. Configuration entries specified as HCL or JSON objects use either snake_case or CamelCase for key names.

Example config specified outside of Kubernetes

Kind = "<supported kind>"
Name = "<name of entry>"

On Kubernetes, Kind is set as the custom resource kind and Name is set as metadata.name:

Example config specified on Kubernetes

apiVersion: consul.hashicorp.com/v1alpha1
kind: <supported kind>
metadata:
  name: <name of entry>

Supported Config Entries

See Service Mesh - Config Entries for the list of supported config entries.

Managing Configuration Entries In Kubernetes

See Kubernetes Custom Resource Definitions.

Managing Configuration Entries Outside Of Kubernetes

Configuration entries outside of Kubernetes should be managed with the Consul CLI or API. Additionally, as a convenience for initial cluster bootstrapping, configuration entries can be specified in all of the Consul servers’s configuration files

Managing Configuration Entries with the CLI

Creating or Updating a Configuration Entry

The consul config write command is used to create and update configuration entries. This command will load either a JSON or HCL file holding the configuration entry definition and then will push this configuration to Consul.

Example HCL Configuration File:

proxy-defaults.hcl

Kind = "proxy-defaults"
Name = "global"
Config {
   local_connect_timeout_ms = 1000
   handshake_timeout_ms = 10000
}

Then to apply this configuration, run:

$ consul config write proxy-defaults.hcl

If you need to make changes to a configuration entry, simple edit that file and then rerun the command. This command will not output anything unless there is an error in applying the configuration entry. The write command also supports a -cas option to enable performing a compare-and-swap operation to prevent overwriting other unknown modifications.

Reading a Configuration Entry

The consul config read command is used to read the current value of a configuration entry. The configuration entry will be displayed in JSON form which is how its transmitted between the CLI client and Consul’s HTTP API.

Example:

$ consul config read -kind service-defaults -name web
{
   "Kind": "service-defaults",
   "Name": "web",
   "Protocol": "http"
}

Listing Configuration Entries

The consul config list command is used to list out all the configuration entries for a given kind.

Example:

$ consul config list -kind service-defaults
web
api
db

Deleting Configuration Entries

The consul config delete command is used to delete an entry by specifying both its kind and name.

Example:

$ consul config delete -kind service-defaults -name web

This command will not output anything when the deletion is successful.

Configuration Entry Management with Namespaces EnterpriseEnterprise

Configuration entry operations support passing a namespace in order to isolate the entry to affect only operations within that namespace. This was added in Consul 1.7.0.

Example:

$ consul config write service-defaults.hcl -namespace foo

$ consul config list -kind service-defaults -namespace foo
web
api

Bootstrapping From A Configuration File

Configuration entries can be bootstrapped by adding them inline to each Consul server’s configuration file. When a server gains leadership, it will attempt to initialize the configuration entries. If a configuration entry does not already exist outside of the servers configuration, then it will create it. If a configuration entry does exist, that matches both kind and name, then the server will do nothing.