consul/website/source/docs/agent/config_entries.html.md

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docs	Configuration Entry Definitions	docs-agent-cfg_entries	Consul allows storing configuration entries centrally to be used as defaults for configuring other aspects of Consul.

Configuration Entries

Configuration entries can be created to provide cluster-wide defaults for various aspects of Consul. Every configuration entry has at least two fields: Kind and Name. Those two fields are used to uniquely identify a configuration entry. When put into configuration files, configuration entries can be specified as HCL or JSON objects using either snake_case or CamelCase for key names.

Example:

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

The supported Kind names for configuration entries are:

• service-router ^(beta) - defines where to send layer 7 traffic based on the HTTP route

• service-splitter ^(beta) - defines how to divide requests for a single HTTP route based on percentages

• service-resolver ^(beta) - matches service instances with a specific Connect upstream discovery requests

• service-defaults - configures defaults for all the instances of a given service

• proxy-defaults - controls proxy configuration

Managing Configuration Entries

Configuration entries 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.

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.

Using Configuration Entries For Service Defaults

When the agent is configured to enable central service configurations, it will look for service configuration defaults that match a registering service instance. If it finds any, the agent will merge those defaults with the service instance configuration. This allows for things like service protocol or proxy configuration to be defined globally and inherited by any affected service registrations.