mirror of https://github.com/status-im/consul.git
61 lines
2.5 KiB
Markdown
61 lines
2.5 KiB
Markdown
---
|
|
layout: "docs"
|
|
page_title: "Service Definition"
|
|
sidebar_current: "docs-agent-services"
|
|
---
|
|
|
|
# Services
|
|
|
|
One of the main goals of service discovery is to provide a catalog of available
|
|
services. To that end, the agent provides a simple service definition format
|
|
to declare the availability of a service, and to potentially associate it with
|
|
a health check. A health check is considered to be application level if it
|
|
associated with a service. A service is defined in a configuration file,
|
|
or added at runtime over the HTTP interface.
|
|
|
|
## Service Definition
|
|
|
|
A service definition that is a script looks like:
|
|
|
|
{
|
|
"service": {
|
|
"name": "redis",
|
|
"tags": ["master"],
|
|
"port": 8000,
|
|
"check": {
|
|
"script": "/usr/local/bin/check_redis.py",
|
|
"interval": "10s"
|
|
}
|
|
}
|
|
}
|
|
|
|
A service definition must include a `name`, and may optionally provide
|
|
an `id`, `tags`, `port`, and `check`. The `id` is set to the `name` if not
|
|
provided. It is required that all services have a unique ID, so if names
|
|
might conflict, then unique ID's should be provided.
|
|
|
|
The `tags` is a list of opaque value to Consul, but can be used to distinguish
|
|
between "master" or "slave" nodes, different versions, or any other service level labels.
|
|
The `port` can be used as well to make a service oriented architecture
|
|
simpler to configure. This way the address and port of a service can
|
|
be discovered.
|
|
|
|
Lastly, a service can have an associated health check. This is a powerful
|
|
feature as it allows a web balancer to gracefully remove failing nodes, or
|
|
a database to replace a failed slave, etc. The health check is strongly integrated
|
|
in the DNS interface as well. If a service is failing it's health check or
|
|
a node has any failing system-level check, the DNS interface will omit that
|
|
node from any service query.
|
|
|
|
There is more information about [checks here](/docs/agent/checks.html). The
|
|
check must be of the script or TTL type. If it is a script type, `script` and
|
|
`interval` must be provided. If it is a TTL type, then only `ttl` must be
|
|
provided. The check name is automatically generated as "service:<service-id>".
|
|
|
|
To configure a service, either provide it as a `-config-file` option to the
|
|
agent, or place it inside the `-config-dir` of the agent. The file must
|
|
end in the ".json" extension to be loaded by Consul. Check definitions can
|
|
also be updated by sending a `SIGHUP` to the agent. Alternatively, the
|
|
service can be registered dynamically using the [HTTP API](/docs/agent/http.html).
|
|
|