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Cameron Ruatta a9761dca33 Updating the docs to include information about registering a check with 
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docs Agent (HTTP) docs-agent-http-agent The Agent endpoints are used to interact with the local Consul agent.

Agent HTTP Endpoint

The Agent endpoints are used to interact with the local Consul agent. Usually, services and checks are registered with an agent which then takes on the burden of keeping that data synchronized with the cluster. For example, the agent registers services and checks with the Catalog and performs anti-entropy to recover from outages.

The following endpoints are supported:

/v1/agent/checks

This endpoint is used to return all the checks that are registered with the local agent. These checks were either provided through configuration files or added dynamically using the HTTP API. It is important to note that the checks known by the agent may be different from those reported by the Catalog. This is usually due to changes being made while there is no leader elected. The agent performs active anti-entropy, so in most situations everything will be in sync within a few seconds.

This endpoint is hit with a GET and returns a JSON body like this:

{
  "service:redis": {
    "Node": "foobar",
    "CheckID": "service:redis",
    "Name": "Service 'redis' check",
    "Status": "passing",
    "Notes": "",
    "Output": "",
    "ServiceID": "redis",
    "ServiceName": "redis"
  }
}

/v1/agent/services

This endpoint is used to return all the services that are registered with the local agent. These services were either provided through configuration files or added dynamically using the HTTP API. It is important to note that the services known by the agent may be different from those reported by the Catalog. This is usually due to changes being made while there is no leader elected. The agent performs active anti-entropy, so in most situations everything will be in sync within a few seconds.

This endpoint is hit with a GET and returns a JSON body like this:

{
  "redis": {
    "ID": "redis",
    "Service": "redis",
    "Tags": null,
    "Address": "",
    "Port": 8000
  }
}

/v1/agent/members

This endpoint is used to return the members the agent sees in the cluster gossip pool. Due to the nature of gossip, this is eventually consistent: the results may differ by agent. The strongly consistent view of nodes is instead provided by "/v1/catalog/nodes".

For agents running in server mode, providing a "?wan=1" query parameter returns the list of WAN members instead of the LAN members returned by default.

This endpoint is hit with a GET and returns a JSON body like:

[
  {
    "Name": "foobar",
    "Addr": "10.1.10.12",
    "Port": 8301,
    "Tags": {
      "bootstrap": "1",
      "dc": "dc1",
      "port": "8300",
      "role": "consul"
    },
    "Status": 1,
    "ProtocolMin": 1,
    "ProtocolMax": 2,
    "ProtocolCur": 2,
    "DelegateMin": 1,
    "DelegateMax": 3,
    "DelegateCur": 3
  }
]

/v1/agent/self

This endpoint is used to return the configuration and member information of the local agent.

It returns a JSON body like this:

{
  "Config": {
    "Bootstrap": true,
    "Server": true,
    "Datacenter": "dc1",
    "DataDir": "/tmp/consul",
    "DNSRecursor": "",
    "DNSRecursors": [],
    "Domain": "consul.",
    "LogLevel": "INFO",
    "NodeName": "foobar",
    "ClientAddr": "127.0.0.1",
    "BindAddr": "0.0.0.0",
    "AdvertiseAddr": "10.1.10.12",
    "Ports": {
      "DNS": 8600,
      "HTTP": 8500,
      "RPC": 8400,
      "SerfLan": 8301,
      "SerfWan": 8302,
      "Server": 8300
    },
    "LeaveOnTerm": false,
    "SkipLeaveOnInt": false,
    "StatsiteAddr": "",
    "Protocol": 1,
    "EnableDebug": false,
    "VerifyIncoming": false,
    "VerifyOutgoing": false,
    "CAFile": "",
    "CertFile": "",
    "KeyFile": "",
    "StartJoin": [],
    "UiDir": "",
    "PidFile": "",
    "EnableSyslog": false,
    "RejoinAfterLeave": false
  },
  "Member": {
    "Name": "foobar",
    "Addr": "10.1.10.12",
    "Port": 8301,
    "Tags": {
      "bootstrap": "1",
      "dc": "dc1",
      "port": "8300",
      "role": "consul",
      "vsn": "1",
      "vsn_max": "1",
      "vsn_min": "1"
    },
    "Status": 1,
    "ProtocolMin": 1,
    "ProtocolMax": 2,
    "ProtocolCur": 2,
    "DelegateMin": 2,
    "DelegateMax": 4,
    "DelegateCur": 4
  }
}

/v1/agent/maintenance

The node maintenance endpoint can place the agent into "maintenance mode". During maintenance mode, the node will be marked as unavailable and will not be present in DNS or API queries. This API call is idempotent. Maintenance mode is persistent and will be automatically restored on agent restart.

The ?enable flag is required. Acceptable values are either true (to enter maintenance mode) or false (to resume normal operation).

The ?reason flag is optional. If provided, its value should be a text string explaining the reason for placing the node into maintenance mode. This is simply to aid human operators. If no reason is provided, a default value will be used instead.

The return code is 200 on success.

/v1/agent/join/<address>

This endpoint is hit with a GET and is used to instruct the agent to attempt to connect to a given address. For agents running in server mode, providing a "?wan=1" query parameter causes the agent to attempt to join using the WAN pool.

The return code is 200 on success.

/v1/agent/force-leave/<node>

This endpoint is hit with a GET and is used to instruct the agent to force a node into the left state. If a node fails unexpectedly, then it will be in a failed state. Once in the failed state, Consul will attempt to reconnect, and the services and checks belonging to that node will not be cleaned up. Forcing a node into the left state allows its old entries to be removed.

The endpoint always returns 200.

/v1/agent/check/register

The register endpoint is used to add a new check to the local agent. There is more documentation on checks here. Checks may be of script, HTTP, or TTL type. The agent is responsible for managing the status of the check and keeping the Catalog in sync.

The register endpoint expects a JSON request body to be PUT. The request body must look like:

{
  "ID": "mem",
  "Name": "Memory utilization",
  "Notes": "Ensure we don't oversubscribe memory",
  "Script": "/usr/local/bin/check_mem.py",
  "HTTP": "http://example.com",
  "Interval": "10s",
  "TTL": "15s"
}

The Name field is mandatory, as is one of Script, HTTP or TTL. Script and HTTP also require that Interval be set.

If an ID is not provided, it is set to Name. You cannot have duplicate ID entries per agent, so it may be necessary to provide an ID.

The Notes field is not used internally by Consul and is meant to be human-readable.

If a Script is provided, the check type is a script, and Consul will evaluate the script every Interval to update the status.

An HTTP check will perform an HTTP GET request against the value of HTTP (expected to be a URL) every Interval. If the response is any 2xx code, the check is passing. If the response is 429 Too Many Requests, the check is warning. Otherwise, the check is critical.

If a TTL type is used, then the TTL update endpoint must be used periodically to update the state of the check.

Optionally, a ServiceID can be provided to associate the registered check with an existing Service provided by the agent.

The return code is 200 on success.

/v1/agent/check/deregister/<checkId>

This endpoint is used to remove a check from the local agent. The CheckID must be passed on the path. The agent will take care of deregistering the check from the Catalog.

The return code is 200 on success.

/v1/agent/check/pass/<checkId>

This endpoint is used with a check that is of the TTL type. When this endpoint is accessed via a GET, the status of the check is set to passing and the TTL clock is reset.

The optional "?note=" query parameter can be used to associate a human-readable message with the status of the check.

The return code is 200 on success.

/v1/agent/check/warn/<checkId>

This endpoint is used with a check that is of the TTL type. When this endpoint is accessed via a GET, the status of the check is set to warning, and the TTL clock is reset.

The optional "?note=" query parameter can be used to associate a human-readable message with the status of the check.

The return code is 200 on success.

/v1/agent/check/fail/<checkId>

This endpoint is used with a check that is of the TTL type. When this endpoint is accessed via a GET, the status of the check is set to critical, and the TTL clock is reset.

The optional "?note=" query parameter can be used to associate a human-readable message with the status of the check.

The return code is 200 on success.

/v1/agent/service/register

The register endpoint is used to add a new service, with an optional health check, to the local agent. There is more documentation on services here. The agent is responsible for managing the status of the service and keeping the Catalog in sync.

The register endpoint expects a JSON request body to be PUT. The request body must look like:

{
  "ID": "redis1",
  "Name": "redis",
  "Tags": [
    "master",
    "v1"
  ],
  "Address": "127.0.0.1",
  "Port": 8000,
  "Check": {
    "Script": "/usr/local/bin/check_redis.py",
    "HTTP": "http://localhost:5000/health",
    "Interval": "10s",
    "TTL": "15s"
  }
}

The Name field is mandatory, If an ID is not provided, it is set to Name. You cannot have duplicate ID entries per agent, so it may be necessary to provide an ID in the case of a collision.

Tags, Address, Port and Check are optional.

Address will default to that of the agent if not provided.

If Check is provided, only one of Script, HTTP, or TTL should be specified. Script and HTTP also require Interval. The created check will be named "service:<ServiceId>". There is more information about checks here.

The return code is 200 on success.

/v1/agent/service/deregister/<serviceId>

The deregister endpoint is used to remove a service from the local agent. The ServiceID must be passed after the slash. The agent will take care of deregistering the service with the Catalog. If there is an associated check, that is also deregistered.

The return code is 200 on success.

/v1/agent/service/maintenance/<serviceId>

The service maintenance endpoint allows placing a given service into "maintenance mode". During maintenance mode, the service will be marked as unavailable and will not be present in DNS or API queries. This API call is idempotent. Maintenance mode is persistent and will be automatically restored on agent restart.

The ?enable flag is required. Acceptable values are either true (to enter maintenance mode) or false (to resume normal operation).

The ?reason flag is optional. If provided, its value should be a text string explaining the reason for placing the service into maintenance mode. This is simply to aid human operators. If no reason is provided, a default value will be used instead.

The return code is 200 on success.