open-consul/website/source/docs/agent/http/health.html.markdown

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docs	Health Checks (HTTP)	docs-agent-http-health	The Health endpoints are used to query health-related information.

Health HTTP Endpoint

The Health endpoints are used to query health-related information. They are provided separately from the Catalog since users may prefer not to use the optional health checking mechanisms. Additionally, some of the query results from the Health endpoints are filtered while the Catalog endpoints provide the raw entries.

The following endpoints are supported:

• /v1/health/node/<node>: Returns the health info of a node
• /v1/health/checks/<service>: Returns the checks of a service
• /v1/health/service/<service>: Returns the nodes and health info of a service
• /v1/health/state/<state>: Returns the checks in a given state

All of the health endpoints support blocking queries and all consistency modes.

/v1/health/node/<node>

This endpoint is hit with a GET and returns the checks specific to the node provided on the path. By default, the datacenter of the agent is queried; however, the dc can be provided using the ?dc= query parameter.

It returns a JSON body like this:

[
  {
    "ID": "40e4a748-2192-161a-0510-9bf59fe950b5",
    "Node": "foobar",
    "CheckID": "serfHealth",
    "Name": "Serf Health Status",
    "Status": "passing",
    "Notes": "",
    "Output": "",
    "ServiceID": "",
    "ServiceName": ""
  },
  {
    "ID": "40e4a748-2192-161a-0510-9bf59fe950b5",
    "Node": "foobar",
    "CheckID": "service:redis",
    "Name": "Service 'redis' check",
    "Status": "passing",
    "Notes": "",
    "Output": "",
    "ServiceID": "redis",
    "ServiceName": "redis"
  }
]

In this case, we can see there is a system level check (that is, a check with no associated ServiceID) as well as a service check for Redis. The serfHealth check is special in that it is automatically present on every node. When a node joins the Consul cluster, it is part of a distributed failure detection provided by Serf. If a node fails, it is detected and the status is automatically changed to critical.

This endpoint supports blocking queries and all consistency modes.

/v1/health/checks/<service>

This endpoint is hit with a GET and returns the checks associated with the service provided on the path. By default, the datacenter of the agent is queried; however, the dc can be provided using the ?dc= query parameter.

Adding the optional ?near= parameter with a node name will sort the node list in ascending order based on the estimated round trip time from that node. Passing ?near=_agent will use the agent's node for the sort.

In Consul 0.7.3 and later, the optional ?node-meta= parameter can be provided with a desired node metadata key/value pair of the form key:value. This parameter can be specified multiple times, and will filter the results to health checks on nodes with the specified key/value pair(s).

It returns a JSON body like this:

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

This endpoint supports blocking queries and all consistency modes.

/v1/health/service/<service>

This endpoint is hit with a GET and returns the nodes providing the service indicated on the path. By default, the datacenter of the agent is queried; however, the dc can be provided using the ?dc= query parameter.

Adding the optional ?near= parameter with a node name will sort the node list in ascending order based on the estimated round trip time from that node. Passing ?near=_agent will use the agent's node for the sort.

By default, all nodes matching the service are returned. The list can be filtered by tag using the ?tag= query parameter.

Providing the ?passing query parameter, added in Consul 0.2, will filter results to only nodes with all checks in the passing state. This can be used to avoid extra filtering logic on the client side.

In Consul 0.7.3 and later, the optional ?node-meta= parameter can be provided with a desired node metadata key/value pair of the form key:value. This parameter can be specified multiple times, and will filter the results to nodes with the specified key/value pair(s).

This endpoint is very similar to the /v1/catalog/service endpoint; however, this endpoint automatically returns the status of the associated health check as well as any system level health checks. This allows a client to avoid sending traffic to nodes that are failing health tests or reporting warnings.

Users can also build in support for dynamic load balancing and other features by incorporating the use of health checks.

It returns a JSON body like this:

[
  {
    "Node": {
      "ID": "40e4a748-2192-161a-0510-9bf59fe950b5",
      "Node": "foobar",
      "Address": "10.1.10.12",
      "TaggedAddresses": {
        "lan": "10.1.10.12",
        "wan": "10.1.10.12"
      },
      "Meta": {
        "instance_type": "t2.medium"
      }
    },
    "Service": {
      "ID": "redis",
      "Service": "redis",
      "Tags": null,
      "Address": "10.1.10.12",
      "Port": 8000
    },
    "Checks": [
      {
        "Node": "foobar",
        "CheckID": "service:redis",
        "Name": "Service 'redis' check",
        "Status": "passing",
        "Notes": "",
        "Output": "",
        "ServiceID": "redis",
        "ServiceName": "redis"
      },
      {
        "Node": "foobar",
        "CheckID": "serfHealth",
        "Name": "Serf Health Status",
        "Status": "passing",
        "Notes": "",
        "Output": "",
        "ServiceID": "",
        "ServiceName": ""
      }
    ]
  }
]

This endpoint supports blocking queries and all consistency modes.

/v1/health/state/<state>

This endpoint is hit with a GET and returns the checks in the state provided on the path. By default, the datacenter of the agent is queried; however, the dc can be provided using the ?dc= query parameter.

Adding the optional ?near= parameter with a node name will sort the node list in ascending order based on the estimated round trip time from that node. Passing ?near=_agent will use the agent's node for the sort.

In Consul 0.7.3 and later, the optional ?node-meta= parameter can be provided with a desired node metadata key/value pair of the form key:value. This parameter can be specified multiple times, and will filter the results to health checks on nodes with the specified key/value pair(s).

The supported states are any, passing, warning, or critical. The any state is a wildcard that can be used to return all checks.

It returns a JSON body like this:

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

This endpoint supports blocking queries and all consistency modes.