open-consul/website/content/api-docs/agent/check.mdx

---
layout: api
page_title: Check - Agent - HTTP API
description: The /agent/check endpoints interact with checks on the local agent in Consul.
---

# Check - Agent HTTP API

The `/agent/check` endpoints interact with checks on the local agent in Consul.
These should not be confused with checks in the catalog.

## List Checks

This endpoint returns all 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](/docs/internals/anti-entropy), so in most situations
everything will be in sync within a few seconds.

| Method | Path            | Produces           |
| ------ | --------------- | ------------------ |
| `GET`  | `/agent/checks` | `application/json` |

The table below shows this endpoint's support for
[blocking queries](/api/features/blocking),
[consistency modes](/api/features/consistency),
[agent caching](/api/features/caching), and
[required ACLs](/api#authentication).

| Blocking Queries | Consistency Modes | Agent Caching | ACL Required             |
| ---------------- | ----------------- | ------------- | ------------------------ |
| `NO`             | `none`            | `none`        | `node:read,service:read` |

### Parameters

- `filter` `(string: "")` - Specifies the expression used to filter the
  queries results prior to returning the data.

### Sample Request

```shell-session
$ curl \
    http://127.0.0.1:8500/v1/agent/checks
```

### Sample Response

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

### Filtering

The filter will be executed against each health check value in the results map with
the following selectors and filter operations being supported:

| Selector      | Supported Operations                               |
| ------------- | -------------------------------------------------- |
| `CheckID`     | Equal, Not Equal, In, Not In, Matches, Not Matches |
| `Name`        | Equal, Not Equal, In, Not In, Matches, Not Matches |
| `Node`        | Equal, Not Equal, In, Not In, Matches, Not Matches |
| `Notes`       | Equal, Not Equal, In, Not In, Matches, Not Matches |
| `Output`      | Equal, Not Equal, In, Not In, Matches, Not Matches |
| `ServiceID`   | Equal, Not Equal, In, Not In, Matches, Not Matches |
| `ServiceName` | Equal, Not Equal, In, Not In, Matches, Not Matches |
| `ServiceTags` | In, Not In, Is Empty, Is Not Empty                 |
| `Status`      | Equal, Not Equal, In, Not In, Matches, Not Matches |

## Register Check

This endpoint adds a new check to the local agent. Checks may be of script,
HTTP, TCP, or TTL type. The agent is responsible for managing the status of the
check and keeping the Catalog in sync.

| Method | Path                    | Produces           |
| ------ | ----------------------- | ------------------ |
| `PUT`  | `/agent/check/register` | `application/json` |

The table below shows this endpoint's support for
[blocking queries](/api/features/blocking),
[consistency modes](/api/features/consistency),
[agent caching](/api/features/caching), and
[required ACLs](/api#authentication).

| Blocking Queries | Consistency Modes | Agent Caching | ACL Required               |
| ---------------- | ----------------- | ------------- | -------------------------- |
| `NO`             | `none`            | `none`        | `node:write,service:write` |

### Parameters

- `Name` `(string: <required>)` - Specifies the name of the check.

- `ID` `(string: "")` - Specifies a unique ID for this check on the node.
  This defaults to the `"Name"` parameter, but it may be necessary to provide an
  ID for uniqueness. This value will return in the response as `"CheckId"`.

- `Interval` `(string: "")` - Specifies the frequency at which to run this
  check. This is required for HTTP and TCP checks.

- `Notes` `(string: "")` - Specifies arbitrary information for humans. This is
  not used by Consul internally.

- `DeregisterCriticalServiceAfter` `(string: "")` - Specifies that checks
  associated with a service should deregister after this time. This is specified
  as a time duration with suffix like "10m". If a check is in the critical state
  for more than this configured value, then its associated service (and all of
  its associated checks) will automatically be deregistered. The minimum timeout
  is 1 minute, and the process that reaps critical services runs every 30
  seconds, so it may take slightly longer than the configured timeout to trigger
  the deregistration. This should generally be configured with a timeout that's
  much, much longer than any expected recoverable outage for the given service.

- `Args` `(array<string>)` - Specifies command arguments to run to update the
  status of the check. Prior to Consul 1.0, checks used a single `Script` field
  to define the command to run, and would always run in a shell. In Consul
  1.0, the `Args` array was added so that checks can be run without a shell. The
  `Script` field is deprecated, and you should include the shell in the `Args` to
  run under a shell, eg. `"args": ["sh", "-c", "..."]`.

  -> **Note:** Consul 1.0 shipped with an issue where `Args` was erroneously named
  `ScriptArgs` in this API. Please use `ScriptArgs` with Consul 1.0 (that will
  continue to be accepted in future versions of Consul), and `Args` in Consul
  1.0.1 and later.

- `AliasNode` `(string: "")` - Specifies the ID of the node for an alias check.
  If no service is specified, the check will alias the health of the node.
  If a service is specified, the check will alias the specified service on
  this particular node.

- `AliasService` `(string: "")` - Specifies the ID of a service for an
  alias check. If the service is not registered with the same agent,
  `AliasNode` must also be specified. Note this is the service _ID_ and
  not the service _name_ (though they are very often the same).

- `DockerContainerID` `(string: "")` - Specifies that the check is a Docker
  check, and Consul will evaluate the script every `Interval` in the given
  container using the specified `Shell`. Note that `Shell` is currently only
  supported for Docker checks.

- `GRPC` `(string: "")` - Specifies a `gRPC` check's endpoint that supports the standard
  [gRPC health checking protocol](https://github.com/grpc/grpc/blob/master/doc/health-checking.md).
  The state of the check will be updated at the given `Interval` by probing the configured
  endpoint. Add the service identifier after the `gRPC` check's endpoint in the following format to check for a specific service instead of the whole gRPC server `/:service_identifier`.

- `GRPCUseTLS` `(bool: false)` - Specifies whether to use TLS for this `gRPC` health check.
  If TLS is enabled, then by default, a valid TLS certificate is expected. Certificate
  verification can be turned off by setting `TLSSkipVerify` to `true`.

- `H2PING` `(string "")` - Specifies an address that uses http2 with TLS to run a ping check on.
  At the specified `Interval`, a connection is made to the address, and a ping is sent.
  If the ping is successful, the check will be classified as `passing`, otherwise it will be marked as `critical`.
  A valid SSL certificate is required by default, but verification can be removed with `TLSSkipVerify`.

- `HTTP` `(string: "")` - Specifies an `HTTP` check to perform a `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`. HTTP checks also support SSL. By default, a valid SSL certificate
  is expected. Certificate verification can be controlled using the
  `TLSSkipVerify`.

- `Method` `(string: "")` - Specifies a different HTTP method to be used
  for an `HTTP` check. When no value is specified, `GET` is used.

- `Body` `(string: "")` - Specifies a body that should be sent with `HTTP` checks.

- `Header` `(map[string][]string: {})` - Specifies a set of headers that should
  be set for `HTTP` checks. Each header can have multiple values.

- `Timeout` `(duration: 10s)` - Specifies a timeout for outgoing connections in the
  case of a Script, HTTP, TCP, or gRPC check. Can be specified in the form of "10s"
  or "5m" (i.e., 10 seconds or 5 minutes, respectively).

- `OutputMaxSize` `(positive int: 4096)` - Allow to put a maximum size of text
  for the given check. This value must be greater than 0, by default, the value
  is 4k.
  The value can be further limited for all checks of a given agent using the
  `check_output_max_size` flag in the agent.

- `TLSServerName` `(string: "")` - Specifies an optional string used to set the
  SNI host when connecting via TLS.
  For an `HTTP` check, this value is set automatically if the URL uses a hostname
  (not an IP address).

- `TLSSkipVerify` `(bool: false)` - Specifies if the certificate for an HTTPS
  check should not be verified.

- `TCP` `(string: "")` - Specifies a `TCP` to connect against the value of `TCP`
  (expected to be an IP or hostname plus port combination) every `Interval`. If
  the connection attempt is successful, the check is `passing`. If the
  connection attempt is unsuccessful, the check is `critical`. In the case of a
  hostname that resolves to both IPv4 and IPv6 addresses, an attempt will be
  made to both addresses, and the first successful connection attempt will
  result in a successful check.

- `TTL` `(string: "")` - Specifies this is a TTL check, and the TTL endpoint
  must be used periodically to update the state of the check.

- `ServiceID` `(string: "")` - Specifies the ID of a service to associate the
  registered check with an existing service provided by the agent.

- `Status` `(string: "")` - Specifies the initial status of the health check.

- `SuccessBeforePassing` `(int: 0)` - Specifies the number of consecutive successful
  results required before check status transitions to passing. Available for HTTP,
  TCP, gRPC, Docker & Monitor checks.

- `FailuresBeforeCritical` `(int: 0)` - Specifies the number of consecutive unsuccessful
  results required before check status transitions to critical. Available for HTTP,
  TCP, gRPC, Docker & Monitor checks.

### Sample Payload

```json
{
  "ID": "mem",
  "Name": "Memory utilization",
  "Notes": "Ensure we don't oversubscribe memory",
  "DeregisterCriticalServiceAfter": "90m",
  "Args": ["/usr/local/bin/check_mem.py"],
  "DockerContainerID": "f972c95ebf0e",
  "Shell": "/bin/bash",
  "HTTP": "https://example.com",
  "Method": "POST",
  "Header": { "Content-Type": ["application/json"] },
  "Body": "{\"check\":\"mem\"}",
  "TCP": "example.com:22",
  "Interval": "10s",
  "Timeout": "5s",
  "TLSSkipVerify": true
}
```

### Sample Request

```shell-session
$ curl \
   --request PUT \
   --data @payload.json \
   http://127.0.0.1:8500/v1/agent/check/register
```

## Deregister Check

This endpoint remove a check from the local agent. The agent will take care of
deregistering the check from the catalog. If the check with the provided ID does
not exist, no action is taken.

| Method | Path                                | Produces           |
| ------ | ----------------------------------- | ------------------ |
| `PUT`  | `/agent/check/deregister/:check_id` | `application/json` |

The table below shows this endpoint's support for
[blocking queries](/api/features/blocking),
[consistency modes](/api/features/consistency),
[agent caching](/api/features/caching), and
[required ACLs](/api#authentication).

| Blocking Queries | Consistency Modes | Agent Caching | ACL Required               |
| ---------------- | ----------------- | ------------- | -------------------------- |
| `NO`             | `none`            | `none`        | `node:write,service:write` |

### Parameters

- `check_id` `(string: "")` - Specifies the unique ID of the check to
  deregister. This is specified as part of the URL.

### Sample Request

```shell-session
$ curl \
    --request PUT \
    http://127.0.0.1:8500/v1/agent/check/deregister/my-check-id
```

## TTL Check Pass

This endpoint is used with a TTL type check to set the status of the check to
`passing` and to reset the TTL clock.

| Method | Path                          | Produces           |
| ------ | ----------------------------- | ------------------ |
| `PUT`  | `/agent/check/pass/:check_id` | `application/json` |

The table below shows this endpoint's support for
[blocking queries](/api/features/blocking),
[consistency modes](/api/features/consistency),
[agent caching](/api/features/caching), and
[required ACLs](/api#authentication).

| Blocking Queries | Consistency Modes | Agent Caching | ACL Required               |
| ---------------- | ----------------- | ------------- | -------------------------- |
| `NO`             | `none`            | `none`        | `node:write,service:write` |

### Parameters

- `check_id` `(string: "")` - Specifies the unique ID of the check to
  use. This is specified as part of the URL.

- `note` `(string: "")` - Specifies a human-readable message. This will be
  passed through to the check's `Output` field.

### Sample Request

```shell-session
$ curl \
    --request PUT \
    http://127.0.0.1:8500/v1/agent/check/pass/my-check-id
```

## TTL Check Warn

This endpoint is used with a TTL type check to set the status of the check to
`warning` and to reset the TTL clock.

| Method | Path                          | Produces           |
| ------ | ----------------------------- | ------------------ |
| `PUT`  | `/agent/check/warn/:check_id` | `application/json` |

The table below shows this endpoint's support for
[blocking queries](/api/features/blocking),
[consistency modes](/api/features/consistency),
[agent caching](/api/features/caching), and
[required ACLs](/api#authentication).

| Blocking Queries | Consistency Modes | Agent Caching | ACL Required               |
| ---------------- | ----------------- | ------------- | -------------------------- |
| `NO`             | `none`            | `none`        | `node:write,service:write` |

### Parameters

- `check_id` `(string: "")` - Specifies the unique ID of the check to
  use. This is specified as part of the URL.

- `note` `(string: "")` - Specifies a human-readable message. This will be
  passed through to the check's `Output` field.

### Sample Request

```shell-session
$ curl \
    http://127.0.0.1:8500/v1/agent/check/warn/my-check-id
```

## TTL Check Fail

This endpoint is used with a TTL type check to set the status of the check to
`critical` and to reset the TTL clock.

| Method | Path                          | Produces           |
| ------ | ----------------------------- | ------------------ |
| `PUT`  | `/agent/check/fail/:check_id` | `application/json` |

The table below shows this endpoint's support for
[blocking queries](/api/features/blocking),
[consistency modes](/api/features/consistency),
[agent caching](/api/features/caching), and
[required ACLs](/api#authentication).

| Blocking Queries | Consistency Modes | Agent Caching | ACL Required               |
| ---------------- | ----------------- | ------------- | -------------------------- |
| `NO`             | `none`            | `none`        | `node:write,service:write` |

### Parameters

- `check_id` `(string: "")` - Specifies the unique ID of the check to
  use. This is specified as part of the URL.

- `note` `(string: "")` - Specifies a human-readable message. This will be
  passed through to the check's `Output` field.

### Sample Request

```shell-session
$ curl \
    http://127.0.0.1:8500/v1/agent/check/fail/my-check-id
```

## TTL Check Update

This endpoint is used with a TTL type check to set the status of the check and
to reset the TTL clock.

| Method | Path                            | Produces           |
| ------ | ------------------------------- | ------------------ |
| `PUT`  | `/agent/check/update/:check_id` | `application/json` |

The table below shows this endpoint's support for
[blocking queries](/api/features/blocking),
[consistency modes](/api/features/consistency),
[agent caching](/api/features/caching), and
[required ACLs](/api#authentication).

| Blocking Queries | Consistency Modes | Agent Caching | ACL Required               |
| ---------------- | ----------------- | ------------- | -------------------------- |
| `NO`             | `none`            | `none`        | `node:write,service:write` |

### Parameters

- `check_id` `(string: "")` - Specifies the unique ID of the check to
  use. This is specified as part of the URL.

- `Status` `(string: "")` - Specifies the status of the check. Valid values are
  `"passing"`, `"warning"`, and `"critical"`.

- `Output` `(string: "")` - Specifies a human-readable message. This will be
  passed through to the check's `Output` field.

### Sample Payload

```json
{
  "Status": "passing",
  "Output": "curl reported a failure:\n\n..."
}
```

### Sample Request

```shell-session
$ curl \
    --request PUT \
    --data @payload.json \
    http://127.0.0.1:8500/v1/agent/check/update/my-check-id
```