apisix/docs/en/latest/health-check.md

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---
title: Health Check
---
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## Health Checks for Upstream
Health Check of APISIX is based on [lua-resty-healthcheck](https://github.com/Kong/lua-resty-healthcheck),
you can use it for upstream.
Note that we only start the health check when the upstream is hit by a request.
There won't be any health check if an upstream is configured but isn't in used.
The following is an example of health check:
```shell
curl http://127.0.0.1:9080/apisix/admin/routes/1 -H 'X-API-KEY: edd1c9f034335f136f87ad84b625c8f1' -X PUT -d '
{
"uri": "/index.html",
"plugins": {
"limit-count": {
"count": 2,
"time_window": 60,
"rejected_code": 503,
"key": "remote_addr"
}
},
"upstream": {
"nodes": {
"127.0.0.1:1980": 1,
"127.0.0.1:1970": 1
},
"type": "roundrobin",
"retries": 2,
"checks": {
"active": {
"timeout": 5,
"http_path": "/status",
"host": "foo.com",
"healthy": {
"interval": 2,
"successes": 1
},
"unhealthy": {
"interval": 1,
"http_failures": 2
},
"req_headers": ["User-Agent: curl/7.29.0"]
},
"passive": {
"healthy": {
"http_statuses": [200, 201],
"successes": 3
},
"unhealthy": {
"http_statuses": [500],
"http_failures": 3,
"tcp_failures": 3
}
}
}
}
}'
```
The configures in `checks` are belong to health check, the type of `checks`
contains: `active` or `passive`.
* `active`: To enable active health checks, you need to specify the configuration items under `checks.active` in the Upstream object configuration.
* `active.timeout`: Socket timeout for active checks (in seconds), support decimals. For example `1.01` means `1010` milliseconds, `2` means `2000` milliseconds.
* `active.http_path`: The HTTP GET request path used to detect if the upstream is healthy.
* `active.host`: The HTTP request host used to detect if the upstream is healthy.
* `active.port`: The customize health check host port (optional), this will override the port in the `upstream` node.
The threshold fields of `healthy` are:
* `active.healthy.interval`: Interval between health checks for healthy targets (in seconds), the minimum is 1.
* `active.healthy.successes`: The number of success times to determine the target is healthy, the minimum is 1.
The threshold fields of `unhealthy` are:
* `active.unhealthy.interval`: Interval between health checks for unhealthy targets (in seconds), the minimum is 1.
* `active.unhealthy.http_failures`: The number of http failures times to determine the target is unhealthy, the minimum is 1.
* `active.req_headers`: Additional request headers. Array format, so you can fill in multiple headers.
* `passive`: To enable passive health checks, you need to specify the configuration items under `checks.passive` in the Upstream object configuration.
The threshold fields of `healthy` are:
* `passive.healthy.http_statuses`: If the current response code is equal to any of these, set the upstream node to the `healthy` state. Otherwise ignore this request.
* `passive.healthy.successes`: Number of successes in proxied traffic (as defined by `passive.healthy.http_statuses`) to consider a target healthy, as observed by passive health checks.
The threshold fields of `unhealthy` are:
* `passive.unhealthy.http_statuses`: If the current response code is equal to any of these, set the upstream node to the `unhealthy` state. Otherwise ignore this request.
* `passive.unhealthy.tcp_failures`: Number of TCP failures in proxied traffic to consider a target unhealthy, as observed by passive health checks.
* `passive.unhealthy.timeouts`: Number of timeouts in proxied traffic to consider a target unhealthy, as observed by passive health checks.
* `passive.unhealthy.http_failures`: Number of HTTP failures in proxied traffic (as defined by `passive.unhealthy.http_statuses`) to consider a target unhealthy, as observed by passive health checks.
The health check status can be fetched via `GET /v1/healthcheck` in [control API](./control-api.md).