97 lines
3.1 KiB
Markdown
97 lines
3.1 KiB
Markdown
|
---
|
||
|
|
title: HTTP SD
|
||
|
|
sort_rank: 7
|
||
|
|
---
|
||
|
|
|
||
|
|
# Writing HTTP Service Discovery
|
||
|
|
|
||
|
|
Prometheus provides a generic [HTTP Service Discovery](https://prometheus.io/docs/prometheus/latest/configuration/configuration/#http_sd_config),
|
||
|
|
that enables it to discover targets over an HTTP endpoint.
|
||
|
|
|
||
|
|
The HTTP Service Discovery is complimentary to the supported service
|
||
|
|
discovery mechanisms, and is an alternative to [File-based Service Discovery](https://prometheus.io/docs/guides/file-sd/#use-file-based-service-discovery-to-discover-scrape-targets).
|
||
|
|
|
||
|
|
## Comparison between File-Based SD and HTTP SD
|
||
|
|
|
||
|
|
Here is a table comparing our two generic Service Discovery implementations.
|
||
|
|
|
||
|
|
| Item | File SD | HTTP SD |
|
||
|
|
| ---- | ------- | ------- |
|
||
|
|
| Event Based | Yes, via inotify | No |
|
||
|
|
| Update frequency | Instant, thanks to inotify | Following refresh_interval |
|
||
|
|
| Format | Yaml or JSON | JSON |
|
||
|
|
| Transport | Local file | HTTP/HTTPS |
|
||
|
|
| Security | File-Based security | TLS, Basic auth, Authorization header, OAuth2 |
|
||
|
|
|
||
|
|
## Requirements of HTTP SD endpoints
|
||
|
|
|
||
|
|
If you implement an HTTP SD endpoint, here is a few requirements you should be
|
||
|
|
aware of.
|
||
|
|
|
||
|
|
The response is consumed as is, unmodified. On each refresh interval (default: 1
|
||
|
|
minute), Prometheus will perform a GET request to the HTTP SD endpoint. The GET
|
||
|
|
request contains a `X-Prometheus-Refresh-Interval-Seconds` HTTP header with the
|
||
|
|
refresh interval.
|
||
|
|
|
||
|
|
The SD endpoint must answer with an HTTP 200 response, with the HTTP Header
|
||
|
|
`Content-Type: application/json`. The answer must be UTF-8 formatted.
|
||
|
|
If no targets should be transmitted, HTTP 200 must also be emitted, with
|
||
|
|
an empty list `[]`. Target lists are unordered.
|
||
|
|
|
||
|
|
Prometheus caches target lists. If an error occurs while fetching an updated
|
||
|
|
targets list, Prometheus keeps using the current targets list. The targets list
|
||
|
|
is not saved across restart.
|
||
|
|
|
||
|
|
The whole list of targets must be returned on every scrape. There is no support
|
||
|
|
for incremental updates. A Prometheus instance does not send its hostname and it
|
||
|
|
is not possible for a SD endpoint to know if the SD requests is the first one
|
||
|
|
after a restart or not.
|
||
|
|
|
||
|
|
The URL to the HTTP SD is not considered secret. The authentication, and any API
|
||
|
|
keys should be passed with the appropriate authentication mechanisms. Prometheus
|
||
|
|
supports TLS authentication, basic authentication, OAuth2, and authorization
|
||
|
|
headers.
|
||
|
|
|
||
|
|
## HTTP_SD format
|
||
|
|
|
||
|
|
```json
|
||
|
|
[
|
||
|
|
{
|
||
|
|
"targets": [ "<host>", ... ],
|
||
|
|
"labels": {
|
||
|
|
"<labelname>": "<labelvalue>", ...
|
||
|
|
}
|
||
|
|
},
|
||
|
|
...
|
||
|
|
]
|
||
|
|
```
|
||
|
|
|
||
|
|
|
||
|
|
Examples:
|
||
|
|
|
||
|
|
```json
|
||
|
|
[
|
||
|
|
{
|
||
|
|
"targets": ["10.0.10.2:9100", "10.0.10.3:9100", "10.0.10.4:9100", "10.0.10.5:9100"],
|
||
|
|
"labels": {
|
||
|
|
"__meta_datacenter": "london",
|
||
|
|
"__meta_prometheus_job": "node"
|
||
|
|
}
|
||
|
|
},
|
||
|
|
{
|
||
|
|
"targets": ["10.0.40.2:9100", "10.0.40.3:9100"],
|
||
|
|
"labels": {
|
||
|
|
"__meta_datacenter": "london",
|
||
|
|
"__meta_prometheus_job": "alertmanager"
|
||
|
|
}
|
||
|
|
},
|
||
|
|
{
|
||
|
|
"targets": ["10.0.40.2:9093", "10.0.40.3:9093"],
|
||
|
|
"labels": {
|
||
|
|
"__meta_datacenter": "newyork",
|
||
|
|
"__meta_prometheus_job": "alertmanager"
|
||
|
|
}
|
||
|
|
}
|
||
|
|
]
|
||
|
|
```
|