# Prometheus

<figure><img src="https://415484505-files.gitbook.io/~/files/v0/b/gitbook-x-prod.appspot.com/o/spaces%2F-LxtoAXZwwOc4XGto8vb%2Fuploads%2FIrU1Y3GVdrNKfKwvpsMU%2FScreenshot%202023-01-03%20at%2013.47.09.png?alt=media&#x26;token=92343a59-8caa-4583-b668-8bf6bc301117" alt=""><figcaption></figcaption></figure>

## Metrics

* Human-readable text-based
* Metrics entries: TYPE and HELP attributes
  * HELP -> description of what metric is
  * TYPE
    * COUNTER: how many times X happened
    * GAUGE: what is a current value of x now
    * HISTOGRAM: how long or how big

<figure><img src="https://415484505-files.gitbook.io/~/files/v0/b/gitbook-x-prod.appspot.com/o/spaces%2F-LxtoAXZwwOc4XGto8vb%2Fuploads%2Fld0XpNxaDKZ6wFZXNm6o%2FScreenshot%202023-01-03%20at%2013.55.19.png?alt=media&#x26;token=76bfc20b-795a-414f-8462-b1d269e18f0b" alt=""><figcaption></figcaption></figure>

Some apps/components have `/metrics` endpoint (e.g. Spring actuator), but some not. E.g. MySQL, Linux. This is how it is working (Exporters list :link:[HERE](https://prometheus.io/docs/instrumenting/exporters/)):

<figure><img src="https://415484505-files.gitbook.io/~/files/v0/b/gitbook-x-prod.appspot.com/o/spaces%2F-LxtoAXZwwOc4XGto8vb%2Fuploads%2Foi5VHRCpg9XOpSK0W37m%2FScreenshot%202023-01-03%20at%2013.57.48.png?alt=media&#x26;token=6296fc04-07b4-4983-8662-9345bd66c1f1" alt=""><figcaption></figcaption></figure>

## Alert Manager

<figure><img src="https://415484505-files.gitbook.io/~/files/v0/b/gitbook-x-prod.appspot.com/o/spaces%2F-LxtoAXZwwOc4XGto8vb%2Fuploads%2FpMPNi8jXWBYh10uVCvrb%2FScreenshot%202023-01-03%20at%2014.11.15.png?alt=media&#x26;token=803ba373-2b05-4d07-8625-b44b9893aa2e" alt=""><figcaption></figcaption></figure>

## Limits

* single node, self containing -> hard to scale
