Prometheus - Time Series Database - Part 1

 

Prometheus Installation:

We can install the Prometheus in different ways.

•  Install through source
• Docker container
• Install through script
• Install through package manager

Prometheus with a metrics comes from node_exporter process from remote hosts. Each metrics has associated with one or more-time series data on it.

Events are point-in-time of record of action occurring during that time.

Prometheus is using a pull-based model for extracting the data from systems it monitors whereas Graphite and Nagios are using push-based model which push the metrics to a remote system.

Components of Prometheus Stack:

• Prometheus Alert manager for routing an alert coming from Prometheus 
• Exporters: It has multiple exporter components depends upon a device such as Node Exporter.
• Grafana: It used to visualize metrics from Prometheus through dashboards.
  

Prometheus has four main components such as time series database [TSDB], scrape manager, rule manager and Web UI.

Time Series Database:

   It is a special kind of database that is optimized for storing data points in a time series manner. The core part of TSDB are head blocks [Write-ahead log] and data format (block, chunks, and indices). The head block is an entry point for samples being scraped and stored in TSDB. 

The chunk gets appending into head block, until chunk hits it sample limit until stays in memory. It will add into WAL at first before added into memory, so we will preserve the data if server is in panic or reboot at automatically.

To increase resource efficiency, some wizardry is done to the chunk data so that it only stores the direct value of the first timestamp (t0) and first value (v0). Subsequent timestamps are set to the delta of the prior timestamp, so starting at t2, all timestamps are the delta of a delta. Similarly, subsequent values are compared to their prior value using a bitwise XOR operator. This just means that the difference between the samples is stored, and if they’re the same, then 0 is stored.

Scrape Manager:

  The scrape manager is a part of Prometheus that handles pulling metrics from applications and exporters by performing scraping and maintaining an internal list of what things should be scraped by Prometheus.

Rule Manager:

  The rule manager is part of Prometheus that handles evaluating alerts and recording the rules as per Prometheus. It is handling evaluating rule groups compromised of alerts and recording rules on regular intervals. 

Web UI/API:

  The Web UI/API is the portion of Prometheus that you can access via your browser. The Prometheus UI/API is a powerful REST API. It provides integration with other graphical tools such as Grafana. 

Alert Manager:

  It is responsible to send an alert to Slack, PagerDuty and other alerting destinations.  Alert Manager handles all of that owns through routing tree-based workflow.