# Turn logs into Nightingale metrics with mtail

Categraf embeds mtail: extract counters, gauges and histograms from log files with regular expressions and expressions, without shipping the logs to a log system first.

Last reviewed 2026-10-13

The mtail input turns logs into metrics. Input is a log file, output is a set of counters, gauges and histograms defined in mtail syntax; underneath it is Go regular expressions plus expression evaluation. It suits cases such as status-code distribution from Nginx access logs or error counts from application logs, with no need to ship the logs into Elasticsearch or Loki first.

Each `[[instances]]` block points at a set of `progs` (mtail program files or a directory) and the log paths to follow. Give different instances different progs, or distinguish them with `labels`, or their metrics will collide.

## What's in the template[​](#whats-in-the-template "Direct link to What's in the template")

* **Categraf collector config**: `input.mtail`

## How to connect[​](#how-to-connect "Direct link to How to connect")

1. [Install Categraf](https://n9e.github.io/docs/data/categraf/install.md), put the config below in `conf/input.mtail/mtail.toml`, fill in your own address and credentials, and restart Categraf. The startup log prints `input: local.mtail started` once the plugin is loaded.

   ```
   [[instances]]

   # progs = "/path/to/prog1" # prog dir1

   # logs = ["/path/to/a.log", "path/to/b.log"]

   # override_timezone = "Asia/Shanghai"

   # emit_metric_timestamp = "true" #string type



   # [[instances]]

   # progs = "/path/to/prog2" # prog dir2

   # logs = ["/path/to/logdir/"]

   # override_timezone = "Asia/Shanghai"

   # emit_metric_timestamp = "true" # string type
   ```

## Related[​](#related "Direct link to Related")

* [Mtail template source](https://github.com/ccfos/nightingale/tree/main/integrations/Mtail): the raw JSON for dashboards, rules and collector config. Pull requests welcome.
* [Import dashboards and alert rules](https://n9e.github.io/docs/data/integrations/import.md)
* [Verify that metrics are stored](https://n9e.github.io/docs/data/integrations/verify.md)
* [All integrations](https://n9e.github.io/integrations.md)