# Prometheus

The `prometheus` data format converts metrics into the Prometheus text
exposition format.  When used with the `prometheus` input, the input should be
use the `metric_version = 2` option in order to properly round trip metrics.

**Warning**: When generating histogram and summary types, output may
not be correct if the metric spans multiple batches.  This issue can be
somewhat, but not fully, mitigated by using outputs that support writing in
"batch format".  When using histogram and summary types, it is recommended to
use only the `prometheus_client` output. Histogram and Summary types
also update their expiration time based on the most recently received data.
If incoming metrics stop updating specific buckets or quantiles but continue
reporting others every bucket/quantile will continue to exist.

## Configuration

```toml
[[outputs.file]]
  files = ["stdout"]
  use_batch_format = true

  ## Include the metric timestamp on each sample.
  prometheus_export_timestamp = false

  ## Sort prometheus metric families and metric samples.  Useful for
  ## debugging.
  prometheus_sort_metrics = false

  ## Output string fields as metric labels; when false string fields are
  ## discarded.
  prometheus_string_as_label = false

  ## Encode metrics without HELP metadata. This helps reduce the payload
  ## size.
  prometheus_compact_encoding = false

  ## Data format to output.
  ## Each data format has its own unique set of configuration options, read
  ## more about them here:
  ##   https://github.com/influxdata/telegraf/blob/master/docs/DATA_FORMATS_INPUT.md
  data_format = "prometheus"
```

### Metrics

A Prometheus metric is created for each integer, float, boolean or unsigned
field.  Boolean values are converted to *1.0* for true and *0.0* for false.

The Prometheus metric names are produced by joining the measurement name with
the field key.  In the special case where the measurement name is `prometheus`
it is not included in the final metric name.

Prometheus labels are produced for each tag.

**Note:** String fields are ignored and do not produce Prometheus metrics.

## Example

### Example Input

```text
cpu,cpu=cpu0 time_guest=8022.6,time_system=26145.98,time_user=92512.89 1574317740000000000
cpu,cpu=cpu1 time_guest=8097.88,time_system=25223.35,time_user=96519.58 1574317740000000000
cpu,cpu=cpu2 time_guest=7386.28,time_system=24870.37,time_user=95631.59 1574317740000000000
cpu,cpu=cpu3 time_guest=7434.19,time_system=24843.71,time_user=93753.88 1574317740000000000
```

### Example Output

```text
# HELP cpu_time_guest Telegraf collected metric
# TYPE cpu_time_guest counter
cpu_time_guest{cpu="cpu0"} 9582.54
cpu_time_guest{cpu="cpu1"} 9660.88
cpu_time_guest{cpu="cpu2"} 8946.45
cpu_time_guest{cpu="cpu3"} 9002.31
# HELP cpu_time_system Telegraf collected metric
# TYPE cpu_time_system counter
cpu_time_system{cpu="cpu0"} 28675.47
cpu_time_system{cpu="cpu1"} 27779.34
cpu_time_system{cpu="cpu2"} 27406.18
cpu_time_system{cpu="cpu3"} 27404.97
# HELP cpu_time_user Telegraf collected metric
# TYPE cpu_time_user counter
cpu_time_user{cpu="cpu0"} 99551.84
cpu_time_user{cpu="cpu1"} 103468.52
cpu_time_user{cpu="cpu2"} 102591.45
cpu_time_user{cpu="cpu3"} 100717.05
```
