# Overview

ClusterCockpit uses the [InfluxData line-protocol](https://docs.influxdata.com/influxdb/v2.1/reference/syntax/line-protocol/) for transferring metrics between its components. The line-protocol is a text-based representation of a metric with a value, time and describing tags. All metrics have the following format (if written to `stdout`):

```
<measurement>,<tag set> <field set> <timestamp>
```

where `<tag set>` and `<field set>` are comma-separated lists of `key=value` entries. In a mind-model, think about tags as `indices` in the database for faster lookup and the `<field set>` as metric values.


# Line-protocol in the ClusterCockpit ecosystem

In ClusterCockpit we limit the flexibility of the InfluxData line-protocol slightly. The idea is to keep the format evaluatable by different components.

Each metric is identifiable by the `measurement` (= metric name), the `hostname`, the `type` and, if required, a `type-id`.

## Mandatory tags per measurement:
* `hostname`
* `type` in `[node, socket, die, memoryDomain, llb, core, hwthread, (accelerator)]`
* `type-id` for further specifying the type like CPU socket or HW Thread identifier

## Mandatory fields per measurement:
The field key is always `value`. No other field keys are evaluated by the ClusterCockpit ecosystem.

## Optional tags depending on the measurment:

In some cases, optional tags are required like `filesystem`, `device` or `version`. While you are free to do that, the ClusterCockpit components in the stack above will recognize `stype` (= sub type) and `stype-id` in the future. So `filesystem=/homes` should be better specified as `stype=filesystem,stype-id=/homes`

## Supported measurements

While the measurements (metric names) can be chosen freely, there is a basic set of measurements which should be present as long as you navigate in the ClusterCockpit ecosystem

* `flops_sp`: Single-precision floating point rate in `Flops/s`
* `flops_dp`: Double-precision floating point rate in `Flops/s`
* `flops_any`: Combined floating point rate in `Flops/s` (often `(flops_dp * 2) + flops_sp`)
* `cpu_load`: The 1m load of the system (see `/proc/loadavg`)
* `mem_used`: The amount of memory used by applications (see `/proc/meminfo`)
* `ipc`: instructions-per-cycle metric
* `mem_bw`: Main memory bandwidth (read and write) in `MByte/s`
* `cpu_power`: Power consumption of the whole CPU package
* `mem_power`: Power consumption of the memory subsystem
* `clock`: CPU clock in `MHz`
* ...

For the whole list, see [job-data schema](../../datastructures/job-data.schema.json)