in_process_exporter_metrics: Add documentation for process_exporter_metrics

SUMMARY.md

@@ -103,6 +103,7 @@
   * [Node Exporter Metrics](pipeline/inputs/node-exporter-metrics.md)
   * [Podman Metrics](pipeline/inputs/podman-metrics.md)
   * [Process Log Based Metrics](pipeline/inputs/process.md)
+  * [Process Exporter Metrics](pipeline/inputs/process-exporter-metrics.md)
   * [Prometheus Scrape Metrics](pipeline/inputs/prometheus-scrape-metrics.md)
   * [Random](pipeline/inputs/random.md)
   * [Serial Interface](pipeline/inputs/serial-interface.md)

pipeline/inputs/process-exporter-metrics.md

@@ -0,0 +1,88 @@
+---
+description: >-
+  A plugin based on Process Exporter to collect process level of metrics of system
+  metrics
+---
+
+# Process Exporter Metrics
+
+[Prometheus Node Exporter](https://github.com/prometheus/node_exporter) is a popular way to collect system level metrics from operating systems, such as CPU / Disk / Network / Process statistics.
+Fluent Bit 2.2 onwards includes a process exporter plugin that builds off the Prometheus design to collect process level metrics without having to manage two separate processes or agents.
+
+The Process Exporter Metrics plugin implements collecting of the various metrics available from [the 3rd party implementation of Prometheus Process Exporter](https://github.com/ncabatoff/process-exporter) and these will be expanded over time as needed.
+
+**Important note:** Metrics collected with Process Exporter Metrics flow through a separate pipeline from logs and current filters do not operate on top of metrics.
+
+This plugin is only supported on Linux based operating systems due to heavily relying on proc filesystem.
+
+macOS does not have procfs. Therefore, this plugin won't work for it.
+
+
+## Configuration
+
+| Key                       | Description                                                                            | Default   |
+| ------------------------- | -------------------------------------------------------------------------------------- | --------- |
+| scrape_interval           | The rate at which metrics are collected.                 | 5 seconds |
+| path.procfs               | The mount point used to collect process information and metrics. Read-only is enough   | /proc/    |
+| process\_include\_pattern | regex to determine which names of processes are included in the metrics produced by this plugin | It is applied for all process unless explicitly set. Default is `.+`. |
+| process\_exclude\_pattern | regex to determine which names of processes are excluded in the metrics produced by this plugin | It is not applied unless explicitly set. Default is `NULL`. |
+
+## Getting Started
+
+### Simple Configuration File
+
+In the following configuration file, the input plugin _process\_exporter\_metrics collects _metrics every 2 seconds and exposes them through our [Prometheus Exporter](../outputs/prometheus-exporter.md) output plugin on HTTP/TCP port 2021.
+
+```
+# Process Exporter Metrics + Prometheus Exporter
+# -------------------------------------------
+# The following example collect host metrics on Linux and expose
+# them through a Prometheus HTTP end-point.
+#
+# After starting the service try it with:
+#
+# $ curl http://127.0.0.1:2021/metrics
+#
+[SERVICE]
+    flush           1
+    log_level       info
+
+[INPUT]
+    name            process_exporter_metrics
+    tag             process_metrics
+    scrape_interval 2
+
+[OUTPUT]
+    name            prometheus_exporter
+    match           process_metrics
+    host            0.0.0.0
+    port            2021
+```
+
+You can see the metrics by using _curl:_
+
+```bash
+curl http://127.0.0.1:2021/metrics
+```
+
+### Container to Collect Host Metrics
+
+When deploying Fluent Bit in a container you will need to specify additional settings to ensure that Fluent Bit has access to the process details.
+The following `docker` command deploys Fluent Bit with a specific mount path for `procfs` and settings enabled to ensure that Fluent Bit can collect from the host. 
+These are then exposed over port 2021.
+
+```
+docker run -ti -v /proc:/host/proc:ro \
+               -p 2021:2021        \
+               fluent/fluent-bit:2.2 \
+               /fluent-bit/bin/fluent-bit \
+                         -i process_exporter_metrics -p path.procfs=/host/proc  \
+                         -o prometheus_exporter -p "add_label=host $HOSTNAME" \
+                         -f 1
+```
+
+## Enhancement Requests
+
+Development prioritises a subset of the available collectors in the [the 3rd party implementation of Prometheus Process Exporter](https://github.com/ncabatoff/process-exporter), to request others please open a Github issue by using the following template:\
+\
+\- [in_process_exporter_metrics](https://github.com/fluent/fluent-bit/issues/new?assignees=\&labels=\&template=feature_request.md\&title=in_process_exporter_metrics:%20add%20ABC%20collector)