# Mermin with OpenTelemetry Collector

* [Mermin with OpenTelemetry Collector](#mermin-with-opentelemetry-collector)
  * [Overview](#overview)
  * [Install](#install)
    * [Debug charts](#debug-charts)

## Overview

This example deploys Mermin with the OpenTelemetry Collector for testing purposes. The OpenTelemetry Collector's output is set to `debug` (`stdout`), and has been tested by using [Kind](https://kind.sigs.k8s.io/)

Notes on the example deployment:

* [Location in the repository](https://github.com/elastiflow/mermin/tree/beta/docs/deployment/examples/local-otel) - `docs/deployment/examples/local-otel`
* Deployment happens in the "current" namespace
* You may optionally customize and use `config.hcl` instead of the default config.
* Mermin values use `mermin:latest` image, it is expected you build it and load to your K8s cluster

## Install

* Create a values file for the OTEL Collector with [contents](https://github.com/elastiflow/mermin/blob/main/docs/deployment/examples/local-otel/values_otel.yaml) or use one from the repo
* Deploy the OTEL Collector chart

  ```sh
  # Deploy OpenTelemetry Collector
  helm repo add open-telemetry https://open-telemetry.github.io/opentelemetry-helm-charts
  helm upgrade -i -n default \
    -f values_otel.yaml \
    otel-collector open-telemetry/opentelemetry-collector
  ```
* Create config file for the Mermin with [contents](https://github.com/elastiflow/mermin/blob/main/docs/deployment/examples/local-otel/config.hcl) or use one from the repo
* Deploy the Mermin chart

  ```sh
  helm repo add mermin https://elastiflow.github.io/mermin/
  helm upgrade -i --wait --timeout 15m -n default \
    --set-file config.content=config.hcl \
    mermin mermin/mermin
  ```
* Optionally install `metrics-server` to get metrics if it has not been installed yet

  ```sh
  kubectl apply -f https://github.com/kubernetes-sigs/metrics-server/releases/download/v0.8.0/components.yaml
  # Patch to use insecure TLS, commonly needed on dev local clusters
  kubectl -n kube-system patch deployment metrics-server --type='json' -p='[{"op":"add","path":"/spec/template/spec/containers/0/args/-","value":"--kubelet-insecure-tls"}]'
  ```

### Debug charts

In order to render K8s manifests you may use following commands

* OpenTelemetry Collector

  ```sh
  rm -rf helm_rendered; helm template \
    -f values_otel.yaml \
    otel-collector open-telemetry/opentelemetry-collector \
    --output-dir helm_rendered

  # Diff with existing K8s resources
  kubectl diff -R -f helm_rendered/mermin/
  ```
* Mermin

  ```sh
  rm -rf helm_rendered; helm template \
    --set-file config.content=config.hcl \
    mermin mermin/mermin \
    --output-dir helm_rendered

  # Diff with existing K8s resources
  kubectl diff -R -f helm_rendered/mermin/
  ```