fix(grafana/stack): review loki and mimir's notes

knowledge base/loki.md

@@ -61,7 +61,16 @@ helm --namespace 'loki' upgrade --create-namespace --install --cleanup-on-fail '
   --repo 'https://grafana.github.io/helm-charts' 'loki-distributed'
 ```
 
-Default configuration file for package-based installations is `/etc/loki/config.yml` or `/etc/loki/loki.yaml`.
+On startup, Loki tries to load a configuration file named `config.yaml` from the current working directory, or from the
+`config/` subdirectory if the first does not exist.<br/>
+Should none of those files exist, it **will** give up and fail.
+
+The default configuration file **for package-based installations** is located at `/etc/loki/config.yml` or
+`/etc/loki/loki.yaml`.<br/>
+The docker image tries using `/etc/loki/local-config.yml` by default (via the `COMMAND` setting).
+
+Some settings are currently **not** reachable via direct CLI flags (e.g. `schema_configs`, `storage_config.aws.*`).<br/>
+Use a configuration file for those.
 
   <details style="padding: 0 0 1em 1em;">
     <summary>Disable reporting</summary>
@@ -79,20 +88,32 @@ Default configuration file for package-based installations is `/etc/loki/config.
   <summary>Usage</summary>
 
 ```sh
-# Verify configuration files
+# Get help.
+loki -help
+docker run --rm --name 'loki-help' 'grafana/loki:3.3.2' -help
+
+# Verify configuration files.
 loki -verify-config
-loki -config.file='/etc/loki/local-config.yaml' -verify-config
+loki -config.file='/etc/loki/local-config.yaml' -print-config-stderr -verify-config
+docker run --rm 'grafana/loki' \
+  -verify-config -config.file '/etc/loki/local-config.yaml'
+docker run --rm -v "$PWD/custom-config.yaml:/etc/loki/local-config.yaml:ro" 'grafana/loki:3.3.2' \
+  -verify-config -config.file '/etc/loki/local-config.yaml' -log-config-reverse-order
 
-# List available component targets
+# List available component targets.
 loki -list-targets
-docker run 'docker.io/grafana/loki' -config.file='/etc/loki/local-config.yaml' -list-targets
+docker run --rm 'docker.io/grafana/loki' -config.file='/etc/loki/local-config.yaml' -list-targets
 
-# Start server components
+# Start server components.
 loki
 loki -target='all'
 loki -config.file='/etc/loki/config.yaml' -target='read'
 
-# Print the final configuration to stderr and start
+# Print the final configuration to the logs and continue.
+loki -log-config-reverse-order …
+loki -log.level='info' -log-config-reverse-order …
+
+# Print the final configuration to stderr and continue.
 loki -print-config-stderr …
 
 # Check the server is working
@@ -108,6 +129,33 @@ curl 'http://loki.fqdn:3101/ready'
 curl 'http://loki.fqdn:3102/ready'
 ```
 
+```plaintext
+GET /ready
+GET /metrics
+GET /services
+```
+
+</details>
+
+<details>
+  <summary>Real world use cases</summary>
+
+```sh
+# Check some values are applied to the final configuration.
+docker run --rm --name 'validate-cli-config' 'grafana/loki:3.3.2' \
+  -verify-config -config.file '/etc/loki/local-config.yaml' -print-config-stderr \
+  -common.storage.ring.instance-addr='127.0.0.1' -server.path-prefix='/loki' \
+  2>&1 \
+| grep -E 'instance_addr' -E 'path_prefix'
+docker run --rm --name 'validate-cli-config' 'grafana/loki:3.3.2' \
+  -verify-config -config.file '/etc/loki/local-config.yaml' -print-config-stderr \
+  -common.storage.ring.instance-addr='127.0.0.1' -server.path-prefix='/loki' \
+  2> '/tmp/loki.config.yaml' \
+&& sed '/msg="config is valid"/d' '/tmp/loki.config.yaml' \
+|  yq -Sy '.common|.instance_addr,.path_prefix' - \
+|| cat '/tmp/loki.config.yaml'
+```
+
 </details>
 
 ## Components

knowledge base/mimir.md

@@ -31,29 +31,34 @@ and set up alerting rules across multiple tenants to leverage tenant federation.
 Scrapers (like Prometheus or Grafana's Alloy) need to send metrics data to Mimir.<br/>
 Mimir will **not** scrape metrics itself.
 
-Mimir listens by default on port `8080` for HTTP and on port `9095` for GRPC.<br/>
+The server listens by default on port `8080` for HTTP and on port `9095` for GRPC.<br/>
 It also internally advertises data or actions to members in the cluster using [hashicorp/memberlist], which implements a
 [gossip protocol]. This uses port `7946` by default, and **must** be reachable by all members in the cluster to work.
 
-Mimir stores time series in TSDB blocks, that are uploaded to an object storage bucket.<br/>
-Such blocks are the same that Prometheus and Thanos use, though each application stores blocks in different places and
-uses slightly different metadata files for them.
+Mimir stores time series in TSDB blocks on the local file system by default.<br/>
+It can uploaded those blocks to an object storage bucket.
+
+The data blocks use the same format that Prometheus and Thanos use for storage, though each application stores blocks in
+different places and uses slightly different metadata files for them.
 
 Mimir supports multiple tenants, and stores blocks on a **per-tenant** level.<br/>
-Multi-tenancy is enabled by default, and can be disabled using the `-auth.multitenancy-enabled=false` option.<br/>
-If enabled, then multi-tenancy **will require every API request** to have the `X-Scope-OrgID` header with the value set
+Multi-tenancy is **enabled** by default. It can be disabled using the `-auth.multitenancy-enabled=false` option.
+
+Multi-tenancy, if **enabled**, **will require every API request** to have the `X-Scope-OrgID` header with the value set
 to the tenant ID one is authenticating for.<br/>
-When multi-tenancy is **disabled**, it will only manage a single tenant going by the name `anonymous`.
+When multi-tenancy is **disabled**, Mimir will store everything under a single tenant going by the name `anonymous`, and
+will assume all API requests are for it by automatically filling the `X-Scope-OrgID` header if not given.
 
 Blocks can be uploaded using the `mimirtool` utility, so that Mimir can access them.<br/>
-Mimir **will** perform some sanitization and validation of each block's metadata.
+The server **will** perform some sanitization and validation of each block's metadata.
 
 ```sh
 mimirtool backfill --address='http://mimir.example.org' --id='anonymous' 'block_1' … 'block_N'
 ```
 
 As a result of validation, Mimir will probably reject Thanos' blocks due to unsupported labels.<br/>
-As a workaround, upload Thanos' blocks directly to Mimir's blocks bucket, using the `<tenant>/<block ID>/` prefix.
+As a workaround, upload Thanos' blocks directly to Mimir's blocks directory, or bucket using the `<tenant>/<block ID>/`
+prefix.
 
 <details>
   <summary>Setup</summary>
@@ -122,7 +127,7 @@ GET /metrics
 Mimir's configuration file is YAML-based.
 
 There is **no** default configuration file, but one _can_ be specified on launch.<br/>
-If no configuration file is given, **only** the default values will be used.
+If no configuration file nor CLI options are given, **only** the default values will be used.
 
 ```sh
 mimir --config.file='./demo.yaml'

knowledge base/prometheus/README.md

@@ -463,7 +463,7 @@ Typically achieved by:
 1. Running a separate AlertManager instance.<br/>
    This would handle alerts from **all** the Prometheus instances, automatically managing eventually duplicated data.
 1. Using tools like [Thanos], [Cortex], or Grafana's [Mimir] to aggregate and deduplicate data.
-1. Directing visualizers like Grafana to the aggregator instead of the Prometheus replicas.
+1. Directing visualizers like [Grafana] to query the aggregator instead of any Prometheus replica.
 
 ## Further readings