metrics: update package documentation (#295)

Signed-off-by: Florian Lehner <[email protected]>

metrics/doc.go

@@ -2,67 +2,20 @@
 // SPDX-License-Identifier: Apache-2.0
 
 /*
-Package metrics contains the code for receiving and reporting host metrics.
-
-The design document can be found at
-
-	https://docs.google.com/document/d/1nGxf-J0gVNqxgGDqJNdJvcw_VBrUa8PVSZYmHj2BH1s
-
-This is the implementation of Proposal C from the design doc.
-
-Example code to initialize metrics reporting:
-
-	defer metrics.Start(mainCtx)()
-
-# Aim
-
-The UI should allow to quickly detect unusual issues. These could be spikes in metrics,
-one or more processes eating 100% CPU over a long time, slowness issues over time,
-unusual increase in error counters, etc.
-
-We should add user stories here.
+Package metrics contains the code for reporting metrics.
 
 # Directory Structure
 
 The current directory structure looks like
 
 	metrics
-	├── [sub packages]
 	├── doc.go          // this file
-	├── metrics.go      // implement Start(), Add() and AddSlice()
+	├── genids/
+	│   └── main.go     // tool to generate Go code from metrics.json
+	├── ids.go          // autogenerated metric IDs
+	├── metrics.go      // implement Add() and AddSlice()
 	├── metrics_test.go // tests the metrics package
-	└── types.go        // definitions of metric ids and Metric, MetricID, MetricValue
-
-# CPU Usage
-
-The CPU usage (sum of user + system read from /proc/stat) is a first 'sub package'
-of the metrics package.
-
-The directory structure is
-
-	metrics
-	└──cpumetrics/
-	   ├── cpu.go
-	   ├── cpu_test.go
-	   └── testdata
-	       ├── procstat.empty
-	       ├── procstat.garbage
-	       └── procstat.ok
-
-# Comments
-
-Clickhouse stores data "columnar" (which means data for a column will be stored sequentially),
-and you can chose different encodings for it.
-For example: If you have data that very rarely changes, you can tell clickhouse to encode
-only the deltas and put ZSTD compression on that. Essentially all you need to do is append
-CODEC(Delta, ZSTD) to your column declaration in the schema.
-
-Clickhouse Overwiev
-
-	https://www.altinity.com/blog/2019/7/new-encodings-to-improve-clickhouse
-
-Clickhouse Docs
-
-	https://clickhouse.tech/docs/en/sql-reference/statements/create/#create-query-specialized-codecs
+	├── metrics.json    // list of known metrics
+	└── types.go        // definitions of Metric, MetricID, MetricValue
 */
 package metrics // import "go.opentelemetry.io/ebpf-profiler/metrics"