metrics: README: update to be accurate and more descriptive

The README has not kept upto date with the code. Update to make it
more useful, but try to keep fairly neutral so it does not rot so
fast.

Signed-off-by: Graham Whaley <graham.whaley@intel.com>

metrics/README.md

@@ -1,18 +1,27 @@
 # Metric testing for scaling on Kubernetes.
 
-The usage is
+This folder contains tools to aid in measuring the scaling capabilities of
+Kubernetes clusters.
 
-```bash
-cd metrics/scaling
-./k8s-scale.sh
-```
+The tools tend to take one of two forms:
 
-The default container runtime is not Kata containers, but Kata can be specified
-setting the environment variable:
+- Tools to take measurements
+- Tools to analyse results
 
-```bash
-use_kata_runtime=yes
-```
+For more details, see individual sub-folders. A brief summary of available tools
+is below:
 
-These tests currently only support single node deployments, but PRs to add
-multi-node support will follow shortly.
+| Tool | Description |
+| ---- | ----------- |
+| lib | General library helper functions for forming and launching workloads, and storing results in a uniform manner to aid later analysis |
+| scaling | Tests to measure scaling, such as linear or parallel launching of pods |
+| report | Rmarkdown based report generator, used to produce a PDF comparison report of 1 or more sets of results |
+
+
+## Results storage and analysis
+
+The tools generate JSON formaated results files via the `lib/json.bash` functions. The `metrics_json_save()`
+function in that file has the ability to also `curl` or `socat` the JSON results to a database defined
+by environment variables (see the file source for details). This method has been used to store results in
+Elasticsearch and InfluxDB databases for instance, but should be adaptable to use with any REST API that accepts
+JSON input.