docs/metrics.md so far explained just the REST API for retrieving current
metrics from a single Scylla node. In this patch, I add basic explanations
on how to use the Prometheus and Grafana tools included in the
"scylla-grafana-monitoring" project.
It is true that technically, what is being explained here doesn't come
with the Scylla project and requires the separate scylla-grafana-monitoring
to be installed as well. Nevertheless, most Scylla developers will need this
knowledge eventually and suprisingly it appears it was never documented
anywhere accessible to newbie developers, and I think metrics.md is the
right place to introduce it.
In fact, I myself wasn't aware until today that Prometheus actually had
its own Web UI on port 9090, and that it is probably more useful for
developers than Grafana is.
Signed-off-by: Nadav Har'El <nyh@scylladb.com>
Reviewed-by: Botond Denes <bdenes@scylladb.com>
Message-Id: <20190129114214.17786-1-nyh@scylladb.com>
Today I realised that although we have per-table metrics, they are not
*really* available by default. I was suprised to find that we don't have
(as far as I can tell) a document explaining why it is so, or how to enable
them anyway. Moreover, the more I investigated this issue, the more I
realised how little I know on Scylla's metrics - how they are calculated,
how they are collected, their different types, and so on.
So I sat down to figure out everything I wanted to learn about Scylla metrics,
and then wrote it all down in a new document, docs/metrics.md.
There are some missing pieces in this document marked by TODO, and probably
additional missing pieces that I'm not aware of, but I think this is already
a good start and can be (and should be) improved-on later.
We really need to have more of these documents describing various Scylla
subsystems to new developers - what each subsystem does, why it does what
it does, where is the code, and so on. I am facing these problems every
day as a seasoned developer - I can't even imagine what our new developers
face when trying to understand a subsystem they are not yet familiar with.
Signed-off-by: Nadav Har'El <nyh@scylladb.com>
Message-Id: <20180920131103.20590-1-nyh@scylladb.com>
