Thanks Peng Hui, Garren. I can definitely see value in having metrics
exposed in Prometheus format.
One aspect I'm unclear about is what _active_tasks metrics would represent.
My expectation is that /_metrics would be scoped to a node (and then leave
the aggregation across nodes to Prometheus or similar), whereas
_active_tasks is scoped to a cluster. What are your thoughts?
On Wed, 23 Sep 2020 at 10:18, jiangph <jiangpeng...@hotmail.com> wrote:
> Thanks Joan for your quick response and suggestion. As we can see, JSON
> is not the standard Prometheus format for _metrics endpoint. In order to be
> compatible with many monitoring tools, what about going with Prometheus
> standard format first and we may add JSON format support later?
>
> Best regards,
> Peng Hui
>
> > On Sep 23, 2020, at 9:41 AM, Joan Touzet <woh...@apache.org> wrote:
> >
> > I like this, but not at the expense of JSON output. It would be the only
> new API surface for CouchDB that isn't JSON-based, and there needs to be
> excellent justification for such. Prometheus is well-known enough to be
> supported, but we should continue to put out JSON stats for the foreseeable
> future.
> >
> > I know that Prometheus can't send a header, but sending an accepts
> application/json to /_metrics and having it send back the same data as
> Prometheus, but in JSON, would be lovely. If you feel up to it :)
> >
> > -Joan "on vacation" Touzet
> >
> > On 2020-09-22 8:55 a.m., jiangph wrote:
> >> Hey all,
> >> We would like to add a Prometheus metrics endpoint for CouchDB and
> wanted to see if the community would be interested in us contributing this
> to CouchDB 4.x.
> >> Prometheus is a CNCF open-source project and the Prometheus metrics
> endpoint format is supported by many monitoring tools. Its data model is
> based around having a metric name which then contains a label name and a
> label value:
> >> <metric name>{<label name>=<label value>, ...}
> >> And it supports the Counter, Gauge, Histogram, and Summary metric types.
> >> The idea for the new Prometheus endpoint, /_metrics, would be that the
> endpoint is a consolidation of the _stats [1], _system [2], and
> _active_tasks [3] endpoints.
> >> For _stats and _system, the conversion from JSON to Prometheus-based
> format seems to be straightforward.
> >> JSON format:
> >> {
> >> "value": {
> >> "min": 0,
> >> "max": 0,
> >> "arithmetic_mean": 0,
> >> "geometric_mean": 0,
> >> "harmonic_mean": 0,
> >> "median": 0,
> >> "variance": 0,
> >> "standard_deviation": 0,
> >> ...
> >> "percentile": [
> >> [
> >> 50,
> >> 0
> >> ],
> >> [
> >> 75,
> >> 0
> >> ],
> >> [
> >> 90,
> >> 0
> >> ],
> >> [
> >> 95,
> >> 0
> >> ],
> >> [
> >> 99,
> >> 0
> >> ],
> >> [
> >> 999,
> >> 0
> >> ]
> >> ],
> >> "histogram": [
> >> [
> >> 0,
> >> 0
> >> ]
> >> ],
> >> }
> >> Prometheus-based format:
> >> couchdb_stats{value="min"} 0
> >> couchdb_stats{value="max"} 0
> >> couchdb_stats{value="percentile50"} 0
> >> couchdb_stats{value="percentile75"} 0
> >> couchdb_stats{value="percentile95"} 0
> >> For _active_tasks, the change will be a bit more complicated, and some
> fields will be added to labels and tags.
> >> JSON format:
> >> {
> >> "checkpointed_source_seq": 68585,
> >> "continuous": false,
> >> "doc_id": null,
> >> "doc_write_failures": 0,
> >> "docs_read": 4524,
> >> "docs_written": 4524,
> >> "missing_revisions_found": 4524,
> >> "pid": "<0.1538.5>",
> >> "progress": 44,
> >> "replication_id": "9bc1727d74d49d9e157e260bb8bbd1d5",
> >> "revisions_checked": 4524,
> >> "source": "mailbox",
> >> "source_seq": 154419,
> >> "started_on": 1376116644,
> >> "target": "http://mailsrv:5984/mailbox <
> http://mailsrv:5984/mailbox> <http://mailsrv:5984/mailbox <
> http://mailsrv:5984/mailbox>>",
> >> "type": "replication",
> >> "updated_on": 1376116651
> >> }
> >> Prometheus-based would look something like:
> >> format:couchdb_active_task{type="replication", source="mailbox",
> target="http://mailsrv:5984/mailbox <http://mailsrv:5984/mailbox> <
> http://mailsrv:5984/mailbox <http://mailsrv:5984/mailbox>>", docs_count =
> "docs_read"} 4524
> >> couchdb_active_task{type="replication", source="mailbox", target="
> http://mailsrv:5984/mailbox <http://mailsrv:5984/mailbox> <
> http://mailsrv:5984/mailbox <http://mailsrv:5984/mailbox>>", docs_count =
> "docs_written"} 4524
> >> couchdb_active_task{type="replication", source="mailbox", target="
> http://mailsrv:5984/mailbox <http://mailsrv:5984/mailbox> <
> http://mailsrv:5984/mailbox <http://mailsrv:5984/mailbox>>", docs_count =
> "missing_revisions_found"} 4524
> >> Best regards,
> >> Garren Smith
> >> Peng Hui Jiang
> >> [1]
> https://docs.couchdb.org/en/latest/api/server/common.html#node-node-name-stats
> <
> https://docs.couchdb.org/en/latest/api/server/common.html#node-node-name-stats>
> <
> https://docs.couchdb.org/en/latest/api/server/common.html#node-node-name-stats
> <
> https://docs.couchdb.org/en/latest/api/server/common.html#node-node-name-stats
> >>
> >> [2]
> https://docs.couchdb.org/en/latest/api/server/common.html#active-tasks <
> https://docs.couchdb.org/en/latest/api/server/common.html#active-tasks> <
> https://docs.couchdb.org/en/latest/api/server/common.html#active-tasks <
> https://docs.couchdb.org/en/latest/api/server/common.html#active-tasks>>
> >> [3]
> https://docs.couchdb.org/en/latest/api/server/common.html#node-node-name-system
> <
> https://docs.couchdb.org/en/latest/api/server/common.html#node-node-name-system>
> <
> https://docs.couchdb.org/en/latest/api/server/common.html#node-node-name-system
> <
> https://docs.couchdb.org/en/latest/api/server/common.html#node-node-name-system
> >>
>
>
