Hi Reddy,
It's not purely for one third-party tool. It could be considered a standard
way to expose metrics. Here are some projects that support a metrics
endpoint
https://prometheus.io/docs/instrumenting/exporters/#software-exposing-prometheus-metrics
There are a few databases CoachroachDB and ScryllaDB that support it out of
the box. Kubernetes also supports the Prometheus metrics endpoint. So we
would be in good company.
Cheers
Garren
On Wed, Sep 23, 2020 at 3:20 PM Reddy B. <redd...@live.fr> wrote:
> I feel like it could feel weird and inconsistent to introduce a new format
> here solely to support a third-party tool. Why not add the missing metrics
> to existing endpoints and let people using prometheus set up an HTTP
> middleware in the application layer? If there is in built-in support for
> Prometheus' format, why not support another format as well, this could
> become messy pretty fast.
>
> 23 sept. 2020 11:18:00 jiangph <jiangpeng...@hotmail.com>:
>
> > 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
> >>
> >
>
