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>>
