Add fake metric entry to populate prometheus #35
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Signed-off-by: Matteo Collina <[email protected]>
Signed-off-by: Matteo Collina <[email protected]>
index.js
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| @@ -27,19 +27,45 @@ module.exports = fp(async function (fastify, opts) { | |||
| return false | |||
| } | |||
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| let needEntrySummary = true | |||
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I would make this optional (disabled by default.)
index.js
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| const summary = new Summary({ | ||
| name: 'http_request_summary_seconds', | ||
| help: 'request duration in seconds summary', | ||
| labelNames, | ||
| registers, | ||
| collect: function () { |
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This will save an "empty" metric every time the prom fetches metrics (every 1s in most cases). Are you sure you need to push a new metric every second and not just save it once after summary/histogram initialisation?
something like summary.observe(0)
index.js
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| const histogram = new Histogram({ | ||
| name: 'http_request_duration_seconds', | ||
| help: 'request duration in seconds', | ||
| labelNames, | ||
| registers, | ||
| collect: function () { |
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Maybe histogram.zero can be useful:
https://github.com/siimon/prom-client?tab=readme-ov-file#zeroing-metrics-with-labels
index.js
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| if (needEntrySummary) { | ||
| const summaryTimer = this.startTimer() | ||
| summaryTimer({ | ||
| method: 'GET', |
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Tiny problem with that solution is that it will work only if you aggregate values when you query the prom metrics. For example if I want to get metrics for all POST requests or all requests with status code 200 they will not have this default values as they stored with labels "GET/__empty_metrics/404".
Obviously we don't know all route labels, but maybe it will make sense to store such metrics for some method + status_code combinations.
Signed-off-by: Matteo Collina <[email protected]>
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@ivan-tymoshenko PTAL |
Alternative implementation of platformatic/platformatic#3883.