Change Details

**Steps to replicate the issue** (include links if applicable): * Go to https://grafana.wikimedia.org/d/jO1rYjwmz/wikidata-lua-function-usage?from=now-30d&orgId=1&to=now&var-prefix=enwiki&viewPanel=7 **What happens?**: Notice that the cache-miss rate is above 2, that is above 200%! **What should have happened instead?**: It should be something that is actually possible. **Other information** (browser name/version, screenshots, etc.): This seems to be caused by the fact that for the last 3 years, we only track a sample of the lua events for performance reason, about 1 in every 1000 events. That was introduced in [Add a sample rate for Lua function call tracking](https://gerrit.wikimedia.org/r/c/mediawiki/extensions/Wikibase/+/674472). That is achieved by comparing the sampling rate to a randomly generated number. **However, the random number generator is never explicitly initialized and so every request gets the exact same list of random numbers!** In practice, this would sadly seem to mean that the [Lua tracking data](https://grafana.wikimedia.org/d/jO1rYjwmz/wikidata-lua-function-usage) of the last 3 years is almost completely worthless.

**Steps to replicate the issue** (include links if applicable): * Go to https://grafana.wikimedia.org/d/jO1rYjwmz/wikidata-lua-function-usage?from=now-30d&orgId=1&to=now&var-prefix=enwiki&viewPanel=7 **What happens?**: Notice that the cache-miss rate is above 2, that is above 200%! **What should have happened instead?**: It should be something that is actually possible. **Other information** (browser name/version, screenshots, etc.): This seems to be caused by the fact that for the last 3 years, we only track a sample of the lua events for performance reason, about 1 in every 1000 events. That was introduced in [Add a sample rate for Lua function call tracking](https://gerrit.wikimedia.org/r/c/mediawiki/extensions/Wikibase/+/674472). That is achieved by comparing the sampling rate to a randomly generated number. **However, the random number generator is never explicitly initialized and so every request gets the exact same list of random numbers!** In practice, this would sadly seem to mean that the [Lua tracking data](https://grafana.wikimedia.org/d/jO1rYjwmz/wikidata-lua-function-usage) of the last 3 years is of questionably worth.

**Steps to replicate the issue** (include links if applicable): * Go to https://grafana.wikimedia.org/d/jO1rYjwmz/wikidata-lua-function-usage?from=now-30d&orgId=1&to=now&var-prefix=enwiki&viewPanel=7 **What happens?**: Notice that the cache-miss rate is above 2, that is above 200%! **What should have happened instead?**: It should be something that is actually possible. **Other information** (browser name/version, screenshots, etc.): This seems to be caused by the fact that for the last 3 years, we only track a sample of the lua events for performance reason, about 1 in every 1000 events. That was introduced in [Add a sample rate for Lua function call tracking](https://gerrit.wikimedia.org/r/c/mediawiki/extensions/Wikibase/+/674472). That is achieved by comparing the sampling rate to a randomly generated number. **However, the random number generator is never explicitly initialized and so every request gets the exact same list of random numbers!** In practice, this would sadly seem to mean that the [Lua tracking data](https://grafana.wikimedia.org/d/jO1rYjwmz/wikidata-lua-function-usage) of the last 3 years is almost completeof questionably worthless.