fix: Prometheus client missing time argument #605
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The Prometheus backend query method does not propagate the timestamp argument passed on from the compute function upstream.
This results in the twin queries used for good/bad ratio method to default to now (see https://github.com/tomoncle/prometheus-http-client/blob/master/prometheus_http_client/prometheus/client.py#L78) separately. In some cases, this very slight delay is sufficient to cause inconsistencies in the SLO calculation.
This problem seems related to issues like #319. The symptoms on my end where exactly the same as #343, though for a Prometheus backend: we observed random spikes of error counts.
As the
timestampargument already existed in the method signature, but was left unused in the code, I assume this is an oversight.Looking deeper into the code, it turns out that the distribution_cut method did not pass the
timestampargument either to the query method. I initially only tested this with the good_bad_ratio method, so the first version of this fix missed this omission as well.