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pageserver: fix division by zero in layer counting metric (#7662)

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For aux file keys (v1 or v2) the vectored read path does not return an
error when they're missing. Instead they are omitted from the resulting
btree (this is a requirement, not a bug). Skip updating the metric in
these cases to avoid infinite results.
This commit is contained in:
Vlad Lazar
2024-05-08 19:29:16 +01:00
committed by GitHub
parent b06eec41fa
commit d5399b729b
1 changed files with 11 additions and 5 deletions
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16
pageserver/src/tenant/timeline.rs
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@@ -1220,11 +1220,17 @@ impl Timeline {
}
reconstruct_timer.stop_and_record();
// Note that this is an approximation. Tracking the exact number of layers visited
// per key requires virtually unbounded memory usage and is inefficient
// (i.e. segment tree tracking each range queried from a layer)
crate::metrics::VEC_READ_NUM_LAYERS_VISITED
.observe(layers_visited as f64 / results.len() as f64);
// For aux file keys (v1 or v2) the vectored read path does not return an error
// when they're missing. Instead they are omitted from the resulting btree
// (this is a requirement, not a bug). Skip updating the metric in these cases
// to avoid infinite results.
if !results.is_empty() {
// Note that this is an approximation. Tracking the exact number of layers visited
// per key requires virtually unbounded memory usage and is inefficient
// (i.e. segment tree tracking each range queried from a layer)
crate::metrics::VEC_READ_NUM_LAYERS_VISITED
.observe(layers_visited as f64 / results.len() as f64);
}
Ok(results)
}