[oximeter] use Cow<'static, str> for FieldValue::String
#5670
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Currently, Oximeter `FieldValue::String` fields are always represented by a `String` value. This is somewhat unfortunate, as it requires allocating a new `String` for every string field value that's emitted to Oximeter, even when the string value is fixed at compile-time --- for example, when an enum is used to generate a metric label with `&'static str` values, they must be alloced into new `String`s to record the metric. This commit changes `FieldValue::String` from holding a `String` to holding a `Cow<'static, str>`, so that static string constants need not be heap-allocated.
This commit changes Oximeter's `self_stats` module to use `Cow<'static, str>` to represent the field value generated by the `FailureReason` enum. This way, a heap-allocated string is only necessary for dynamically formatted variants (the `FailureReason::Other` variant, which owns an HTTP `StatusCode`). For the `FailureReason::Unreachable` and `FailureReason::Deserialization` variants, we can just emit a `&'static str` without allocating. Hopefully, this reduces resident memory for the collector process somewhat when encountering a lot of failures.
bnaecker
approved these changes
May 8, 2024
No worries --- thanks for taking a look! |
hawkw
added a commit
that referenced
this pull request
May 9, 2024
Fixes #5664. Currently, Oximeter `FieldValue::String` fields are always represented by a `String` value. This is somewhat unfortunate, as it requires allocating a new `String` for every string field value that's emitted to Oximeter, even when the string value is fixed at compile-time --- for example, when an enum is used to generate a metric label with `&'static str` values, they must be alloced into new `String`s to record the metric. This commit changes `FieldValue::String` from holding a `String` to holding a `Cow<'static, str>`, so that static string constants need not be heap-allocated. Additionally, I've changed Oximeter's `self_stats` module to use `Cow<'static, str>` to represent the field value generated by the `FailureReason` enum. This way, a heap-allocated string is only necessary for dynamically formatted variants (the `FailureReason::Other` variant, which owns an HTTP `StatusCode`). For the `FailureReason::Unreachable` and `FailureReason::Deserialization` variants, we can just emit a `&'static str` without allocating. Hopefully, this reduces resident memory for the collector process somewhat when encountering a lot of failures.
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Fixes #5664.
Currently, Oximeter
FieldValue::Stringfields are always representedby a
Stringvalue. This is somewhat unfortunate, as it requiresallocating a new
Stringfor every string field value that's emitted toOximeter, even when the string value is fixed at compile-time --- for
example, when an enum is used to generate a metric label with
&'static strvalues, they must be alloced into newStrings to record themetric.
This commit changes
FieldValue::Stringfrom holding aStringtoholding a
Cow<'static, str>, so that static string constants need notbe heap-allocated.
Additionally, I've changed Oximeter's
self_statsmodule to useCow<'static, str>to represent the field value generated by theFailureReasonenum. This way, a heap-allocated string is onlynecessary for dynamically formatted variants (the
FailureReason::Othervariant, which owns an HTTP
StatusCode). For theFailureReason::UnreachableandFailureReason::Deserializationvariants, we can just emit a
&'static strwithout allocating.Hopefully, this reduces resident memory for the collector process
somewhat when encountering a lot of failures.