feat: add instrumented go-cache wrapper with Prometheus metrics - #214
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DerekFrank wants to merge 1 commit into
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feat: add instrumented go-cache wrapper with Prometheus metrics#214DerekFrank wants to merge 1 commit into
DerekFrank wants to merge 1 commit into
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Add operatorpkg/cache, a near drop-in wrapper around patrickmn/go-cache
that emits Prometheus metrics under the operator_cache_* subsystem:
- gets_total{name,result=hit|miss}
- adds_total{name,result=added|exists} (exists = suppressed duplicate)
- evictions_total{name} (TTL expiry)
- deletes_total{name,type=explicit|flush}
- flushes_total{name}
- flush_size{name} (histogram, entries per flush)
- entries{name} (gauge)
The wrapper embeds *cache.Cache so every underlying method still works;
only Get/Set/SetDefault/Add/Delete/Flush are overridden. Counter/gauge
series are pre-initialized to 0 to avoid sparse series. The entries gauge
is updated on mutation (never at scrape time) so scrapes do no cache work.
A caller-supplied OnEvicted callback is chained, not replaced.
ryan-mist
reviewed
Aug 12, 2026
| // Get records a hit or miss and delegates to the underlying cache. | ||
| func (c *Cache) Get(k string) (interface{}, bool) { | ||
| v, ok := c.Cache.Get(k) | ||
| if ok { |
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Theres a pretty small perf hit here because theres a bunch of allocations + the metric itself - it tripled the CPU usage on every cache.Get()
I don't think its that large, but since there is limited value in the metric it might not be worth it
Test Scenario: 9 NodeClasses, 9 NodePools, 0 pods
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Yea I think we can drop it
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Add operatorpkg/cache, a near drop-in wrapper around patrickmn/go-cache that emits Prometheus metrics under the operator_cache_* subsystem:
The wrapper embeds *cache.Cache so every underlying method still works; only Get/Set/SetDefault/Add/Delete/Flush are overridden. Counter/gauge series are pre-initialized to 0 to avoid sparse series. The entries gauge is updated on mutation (never at scrape time) so scrapes do no cache work. A caller-supplied OnEvicted callback is chained, not replaced.
Issue #, if available:
Description of changes:
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