TrueCloudLab/coredns
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Update cache metrics (#4781)

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Add a total cache request counter to follow Prometheus conventions[0].
Mark the existing cache miss metric as deprecated.

> Similarly, with hit or miss for caches, it’s better to have one
> metric for total and another for hits.

[0]: https://prometheus.io/docs/instrumenting/writing_exporters/#naming

Signed-off-by: SuperQ <superq@gmail.com>
This commit is contained in:
Ben Kochie 2021-08-16 07:54:36 +02:00 • committed by GitHub
parent 88d94dc148
commit 7d542fec67
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GPG key ID: 4AEE18F83AFDEB23
3 changed files with 13 additions and 3 deletions
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3
plugin/cache/README.md vendored
View file

@ -75,7 +75,8 @@ If monitoring is enabled (via the *prometheus* plugin) then the following metric
* `coredns_cache_entries{server, type}` - Total elements in the cache by cache type.
* `coredns_cache_hits_total{server, type}` - Counter of cache hits by cache type.
* `coredns_cache_misses_total{server}` - Counter of cache misses.
* `coredns_cache_misses_total{server}` - Counter of cache misses. - Deprecated, derive misses from cache hits/requests counters.
* `coredns_cache_requests_total{server}` - Counter of cache requests.
* `coredns_cache_prefetch_total{server}` - Counter of times the cache has prefetched a cached item.
* `coredns_cache_drops_total{server}` - Counter of responses excluded from the cache due to request/response question name mismatch.
* `coredns_cache_served_stale_total{server}` - Counter of requests served from stale cache entries.

2
plugin/cache/handler.go vendored
View file

@ -91,6 +91,7 @@ func (c *Cache) Name() string { return "cache" }
func (c *Cache) get(now time.Time, state request.Request, server string) (*item, bool) {
k := hash(state.Name(), state.QType())
cacheRequests.WithLabelValues(server).Inc()
if i, ok := c.ncache.Get(k); ok && i.(*item).ttl(now) > 0 {
cacheHits.WithLabelValues(server, Denial).Inc()
@ -108,6 +109,7 @@ func (c *Cache) get(now time.Time, state request.Request, server string) (*item,
// getIgnoreTTL unconditionally returns an item if it exists in the cache.
func (c *Cache) getIgnoreTTL(now time.Time, state request.Request, server string) *item {
k := hash(state.Name(), state.QType())
cacheRequests.WithLabelValues(server).Inc()
if i, ok := c.ncache.Get(k); ok {
ttl := i.(*item).ttl(now)

11
plugin/cache/metrics.go vendored
View file

@ -15,6 +15,13 @@ var (
Name: "entries",
Help: "The number of elements in the cache.",
}, []string{"server", "type"})
// cacheRequests is a counter of all requests through the cache.
cacheRequests = promauto.NewCounterVec(prometheus.CounterOpts{
Namespace: plugin.Namespace,
Subsystem: "cache",
Name: "requests_total",
Help: "The count of cache requests.",
}, []string{"server"})
// cacheHits is counter of cache hits by cache type.
cacheHits = promauto.NewCounterVec(prometheus.CounterOpts{
Namespace: plugin.Namespace,
@ -22,12 +29,12 @@ var (
Name: "hits_total",
Help: "The count of cache hits.",
}, []string{"server", "type"})
// cacheMisses is the counter of cache misses.
// cacheMisses is the counter of cache misses. - Deprecated
cacheMisses = promauto.NewCounterVec(prometheus.CounterOpts{
Namespace: plugin.Namespace,
Subsystem: "cache",
Name: "misses_total",
Help: "The count of cache misses.",
Help: "The count of cache misses. Deprecated, derive misses from cache hits/requests counters.",
}, []string{"server"})
// cachePrefetches is the number of time the cache has prefetched a cached item.
cachePrefetches = promauto.NewCounterVec(prometheus.CounterOpts{