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Merged
sendya merged 1 commit into from
Jan 21, 2026
Merged

feat(purge): add Prometheus metrics for purge request tracking #35

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22 changes: 22 additions & 0 deletions plugin/purge/metrics.go
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Original file line number Diff line number Diff line change
@@ -0,0 +1,22 @@
package purge

import "github.com/prometheus/client_golang/prometheus"

var (
_metricPurgeRequestsTotal = prometheus.NewCounterVec(prometheus.CounterOpts{
Namespace: "tr",
Subsystem: "tavern",
Name: "purge_requests_total",
Help: "Total number of purge requests",
}, []string{"code"})
)

func init() {
prometheus.MustRegister(_metricPurgeRequestsTotal)

// docs/purge.md references these labels
_metricPurgeRequestsTotal.WithLabelValues("200")
_metricPurgeRequestsTotal.WithLabelValues("403")
_metricPurgeRequestsTotal.WithLabelValues("404")
_metricPurgeRequestsTotal.WithLabelValues("500")
}
31 changes: 29 additions & 2 deletions plugin/purge/purge.go
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Original file line number Diff line number Diff line change
Expand Up @@ -2,6 +2,7 @@ package purge

import (
"context"
"encoding/binary"
"errors"
"fmt"
"net/http"
Expand All @@ -13,6 +14,7 @@ import (
storagev1 "github.com/omalloc/tavern/api/defined/v1/storage"
"github.com/omalloc/tavern/contrib/log"
"github.com/omalloc/tavern/internal/constants"
"github.com/omalloc/tavern/pkg/encoding"
"github.com/omalloc/tavern/plugin"
"github.com/omalloc/tavern/storage"
)
Expand Down Expand Up @@ -48,10 +50,26 @@ func (r *PurgePlugin) Stop(ctx context.Context) error {
}

func (r *PurgePlugin) AddRouter(router *http.ServeMux) {

codec := encoding.GetDefaultCodec()
sharedkv := storage.Current().SharedKV()

router.Handle("/plugin/purge/tasks", http.HandlerFunc(func(w http.ResponseWriter, req *http.Request) {
// TODO: query sharedkv purge task list
// query sharedkv purge task list

purgeTaskMap := make(map[string]uint64)

sharedkv.IteratePrefix(req.Context(), []byte("dir/"), func(key, val []byte) error {
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The binary.LittleEndian.Uint64(val) call will panic if val is less than 8 bytes long. Add a length check to ensure len(val) >= 8 before calling Uint64, or skip entries with invalid value lengths to prevent a potential runtime panic.

Suggested change
sharedkv.IteratePrefix(req.Context(), []byte("dir/"), func(key, val []byte) error {
sharedkv.IteratePrefix(req.Context(), []byte("dir/"), func(key, val []byte) error {
if len(val) < 8 {
// Skip entries with invalid value lengths to avoid panic in Uint64
return nil
}

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Comment on lines +55 to +62
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The sharedkv variable is captured from storage.Current().SharedKV() at AddRouter initialization time (outside the handler), rather than being retrieved inside the handler function when it's actually needed. If storage.Current() can change or be reinitialized during the application lifecycle, this could lead to stale references. Consider retrieving the SharedKV inside the handler function to ensure you always have the current storage instance, consistent with the pattern used in HandleFunc at line 113.

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purgeTaskMap[string(key)[4:]] = binary.LittleEndian.Uint64(val)
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The string slicing operation string(key)[4:] will panic if the key length is less than 4 bytes. Before slicing, add a length check to ensure len(key) >= 4, or skip keys that are too short to prevent a potential runtime panic.

Suggested change
purgeTaskMap[string(key)[4:]] = binary.LittleEndian.Uint64(val)
if len(key) >= 4 {
purgeTaskMap[string(key)[4:]] = binary.LittleEndian.Uint64(val)
}

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return nil
})
Comment on lines +62 to +65
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The error returned by IteratePrefix is being ignored. If the iteration fails, the handler will still return a 200 OK status with potentially incomplete data. Consider checking the error and returning an appropriate HTTP error status if the iteration fails.

Suggested change
sharedkv.IteratePrefix(req.Context(), []byte("dir/"), func(key, val []byte) error {
purgeTaskMap[string(key)[4:]] = binary.LittleEndian.Uint64(val)
return nil
})
if err := sharedkv.IteratePrefix(req.Context(), []byte("dir/"), func(key, val []byte) error {
purgeTaskMap[string(key)[4:]] = binary.LittleEndian.Uint64(val)
return nil
}); err != nil {
w.WriteHeader(http.StatusInternalServerError)
return
}

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var payload []byte
// marshal to json
payload, err := codec.Marshal(purgeTaskMap)
if err != nil {
w.WriteHeader(http.StatusInternalServerError)
return
}

w.Header().Set("Content-Length", fmt.Sprintf("%d", len(payload)))
w.Header().Set("Content-Type", "application/json")
Expand All @@ -72,6 +90,7 @@ func (r *PurgePlugin) HandleFunc(next http.HandlerFunc) http.HandlerFunc {
ipPort := strings.Split(req.RemoteAddr, ":")
if _, ok := r.allowAddr[ipPort[0]]; !ok {
w.WriteHeader(http.StatusForbidden)
_metricPurgeRequestsTotal.WithLabelValues("403").Inc()
return
}

Expand All @@ -83,6 +102,7 @@ func (r *PurgePlugin) HandleFunc(next http.HandlerFunc) http.HandlerFunc {
u, err1 := url.Parse(storeUrl)
if err1 != nil {
r.log.Errorf("failed to parse storeUrl %s: %s", storeUrl, err1)
_metricPurgeRequestsTotal.WithLabelValues("500").Inc()
return
}

Expand All @@ -98,6 +118,7 @@ func (r *PurgePlugin) HandleFunc(next http.HandlerFunc) http.HandlerFunc {
if _, err := current.SharedKV().Get(context.Background(),
[]byte(fmt.Sprintf("if/domain/%s", u.Host))); err != nil && errors.Is(err, storagev1.ErrKeyNotFound) {
r.log.Infof("purge dir %s but is not caching in the service", u.Host)
_metricPurgeRequestsTotal.WithLabelValues("404").Inc()
return
}

Expand All @@ -106,11 +127,13 @@ func (r *PurgePlugin) HandleFunc(next http.HandlerFunc) http.HandlerFunc {
w.Header().Set("Content-Length", "0")
w.Header().Set("Content-Type", "application/json; charset=utf-8")
w.WriteHeader(http.StatusNotFound)
_metricPurgeRequestsTotal.WithLabelValues("404").Inc()
return
}

r.log.Errorf("purge dir %s failed: %v", storeUrl, err)
w.WriteHeader(http.StatusInternalServerError)
_metricPurgeRequestsTotal.WithLabelValues("500").Inc()
return
}

Expand All @@ -119,6 +142,7 @@ func (r *PurgePlugin) HandleFunc(next http.HandlerFunc) http.HandlerFunc {
w.Header().Set("Content-Type", "application/json; charset=utf-8")
w.WriteHeader(http.StatusOK)
_, _ = w.Write(payload)
_metricPurgeRequestsTotal.WithLabelValues("200").Inc()
return
}

Expand All @@ -129,12 +153,14 @@ func (r *PurgePlugin) HandleFunc(next http.HandlerFunc) http.HandlerFunc {
w.Header().Set("Content-Length", "0")
w.Header().Set("Content-Type", "application/json; charset=utf-8")
w.WriteHeader(http.StatusNotFound)
_metricPurgeRequestsTotal.WithLabelValues("404").Inc()
return
}

// others error
r.log.Errorf("purge %s failed: %v", storeUrl, err)
w.WriteHeader(http.StatusInternalServerError)
_metricPurgeRequestsTotal.WithLabelValues("500").Inc()
return
}

Expand All @@ -143,6 +169,7 @@ func (r *PurgePlugin) HandleFunc(next http.HandlerFunc) http.HandlerFunc {
w.Header().Set("Content-Type", "application/json; charset=utf-8")
w.WriteHeader(http.StatusOK)
_, _ = w.Write(payload)
_metricPurgeRequestsTotal.WithLabelValues("200").Inc()
}
}

Expand Down
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