consume PKCE verifiers atomically via a GetDel cache op

management/server/cache/store_test.go

@@ -0,0 +1,55 @@
+package cache_test
+
+import (
+	"context"
+	"testing"
+
+	"github.com/stretchr/testify/require"
+
+	"github.com/netbirdio/netbird/management/server/cache"
+)
+
+func assertGetDelConsumedOnce(ctx context.Context, t *testing.T, stores []cache.Store, key, value string) {
+	t.Helper()
+
+	const getDelAttempts = 64
+
+	type getDelResult struct {
+		value string
+		found bool
+		err   error
+	}
+
+	start := make(chan struct{})
+	results := make(chan getDelResult, getDelAttempts)
+	for i := range getDelAttempts {
+		cacheStore := stores[i%len(stores)]
+		go func() {
+			<-start
+			value, found, err := cacheStore.GetDel(ctx, key)
+			results <- getDelResult{value: value, found: found, err: err}
+		}()
+	}
+	close(start)
+
+	consumers := 0
+	for range getDelAttempts {
+		result := <-results
+		require.NoError(t, result.err, "concurrent GetDel failed")
+		if !result.found {
+			continue
+		}
+		consumers++
+		require.Equal(t, value, result.value, "consumed value doesn't match testing data")
+	}
+	require.Equal(t, 1, consumers, "expected exactly one consumer")
+}
+
+func assertGetDelMisses(ctx context.Context, t *testing.T, cacheStore cache.Store, key string) {
+	t.Helper()
+
+	value, found, err := cacheStore.GetDel(ctx, key)
+	require.NoError(t, err, "GetDel on a missing key should not error")
+	require.False(t, found, "GetDel should not find key %q, got value %q", key, value)
+	require.Empty(t, value, "GetDel should return an empty value when not found")
+}