GetMetrics fetches metrics from cache or delegates to the appropriate provider. The provider is looked up from the registered providers by datasource type. On cache hit (non-expired entry), returns cached metrics immediately. On cache miss or expiration, fetches from provider and caches the result.
(ctx context.Context, orgID int64, dsType, datasourceUID, datasourceURL string, client *http.Client)
| 82 | // On cache hit (non-expired entry), returns cached metrics immediately. |
| 83 | // On cache miss or expiration, fetches from provider and caches the result. |
| 84 | func (c *MetricsCache) GetMetrics(ctx context.Context, orgID int64, dsType, datasourceUID, datasourceURL string, |
| 85 | client *http.Client) ([]string, error) { |
| 86 | cacheKey := fmt.Sprintf("%d/%s", orgID, datasourceUID) |
| 87 | |
| 88 | // Check cache first (read lock) |
| 89 | c.mu.RLock() |
| 90 | cached, exists := c.entries[cacheKey] |
| 91 | provider := c.providers[dsType] |
| 92 | c.mu.RUnlock() |
| 93 | |
| 94 | if exists && time.Now().Before(cached.expiresAt) { |
| 95 | return cached.metrics, nil |
| 96 | } |
| 97 | |
| 98 | // Verify provider exists |
| 99 | if provider == nil { |
| 100 | return nil, fmt.Errorf("no metrics provider registered for datasource type: %s", dsType) |
| 101 | } |
| 102 | |
| 103 | // Cache miss or expired — use singleflight to coalesce concurrent fetches |
| 104 | v, err, _ := c.sf.Do(cacheKey, func() (any, error) { |
| 105 | // Re-check cache: another goroutine may have populated it while we waited |
| 106 | c.mu.RLock() |
| 107 | cached, exists := c.entries[cacheKey] |
| 108 | c.mu.RUnlock() |
| 109 | if exists && time.Now().Before(cached.expiresAt) { |
| 110 | return cached.metrics, nil |
| 111 | } |
| 112 | |
| 113 | result, err := provider.GetMetrics(ctx, datasourceUID, datasourceURL, client) |
| 114 | if err != nil { |
| 115 | return nil, err |
| 116 | } |
| 117 | |
| 118 | // Don't cache results with zero TTL |
| 119 | if result.TTL > 0 { |
| 120 | c.mu.Lock() |
| 121 | c.entries[cacheKey] = &cacheEntry{ |
| 122 | metrics: result.Metrics, |
| 123 | metricsSet: toMetricsSet(result.Metrics), |
| 124 | expiresAt: time.Now().Add(result.TTL), |
| 125 | } |
| 126 | c.mu.Unlock() |
| 127 | } |
| 128 | |
| 129 | return result.Metrics, nil |
| 130 | }) |
| 131 | if err != nil { |
| 132 | return nil, err |
| 133 | } |
| 134 | |
| 135 | return v.([]string), nil |
| 136 | } |
| 137 | |
| 138 | // GetMetricsSet returns the cached metrics as a set (map[string]bool) for O(1) lookup. |
| 139 | // This avoids rebuilding the set from []string on every call — critical when the |