Add: redis memory gauge

src/cache.js

@@ -47,6 +47,35 @@ export const versionCountGauge = new Gauge({
   }
 })
 
+export const usedMemoryGauge = new Gauge({
+  name: 'redis_used_ram',
+  help: 'Total used memory in human readable units and as a percentage (RSS / total memory)',
+  labelNames: ['memory_type'],
+  async collect () {
+    redis.client.info('memory', (err, result) => {
+      if (err) {
+        throw err
+      }
+
+      // Parse the result
+      const infoLines = result.split('\r\n')
+      const memoryInfo = {}
+
+      for (const line of infoLines) {
+        const [key, value] = line.split(':')
+        if (key && value) {
+          memoryInfo[key] = value
+        }
+      }
+      const usedMemoryRSS = parseFloat(memoryInfo.used_memory_rss)
+      const memoryTotal = parseFloat(memoryInfo.total_system_memory)
+
+      this.set({ memory_type: 'usedMemoryRSSHuman' }, usedMemoryRSS)
+      this.set({ memory_type: 'totalUsedMemoryPercentage' }, usedMemoryRSS / memoryTotal)
+    })
+  }
+})
+
 export function set (key, value, timeout) {
   logger.debug(`[Cache] Set ${key}`)
   if (cache[key] === value) return
@@ -62,7 +91,6 @@ export async function clear () {
   }
   fileCacheSizeGauge.reset()
 }
-
 export async function get (key, fallback) {
   if (cache[key]) {
     logger.debug(`[Cache] Resolve from memory: ${key}`)