Better locking in local cache

Fixes occassional lock expired errors after updating presets, etc.

lib/cache.ts

@@ -86,21 +86,11 @@ export async function acquireLock(
     if (Math.abs(v["timestamp"].getTime() - now) > CLOCK_SKEW_TOLERANCE)
       throw new Error("Database clock skew too great");
   } catch (err) {
-    if (err.code === 11000) {
-      if (timeout > 0) {
-        return new Promise((resolve, reject) => {
-          const w = 50 + Math.random() * 50;
-          setTimeout(() => {
-            acquireLock(lockName, ttl, timeout - w, token).then(
-              resolve,
-              reject
-            );
-          }, w);
-        });
-      }
-      throw new Error("Failed to acquire lock");
-    }
-    throw err;
+    if (err.code !== 11000) throw err;
+    if (!(timeout > 0)) return null;
+    const w = 50 + Math.random() * 50;
+    await new Promise((resolve) => setTimeout(resolve, w));
+    return acquireLock(lockName, ttl, timeout - w, token);
   }
 
   return token;

lib/cwmp.ts

@@ -213,12 +213,13 @@ async function writeResponse(
     currentSessions.set(connection, sessionContext);
     if (now >= sessionContext.extendLock) {
       sessionContext.extendLock = now + 10000;
-      await cache.acquireLock(
+      const lockToken = await cache.acquireLock(
         `cwmp_session_${sessionContext.deviceId}`,
         sessionContext.timeout * 1000 + 15000,
         0,
         sessionContext.sessionId
       );
+      if (!lockToken) throw new Error("Failed to extend lock");
     }
   }
 }
@@ -1149,15 +1150,15 @@ async function processRequest(
       }
     }
 
-    try {
-      sessionContext.extendLock = sessionContext.timestamp + 10000;
-      await cache.acquireLock(
-        `cwmp_session_${sessionContext.deviceId}`,
-        sessionContext.timeout * 1000 + 15000,
-        0,
-        sessionContext.sessionId
-      );
-    } catch (err) {
+    sessionContext.extendLock = sessionContext.timestamp + 10000;
+    const lockToken = await cache.acquireLock(
+      `cwmp_session_${sessionContext.deviceId}`,
+      sessionContext.timeout * 1000 + 15000,
+      0,
+      sessionContext.sessionId
+    );
+
+    if (!lockToken) {
       logger.accessError({
         message: "CPE already in session",
         sessionContext: sessionContext,

lib/local-cache.ts

@@ -380,13 +380,15 @@ async function fetchConfig(): Promise<[Config, UiConfig]> {
 async function refresh(): Promise<void> {
   if (!nextRefresh) {
     await new Promise((resolve) => setTimeout(resolve, 20));
-    await refresh();
-    return;
+    return refresh();
   }
 
-  nextRefresh = 0;
   const now = Date.now();
 
+  if (now < nextRefresh) return;
+
+  nextRefresh = 0;
+
   const dbHash = await cache.get("presets_hash");
 
   if (currentSnapshot && dbHash === currentSnapshot) {
@@ -394,7 +396,7 @@ async function refresh(): Promise<void> {
     return;
   }
 
-  const lockToken = await cache.acquireLock("presets_hash_lock", 5000, 5000);
+  const lockToken = await cache.acquireLock("presets_hash_lock", 5000);
 
   const res = await Promise.all([
     fetchPresets(),
@@ -427,8 +429,12 @@ async function refresh(): Promise<void> {
 
   currentSnapshot = computeHash(snapshot);
   snapshots.set(currentSnapshot, snapshot);
-  await cache.set("presets_hash", currentSnapshot, 300);
-  await cache.releaseLock("presets_hash_lock", lockToken);
+
+  if (lockToken) {
+    if (currentSnapshot !== dbHash)
+      await cache.set("presets_hash", currentSnapshot, 300);
+    await cache.releaseLock("presets_hash_lock", lockToken);
+  }
 
   nextRefresh = now + (REFRESH - (now % REFRESH));
 }