Only serialise and write cache chunks to disk when changed

packages/core/core/src/RequestTracker.js

@@ -856,6 +856,7 @@ export default class RequestTracker {
   farm: WorkerFarm;
   options: ParcelOptions;
   signal: ?AbortSignal;
+  cachedRequestsLastChunk: number | null;
 
   constructor({
     graph,
@@ -869,6 +870,7 @@ export default class RequestTracker {
     this.graph = graph || new RequestGraph();
     this.farm = farm;
     this.options = options;
+    this.cachedRequestsLastChunk = null;
   }
 
   // TODO: refactor (abortcontroller should be created by RequestTracker)
@@ -1123,7 +1125,7 @@ export default class RequestTracker {
       return;
     }
 
-    const serialisedGraph = this.graph.serialize();
+    let serialisedGraph = this.graph.serialize();
 
     let total = 0;
     const serialiseAndSet = async (
@@ -1155,7 +1157,7 @@ export default class RequestTracker {
       });
     };
 
-    const queue = new PromiseQueue({
+    let queue = new PromiseQueue({
       maxConcurrent: 32,
     });
 
@@ -1167,9 +1169,9 @@ export default class RequestTracker {
     });
 
     // Preallocating a sparse array is faster than pushing when N is high enough
-    const cacheableNodes = new Array(serialisedGraph.nodes.length);
+    let cacheableNodes = new Array(serialisedGraph.nodes.length);
     for (let i = 0; i < serialisedGraph.nodes.length; i += 1) {
-      const node = serialisedGraph.nodes[i];
+      let node = serialisedGraph.nodes[i];
 
       let resultCacheKey = node?.resultCacheKey;
       if (
@@ -1181,14 +1183,21 @@ export default class RequestTracker {
           .add(() => serialiseAndSet(resultCacheKey, node.result))
           .catch(() => {});
         // eslint-disable-next-line no-unused-vars
-        const {result: _, ...newNode} = node;
+        let {result: _, ...newNode} = node;
         cacheableNodes[i] = newNode;
       } else {
         cacheableNodes[i] = node;
       }
     }
 
     for (let i = 0; i * NODES_PER_BLOB < cacheableNodes.length; i += 1) {
+      if (
+        this.cachedRequestsLastChunk !== null &&
+        i < this.cachedRequestsLastChunk
+      ) {
+        continue;
+      }
+
       queue
         .add(() =>
           serialiseAndSet(
@@ -1197,6 +1206,7 @@ export default class RequestTracker {
           ),
         )
         .catch(() => {});
+      this.cachedRequestsLastChunk = i;
     }
 
     queue
@@ -1272,8 +1282,8 @@ async function loadRequestGraph(options): Async<RequestGraph> {
       i += 1;
     }
 
-    const serializedRequestGraph = await getAndDeserialize(requestGraphKey);
-    const requestGraph = RequestGraph.deserialize({
+    let serializedRequestGraph = await getAndDeserialize(requestGraphKey);
+    let requestGraph = RequestGraph.deserialize({
       ...serializedRequestGraph,
       nodes: (await Promise.all(nodePromises)).flatMap(nodeChunk => nodeChunk),
     });