839 lines
38 KiB
JavaScript
839 lines
38 KiB
JavaScript
"use strict";
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Object.defineProperty(exports, "__esModule", {
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value: true
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});
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0 && (module.exports = {
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cancelPrefetchTask: null,
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pingPrefetchTask: null,
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reschedulePrefetchTask: null,
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schedulePrefetchTask: null
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});
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function _export(target, all) {
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for(var name in all)Object.defineProperty(target, name, {
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enumerable: true,
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get: all[name]
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});
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}
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_export(exports, {
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cancelPrefetchTask: function() {
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return cancelPrefetchTask;
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},
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pingPrefetchTask: function() {
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return pingPrefetchTask;
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},
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reschedulePrefetchTask: function() {
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return reschedulePrefetchTask;
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},
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schedulePrefetchTask: function() {
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return schedulePrefetchTask;
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}
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});
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const _matchsegments = require("../match-segments");
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const _cache = require("./cache");
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const _segmentcache = require("../segment-cache");
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const scheduleMicrotask = typeof queueMicrotask === 'function' ? queueMicrotask : (fn)=>Promise.resolve().then(fn).catch((error)=>setTimeout(()=>{
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throw error;
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}));
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const taskHeap = [];
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// This is intentionally low so that when a navigation happens, the browser's
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// internal network queue is not already saturated with prefetch requests.
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const MAX_CONCURRENT_PREFETCH_REQUESTS = 3;
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let inProgressRequests = 0;
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let sortIdCounter = 0;
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let didScheduleMicrotask = false;
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function schedulePrefetchTask(key, treeAtTimeOfPrefetch, includeDynamicData, priority) {
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// Spawn a new prefetch task
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const task = {
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key,
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treeAtTimeOfPrefetch,
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priority,
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phase: 1,
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hasBackgroundWork: false,
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includeDynamicData,
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sortId: sortIdCounter++,
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isCanceled: false,
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_heapIndex: -1
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};
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heapPush(taskHeap, task);
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// Schedule an async task to process the queue.
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//
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// The main reason we process the queue in an async task is for batching.
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// It's common for a single JS task/event to trigger multiple prefetches.
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// By deferring to a microtask, we only process the queue once per JS task.
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// If they have different priorities, it also ensures they are processed in
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// the optimal order.
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ensureWorkIsScheduled();
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return task;
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}
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function cancelPrefetchTask(task) {
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// Remove the prefetch task from the queue. If the task already completed,
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// then this is a no-op.
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//
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// We must also explicitly mark the task as canceled so that a blocked task
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// does not get added back to the queue when it's pinged by the network.
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task.isCanceled = true;
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heapDelete(taskHeap, task);
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}
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function reschedulePrefetchTask(task, treeAtTimeOfPrefetch, includeDynamicData, priority) {
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// Bump the prefetch task to the top of the queue, as if it were a fresh
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// task. This is essentially the same as canceling the task and scheduling
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// a new one, except it reuses the original object.
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//
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// The primary use case is to increase the priority of a Link-initated
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// prefetch on hover.
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// Un-cancel the task, in case it was previously canceled.
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task.isCanceled = false;
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task.phase = 1;
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// Assign a new sort ID to move it ahead of all other tasks at the same
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// priority level. (Higher sort IDs are processed first.)
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task.sortId = sortIdCounter++;
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task.priority = priority;
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task.treeAtTimeOfPrefetch = treeAtTimeOfPrefetch;
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task.includeDynamicData = includeDynamicData;
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if (task._heapIndex !== -1) {
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// The task is already in the queue.
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heapResift(taskHeap, task);
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} else {
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heapPush(taskHeap, task);
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}
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ensureWorkIsScheduled();
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}
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function ensureWorkIsScheduled() {
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if (didScheduleMicrotask || !hasNetworkBandwidth()) {
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// Either we already scheduled a task to process the queue, or there are
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// too many concurrent requests in progress. In the latter case, the
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// queue will resume processing once more bandwidth is available.
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return;
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}
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didScheduleMicrotask = true;
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scheduleMicrotask(processQueueInMicrotask);
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}
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/**
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* Checks if we've exceeded the maximum number of concurrent prefetch requests,
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* to avoid saturating the browser's internal network queue. This is a
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* cooperative limit — prefetch tasks should check this before issuing
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* new requests.
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*/ function hasNetworkBandwidth() {
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// TODO: Also check if there's an in-progress navigation. We should never
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// add prefetch requests to the network queue if an actual navigation is
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// taking place, to ensure there's sufficient bandwidth for render-blocking
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// data and resources.
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return inProgressRequests < MAX_CONCURRENT_PREFETCH_REQUESTS;
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}
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function spawnPrefetchSubtask(prefetchSubtask) {
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// When the scheduler spawns an async task, we don't await its result.
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// Instead, the async task writes its result directly into the cache, then
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// pings the scheduler to continue.
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//
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// We process server responses streamingly, so the prefetch subtask will
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// likely resolve before we're finished receiving all the data. The subtask
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// result includes a promise that resolves once the network connection is
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// closed. The scheduler uses this to control network bandwidth by tracking
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// and limiting the number of concurrent requests.
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inProgressRequests++;
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return prefetchSubtask.then((result)=>{
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if (result === null) {
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// The prefetch task errored before it could start processing the
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// network stream. Assume the connection is closed.
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onPrefetchConnectionClosed();
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return null;
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}
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// Wait for the connection to close before freeing up more bandwidth.
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result.closed.then(onPrefetchConnectionClosed);
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return result.value;
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});
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}
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function onPrefetchConnectionClosed() {
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inProgressRequests--;
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// Notify the scheduler that we have more bandwidth, and can continue
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// processing tasks.
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ensureWorkIsScheduled();
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}
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function pingPrefetchTask(task) {
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// "Ping" a prefetch that's already in progress to notify it of new data.
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if (// Check if prefetch was canceled.
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task.isCanceled || // Check if prefetch is already queued.
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task._heapIndex !== -1) {
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return;
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}
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// Add the task back to the queue.
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heapPush(taskHeap, task);
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ensureWorkIsScheduled();
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}
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function processQueueInMicrotask() {
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didScheduleMicrotask = false;
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// We aim to minimize how often we read the current time. Since nearly all
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// functions in the prefetch scheduler are synchronous, we can read the time
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// once and pass it as an argument wherever it's needed.
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const now = Date.now();
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// Process the task queue until we run out of network bandwidth.
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let task = heapPeek(taskHeap);
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while(task !== null && hasNetworkBandwidth()){
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const route = (0, _cache.readOrCreateRouteCacheEntry)(now, task);
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const exitStatus = pingRootRouteTree(now, task, route);
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// The `hasBackgroundWork` field is only valid for a single attempt. Reset
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// it immediately upon exit.
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const hasBackgroundWork = task.hasBackgroundWork;
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task.hasBackgroundWork = false;
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switch(exitStatus){
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case 0:
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// The task yielded because there are too many requests in progress.
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// Stop processing tasks until we have more bandwidth.
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return;
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case 1:
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// The task is blocked. It needs more data before it can proceed.
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// Keep the task out of the queue until the server responds.
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heapPop(taskHeap);
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// Continue to the next task
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task = heapPeek(taskHeap);
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continue;
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case 2:
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if (task.phase === 1) {
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// Finished prefetching the route tree. Proceed to prefetching
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// the segments.
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task.phase = 0;
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heapResift(taskHeap, task);
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} else if (hasBackgroundWork) {
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// The task spawned additional background work. Reschedule the task
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// at background priority.
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task.priority = _segmentcache.PrefetchPriority.Background;
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heapResift(taskHeap, task);
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} else {
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// The prefetch is complete. Continue to the next task.
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heapPop(taskHeap);
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}
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task = heapPeek(taskHeap);
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continue;
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default:
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exitStatus;
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}
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}
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}
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/**
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* Check this during a prefetch task to determine if background work can be
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* performed. If so, it evaluates to `true`. Otherwise, it returns `false`,
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* while also scheduling a background task to run later. Usage:
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*
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* @example
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* if (background(task)) {
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* // Perform background-pri work
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* }
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*/ function background(task) {
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if (task.priority === _segmentcache.PrefetchPriority.Background) {
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return true;
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}
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task.hasBackgroundWork = true;
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return false;
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}
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function pingRootRouteTree(now, task, route) {
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switch(route.status){
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case _cache.EntryStatus.Empty:
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{
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// Route is not yet cached, and there's no request already in progress.
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// Spawn a task to request the route, load it into the cache, and ping
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// the task to continue.
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// TODO: There are multiple strategies in the <Link> API for prefetching
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// a route. Currently we've only implemented the main one: per-segment,
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// static-data only.
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//
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// There's also <Link prefetch={true}> which prefetches both static *and*
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// dynamic data. Similarly, we need to fallback to the old, per-page
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// behavior if PPR is disabled for a route (via the incremental opt-in).
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//
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// Those cases will be handled here.
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spawnPrefetchSubtask((0, _cache.fetchRouteOnCacheMiss)(route, task));
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// If the request takes longer than a minute, a subsequent request should
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// retry instead of waiting for this one. When the response is received,
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// this value will be replaced by a new value based on the stale time sent
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// from the server.
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// TODO: We should probably also manually abort the fetch task, to reclaim
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// server bandwidth.
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route.staleAt = now + 60 * 1000;
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// Upgrade to Pending so we know there's already a request in progress
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route.status = _cache.EntryStatus.Pending;
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// Intentional fallthrough to the Pending branch
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}
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case _cache.EntryStatus.Pending:
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{
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// Still pending. We can't start prefetching the segments until the route
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// tree has loaded. Add the task to the set of blocked tasks so that it
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// is notified when the route tree is ready.
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const blockedTasks = route.blockedTasks;
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if (blockedTasks === null) {
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route.blockedTasks = new Set([
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task
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]);
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} else {
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blockedTasks.add(task);
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}
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return 1;
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}
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case _cache.EntryStatus.Rejected:
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{
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// Route tree failed to load. Treat as a 404.
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return 2;
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}
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case _cache.EntryStatus.Fulfilled:
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{
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if (task.phase !== 0) {
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// Do not prefetch segment data until we've entered the segment phase.
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return 2;
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}
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// Recursively fill in the segment tree.
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if (!hasNetworkBandwidth()) {
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// Stop prefetching segments until there's more bandwidth.
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return 0;
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}
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const tree = route.tree;
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// Determine which fetch strategy to use for this prefetch task.
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const fetchStrategy = task.includeDynamicData ? _cache.FetchStrategy.Full : route.isPPREnabled ? _cache.FetchStrategy.PPR : _cache.FetchStrategy.LoadingBoundary;
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switch(fetchStrategy){
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case _cache.FetchStrategy.PPR:
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// Individually prefetch the static shell for each segment. This is
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// the default prefetching behavior for static routes, or when PPR is
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// enabled. It will not include any dynamic data.
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return pingPPRRouteTree(now, task, route, tree);
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case _cache.FetchStrategy.Full:
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case _cache.FetchStrategy.LoadingBoundary:
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{
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// Prefetch multiple segments using a single dynamic request.
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const spawnedEntries = new Map();
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const dynamicRequestTree = diffRouteTreeAgainstCurrent(now, task, route, task.treeAtTimeOfPrefetch, tree, spawnedEntries, fetchStrategy);
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const needsDynamicRequest = spawnedEntries.size > 0;
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if (needsDynamicRequest) {
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// Perform a dynamic prefetch request and populate the cache with
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// the result
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spawnPrefetchSubtask((0, _cache.fetchSegmentPrefetchesUsingDynamicRequest)(task, route, fetchStrategy, dynamicRequestTree, spawnedEntries));
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}
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return 2;
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}
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default:
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fetchStrategy;
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}
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break;
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}
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default:
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{
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route;
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}
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}
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return 2;
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}
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function pingPPRRouteTree(now, task, route, tree) {
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const segment = (0, _cache.readOrCreateSegmentCacheEntry)(now, task, route, tree.key);
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pingPerSegment(now, task, route, segment, task.key, tree.key);
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if (tree.slots !== null) {
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if (!hasNetworkBandwidth()) {
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// Stop prefetching segments until there's more bandwidth.
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return 0;
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}
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// Recursively ping the children.
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for(const parallelRouteKey in tree.slots){
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const childTree = tree.slots[parallelRouteKey];
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const childExitStatus = pingPPRRouteTree(now, task, route, childTree);
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if (childExitStatus === 0) {
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// Child yielded without finishing.
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return 0;
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}
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}
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}
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// This segment and all its children have finished prefetching.
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return 2;
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}
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function diffRouteTreeAgainstCurrent(now, task, route, oldTree, newTree, spawnedEntries, fetchStrategy) {
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// This is a single recursive traversal that does multiple things:
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// - Finds the parts of the target route (newTree) that are not part of
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// of the current page (oldTree) by diffing them, using the same algorithm
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// as a real navigation.
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// - Constructs a request tree (FlightRouterState) that describes which
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// segments need to be prefetched and which ones are already cached.
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// - Creates a set of pending cache entries for the segments that need to
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// be prefetched, so that a subsequent prefetch task does not request the
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// same segments again.
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const oldTreeChildren = oldTree[1];
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const newTreeChildren = newTree.slots;
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let requestTreeChildren = {};
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if (newTreeChildren !== null) {
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for(const parallelRouteKey in newTreeChildren){
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const newTreeChild = newTreeChildren[parallelRouteKey];
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const newTreeChildSegment = newTreeChild.segment;
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const oldTreeChild = oldTreeChildren[parallelRouteKey];
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const oldTreeChildSegment = oldTreeChild == null ? void 0 : oldTreeChild[0];
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if (oldTreeChildSegment !== undefined && (0, _matchsegments.matchSegment)(newTreeChildSegment, oldTreeChildSegment)) {
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// This segment is already part of the current route. Keep traversing.
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const requestTreeChild = diffRouteTreeAgainstCurrent(now, task, route, oldTreeChild, newTreeChild, spawnedEntries, fetchStrategy);
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requestTreeChildren[parallelRouteKey] = requestTreeChild;
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} else {
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// This segment is not part of the current route. We're entering a
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// part of the tree that we need to prefetch (unless everything is
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// already cached).
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switch(fetchStrategy){
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case _cache.FetchStrategy.LoadingBoundary:
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{
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// When PPR is disabled, we can't prefetch per segment. We must
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// fallback to the old prefetch behavior and send a dynamic request.
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// Only routes that include a loading boundary can be prefetched in
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// this way.
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//
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// This is simlar to a "full" prefetch, but we're much more
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// conservative about which segments to include in the request.
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//
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// The server will only render up to the first loading boundary
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// inside new part of the tree. If there's no loading boundary, the
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// server will never return any data. TODO: When we prefetch the
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// route tree, the server should indicate whether there's a loading
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// boundary so the client doesn't send a second request for no
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// reason.
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const requestTreeChild = pingPPRDisabledRouteTreeUpToLoadingBoundary(now, task, route, newTreeChild, null, spawnedEntries);
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requestTreeChildren[parallelRouteKey] = requestTreeChild;
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break;
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}
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case _cache.FetchStrategy.Full:
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{
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// This is a "full" prefetch. Fetch all the data in the tree, both
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// static and dynamic. We issue roughly the same request that we
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// would during a real navigation. The goal is that once the
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// navigation occurs, the router should not have to fetch any
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// additional data.
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//
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// Although the response will include dynamic data, opting into a
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// Full prefetch — via <Link prefetch={true}> — implicitly
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// instructs the cache to treat the response as "static", or non-
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// dynamic, since the whole point is to cache it for
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// future navigations.
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//
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// Construct a tree (currently a FlightRouterState) that represents
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// which segments need to be prefetched and which ones are already
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// cached. If the tree is empty, then we can exit. Otherwise, we'll
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// send the request tree to the server and use the response to
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// populate the segment cache.
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const requestTreeChild = pingRouteTreeAndIncludeDynamicData(now, task, route, newTreeChild, false, spawnedEntries);
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requestTreeChildren[parallelRouteKey] = requestTreeChild;
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break;
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}
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default:
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fetchStrategy;
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}
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}
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}
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}
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const requestTree = [
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newTree.segment,
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requestTreeChildren,
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null,
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null,
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newTree.isRootLayout
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];
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return requestTree;
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}
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function pingPPRDisabledRouteTreeUpToLoadingBoundary(now, task, route, tree, refetchMarkerContext, spawnedEntries) {
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// This function is similar to pingRouteTreeAndIncludeDynamicData, except the
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// server is only going to return a minimal loading state — it will stop
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// rendering at the first loading boundary. Whereas a Full prefetch is
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// intentionally aggressive and tries to pretfetch all the data that will be
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// needed for a navigation, a LoadingBoundary prefetch is much more
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// conservative. For example, it will omit from the request tree any segment
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// that is already cached, regardles of whether it's partial or full. By
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// contrast, a Full prefetch will refetch partial segments.
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// "inside-shared-layout" tells the server where to start looking for a
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// loading boundary.
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let refetchMarker = refetchMarkerContext === null ? 'inside-shared-layout' : null;
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const segment = (0, _cache.readOrCreateSegmentCacheEntry)(now, task, route, tree.key);
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switch(segment.status){
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case _cache.EntryStatus.Empty:
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{
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// This segment is not cached. Add a refetch marker so the server knows
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// to start rendering here.
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// TODO: Instead of a "refetch" marker, we could just omit this subtree's
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// FlightRouterState from the request tree. I think this would probably
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// already work even without any updates to the server. For consistency,
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// though, I'll send the full tree and we'll look into this later as part
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// of a larger redesign of the request protocol.
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// Add the pending cache entry to the result map.
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spawnedEntries.set(tree.key, (0, _cache.upgradeToPendingSegment)(segment, // Set the fetch strategy to LoadingBoundary to indicate that the server
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// might not include it in the pending response. If another route is able
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// to issue a per-segment request, we'll do that in the background.
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_cache.FetchStrategy.LoadingBoundary));
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if (refetchMarkerContext !== 'refetch') {
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refetchMarker = refetchMarkerContext = 'refetch';
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} else {
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// There's already a parent with a refetch marker, so we don't need
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// to add another one.
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}
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break;
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}
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case _cache.EntryStatus.Fulfilled:
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{
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// The segment is already cached.
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|
// TODO: The server should include a `hasLoading` field as part of the
|
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// route tree prefetch.
|
|
if (segment.loading !== null) {
|
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// This segment has a loading boundary, which means the server won't
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// render its children. So there's nothing left to prefetch along this
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|
// path. We can bail out.
|
|
return (0, _cache.convertRouteTreeToFlightRouterState)(tree);
|
|
}
|
|
break;
|
|
}
|
|
case _cache.EntryStatus.Pending:
|
|
{
|
|
break;
|
|
}
|
|
case _cache.EntryStatus.Rejected:
|
|
{
|
|
break;
|
|
}
|
|
default:
|
|
segment;
|
|
}
|
|
const requestTreeChildren = {};
|
|
if (tree.slots !== null) {
|
|
for(const parallelRouteKey in tree.slots){
|
|
const childTree = tree.slots[parallelRouteKey];
|
|
requestTreeChildren[parallelRouteKey] = pingPPRDisabledRouteTreeUpToLoadingBoundary(now, task, route, childTree, refetchMarkerContext, spawnedEntries);
|
|
}
|
|
}
|
|
const requestTree = [
|
|
tree.segment,
|
|
requestTreeChildren,
|
|
null,
|
|
refetchMarker,
|
|
tree.isRootLayout
|
|
];
|
|
return requestTree;
|
|
}
|
|
function pingRouteTreeAndIncludeDynamicData(now, task, route, tree, isInsideRefetchingParent, spawnedEntries) {
|
|
// The tree we're constructing is the same shape as the tree we're navigating
|
|
// to. But even though this is a "new" tree, some of the individual segments
|
|
// may be cached as a result of other route prefetches.
|
|
//
|
|
// So we need to find the first uncached segment along each path add an
|
|
// explicit "refetch" marker so the server knows where to start rendering.
|
|
// Once the server starts rendering along a path, it keeps rendering the
|
|
// entire subtree.
|
|
const segment = (0, _cache.readOrCreateSegmentCacheEntry)(now, task, route, tree.key);
|
|
let spawnedSegment = null;
|
|
switch(segment.status){
|
|
case _cache.EntryStatus.Empty:
|
|
{
|
|
// This segment is not cached. Include it in the request.
|
|
spawnedSegment = (0, _cache.upgradeToPendingSegment)(segment, _cache.FetchStrategy.Full);
|
|
break;
|
|
}
|
|
case _cache.EntryStatus.Fulfilled:
|
|
{
|
|
// The segment is already cached.
|
|
if (segment.isPartial) {
|
|
// The cached segment contians dynamic holes. Since this is a Full
|
|
// prefetch, we need to include it in the request.
|
|
spawnedSegment = pingFullSegmentRevalidation(now, task, route, segment, tree.key);
|
|
}
|
|
break;
|
|
}
|
|
case _cache.EntryStatus.Pending:
|
|
case _cache.EntryStatus.Rejected:
|
|
{
|
|
// There's either another prefetch currently in progress, or the previous
|
|
// attempt failed. If it wasn't a Full prefetch, fetch it again.
|
|
if (segment.fetchStrategy !== _cache.FetchStrategy.Full) {
|
|
spawnedSegment = pingFullSegmentRevalidation(now, task, route, segment, tree.key);
|
|
}
|
|
break;
|
|
}
|
|
default:
|
|
segment;
|
|
}
|
|
const requestTreeChildren = {};
|
|
if (tree.slots !== null) {
|
|
for(const parallelRouteKey in tree.slots){
|
|
const childTree = tree.slots[parallelRouteKey];
|
|
requestTreeChildren[parallelRouteKey] = pingRouteTreeAndIncludeDynamicData(now, task, route, childTree, isInsideRefetchingParent || spawnedSegment !== null, spawnedEntries);
|
|
}
|
|
}
|
|
if (spawnedSegment !== null) {
|
|
// Add the pending entry to the result map.
|
|
spawnedEntries.set(tree.key, spawnedSegment);
|
|
}
|
|
// Don't bother to add a refetch marker if one is already present in a parent.
|
|
const refetchMarker = !isInsideRefetchingParent && spawnedSegment !== null ? 'refetch' : null;
|
|
const requestTree = [
|
|
tree.segment,
|
|
requestTreeChildren,
|
|
null,
|
|
refetchMarker,
|
|
tree.isRootLayout
|
|
];
|
|
return requestTree;
|
|
}
|
|
function pingPerSegment(now, task, route, segment, routeKey, segmentKey) {
|
|
switch(segment.status){
|
|
case _cache.EntryStatus.Empty:
|
|
// Upgrade to Pending so we know there's already a request in progress
|
|
spawnPrefetchSubtask((0, _cache.fetchSegmentOnCacheMiss)(route, (0, _cache.upgradeToPendingSegment)(segment, _cache.FetchStrategy.PPR), routeKey, segmentKey));
|
|
break;
|
|
case _cache.EntryStatus.Pending:
|
|
{
|
|
// There's already a request in progress. Depending on what kind of
|
|
// request it is, we may want to revalidate it.
|
|
switch(segment.fetchStrategy){
|
|
case _cache.FetchStrategy.PPR:
|
|
case _cache.FetchStrategy.Full:
|
|
break;
|
|
case _cache.FetchStrategy.LoadingBoundary:
|
|
// There's a pending request, but because it's using the old
|
|
// prefetching strategy, we can't be sure if it will be fulfilled by
|
|
// the response — it might be inside the loading boundary. Perform
|
|
// a revalidation, but because it's speculative, wait to do it at
|
|
// background priority.
|
|
if (background(task)) {
|
|
// TODO: Instead of speculatively revalidating, consider including
|
|
// `hasLoading` in the route tree prefetch response.
|
|
pingPPRSegmentRevalidation(now, task, segment, route, routeKey, segmentKey);
|
|
}
|
|
break;
|
|
default:
|
|
segment.fetchStrategy;
|
|
}
|
|
break;
|
|
}
|
|
case _cache.EntryStatus.Rejected:
|
|
{
|
|
// The existing entry in the cache was rejected. Depending on how it
|
|
// was originally fetched, we may or may not want to revalidate it.
|
|
switch(segment.fetchStrategy){
|
|
case _cache.FetchStrategy.PPR:
|
|
case _cache.FetchStrategy.Full:
|
|
break;
|
|
case _cache.FetchStrategy.LoadingBoundary:
|
|
// There's a rejected entry, but it was fetched using the loading
|
|
// boundary strategy. So the reason it wasn't returned by the server
|
|
// might just be because it was inside a loading boundary. Or because
|
|
// there was a dynamic rewrite. Revalidate it using the per-
|
|
// segment strategy.
|
|
//
|
|
// Because a rejected segment will definitely prevent the segment (and
|
|
// all of its children) from rendering, we perform this revalidation
|
|
// immediately instead of deferring it to a background task.
|
|
pingPPRSegmentRevalidation(now, task, segment, route, routeKey, segmentKey);
|
|
break;
|
|
default:
|
|
segment.fetchStrategy;
|
|
}
|
|
break;
|
|
}
|
|
case _cache.EntryStatus.Fulfilled:
|
|
break;
|
|
default:
|
|
segment;
|
|
}
|
|
// Segments do not have dependent tasks, so once the prefetch is initiated,
|
|
// there's nothing else for us to do (except write the server data into the
|
|
// entry, which is handled by `fetchSegmentOnCacheMiss`).
|
|
}
|
|
function pingPPRSegmentRevalidation(now, task, currentSegment, route, routeKey, segmentKey) {
|
|
const revalidatingSegment = (0, _cache.readOrCreateRevalidatingSegmentEntry)(now, currentSegment);
|
|
switch(revalidatingSegment.status){
|
|
case _cache.EntryStatus.Empty:
|
|
// Spawn a prefetch request and upsert the segment into the cache
|
|
// upon completion.
|
|
upsertSegmentOnCompletion(task, route, segmentKey, spawnPrefetchSubtask((0, _cache.fetchSegmentOnCacheMiss)(route, (0, _cache.upgradeToPendingSegment)(revalidatingSegment, _cache.FetchStrategy.PPR), routeKey, segmentKey)));
|
|
break;
|
|
case _cache.EntryStatus.Pending:
|
|
break;
|
|
case _cache.EntryStatus.Fulfilled:
|
|
case _cache.EntryStatus.Rejected:
|
|
break;
|
|
default:
|
|
revalidatingSegment;
|
|
}
|
|
}
|
|
function pingFullSegmentRevalidation(now, task, route, currentSegment, segmentKey) {
|
|
const revalidatingSegment = (0, _cache.readOrCreateRevalidatingSegmentEntry)(now, currentSegment);
|
|
if (revalidatingSegment.status === _cache.EntryStatus.Empty) {
|
|
// During a Full prefetch, a single dynamic request is made for all the
|
|
// segments that we need. So we don't initiate a request here directly. By
|
|
// returning a pending entry from this function, it signals to the caller
|
|
// that this segment should be included in the request that's sent to
|
|
// the server.
|
|
const pendingSegment = (0, _cache.upgradeToPendingSegment)(revalidatingSegment, _cache.FetchStrategy.Full);
|
|
upsertSegmentOnCompletion(task, route, segmentKey, (0, _cache.waitForSegmentCacheEntry)(pendingSegment));
|
|
return pendingSegment;
|
|
} else {
|
|
// There's already a revalidation in progress.
|
|
const nonEmptyRevalidatingSegment = revalidatingSegment;
|
|
if (nonEmptyRevalidatingSegment.fetchStrategy !== _cache.FetchStrategy.Full) {
|
|
// The existing revalidation was not fetched using the Full strategy.
|
|
// Reset it and start a new revalidation.
|
|
const emptySegment = (0, _cache.resetRevalidatingSegmentEntry)(nonEmptyRevalidatingSegment);
|
|
const pendingSegment = (0, _cache.upgradeToPendingSegment)(emptySegment, _cache.FetchStrategy.Full);
|
|
upsertSegmentOnCompletion(task, route, segmentKey, (0, _cache.waitForSegmentCacheEntry)(pendingSegment));
|
|
return pendingSegment;
|
|
}
|
|
switch(nonEmptyRevalidatingSegment.status){
|
|
case _cache.EntryStatus.Pending:
|
|
// There's already an in-progress prefetch that includes this segment.
|
|
return null;
|
|
case _cache.EntryStatus.Fulfilled:
|
|
case _cache.EntryStatus.Rejected:
|
|
// A previous revalidation attempt finished, but we chose not to replace
|
|
// the existing entry in the cache. Don't try again until or unless the
|
|
// revalidation entry expires.
|
|
return null;
|
|
default:
|
|
nonEmptyRevalidatingSegment;
|
|
return null;
|
|
}
|
|
}
|
|
}
|
|
const noop = ()=>{};
|
|
function upsertSegmentOnCompletion(task, route, key, promise) {
|
|
// Wait for a segment to finish loading, then upsert it into the cache
|
|
promise.then((fulfilled)=>{
|
|
if (fulfilled !== null) {
|
|
// Received new data. Attempt to replace the existing entry in the cache.
|
|
const keypath = (0, _cache.getSegmentKeypathForTask)(task, route, key);
|
|
(0, _cache.upsertSegmentEntry)(Date.now(), keypath, fulfilled);
|
|
}
|
|
}, noop);
|
|
}
|
|
// -----------------------------------------------------------------------------
|
|
// The remainder of the module is a MinHeap implementation. Try not to put any
|
|
// logic below here unless it's related to the heap algorithm. We can extract
|
|
// this to a separate module if/when we need multiple kinds of heaps.
|
|
// -----------------------------------------------------------------------------
|
|
function compareQueuePriority(a, b) {
|
|
// Since the queue is a MinHeap, this should return a positive number if b is
|
|
// higher priority than a, and a negative number if a is higher priority
|
|
// than b.
|
|
// `priority` is an integer, where higher numbers are higher priority.
|
|
const priorityDiff = b.priority - a.priority;
|
|
if (priorityDiff !== 0) {
|
|
return priorityDiff;
|
|
}
|
|
// If the priority is the same, check which phase the prefetch is in — is it
|
|
// prefetching the route tree, or the segments? Route trees are prioritized.
|
|
const phaseDiff = b.phase - a.phase;
|
|
if (phaseDiff !== 0) {
|
|
return phaseDiff;
|
|
}
|
|
// Finally, check the insertion order. `sortId` is an incrementing counter
|
|
// assigned to prefetches. We want to process the newest prefetches first.
|
|
return b.sortId - a.sortId;
|
|
}
|
|
function heapPush(heap, node) {
|
|
const index = heap.length;
|
|
heap.push(node);
|
|
node._heapIndex = index;
|
|
heapSiftUp(heap, node, index);
|
|
}
|
|
function heapPeek(heap) {
|
|
return heap.length === 0 ? null : heap[0];
|
|
}
|
|
function heapPop(heap) {
|
|
if (heap.length === 0) {
|
|
return null;
|
|
}
|
|
const first = heap[0];
|
|
first._heapIndex = -1;
|
|
const last = heap.pop();
|
|
if (last !== first) {
|
|
heap[0] = last;
|
|
last._heapIndex = 0;
|
|
heapSiftDown(heap, last, 0);
|
|
}
|
|
return first;
|
|
}
|
|
function heapDelete(heap, node) {
|
|
const index = node._heapIndex;
|
|
if (index !== -1) {
|
|
node._heapIndex = -1;
|
|
if (heap.length !== 0) {
|
|
const last = heap.pop();
|
|
if (last !== node) {
|
|
heap[index] = last;
|
|
last._heapIndex = index;
|
|
heapSiftDown(heap, last, index);
|
|
}
|
|
}
|
|
}
|
|
}
|
|
function heapResift(heap, node) {
|
|
const index = node._heapIndex;
|
|
if (index !== -1) {
|
|
if (index === 0) {
|
|
heapSiftDown(heap, node, 0);
|
|
} else {
|
|
const parentIndex = index - 1 >>> 1;
|
|
const parent = heap[parentIndex];
|
|
if (compareQueuePriority(parent, node) > 0) {
|
|
// The parent is larger. Sift up.
|
|
heapSiftUp(heap, node, index);
|
|
} else {
|
|
// The parent is smaller (or equal). Sift down.
|
|
heapSiftDown(heap, node, index);
|
|
}
|
|
}
|
|
}
|
|
}
|
|
function heapSiftUp(heap, node, i) {
|
|
let index = i;
|
|
while(index > 0){
|
|
const parentIndex = index - 1 >>> 1;
|
|
const parent = heap[parentIndex];
|
|
if (compareQueuePriority(parent, node) > 0) {
|
|
// The parent is larger. Swap positions.
|
|
heap[parentIndex] = node;
|
|
node._heapIndex = parentIndex;
|
|
heap[index] = parent;
|
|
parent._heapIndex = index;
|
|
index = parentIndex;
|
|
} else {
|
|
// The parent is smaller. Exit.
|
|
return;
|
|
}
|
|
}
|
|
}
|
|
function heapSiftDown(heap, node, i) {
|
|
let index = i;
|
|
const length = heap.length;
|
|
const halfLength = length >>> 1;
|
|
while(index < halfLength){
|
|
const leftIndex = (index + 1) * 2 - 1;
|
|
const left = heap[leftIndex];
|
|
const rightIndex = leftIndex + 1;
|
|
const right = heap[rightIndex];
|
|
// If the left or right node is smaller, swap with the smaller of those.
|
|
if (compareQueuePriority(left, node) < 0) {
|
|
if (rightIndex < length && compareQueuePriority(right, left) < 0) {
|
|
heap[index] = right;
|
|
right._heapIndex = index;
|
|
heap[rightIndex] = node;
|
|
node._heapIndex = rightIndex;
|
|
index = rightIndex;
|
|
} else {
|
|
heap[index] = left;
|
|
left._heapIndex = index;
|
|
heap[leftIndex] = node;
|
|
node._heapIndex = leftIndex;
|
|
index = leftIndex;
|
|
}
|
|
} else if (rightIndex < length && compareQueuePriority(right, node) < 0) {
|
|
heap[index] = right;
|
|
right._heapIndex = index;
|
|
heap[rightIndex] = node;
|
|
node._heapIndex = rightIndex;
|
|
index = rightIndex;
|
|
} else {
|
|
// Neither child is smaller. Exit.
|
|
return;
|
|
}
|
|
}
|
|
}
|
|
|
|
if ((typeof exports.default === 'function' || (typeof exports.default === 'object' && exports.default !== null)) && typeof exports.default.__esModule === 'undefined') {
|
|
Object.defineProperty(exports.default, '__esModule', { value: true });
|
|
Object.assign(exports.default, exports);
|
|
module.exports = exports.default;
|
|
}
|
|
|
|
//# sourceMappingURL=scheduler.js.map
|