⚡ Bolt: Optimize session history loading with bounded concurrency - #51
Conversation
Replaces sequential file reading with batched Promise.all (bounded concurrency) when loading chat sessions, history summaries, and plan sessions. This addresses an I/O bottleneck when loading list views with many sessions. Performance Impact: Provides a ~3-4x speedup over sequential reads while avoiding EMFILE errors.
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Pull request overview
Optimizes loading of session/history lists by replacing sequential per-file reads with bounded concurrent reads (chunked Promise.all) to reduce I/O bottlenecks in file-per-session storage.
Changes:
- Implement chunked concurrent JSON file reads (limit 20) in
SessionManager.listSessions,HistoryManager.list, andPlanSessionManager.listRecent. - Filter to
.jsonfiles up-front before reading/parsing. - Document the performance learning and bounded-concurrency guideline in
.jules/bolt.md.
Reviewed changes
Copilot reviewed 4 out of 4 changed files in this pull request and generated 3 comments.
| File | Description |
|---|---|
| src/core/session-manager.ts | Batched concurrent reads for session metadata loading. |
| src/core/plan-session.ts | Batched concurrent reads for recent plan sessions loading. |
| src/core/history-manager.ts | Batched concurrent reads for conversation summaries loading. |
| .jules/bolt.md | Notes the bounded concurrency approach and benchmark results. |
Comments suppressed due to low confidence (1)
src/core/history-manager.ts:149
HistoryManagerhas tests forsummarizeTitle, but the updatedlist()behavior (bounded concurrency + skipping corrupted files + sorting) isn’t covered. Please add tests that mockreaddir/readFileto validatelist()returns correctly sorted summaries and continues past corrupted/unreadable files.
async list(): Promise<ConversationSummary[]> {
await this.ensureDir();
try {
const files = await fs.readdir(this.projectDir);
const summaries: ConversationSummary[] = [];
const jsonFiles = files.filter((file) => file.endsWith('.json'));
// Bounded concurrency to speed up reading many session files
const CONCURRENCY_LIMIT = 20;
for (let i = 0; i < jsonFiles.length; i += CONCURRENCY_LIMIT) {
const chunk = jsonFiles.slice(i, i + CONCURRENCY_LIMIT);
await Promise.all(
chunk.map(async (file) => {
try {
const filePath = path.join(this.projectDir, file);
const content = await fs.readFile(filePath, 'utf-8');
const conv = JSON.parse(content) as SavedConversation;
summaries.push({
id: conv.id,
title: conv.title,
created: conv.created,
updated: conv.updated,
messageCount: conv.messages.length,
model: conv.model,
});
} catch {
// Skip corrupted files
}
})
);
}
// Sort by updated time, newest first
summaries.sort((a, b) => new Date(b.updated).getTime() - new Date(a.updated).getTime());
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| // Bounded concurrency (chunks of 20) to prevent EMFILE errors while speeding up IO | ||
| const CONCURRENCY_LIMIT = 20; | ||
| for (let i = 0; i < jsonFiles.length; i += CONCURRENCY_LIMIT) { | ||
| const chunk = jsonFiles.slice(i, i + CONCURRENCY_LIMIT); | ||
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| await Promise.all( | ||
| chunk.map(async (file) => { | ||
| const fullPath = path.join(this.sessionsDir, file); | ||
| try { | ||
| const raw = await fs.readFile(fullPath, 'utf-8'); | ||
| const data = JSON.parse(raw) as ChatSession; | ||
| const { messages: _messages, stats: _stats, ...meta } = data; | ||
| metas.push(meta); | ||
| } catch { | ||
| // Ignore malformed files | ||
| } | ||
| }) | ||
| ); |
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The bounded-concurrency chunking logic is duplicated here and also mutates metas from within concurrent tasks via metas.push(...). Consider extracting a shared helper (e.g., mapWithConcurrencyLimit / runWithConcurrency) and have each task return its meta, then append results after Promise.all to avoid shared mutable state and reduce duplication across session/history/plan loaders.
| const jsonFiles = files.filter(f => f.endsWith('.json')); | ||
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| // Bounded concurrency | ||
| const CONCURRENCY_LIMIT = 20; | ||
| for (let i = 0; i < jsonFiles.length; i += CONCURRENCY_LIMIT) { | ||
| const chunk = jsonFiles.slice(i, i + CONCURRENCY_LIMIT); | ||
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| await Promise.all( | ||
| chunk.map(async (file) => { | ||
| try { | ||
| const raw = await fs.readFile(path.join(this.sessionDir, file), 'utf8'); | ||
| sessions.push(JSON.parse(raw) as PlanSession); | ||
| } catch { | ||
| // Ignore malformed session files to avoid breaking the list. | ||
| } | ||
| }) | ||
| ); |
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This change introduces new bounded-concurrency behavior in listRecent but there’s no test coverage asserting it still (1) ignores malformed JSON files and (2) returns the correct sorted+limited results when multiple session files exist. Since this module already has tests, please add/extend tests to cover listRecent with mocked readdir/readFile inputs.
| // Bounded concurrency to speed up reading many session files | ||
| const CONCURRENCY_LIMIT = 20; | ||
| for (let i = 0; i < jsonFiles.length; i += CONCURRENCY_LIMIT) { | ||
| const chunk = jsonFiles.slice(i, i + CONCURRENCY_LIMIT); | ||
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| await Promise.all( | ||
| chunk.map(async (file) => { | ||
| try { | ||
| const filePath = path.join(this.projectDir, file); | ||
| const content = await fs.readFile(filePath, 'utf-8'); | ||
| const conv = JSON.parse(content) as SavedConversation; | ||
| summaries.push({ | ||
| id: conv.id, | ||
| title: conv.title, | ||
| created: conv.created, | ||
| updated: conv.updated, | ||
| messageCount: conv.messages.length, | ||
| model: conv.model, | ||
| }); | ||
| } catch { | ||
| // Skip corrupted files | ||
| } | ||
| }) | ||
| ); |
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The bounded-concurrency implementation is duplicated across several managers and relies on mutating summaries from inside concurrent tasks. Consider extracting a shared concurrency helper and returning per-file summaries from the async callback (then merging) to keep the code easier to reason about and avoid shared mutable state in async flows.
…-loading-5635981684457449265 ⚡ Bolt: Optimize session history loading with bounded concurrency
💡 What: Replaced sequential file reads (
for...of) with batched concurrent reads usingPromise.all(chunk size 20) acrosssession-manager.ts,history-manager.ts, andplan-session.ts.🎯 Why: The file-per-session storage architecture created a significant I/O bottleneck when loading list views (e.g., thousands of chat sessions or plan sessions), making the load time O(n). Sequential reading is unnecessarily slow for independent file operations.
📊 Impact: ~3-4x speedup in loading times for users with many historical sessions, without hitting OS-level EMFILE (too many open files) errors thanks to the bounded chunk size.
🔬 Measurement: Verified with a local benchmark reading 5,000 mock JSON session files (Sequential: ~3046ms vs Batched: ~809ms). Tests pass successfully and code passes
pnpm run build. Critical learning logged to.jules/bolt.md.PR created automatically by Jules for task 5635981684457449265 started by @iotserver24