This fixes a critical bug where `http.Agent` with `keepAlive: true` was
not reusing connections, causing a 66% performance degradation compared
to Node.js. Every request was establishing a new TCP/TLS connection
instead of reusing existing ones.
**Root Cause:**
Three independent bugs were causing the connection pool to fail:
1. **TypeScript layer** (`src/js/node/_http_client.ts:271`)
- Reading wrong property: `keepalive` instead of `keepAlive`
- User's `keepAlive: true` setting was being ignored
2. **Request header handling** (`src/http.zig:591`)
- Only handled `Connection: close`, ignored `Connection: keep-alive`
- Missing explicit flag update for keep-alive header
3. **Response header handling** (`src/http.zig:2240`)
- Used compile-time function `eqlComptime` at runtime (always failed)
- Inverted logic: disabled pool when NOT "keep-alive"
- Ignored case-sensitivity (should use `eqlIgnoreCase` per RFC 7230)
**Performance Impact:**
- **Before**: All requests ~940ms, stddev 33ms (0% improvement) ❌
- **After**: First request ~930ms, subsequent ~320ms (65.9% improvement)
✅
- Performance now matches Node.js (65.9% vs 66.5% improvement)
- QPS increased from 4.2 to 12.2 req/s (190% improvement)
**Files Changed:**
- `src/js/node/_http_client.ts` - Fix property name (1 line)
- `src/http.zig` - Fix request/response header handling (5 lines)
Fixes#12053
### What does this PR do?
This PR fixes the HTTP connection pool by correcting three bugs:
1. **Fixes TypeScript property name**: Changes `this[kAgent]?.keepalive`
to `this[kAgent]?.keepAlive` to properly read the user's keepAlive
setting from http.Agent
2. **Adds keep-alive request header handling**: Explicitly sets
`disable_keepalive = false` when receiving `Connection: keep-alive`
header
3. **Fixes response header parsing**:
- Replaces compile-time `strings.eqlComptime()` with runtime
`std.ascii.eqlIgnoreCase()`
- Corrects inverted logic to properly enable connection pool on
`Connection: keep-alive`
- Makes header comparison case-insensitive per RFC 7230
All three bugs must be fixed together - any single bug would cause the
connection pool to fail.
### How did you verify your code works?
**Test 1: Minimal reproduction with 10 sequential HTTPS requests**
```typescript
const agent = new https.Agent({ keepAlive: true });
// Make 10 requests to https://api.example.com
```
Results:
- First request: 930ms (cold start with TCP/TLS handshake)
- Subsequent requests: ~320ms average (connection reused)
- **Improvement: 65.9%** (matches Node.js 66.5%)
- Verified across 3 repeated test runs for stability
**Test 2: Response header validation**
- Confirmed server returns `Connection: Keep-Alive`
- Verified Bun correctly parses and applies the header
**Test 3: Performance comparison**
| Runtime | First Request | Subsequent Avg | Improvement | QPS |
|---------|--------------|----------------|-------------|-----|
| Node.js v20.18.0 | 938ms | 314ms | **66.5%** | 12.2 |
| Bun v1.3.1 (broken) | 935ms | 942ms | -0.7% ❌ | 4.2 |
| Bun v1.3.2 (fixed) | 930ms | 317ms | **65.9%** ✅ | 12.2 |
Bun now performs identically to Node.js, confirming the connection pool
works correctly.
a4aaec5b2f
