## Summary
Many teams self-host Gitea + Act Runner at scale. The current runner design causes excessive HTTP requests to the Gitea server, leading to high server load. This PR addresses three root causes: aggressive fixed-interval polling, per-task status reporting every 1 second regardless of activity, and unoptimized HTTP client configuration.
## Problem
The original architecture has these issues:
**1. Fixed 1-second reporting interval (RunDaemon)**
- Every running task calls ReportLog + ReportState every 1 second (2 HTTP requests/sec/task)
- These requests are sent even when there are no new log rows or state changes
- With 200 runners × 3 tasks each = **1,200 req/sec just for status reporting**
**2. Fixed 2-second polling interval (no backoff)**
- Idle runners poll FetchTask every 2 seconds forever, even when no jobs are queued
- No exponential backoff or jitter — all runners can synchronize after network recovery (thundering herd)
- 200 idle runners = **100 req/sec doing nothing useful**
**3. HTTP client not tuned**
- Uses http.DefaultClient with MaxIdleConnsPerHost=2, causing frequent TCP/TLS reconnects
- Creates two separate http.Client instances (one for Ping, one for Runner service) instead of sharing
**Total: ~1,300 req/sec for 200 runners with 3 tasks each**
## Solution
### Adaptive Event-Driven Log Reporting
Replace the recursive `time.AfterFunc(1s)` pattern in RunDaemon with a goroutine-based select event loop using three trigger mechanisms:
| Trigger | Default | Purpose |
|---------|---------|---------|
| `log_report_max_latency` | 3s | Guarantee even a single log line is delivered within this time |
| `log_report_interval` | 5s | Periodic sweep — steady-state cadence |
| `log_report_batch_size` | 100 rows | Immediate flush during bursty output (e.g., npm install) |
**Key design**: `log_report_max_latency` (3s) must be less than `log_report_interval` (5s) so the max-latency timer fires before the periodic ticker for single-line scenarios.
State reporting is decoupled to its own `state_report_interval` (default 5s), with immediate flush on step transitions (start/stop) via a stateNotify channel for responsive frontend UX.
Additionally:
- Skip ReportLog when `len(rows) == 0` (no pending log rows)
- Skip ReportState when `stateChanged == false && len(outputs) == 0` (nothing changed)
- Move expensive `proto.Clone` after the early-return check to avoid deep copies on no-op paths
### Polling Backoff with Jitter
Replace fixed `rate.Limiter` with adaptive exponential backoff:
- Track `consecutiveEmpty` and `consecutiveErrors` counters
- Interval doubles with each empty/error response: `base × 2^(n-1)`, capped at `fetch_interval_max` (default 60s)
- Add ±20% random jitter to prevent thundering herd
- Fetch first, sleep after ��� preserves burst=1 behavior for immediate first fetch on startup and after task completion
### HTTP Client Tuning
- Configure custom `http.Transport` with `MaxIdleConnsPerHost=10` (was 2)
- Share a single `http.Client` between PingService and RunnerService
- Add `IdleConnTimeout=90s` for clean connection lifecycle
## Load Reduction
For 200 runners × 3 tasks (70% with active log output):
| Component | Before | After | Reduction |
|-----------|--------|-------|-----------|
| Polling (idle) | 100 req/s | ~3.4 req/s | 97% |
| Log reporting | 420 req/s | ~84 req/s | 80% |
| State reporting | 126 req/s | ~25 req/s | 80% |
| **Total** | **~1,300 req/s** | **~113 req/s** | **~91%** |
## Frontend UX Impact
| Scenario | Before | After | Notes |
|----------|--------|-------|-------|
| Continuous output (npm install) | ~1s | ~5s | Periodic ticker sweep |
| Single line then silence | ~1s | ≤3s | maxLatencyTimer guarantee |
| Bursty output (100+ lines) | ~1s | <1s | Batch size immediate flush |
| Step start/stop | ~1s | <1s | stateNotify immediate flush |
| Job completion | ~1s | ~1s | Close() retry unchanged |
## New Configuration Options
All have safe defaults — existing config files need no changes:
```yaml
runner:
fetch_interval_max: 60s # Max backoff interval when idle
log_report_interval: 5s # Periodic log flush interval
log_report_max_latency: 3s # Max time a log row waits (must be < log_report_interval)
log_report_batch_size: 100 # Immediate flush threshold
state_report_interval: 5s # State flush interval (step transitions are always immediate)
```
Config validation warns on invalid combinations:
- `fetch_interval_max < fetch_interval` → auto-corrected
- `log_report_max_latency >= log_report_interval` → warning (timer would be redundant)
## Test Plan
- [x] `go build ./...` passes
- [x] `go test ./...` passes (all existing + 3 new tests)
- [x] `golangci-lint run` — 0 issues
- [x] TestReporter_MaxLatencyTimer — verifies single log line flushed by maxLatencyTimer before logTicker
- [x] TestReporter_BatchSizeFlush — verifies batch size threshold triggers immediate flush
- [x] TestReporter_StateNotifyFlush — verifies step transition triggers immediate state flush
- [x] TestReporter_EphemeralRunnerDeletion — verifies Close/RunDaemon race safety
- [x] TestReporter_RunDaemonClose_Race — verifies concurrent Close safety
Reviewed-on: https://gitea.com/gitea/act_runner/pulls/819
Reviewed-by: Nicolas <173651+bircni@noreply.gitea.com>
Co-authored-by: Bo-Yi Wu <appleboy.tw@gmail.com>
Co-committed-by: Bo-Yi Wu <appleboy.tw@gmail.com>
