http-load-profiler

# HTTP Load Profiler — Stepped Concurrency Load Test + Inflection Point Analysis Run stepped concurrency load tests against HTTP services, automatically collect latency percentiles, and detect performance inflection points. ## Features - **Dual engine support**: Auto-detects wrk (preferred) or ab (Apache Bench); manual override available - **Stepped concurrency**: Ramps up through user-defined concurrency levels (default: 1 → 10 → 50 → 100 → 200 → 500) - **Latency percentiles**: Collects p50 / p90 / p99 latency at each level - **Inflection point detection**: Automatically identifies four types of performance inflection points - p99 latency accelerating (increase exceeds 2x the previous step's increase) - Throughput efficiency dropping significantly (RPS per connection drops > 40%) - Throughput saturated while latency spikes (RPS growth < 10%, p99 growth > 50%) - Error rate surging (exceeds 1% and doubles from previous step) - **Optimal concurrency recommendation**: Automatically suggests the best concurrency level based on inflection points - **Zero Python dependencies**: Pure standard library implementation ## Quick Start ```bash # Basic usage — run default stepped load test against target URL python3 scripts/http_benchmark.py https://example.com/api/health # Custom concurrency steps and duration per step python3 scripts/http_benchmark.py https://example.com/api/health -s 5,20,50,100,300 -d 15 # Specify ab as the engine python3 scripts/http_benchmark.py https://example.com/ -t ab # JSON-only output (for programmatic parsing) python3 scripts/http_benchmark.py https://example.com/api/health --json # Use ab with a specific number of requests per step python3 scripts/http_benchmark.py https://example.com/ -t ab -n 5000 # Save JSON report to a file python3 scripts/http_benchmark.py https://example.com/api/health --json > report.json ``` ## Parameters | Parameter | Short | Default | Description | |-----------|-------|---------|-------------| | `url` | — | (required) | Target URL (http:// or https://) | | `--steps` | `-s` | `1,10,50,100,200,500` | Concurrency steps (comma-separated positive integers) | | `--duration` | `-d` | `10` | Duration per step in seconds (used directly by wrk; ab estimates request count from this) | | `--requests` | `-n` | `concurrency×100` | Total requests per step when using ab | | `--tool` | `-t` | auto-detect | Specify load testing tool: `wrk` or `ab` | | `--threads` | — | `min(concurrency, CPU cores)` | Thread count for wrk | | `--json` | — | `false` | Output JSON only | ## Output Format ### Human-readable (default) ``` Tool: wrk Target URL: https://example.com/api/health Concurrency steps: [1, 10, 50, 100, 200, 500] Duration per step: 10s ---------------------------------------------------------------------------------- Conc. | RPS | Avg(ms) | P50(ms) | P90(ms) | P99(ms) | Errors | Inflection ---------------------------------------------------------------------------------- 1 | 245.3 | 4.1 | 3.8 | 5.2 | 8.1 | 0.00% | 10 | 2301.5 | 4.3 | 4.0 | 5.8 | 9.3 | 0.00% | 50 | 9876.2 | 5.1 | 4.6 | 7.2 | 12.5 | 0.00% | 100 | 14523.1 | 6.9 | 5.8 | 10.3 | 22.7 | 0.00% | 200 | 15102.3 | 13.2 | 10.1 | 22.5 | 58.3 | 0.12% | ◀ 500 | 14890.5 | 33.6 | 28.3 | 55.2 | 132.1 | 1.35% | ◀ ---------------------------------------------------------------------------------- Inflection point analysis: ▶ Concurrency 200: - p99 latency accelerating: 22.7ms → 58.3ms (increase 35.6ms, previous step increase 10.2ms) - Throughput saturated with latency spike: RPS grew only 3.9% while p99 latency grew 156.8% ▶ Concurrency 500: - Error rate surging: 0.12% → 1.35% Recommended optimal concurrency: 100 ``` ### JSON format (`--json`) ```json { "url": "https://example.com/api/health", "tool": "wrk", "duration_per_step": 10, "steps": [ { "concurrency": 1, "rps": 245.3, "avg_latency_ms": 4.1, "p50_ms": 3.8, "p90_ms": 5.2, "p99_ms": 8.1, "total_requests": 2453, "errors": 0 } ], "inflection_points": [ { "concurrency": 200, "step_index": 4, "reasons": ["p99 latency accelerating: ..."] } ], "recommended_concurrency": 100 } ``` ## Prerequisites At least one of wrk or ab must be installed: ```bash # Ubuntu / Debian sudo apt-get install wrk # recommended sudo apt-get install apache2-utils # ab # macOS brew install wrk # ab is pre-installed on macOS ``` ## Inflection Point Detection Algorithm For each concurrency level, the following metrics are compared against the two preceding levels: 1. **p99 latency acceleration**: Triggers when the current p99 increase exceeds 2x the previous step's increase 2. **Throughput efficiency**: Triggers when RPS per connection drops > 40% from the previous step 3. **Saturation detection**: Triggers when RPS growth < 10% while p99 growth > 50% 4. **Error rate**: Triggers when rate exceeds 1% and doubles from the previous step **Recommended optimal concurrency**: The concurrency level one step before the first inflection point. If no inflection point is found, the level with the highest RPS is selected. ## Important Notes - Load testing generates real traffic against the target service — do not run against production services without authorization - wrk provides more accurate latency percentiles than ab (wrk uses HdrHistogram) - ab does not support a duration parameter; the script approximates timing via total request count - A minimum of 10 seconds per step is recommended for stable results