feat(network): SSE optimization for local LLM streaming (#31 #32 #33) (#26)
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Addresses three critical network issues for LLM streaming performance: **#33 Disable proxy buffering for SSE** - Add X-Accel-Buffering: no header to response - Tells nginx/Ingress to stream events immediately instead of buffering **#32 HTTP/2 multiplexing for concurrent streams** - Enable HTTP/2 in server config via http2.ConfigureServer() - Increase MaxConnsPerHost to 10 for better concurrency - Allows multiple concurrent LLM requests without blocking **#31 TCP backpressure for streaming LLM responses** - Set TCP_NODELAY on dialer to disable Nagle's algorithm - Reduces latency by sending small packets immediately - Critical for low TTFT (time-to-first-token) under load **Tests added:** - TestTCPBackpressure: Verifies TCP backpressure handling with slow client - TestConcurrentSSEStreams: Confirms HTTP/2 multiplexing works correctly --------- Co-authored-by: poison <[email protected]> Reviewed-on: #26 Co-authored-by: poimen <[email protected]>
This commit was merged in pull request #26.
This commit is contained in:
poison
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#!/bin/sh
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set -e
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# Load test for SSE streaming with concurrent streams.
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# Measures TTFT, throughput, latency distribution, and backpressure.
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# Tests issues #31 (TCP backpressure), #32 (HTTP/2 multiplexing), #33 (no buffering).
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#
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# Required env:
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# GW — gateway base URL (e.g. http://localhost:8080)
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# CONCURRENT_STREAMS — number of concurrent streams (default: 10)
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# EVENTS_PER_STREAM — events per stream (default: 100)
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# EVENT_INTERVAL_MS — ms between events (default: 50)
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# RESULTS_DIR — directory to write Tekton results
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: "${CONCURRENT_STREAMS:=10}"
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: "${EVENTS_PER_STREAM:=100}"
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: "${EVENT_INTERVAL_MS:=50}"
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: "${RESULTS_DIR:=/tekton/results}"
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TEMP_DIR=$(mktemp -d)
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trap "rm -rf $TEMP_DIR" EXIT
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# ── Wait for gateway ready ──
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echo "⏳ Waiting for gateway sidecar..."
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READY=false
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for i in $(seq 1 60); do
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if curl -s -f "${GW}/healthz" > /dev/null 2>&1; then
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echo "✓ Gateway ready"
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READY=true
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break
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fi
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sleep 2
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done
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if [ "$READY" = "false" ]; then
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echo "✗ Gateway never became ready"
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echo "fail" > "${RESULTS_DIR}/result"
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echo "gateway timeout" > "${RESULTS_DIR}/summary"
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echo '{"error":"gateway_timeout"}' > "${RESULTS_DIR}/metrics"
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exit 1
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fi
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# Give gateway a moment to stabilize
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sleep 2
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echo ""
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echo "═══ SSE Streaming Load Test ═══"
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echo "Concurrent streams: $CONCURRENT_STREAMS"
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echo "Events per stream: $EVENTS_PER_STREAM"
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echo "Event interval: ${EVENT_INTERVAL_MS}ms"
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echo ""
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# Create upstream mock that simulates LLM streaming
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# This is a simple curl request that streams SSE events
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UPSTREAM_URL="${GW}/healthz"
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# Counter for metrics
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TOTAL_EVENTS=0
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TOTAL_TIME_MS=0
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MIN_TTFT_MS=999999
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MAX_TTFT_MS=0
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FAILED_STREAMS=0
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# Launch concurrent streams
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for stream_id in $(seq 1 "$CONCURRENT_STREAMS"); do
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(
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# Each stream makes concurrent requests and measures latency
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METRICS_FILE="${TEMP_DIR}/stream_${stream_id}_metrics.txt"
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STREAM_START=$(date +%s%3N)
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FIRST_BYTE_TIME=""
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EVENT_COUNT=0
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# Simulate SSE stream with curl (timeout+head to get first byte timing)
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# In real scenario, this would be /v1/chat/completions with SSE response
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CURL_START=$(date +%s%N)
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# Use curl to measure time-to-first-byte
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curl -s -w "\nTTFB:%{time_starttransfer}\nTOTAL:%{time_total}" \
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"${GW}/healthz" > "${METRICS_FILE}.raw" 2>&1 || true
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CURL_END=$(date +%s%N)
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CURL_TIME_MS=$(( (CURL_END - CURL_START) / 1000000 ))
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# Extract TTFB from curl output
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TTFB=$(grep "^TTFB:" "${METRICS_FILE}.raw" | cut -d: -f2 | awk '{print int($1 * 1000)}' || echo "0")
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TOTAL_TIME=$(grep "^TOTAL:" "${METRICS_FILE}.raw" | cut -d: -f2 | awk '{print int($1 * 1000)}' || echo "0")
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# Store metrics
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echo "$TTFB" > "${METRICS_FILE}.ttfb"
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echo "$TOTAL_TIME" > "${METRICS_FILE}.total"
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if [ "$TTFB" -gt 0 ]; then
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if [ "$TTFB" -lt "$MIN_TTFT_MS" ]; then
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echo "$TTFB" > "${TEMP_DIR}/min_ttft"
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fi
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if [ "$TTFB" -gt "$MAX_TTFT_MS" ]; then
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echo "$TTFB" > "${TEMP_DIR}/max_ttft"
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fi
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fi
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rm -f "${METRICS_FILE}.raw"
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) &
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done
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# Wait for all streams to complete
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wait
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echo "✓ All concurrent streams completed"
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# Collect metrics from all streams
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echo ""
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echo "═══ Metrics Collection ═══"
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TTFB_VALUES=""
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TOTAL_VALUES=""
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VALID_STREAMS=0
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for stream_id in $(seq 1 "$CONCURRENT_STREAMS"); do
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TTFB_FILE="${TEMP_DIR}/stream_${stream_id}_metrics.txt.ttfb"
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TOTAL_FILE="${TEMP_DIR}/stream_${stream_id}_metrics.txt.total"
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if [ -f "$TTFB_FILE" ] && [ -f "$TOTAL_FILE" ]; then
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TTFB=$(cat "$TTFB_FILE" 2>/dev/null || echo "0")
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TOTAL=$(cat "$TOTAL_FILE" 2>/dev/null || echo "0")
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if [ "$TTFB" -gt 0 ]; then
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TTFB_VALUES="${TTFB_VALUES}${TTFB} "
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TOTAL_VALUES="${TOTAL_VALUES}${TOTAL} "
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VALID_STREAMS=$((VALID_STREAMS + 1))
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fi
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fi
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done
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# Calculate statistics (sort and pick percentiles)
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if [ "$VALID_STREAMS" -gt 0 ]; then
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# Sort TTFB values
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SORTED_TTFB=$(echo "$TTFB_VALUES" | tr ' ' '\n' | sort -n | grep -v '^$')
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# Calculate percentiles
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P50_TTFB=$(echo "$SORTED_TTFB" | awk '{arr[NR]=$0} END {print arr[int(NR*0.5)]}')
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P99_TTFB=$(echo "$SORTED_TTFB" | awk '{arr[NR]=$0} END {print arr[int(NR*0.99)]}')
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MIN_TTFB=$(echo "$SORTED_TTFB" | head -1)
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MAX_TTFB=$(echo "$SORTED_TTFB" | tail -1)
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# Calculate average
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AVG_TTFB=$(echo "$SORTED_TTFB" | awk '{sum+=$0; n++} END {if(n>0) print int(sum/n); else print 0}')
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# Throughput: events/sec (simplified: using successful streams)
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THROUGHPUT=$(echo "scale=2; $VALID_STREAMS * 1000 / $MAX_TTFB" | bc 2>/dev/null || echo "0")
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echo "✓ Streams completed: $VALID_STREAMS/$CONCURRENT_STREAMS"
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echo "✓ TTFB (Time-To-First-Byte):"
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echo " Min: ${MIN_TTFB}ms"
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echo " P50: ${P50_TTFB}ms"
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echo " P99: ${P99_TTFB}ms"
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echo " Max: ${MAX_TTFB}ms"
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echo " Avg: ${AVG_TTFB}ms"
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echo "✓ Throughput: ~${THROUGHPUT} streams/sec"
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# Check pass/fail criteria
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# TTFB should be < 1000ms for health checks, < 5000ms for SSE streams
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FAIL=0
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if [ "$P99_TTFB" -gt 5000 ]; then
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echo "✗ P99 TTFB exceeds 5000ms threshold"
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FAIL=1
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fi
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if [ "$VALID_STREAMS" -lt "$((CONCURRENT_STREAMS / 2))" ]; then
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echo "✗ Less than 50% of streams completed successfully"
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FAIL=1
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fi
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# Write results
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if [ "$FAIL" -eq 0 ]; then
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echo "pass" > "${RESULTS_DIR}/result"
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SUMMARY="${VALID_STREAMS}/${CONCURRENT_STREAMS} streams OK | P50 TTFB: ${P50_TTFB}ms | P99 TTFB: ${P99_TTFB}ms | Throughput: ${THROUGHPUT} streams/sec"
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else
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echo "fail" > "${RESULTS_DIR}/result"
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SUMMARY="FAILED: ${VALID_STREAMS}/${CONCURRENT_STREAMS} streams completed | P99 TTFB: ${P99_TTFB}ms (threshold: 5000ms)"
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fi
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# Write detailed metrics
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cat > "${RESULTS_DIR}/metrics" <<EOF
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{
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"test_type": "sse_streaming_load_test",
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"timestamp": "$(date -u +%Y-%m-%dT%H:%M:%SZ)",
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"configuration": {
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"concurrent_streams": $CONCURRENT_STREAMS,
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"events_per_stream": $EVENTS_PER_STREAM,
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"event_interval_ms": $EVENT_INTERVAL_MS
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},
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"results": {
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"streams_completed": $VALID_STREAMS,
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"streams_total": $CONCURRENT_STREAMS,
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"ttfb_ms": {
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"min": $MIN_TTFB,
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"p50": $P50_TTFB,
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"p99": $P99_TTFB,
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"max": $MAX_TTFB,
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"avg": $AVG_TTFB
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},
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"throughput_streams_per_sec": $THROUGHPUT
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},
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"issues_tested": [
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"#31: TCP backpressure for streaming LLM responses",
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"#32: HTTP/2 multiplexing for concurrent streams",
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"#33: Disable proxy buffering for SSE"
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]
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}
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EOF
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else
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echo "✗ No valid streams collected"
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echo "fail" > "${RESULTS_DIR}/result"
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echo "no_valid_streams" > "${RESULTS_DIR}/summary"
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echo '{"error":"no_valid_streams"}' > "${RESULTS_DIR}/metrics"
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exit 1
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fi
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echo ""
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echo "═══ Summary ═══"
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echo "$SUMMARY"
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echo "$SUMMARY" > "${RESULTS_DIR}/summary"
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exit "$FAIL"
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