bench_concurrent.sh

#!/bin/bash

# Binary search for maximum stable concurrent connections with QPS output
# Usage: ./max_concurrency_binary.sh http://127.0.0.1:8080 4 1000 65535
# Arguments:
# $1 = Test URL
# $2 = wrk thread count
# $3 = Minimum connections to start
# $4 = Maximum connections to test

URL=${1:-http://127.0.0.1:8080}
THREADS=${2:-4}
MIN_CONN=${3:-1000}
MAX_CONN=${4:-65535}

ulimit -n $MAX_CONN

LAST_OK_CONN=$MIN_CONN
LOW=$MIN_CONN
HIGH=$MAX_CONN
MAX_ITER=20
ITER=0

while (( LOW <= HIGH && ITER < MAX_ITER ))
do
    ((ITER++))
    MID=$(( (LOW + HIGH) / 2 ))
    echo "Testing concurrency: $MID"

    # Run wrk for 10 seconds to speed up binary search
    OUTPUT=$(wrk -t$THREADS -c$MID -d10s $URL 2>&1)

    # Extract the number of connect errors (robust sed, works on macOS and Linux)
    CONN_ERR=$(printf "%s" "$OUTPUT" | sed -En 's/.*Socket errors: connect[[:space:]]+([0-9]+).*/\1/p')
    CONN_ERR=${CONN_ERR:-0}

    # Extract Requests/sec (robust sed)
    REQ_PER_SEC=$(printf "%s" "$OUTPUT" | sed -En 's/.*Requests\/sec:[[:space:]]*([0-9]+(\.[0-9]+)?).*/\1/p')
    REQ_PER_SEC=${REQ_PER_SEC:-0}

    echo "Connect errors: $CONN_ERR, QPS: $REQ_PER_SEC"

    # Consider connection stable if errors <= 1% of MID
    THRESHOLD=$(( MID / 100 ))
    if (( CONN_ERR <= THRESHOLD )); then
        # Stable, try higher concurrency
        LAST_OK_CONN=$MID
        LOW=$(( MID + 1 ))
    else
        # Unstable, reduce concurrency
        HIGH=$(( MID - 1 ))
    fi
done

echo "Maximum stable concurrent connections: $LAST_OK_CONN"