metrics.sh

#!/bin/sh

# Usage check
if [ "$#" -ne 1 ]; then
    echo "Usage: $0 <prefix>"
    exit 1
fi

prefix="$1"

# Generate a random float between min and max
random_in_range() {
    min=$1
    max=$2
    awk -v min="$min" -v max="$max" -v seed="$RANDOM" 'BEGIN {
        srand(seed);
        print rand() * (max - min) + min
    }'
}

# Generate a varying value around a base
generate_varying_value() {
    base=$1
    variance=$2
    neg_variance=$(awk -v v="$variance" 'BEGIN { print -v }')
    offset=$(random_in_range "$neg_variance" "$variance")
    awk -v b="$base" -v o="$offset" 'BEGIN { print b + o }'
}

# Occasionally spike a value
maybe_spike() {
    value=$1
    spike_min=$2
    spike_max=$3
    probability=$4  # e.g. 10 = 1-in-10 chance

    if [ $((RANDOM % $probability)) -eq 0 ]; then
        random_spike=$(random_in_range "$spike_min" "$spike_max")
        echo "$(awk -v v="$random_spike" 'BEGIN { print int(v) }')"
    else
        echo "$value"
    fi
}

generate_metrics() {
    # Normal base values
    base_dns=$(maybe_spike 3 15 60 15)        # 1 in 15 chance DNS spikes to 15-60ms
    base_connect=$(maybe_spike 35 80 180 18)  # 1 in 18 chance connect spikes to 80-180ms
    base_tls=$(maybe_spike 45 60 130 20)      # 1 in 20 chance tls spikes to 60-130ms
    base_ttfb=$(maybe_spike 200 400 800 15)   # 1 in 15 chance ttfb spikes to 400-800ms
    base_ttlb=$(maybe_spike 210 410 950 17)   # 1 in 17 chance ttlb spikes to 410-950ms

    # Generate TTFB with offset
    ttfb_offset=$(random_in_range -30 50)
    ttfb_value=$(awk -v b="$base_ttfb" -v o="$ttfb_offset" 'BEGIN { print b + o }')

    # TTLB is TTFB plus a small offset
    ttlb_offset=$(random_in_range 5 15)
    ttlb_value=$(awk -v t="$ttfb_value" -v o="$ttlb_offset" 'BEGIN { print t + o }')

    # Generate buckets for TTFB and TTLB
    ttfb_b1=$(generate_varying_value 40 15 | awk '{ print int($1) }')
    ttfb_b2=$(generate_varying_value 75 10 | awk '{ print int($1) }')
    ttfb_b3=$(generate_varying_value 95 3 | awk '{ print int($1) }')
    ttlb_b1_base=$(generate_varying_value 35 15 | awk '{ print int($1) }')
    ttlb_b2_base=$(generate_varying_value 70 10 | awk '{ print int($1) }')
    ttlb_b3_base=$(generate_varying_value 90 3 | awk '{ print int($1) }')
    ttlb_b1=$(awk -v t="$ttfb_b1" -v b="$ttlb_b1_base" 'BEGIN { v = t - 5; print (b < v) ? b : v }')
    ttlb_b2=$(awk -v t="$ttfb_b2" -v b="$ttlb_b2_base" 'BEGIN { v = t - 5; print (b < v) ? b : v }')
    ttlb_b3=$(awk -v t="$ttfb_b3" -v b="$ttlb_b3_base" 'BEGIN { v = t - 5; print (b < v) ? b : v }')

    # Calculate sum values in seconds
    dns_sum=$(awk -v d="$base_dns" 'BEGIN { printf "%.3f", d / 1000 }')
    connect_offset=$(random_in_range -15 25)
    connect_sum=$(awk -v c="$base_connect" -v o="$connect_offset" 'BEGIN { printf "%.3f", (c + o) / 1000 }')
    tls_offset=$(random_in_range -5 10)
    tls_sum=$(awk -v t="$base_tls" -v o="$tls_offset" 'BEGIN { printf "%.3f", (t + o) / 1000 }')
    ttfb_sum=$(awk -v t="$ttfb_value" 'BEGIN { printf "%.3f", t / 1000 }')
    ttlb_sum=$(awk -v t="$ttlb_value" 'BEGIN { printf "%.3f", t / 1000 }')

    # Output metrics (with prefix)
    cat << EOF
# HELP ${prefix}_http_timing_seconds HTTP request timing in seconds
# TYPE ${prefix}_http_timing_seconds histogram
${prefix}_http_timing_seconds_bucket{stage="dns",le="0.005"} $(generate_varying_value 85 10 | awk '{ print int($1) }')
${prefix}_http_timing_seconds_bucket{stage="dns",le="0.01"} $(generate_varying_value 95 3 | awk '{ print int($1) }')
${prefix}_http_timing_seconds_bucket{stage="dns",le="0.02"} $(generate_varying_value 98 1 | awk '{ print int($1) }')
${prefix}_http_timing_seconds_bucket{stage="dns",le="+Inf"} 100
${prefix}_http_timing_seconds_sum{stage="dns"} $dns_sum
${prefix}_http_timing_seconds_count{stage="dns"} 100
${prefix}_http_timing_seconds_bucket{stage="connect",le="0.02"} $(generate_varying_value 70 15 | awk '{ print int($1) }')
${prefix}_http_timing_seconds_bucket{stage="connect",le="0.05"} $(generate_varying_value 90 5 | awk '{ print int($1) }')
${prefix}_http_timing_seconds_bucket{stage="connect",le="0.1"} $(generate_varying_value 98 1 | awk '{ print int($1) }')
${prefix}_http_timing_seconds_bucket{stage="connect",le="+Inf"} 100
${prefix}_http_timing_seconds_sum{stage="connect"} $connect_sum
${prefix}_http_timing_seconds_count{stage="connect"} 100
${prefix}_http_timing_seconds_bucket{stage="tls",le="0.04"} $(generate_varying_value 75 10 | awk '{ print int($1) }')
${prefix}_http_timing_seconds_bucket{stage="tls",le="0.05"} $(generate_varying_value 95 3 | awk '{ print int($1) }')
${prefix}_http_timing_seconds_bucket{stage="tls",le="0.06"} $(generate_varying_value 98 1 | awk '{ print int($1) }')
${prefix}_http_timing_seconds_bucket{stage="tls",le="+Inf"} 100
${prefix}_http_timing_seconds_sum{stage="tls"} $tls_sum
${prefix}_http_timing_seconds_count{stage="tls"} 100
${prefix}_http_timing_seconds_bucket{stage="ttfb",le="0.15"} $ttfb_b1
${prefix}_http_timing_seconds_bucket{stage="ttfb",le="0.25"} $ttfb_b2
${prefix}_http_timing_seconds_bucket{stage="ttfb",le="0.35"} $ttfb_b3
${prefix}_http_timing_seconds_bucket{stage="ttfb",le="+Inf"} 100
${prefix}_http_timing_seconds_sum{stage="ttfb"} $ttfb_sum
${prefix}_http_timing_seconds_count{stage="ttfb"} 100
${prefix}_http_timing_seconds_bucket{stage="ttlb",le="0.16"} $ttlb_b1
${prefix}_http_timing_seconds_bucket{stage="ttlb",le="0.26"} $ttlb_b2
${prefix}_http_timing_seconds_bucket{stage="ttlb",le="0.36"} $ttlb_b3
${prefix}_http_timing_seconds_bucket{stage="ttlb",le="+Inf"} 100
${prefix}_http_timing_seconds_sum{stage="ttlb"} $ttlb_sum
${prefix}_http_timing_seconds_count{stage="ttlb"} 100
# HELP ${prefix}_http_errors_total Total number of HTTP errors
# TYPE ${prefix}_http_errors_total counter
${prefix}_http_errors_total{status_code="500"} 2
${prefix}_http_errors_total{status_code="404"} 1
EOF
}

# Main
generate_metrics