Opensearch/Elasticsearch CPU load per node ascii chart

opensearch_cpu_graph.sh

#!/bin/bash

ENDPOINTS=(
    "https://wi-node-1:9200"
    "https://wi-node-2:9200"
    "https://wi-node-3:9200"
)
INTERVAL=1
MIN_PANEL_HEIGHT=10
LOG_FILE="/tmp/opensearch_cpu_log.txt"

username=admin
read -s -p "Password: " password
echo
AUTH="-u $username:$password"

declare -A cpu_data
declare -A cpu_history
declare -a all_nodes
declare -A scroll_offset

curl_elapsed_time=0

get_terminal_size() {
    TERMINAL_HEIGHT=$(tput lines)
    TERMINAL_WIDTH=$(tput cols)
    CHART_HEIGHT=$MIN_PANEL_HEIGHT
    CHART_WIDTH=$((TERMINAL_WIDTH - 10))
    MAX_HISTORY=$(( 2*CHART_WIDTH ))
}

trap ctrl_c INT
ctrl_c() {
    tput cnorm
    echo -e "\n[INFO] Interrupted..."
    exit 0
}

fetch_cpu_usage() {
    local json
    random_endpoint=$(echo "${ENDPOINTS[@]}" | tr ' ' '\n' | shuf -n 1)
    json=$(curl -ks $AUTH "$random_endpoint/_nodes/stats/os")
    echo "$json" | jq -r '.nodes | to_entries[] | "\(.value.name) \(.value.os.cpu.percent)"'
}

update_data() {
    local nodes=()
    while IFS=' ' read -r node usage; do
        usage=${usage:-0}
        cpu_data["$node"]="$usage"
        nodes+=("$node")

        # Update history
        local old="${cpu_history[$node]}"
        cpu_history[$node]="$old $usage"
        # Limit history
        local words
        words=$(echo "${cpu_history[$node]}" | wc -w)
        if (( words > MAX_HISTORY )); then
            cpu_history[$node]=$(echo "${cpu_history[$node]}" | awk -v max=$MAX_HISTORY '{
                start = (NF > max) ? NF - max + 1 : 1;
                for (i=start; i<=NF; i++) printf $i " ";
                print ""
            }') #'
        fi

        # Update scrolling offset, in case history is longer than the panel
        history_length=$(echo "${cpu_history[$node]}" | wc -w)
        if (( history_length > CHART_WIDTH )); then
            scroll_offset[$node]=$((scroll_offset[$node] + 1))
        else
            scroll_offset[$node]=0
        fi

        # Log
#        echo "$(date +'%Y-%m-%d %H:%M:%S') $node CPU: $usage%; words: $words; length: $history_length" >> "$LOG_FILE"
#        echo "$(date +'%Y-%m-%d %H:%M:%S') $node ${cpu_history[$node]}" >> "$LOG_FILE.hist"
    done < <(fetch_cpu_usage)

    # Sorting nodes alphabetically
    all_nodes=($(printf "%s\n" "${nodes[@]}" | sort))
}

simple_print() {
    if (( scaled > row )); then
        if (( val > 80 )); then
            tput setaf 1; printf "█"; tput sgr0
        elif (( val < 10 )); then
            printf "▄"
        else
            printf "█"
        fi
    elif (( row == 0 && val > 0 && val < 10 )); then
        printf "▄"
    else
        printf " "
    fi
}

# Draw chart using history
draw_chart() {
    local node="$1"
    local history="${cpu_history[$node]}"
    local -a values=($history)
    local total=${#values[@]}
    local offset=${scroll_offset[$node]:-0}

    if (( offset + CHART_WIDTH > total )); then
        offset=$(( total > CHART_WIDTH ? total - CHART_WIDTH : 0 ))
        scroll_offset[$node]=$offset
    fi

    printf "\nNode: %s\n" "$node (${cpu_data[$node]}%)"

    for ((row=CHART_HEIGHT; row>=0; row--)); do
        level=$((row * 100 / CHART_HEIGHT))
        printf "%3d │" "$level"

        local count=0
        local val

        for ((col=0; col<CHART_WIDTH; col++)); do
            idx=$((offset + col))
            val=${values[$idx]:-0}
            scaled=$(( val * CHART_HEIGHT / 100 ))
            simple_print
        done

        echo
    done

    printf "    └"
    printf "─%.0s" $(seq 1 $CHART_WIDTH)
    echo
}

get_terminal_size
tput clear
tput civis

# Main loop
while true; do
    tput cup 0 0

    update_data

    for node in "${all_nodes[@]}"; do
        draw_chart "$node"
    done

    sleep "$INTERVAL"
done
tput cnorm