A simple bokeh app to plot ping to some hosts

minimon.py

#!/bin/env python3

# A simple bokeh app to plot ping to some hosts
# Run this program with:
#     bokeh server --show minimon.py --args host1 host2 host3
# MIT Licensed

import re
import time
import select
import argparse
import itertools
import subprocess

from bokeh.core.properties import value
from bokeh.plotting import figure, show, curdoc
from bokeh.palettes import Dark2_5 as palette
from bokeh.models import ColumnDataSource


def setup_args():
    parser = argparse.ArgumentParser()
    parser.add_argument('hosts', nargs='+', help='Hosts to ping')
    return parser.parse_args()


def main():
    args = setup_args()

    data = {'tick': []}
    reads = {}
    hosts = set()
    for host in args.hosts:
        # -n numeric only: no DNS lookup
        proc = subprocess.Popen(['ping', '-n', host], stdout=subprocess.PIPE)
        fd = proc.stdout.fileno()
        reads[fd] = (host, proc)
        data[host] = []  # Setup initial data for this host

    # Setup plot
    src = ColumnDataSource(data=data)
    p = figure()
    colors = itertools.cycle(palette)
    for host, col in zip(args.hosts, colors):
        p.line(x='tick', y=host, legend=value(host), color=col, source=src)

    p.legend.location = 'top_left'
    p.legend.click_policy = 'hide'

    # Add plot to current root
    curdoc().add_root(p)

    # Conversion table for time units
    timeunit = {
        'ms': 1,
        'msec': 1,
        's': 1000,
        'sec': 1000,
    }
    ticks = 0
    def update():
        nonlocal ticks, reads
        hosts = set(args.hosts)

        # Updated data
        data = {'tick': [ticks]}

        # Get ready read descriptors
        readable, _, _ = select.select(reads.keys(), [], [])
        read = set()
        for fd in readable:
            host, proc = reads[fd]

            row = proc.stdout.readline().decode()
            if row.startswith('PING'):
                continue

            read.add(host)
            # icmp_seq = re.search(r'icmp_seq=(\d+)', row).group(1)
            time = re.search(r'time=(\d+\.\d+|\d+)\s+(ms|s)$', row)
            time = time.group(1) * timeunit[time.group(2)]
            #src.stream({'icmp_seq': [icmp_seq], host: [time]})
            data[host] = [time]

        # Set data for missing hosts
        for host in hosts - read:
            data[host] = [-1]

        src.stream(data)

        ticks += 1
    return update


update = main()
curdoc().add_periodic_callback(update, 1000)