Monitoring PredictionIO with Monit

PioMonit.md

#Monitoring PredictionIO with Monit

If you're using PredictionIO in a production setting, you'll want some way to make sure it is always up. Monit is a tool which will monitor important processes and programs. This guide will show how to set up monit on your PredictionIO server to keep an engine always up and running.

##Install You can install monit on ubuntu with

sudo apt-get install monit

###Configure Basics Now we can configure monit by the configuration file /etc/monit/monitrc with your favorite editor. You will notice that this file contains quite a bit already, most of which is commented intructions/examples.

First, choose the interval on which you want monit to check the status of your system. Use the set daemon command for this, it should already exist in the configuration file.

set daemon 60 #checks at 1-minute intervals

The check system block should also already be present, under the services block.

  check system 127.0.0.1 
    if memory usage > 75% then alert
    if swap usage > 25% then alert
    if loadavg (1min) > 4 then alert
    if loadavg (5min) > 2 then alert
    if cpu usage (user) > 70% then alert
    if cpu usage (system) > 30% then alert
    if cpu usage (wait) > 20% then alert

You might also want to configure the built in web server.

set httpd port 2812
     allow admin:yourpassword      # require user 'admin' with password 'yourpassword'

More examples on configuring the web server are included in the default config file.

Configuration blocks for common services like apache, nginx, or PostgreSQL can be found here

###Event Server Now the interesting stuff, lets add monitoring for the event server.

check process eventserver
	matching "Console eventserver"
        start program = "/etc/monit/modebug /home/ubuntu/event_scripts.sh start"
        stop program = "/etc/monit/modebug /home/ubuntu/event_scripts.sh stop"
        if cpu usage > 95% for 10 cycles then restart

This block references a script, event_scripts.sh. This script tell monit how to restart the engine and event server if they go down.

The script might differ slightly depending on your environment but it should look something like what is shown below. Assume SimilarProduct is the your pio app directory.

#!/bin/bash
 case $1 in
    start)
       cd /home/ubuntu/SimilarProduct/
       nohup /opt/PredictionIO/bin/pio eventserver > /home/ubuntu/events.log &
       ;;
     stop) 
       event_pid=`pgrep -f "Console eventserver"`
       kill "$event_pid"
       ;;
     *) 
 esac
 exit 0

Note that this is dumping output to an events log at /home/ubuntu/events.log. Also, be sure that this file is executable with sudo chmod +x event_scripts.sh

###Engine The first step here is similar to checking the engine process.

check process pioengine
        matching "Console deploy"
        start program = "/etc/monit/modebug /home/ubuntu/engine_scripts.sh start"
        stop program = "/etc/monit/modebug /home/ubuntu/engine_scripts.sh stop"
        if cpu usage > 95% for 10 cycles then restart

Be sure to adjust your deploy command to your environment (driver-memry, postgres jar path)

#!/bin/bash
 case $1 in
    start)
       cd /home/ubuntu/SimilarProduct/
       nohup /opt/PredictionIO/bin/pio deploy -- --driver-class-path /home/ubuntu/postgresql-9.4.1208.jre6.jar --driver-memory 16G > /home/ubuntu/deploy.log &
       ;;
     stop) 
       deploy_pid=`pgrep -f "Console deploy"`
       kill "$deploy_pid"
       ;;
     *) 
 esac
 exit 0

I ran into an strange case using only this check process block to monitor my engine. I believe the spray REST API used by PredictionIO crashed, causing the engine to fail when queried. The problem was that the process was still running, but requests to the engine were getting errors back.

This sort of crash can be taken care of by using monits check program capability.

check program pioengine-http with path "/etc/monit/bin/check_engine.sh"
        start program = "/etc/monit/modebug /home/ubuntu/engine_scripts.sh start"
        stop program = "/etc/monit/modebug /home/ubuntu/engine_scripts.sh stop"
	if status != 1
	then restart

This block executes the script at /etc/monit/bin/check_engine.sh and reads the exit status. Depending on the exit status, the block can run a restart script. The restart script can be the same as what is used in the process monitor, but we need a check_engine script.

#!/bin/bash
# source: /etc/monit/bin/check_engine.sh
url="http://127.0.0.1:8000/queries.json"
check_string="itemScores"
response=$(curl -H "Content-Type: application/json" -d '{ "user": "1", "num": 0}' $url)

if [[ "$response" =~ "$check_string" ]]
then
  exit 1
else
  exit 0
fi

This script does a curl request and checks the response. In my case, I use a user that I know exists and make sure the json returned has "itemScores". This can vary between use cases but the idea should be similar.

Again, make sure this file is executable.

###Start it All Up Now we can get monit running with

sudo service monit restart

Navigate to http://:2812/ to check out your status page. Screenshot of the status page is in the comments.

###Testing To test, simply try killing your deployed engine or event server and see if monit brings it back up. You can even use the scripts we described above to do this

sudo ./engine_scripts.sh stop

Remember that monit checks only as often as you tell it to, so it may need a few minutes.