Sunday, 23 October 2016

How to set up e-mail notifications for Cron


Last week, I found myself setting up some jobs in a Unix environment (Centos 7) for which I wanted to get error email notifications and I ran into some troubles setting up the proper configuration, so I would like to take the chance and share the actions I took in case anyone finds him/herself in the same situation.

Please note that we are going to use Postfix as mail service here!

Initial Crontab setup

This was the setup I was facing, some jobs scheduled that might fail sometimes and one that will always fail as it was badly written:
$crontab -l

30 15 * * * java -jar /path_to_your_jar_app/job.jar
45 13 * * * /path_to_some_script/
45 19 * * * obviously_wrong_command
I wanted to be notified by email of any failure (and as I was using Cron, the expected behavior was to get an email  notification when either process returns a non-zero exit code).

This is an example of an email that should be generated for the above setup:
Message  1:
From cron_user@homepc  Sun Oct 23 19:45:01 2016
From: "(Cron Daemon)" 
Subject: Cron  obviously_wrong_command
Content-Type: text/plain; charset=UTF-8
Auto-Submitted: auto-generated
Precedence: bulk
X-Cron-Env: XDG_SESSION_ID=3289
X-Cron-Env: XDG_RUNTIME_DIR=/run/user/3001
X-Cron-Env: LANG=en_US.UTF-8
X-Cron-Env: MAIL_TO=admin_user_alias
X-Cron-Env: SHELL=/bin/sh
X-Cron-Env: HOME=/home/cron_user
X-Cron-Env: PATH=/usr/bin:/bin
X-Cron-Env: LOGNAME=cron_user
X-Cron-Env: USER=cron_user
Date: Sun, 23 Oct 2016 19:45:01 +0200 (CEST)
Status: RO

/bin/sh: obviously_wrong_command: command not found
Keep reading if you want to get the same setup! 

Sunday, 16 October 2016

Introduction to Spring Cloud Dataflow (I)


This is the first of a series of posts on how to develop data-driven micro-services with Spring Cloud Dataflow (SCDF from now on).  For now, we will see what is the approach proposed by this framework and how to build locally the basic components: Source, Sink and Processor.

Also, if you are familiar with Spring, we will take a look to the already-made components that are available for you to use so you don´t have to reinvent the wheel.

  • What is Spring Cloud DataFlow?
  • Introduction to the API: A simple Producer (Source), Consumer (sink) setup.
  • Prerequisites: Kafka and Zookeeper.
  • Coding a simple Source: HTTP Poller that retrieves live stock prices.
  • Coding a simple Sink that store the results in a file.
  • Writing an additional Batch Source.
  • Summary & Resources.