January 2019 - Coding Bot

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Monday, 14 January 2019

Log4j SMTP Appender Using System Environment Variables

Hey friends!

Earlier last week, I was stuck for a short while in a what should've been an easy task, but took my more than expected working hours to completely solve that: SMTP appender for Log4j.

So as we all know, SMTP or Simple Mail Transfer Protocol is used to send emails from your java program, generally when a particular level of exception occurs in your code. Log4j is a well known Java logging utility, but this particular appender wasn't discussed as about much as I expected earlier. 


LOG4J SMTP APPENDER

Earlier I was using log4j2.yml file for logging but due to some versioning reasons, it wasn't picking up the Log4j keywords properly from the version of Log4j that I added. So eventually I had to shift to using the XML version.



Thursday, 10 January 2019

Fixed — ElasticSearch CrateDB Logstash — ClusterBlockException Forbidden Index Read-Only

Hey friends,

Ever since I started working with ElasticSearch, CrateDB and Logstash, I have faced plenty of issues and exceptions that maybe had a clear reason and fix but were not documented well anywhere. I had to research through tons and tons of documentation and StackOverFlow pages to atleast get some hints as to what might be causing the issue and how to fix it. 


It was then I decided that I will document such problems for easy access and quick solution for others. One such exception that I got multiple times was:



09:46:07.741 [main] ERROR
 io.crate.shade.org.postgresql.util.PSQLException: ERROR: ClusterBlockException: blocked by: [FORBIDDEN/12/index read-only / allow delete (api)];
    at io.crate.shade.org.postgresql.core.v3.QueryExecutorImpl.receiveErrorResponse(QueryExecutorImpl.java:2458)
    at io.crate.shade.org.postgresql.core.v3.QueryExecutorImpl.processResults(QueryExecutorImpl.java:2158)
    at io.crate.shade.org.postgresql.core.v3.QueryExecutorImpl.execute(QueryExecutorImpl.java:291)


This was due to:
[WARN ][o.e.c.r.a.DiskThresholdMonitor] [Piz Roseg] high disk watermark [90%] exceeded on [Piz Roseg][/crate/
[WARN ][o.e.c.r.a.DiskThresholdMonitor] [Piz Roseg] high disk watermark [90%] exceeded on [Piz Roseg][/crate/
[WARN ][o.e.c.r.a.DiskThresholdMonitor] [Piz Roseg] rerouting shards: [high disk watermark exceeded on one or more nodes]
[WARN ][o.e.c.r.a.DiskThresholdMonitor] [Piz Roseg] high disk watermark [90%] exceeded on [Piz Roseg][/crate/
[WARN ][o.e.c.r.a.DiskThresholdMonitor] [Piz Roseg] high disk watermark [90%] exceeded on [Piz Roseg][/crate/
[INFO ][o.e.c.r.a.DiskThresholdMonitor] [Piz Roseg] rerouting shards: [high disk watermark exceeded on one or more nodes]
[WARN ][o.e.c.r.a.DiskThresholdMonitor] [Piz Roseg] high disk watermark [90%] exceeded on [Piz Roseg][/crate/
[WARN ][o.e.c.r.a.DiskThresholdMonitor] [Piz Roseg] high disk watermark [90%] exceeded on [Piz Roseg][/crate/
[INFO ][o.e.c.r.a.DiskThresholdMonitor] [Piz Roseg] rerouting shards: [high disk watermark exceeded on one or more nodes]

The Cause:

This particular exception is caused by a very simple problem - Disk Space. You are definitely running out of disk space on the disk where ElasticSearch/Logstash/CrateDB is installed. 



Wednesday, 9 January 2019

Add/Edit Startup Applications in Ubuntu Linux

Hey friends,

I recently switched over to Ubuntu and I must say it feels a better and crunchier experience as compared to my alternate previous OS, the Windows. That said, switching over to Ubuntu brought its own set of problems and Ububtu 18.10 (Bionic Beaver) is not as stable as 17.04 was for me. 

So today I am going to share a very easy way to edit the startup applications on your Ubuntu machine. This approach should work for previous versions as well.

Now just like Windows, there are some startup applications in Linux which can be added/deleted as per your own convenience. Without further ado, let me show you how:

  • The most easy way is to first press Alt + F2 keys together.

  • Then write gnome-session-properties and press Enter. You will be presented with the following screen.