We Crunched 1 Billion Java Logged Errors – Here’s What Causes 97% of Them

 ● 07th Jul 2021

5 min read

97% of Logged Errors are Caused by 10 Unique Errors

It’s 2021 and one thing hasn’t changed in 30 years. DevOps teams still rely on log files to troubleshoot application issues. We trust log files implicitly because we think the truth is hidden within them. If you just grep hard enough, or write the perfect regex query, the answer will magically present itself in front of you.

Tools like Splunk, ELK and Sumologic have made it faster to search logs but all these tools suffer from one thing – operational noise. Operational noise is the silent killer of IT and your business today. It’s the reason why application issues go undetected and take days to resolve.

Log Reality

Here’s a dose of reality, you will only log what you think will break an application, and you’re constrained by how much you can log without incurring unnecessary overhead on your application. This is why debugging through logging doesn’t work in production and why most application issues go undetected.

Let’s assume you do manage to find all the relevant log events, that’s not the end of the story. The data you need usually isn’t there, and leaves you adding additional logging statements, creating a new build, testing, deploying and hoping the error happens again. Ouch.

Time for Some Analysis

At OverOps we capture and analyze every error or exception that is thrown by Java applications in production. This is what we found from analyzing over 1,000 applications monitored by OverOps. High-level aggregate findings:

  • Avg. Java application will throw 9.2 million errors/month
  • Avg. Java application generates about 2.7TB of storage/month
  • Avg. Java application contains 53 unique errors/month
  • Top 10 Java Errors by Frequency were
    • NullPointerException
    • NumberFormatException
    • IllegalArgumentException
    • RuntimeException
    • IllegalStateException
    • NoSuchMethodException
    • ClassCastException
    • Exception
    • ParseException
    • InvocationTargetException

So there you have it, the  NullPointerException is to blame for all that’s broken in log files. Here are some numbers from a random selection of enterprise production application over the past 30 days:

  • 25 JVMs
  • 29,965,285 errors
  • ~8.7TB of storage
  • 353 unique errors
  • Top Java errors by frequency were:
    • NumberFormatException
    • NoSuchMethodException
    • Custom Exception
    • StringIndexOutOfBoundsException
    • IndexOutOfBoundsException
    • IllegalArgumentException
    • IllegalStateException
    • RuntimeException
    • Custom Exception
    • Custom Exception

Time for Trouble (shooting)

If you work in DevOps and have been asked to troubleshoot the above application, which generates a million errors a day, what do you do? Let’s zoom in on when the application had an issue right? Let’s pick a 15 minute period. However, that’s still 10,416 errors you’ll be looking at for those 15 minutes.

You now see this problem called operational noise. This is why humans struggle to detect and troubleshoot applications and it’s not going to get any easier.

What if we Just Fixed 10 Errors?

Let’s say we fixed 10 errors in the above application. What percent reduction do you think these 10 errors would have on the error count, storage and operational noise that this application generates every month? 1%, 5%, 10%, 25%, 50%?

How about 97.3%. Yes, you read that. Fixing just 10 errors in this application would reduce the error count, storage and operational noise by 97.3%.

The top 10 errors in this application by frequency are responsible for 29,170,210 errors out of the total 29,965,285 errors thrown over the past 30 days.

Take the Junk Out of Your App

The vast majority of application log files contain duplicate info which you’re paying to manage every single day in your IT environment. You pay for:

  • Disk storage to host log files on servers
  • Log management software licenses to parse, transmit, index and store this data over your network
  • Servers to run your log management software
  • Humans to analyze and manage this operational noise

The easiest way to solve operational noise is to fix application errors versus ignore them. Not only will this dramatically improve the operational insight of your teams, you’ll help them detect more issues and troubleshoot much faster because they’ll actually see the things that hurt your applications and business.

The Solution

If you want to identify and fix the top 10 errors in your application, download OverOps for free,  install it on a few production JVMs, wait a few hours, sort the errors captured by frequency and in one-click OverOps will show you the exact source code, object, and variable values that caused each of them. In a few hours your developers will be able to make the fixes.

The next time you do a code deployment in production, OverOps will instantly notify you of new errors which were introduced and you can repeat this process.

Here are two ways we use OverOps at OverOps to detect new errors in our SaaS platform:

  1. Slack Real-time Notifications inform our team of every new error introduced in production as soon as it’s thrown, and a one-click link to the exact root cause (source code, objects & variable values that caused the error).
  2. Email Deployment Digest Report showing the top 5 new errors introduced with direct links to the exact root cause.

Final Thoughts

We see time and time again that the top few logged errors in production are pulling away most of the time and logging resources. The damage these top few events cause, each happening millions of times, is disproportionate to the time and effort it takes to solve them.

Troubleshooting Apache Spark Applications with OverOps OverOps’ ability to detect precisely why something broke and to see variable state is invaluable in a distributed compute environment.
Troubleshooting Apache Spark Applications with OverOps

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