How to Monitor strace in a Loop and Restart a Process on Error on Raspberry Pi

Learn how to effectively monitor strace for a proprietary app on Raspberry Pi, detect performance issues, and automatically restart the process.
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How to Monitor strace in a Loop and Restart a Process on Error on Raspberry Pi

Raspberry Pi is a towering name in the maker community, with many users opting for proprietary applications that come with their own sets of challenges. One common issue that users face is when an application starts to lag or perform poorly over time without fully crashing. Fortunately, for users on the Raspberry Pi 4 who encounter such issues, there’s a way to monitor the application and mitigate the problem automatically.

The Problem

Imagine you're running a proprietary app on your Raspberry Pi 4, and after some duration of usage, it begins to slow down significantly. The application does not crash, but instead, it becomes sub-optimal, which can be frustrating. A hallmark of this performance issue is logged in the console output of the app: "Time taken to process image --249." This string indicates that the application is exceeding its maximum processing time.

So, how do you monitor these console outputs for this specific string and restart the process when it appears? You want your solution to be efficient and not require writing logs to disk, which could quickly wear out your SD card.

The Solution

The good news is that you can create a simple shell script that uses strace, a powerful diagnostic, debugging, and instructional userspace utility for Linux. The idea is to run the strace command and pipe the output to grep, which will search for the specific error string. When it detects the string, the script will restart the application. Let’s break it down step-by-step.

Step-by-Step Guide

Create the shell script:
Open a terminal on your Raspberry Pi and create a new shell script file. You can name it something like monitor_app.sh.

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Write the monitoring logic:
In the script, include the following lines of code:

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Replace app with the actual command you use to run your application, and adjust X in the sleep command to a duration suitable for your needs.

Make the script executable:
Make sure to give execution permissions to your newly created script.

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Run your script:
Now you can execute your script to monitor the application.

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Explanation of the Script

strace -vF app: This command runs your app while tracing system calls made by it. The -v flag provides verbose output, and -F ensures it follows any child processes.

2>&1: This redirects standard error to standard output, allowing us to catch all messages from the app.

grep -q -m1 -- '--249': This part of the code searches for the string --249. The -q flag tells grep to run quietly (no output), and -m1 limits it to stop searching after finding the first match.

sleep X: You can adjust the time the script waits before restarting the application. This ensures your app gets a moment without immediately being restarted.

Conclusion

By following these simple steps, you can effectively monitor your application's performance on a Raspberry Pi 4 and automatically restart it when it begins to lag, all without writing persistent logs to deter SD card wear. This will allow you to maintain better control over the behavior of your applications and enhance your user experience!

Remember, you might also want to consider reaching out to the developers of the proprietary app to resolve the underlying issues causing the performance dips.

Видео How to Monitor strace in a Loop and Restart a Process on Error on Raspberry Pi канала vlogize
Monitor strace in a loop restart process when error string is matched, linux, bash, strace