[JENKINS-51532] Plot plugin extreme memory leak with matrix jobs

After a day or two, our Jenkins master becomes very unresponsive, taking 100% CPU of all available cores. The response time drops to tens of seconds, or sometimes even minutes to load a single page.

Investigation with VisualVM shows much garbage collection taking place, with the heap nearly maxed out (at 1GB use of 1.25GB max). Looking at a heap snapshot, I discovered that the majority of memory is taken up by String[] objects, containing 5-tuples of Strings (referencing char[] arrays in turn). There are over a million of these small string arrays, each having contents similar to ["35300", "Size", "709", "1526866800302", ""].

Tracing the references of the objects reveals that they are held by the rawPlotData of MatrixPlotPublisher objects. rawPlotData is itself an array; a single sample object in our snapshot contains 106710 string arrays like the one above.

The most likely plot that's causing this is a CSVSeries plot tracking the size of ~7000 generated files (per matrix build). That's still several orders of magnitude less than the number of objects being built internally.

 

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Originally reported by cameron314, imported from: Plot plugin extreme memory leak with matrix jobs

• assignee: vgaidarji
  
• status: Open
  
• priority: Minor
  
• component(s): plot-plugin
  
• label(s): memory-leak, plugins
  
• resolution: Unresolved
  
• votes: 1
  
• watchers: 2
  
• imported: 20260512-210953
  

Raw content of original issue

After a day or two, our Jenkins master becomes very unresponsive, taking 100% CPU of all available cores. The response time drops to tens of seconds, or sometimes even minutes to load a single page.


Investigation with VisualVM shows much garbage collection taking place, with the heap nearly maxed out (at 1GB use of 1.25GB max). Looking at a heap snapshot, I discovered that the majority of memory is taken up by String[] objects, containing 5-tuples of Strings (referencing char[] arrays in turn). There are over a million of these small string arrays, each having contents similar to ["35300", "Size", "709", "1526866800302", ""].


Tracing the references of the objects reveals that they are held by the rawPlotData of MatrixPlotPublisher objects. rawPlotData is itself an array; a single sample object in our snapshot contains 106710 string arrays like the one above.


The most likely plot that's causing this is a CSVSeries plot tracking the size of ~7000 generated files (per matrix build). That's still several orders of magnitude less than the number of objects being built internally.

 

• environment: Jenkins 2.107.2 + Plot plugin 2.04; master running on openjdk-1.8.0/linux.

1 attachment

- [memory histogram of our Jenkins controller.png](https://raw.githubusercontent.com/jenkinsci/attachments-from-jira-issues-last/refs/heads/main/attachments/61966/memory%20histogram%20of%20our%20Jenkins%20controller.png)
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