performance

Three Memory Leak Patterns

Cassia Scheffer

— 1 min read

Normal Memory Usage

In a typical application, memory consumption should increase when the application boots and then stabilize. This pattern will repeat every time the application is deployed.

Memory
  ^
  |
  |        ███████████████████████        ████████████████████
  |  █████████████████████████████  ██████████████████████████
  |  █████████████████████████████████████████████████████████ > Time
    Boot         Stable Runtime      Deploy        Stable Runtime

Gradual Leak

In an application with a gradual memory leak, the memory usage will increase sporadically. This is usually due to specific code paths that are only executed sporadically, causing memory leaks. This pattern looks like a very gradual increase in memory over time that never plateaus and gets reset every time an application is deployed. This is a challenging memory leak to identify because frequent deploys can mask it.

Memory
  ^
  |
  |                        ███████████                 ████████████
  |                      █████████████              ███████████████
  |                 ██████████████████           ██████████████████
  |     ██████████████████████████████  ███████████████████████████
  |     ██████████████████████████████  ███████████████████████████
  | ███████████████████████████████████████████████████████████████ > Time
    Boot    Gradual Memory Growth      Deploy    Gradual Memory Growth

Spiky Memory Leak

A memory leak that causes a dramatic spike in memory will often cause the application to churn, meaning it boots up, memory increases continually, it hits the limit, it runs out of memory, and reboots. This happens over and over and over. These are very easy to identify memory leaks, although the source may be challenging to locate.

Memory
  ^
  |
  |            ████              ████
  |         ███████           ███████  
  |      ██████████        ██████████
  |   █████████████     █████████████
  |████████████████  ████████████████
  |██████████████████████████████████████████████ > Time
    Boot |Rapid Growth | Repeat
                     CRASH!

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