Fix memory leak. (backport #828)

[mergify]

This is an automatic backport of pull request #828 done by Mergify.

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[fujitatomoya]

CC: @aprotyas

[cottsay]

Thanks for backporting.

[aprotyas]

CI (build/test: --packages-above-and-dependencies rclpy)

• Linux
• Linux-aarch64
• macOS
• Windows

[aprotyas]

Apologies for the botched CI, I ran it on Rolling and not Galactic. 🤦

CI (build: --packages-above-and-dependencies rclpy, test: --packages-above rclpy)

• Linux
• Linux-aarch64
• macOS
• Windows

[clalancette]

I think we are just waiting on the Galactic sync to go out, then we can merge this. Assigning to @cottsay to merge once Galactic sync is done.

[aditya2592]

Hi, just checking if this can be merged? We have a ROS service that needs to run at a high Hz and the memory fills up pretty fast on the client process. I wanted to check if this fixes it

[aditya2592]

After building from source with this PR merged, the memory leak still exists on Galactic. Its not present on a build from Master. Are there are any other PRs that need to be merged for this to work?

[fujitatomoya]

@aditya2592

the memory leak still exists on Galactic.

do you mean that we still have the memory leak with using https://github.com/ros2/ros2/tree/galactic source build?

[aprotyas]

After building from source with this PR merged, the memory leak still exists on Galactic. Its not present on a build from Master. Are there are any other PRs that need to be merged for this to work?

@aditya2592 can you share a small example to check this?

I recorded a simple client's memory usage with this demo against rclpy built from source (galactic branch) in the latest ros:galactic Docker image and the trace in blue isn't indicative of a memory leak. Thoughts? For reference, here's a visual of the memory leak diagnosed in #822.

[aditya2592]

@aprotyas I am trying to recreate what I am seeing as an example, but basically the leak happens now when multiple clients are requesting the same service and the depth in QOS is > 1. The memory leak is not there when the depth in client is 1. So this makes me think that its related to multiple clients requesting a given service and not necessarily the issue that was fixed in this PR

[aprotyas]

@aprotyas I am trying to recreate what I am seeing as an example, but basically the leak happens now when multiple clients are requesting the same service and the depth in QOS is > 1. The memory leak is not there when the depth in client is 1. So this makes me think that its related to multiple clients requesting a given service and not necessarily the issue that was fixed in this PR

Do you mind sharing a simple example to reproduce?