en memory increase

[yoomee1313]

Describe the bug
There's an issue reported that EN memory is keep increasing.

How to reproduce
Call debug_traceBlockByNumberRange for the latest 10 blocks once every 10 seconds.
But it seems that debug_traceBlockByNumber also can reproduce the problem.

Expected memory usage
The memory usage should be stable. The binary version of the next screenshot is kaia-v1.0.2 + #73, #74.

[calebcall]

We are also seeing this same memory growth issue. It'll consume up to the system limit and then OOM. We originally had our node on a 64Gb system and saw OOM errors, moved to a 128Gb system and the errors continued (just longer between)

[yoomee1313]

Yes, we confirmed that there was a memory leak, and by applying the #73, #74, we can see that the memory is stabilized(expected memory usage). �Debug trace API is called periodically, isn't it? It might be good to try applying the above changes.

[yoomee1313]

You can use https://github.com/kaiachain/kaia/tree/oom-fix branch. Or if you want a binary, please let us know.