ConcurrentAccessException on CodeObject.children

Hmm. Perhaps this is the cause, and if it is I believe the call site can be synchronized to avoid making CodeObject/CodeObjectTree thread safe:
https://github.com/applandinc/appmap-java/blob/less-mem_20200817/src/main/java/com/appland/appmap/record/Recorder.java#L110-L113

In short, writeEvent used to be synchronized. It's no longer synchronized due to the fact that we can encounter a lock when calling toString into the client application. It's certainly worth looking into. I'll defer to you @apotterri if you'd like to look into it now or as a follow on item.

Originally posted by @dustinbyrne in https://github.com/applandinc/appmap-java/pull/29#discussion_r475896188

从第 110-113 行所引用的 writeEvent 调用位置开始检查 Recorder.java，然后检查 CodeObject.children 和 CodeObjectTree，以追踪报告中的并发访问路径。复现或以其他方式确认未同步的 writeEvent 是否会导致 ConcurrentAccessException，并为该故障确定经过验证的解决方案。