ACL checks

[PranishShresth]

Hi @halfgaar, hope you are well.

I want to understand if ACLs are cached. Is there any impact on performance if it's not cached since it has to look up to ACL tree everytime publish happens.

[halfgaar]

If you want to see the impact of the ACLs on CPU, you can download the load simulator off flashmq.org and test with and without. I'd actually be interested in your test results.

But to answer your question more directly: they are not cached. However, caching may not actually be faster. The tree lookups should be pretty fast. However, the ACL code has not been benchmarked extensively. The reason is that when very high performance is required, it often makes more sense to write a plugin dedicated to the situation.

[PranishShresth]

Thanks. We had written implementation for caching on mosquitto too with custom auth plugin. Some of the enterprise mqtt like hive or emqx seems to provide caching behaviour so was thinking if flashmq did the same.

I will test and benchmark w/o acls.

Also if the custom plugin implements the ACL check ? Is the precedence goes smth like ACL file, then custom plugin method ? Thats what i understood from the man pages.

[halfgaar]

This code should answer your question about precedence of checks.