Joerg Hoh created SLING-11654:
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Summary: Create repository access metrics
Key: SLING-11654
URL: https://issues.apache.org/jira/browse/SLING-11654
Project: Sling
Issue Type: Improvement
Components: JCR
Affects Versions: JCR Resource 3.2.2
Reporter: Joerg Hoh
In recent rounds of performance analysis and improvement in AEM I found that
large improvements in rendering time can be achieved the easiest by removing
access to the Sling/Oak repository.
Prominent ways for repository access are these
* ResourecResolver.getResource(path)
* Resource.getValueMap()
* (and others)
This is mostly interesting in the context of JCR/Oak, as there the amount of
code to run behind these calls is much higher than in the case of
SyntheticResources or Servlets, where I never saw performance problems.
My goal:
* Look at a single request and see in what situations it does a repository
access. Having a suitable amount of the stack helps to map it back to a
specific point in the rendering process. And from there it can be assessed if
any improvements are possible.
* Unlike a profiler which calculates wall-time (CPU time spent in processing)
I am interested in the pure number of invocations of the above operations. This
allows to perform the analysis on a developer machine by performing single
requests.
* In that situation the performance overhead is a no problem. It's just that
if this feature is not used there should not be a negative impact.
I am not aware of any tooling in Sling which allows us to get that information;
while I could probably get the raw numbers from Oak, I cannot get any context
from there.
I thought about the use of profiler, but these often sample the stacks at a
defined frequency (often in the range of miliseconds), which makes them miss
repository access, as these normally are done in a sub-milisecond range in case
of a TarMK repository. Also I already know what takes long (the repository
access itself), so the wall-time information does not help much.
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