Make history cache generation quicker

[ChristopheBordieu]

Hi,

Generating history cache for some of our Git repositories takes very long time...
Using OpenGrok 1.3.16 / Openjdk 11.0.7 / Tomcat 9.0.36 on our docker image.

What are the various way OpenGrok could offer to speed up this runtime?

• finetune hard resources (memory size, # of CPUs)? how?
• run history cache in background while file indexinf is run?
• ...

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My branch containing that work was really trying to massively speed up history, since FreeBSD history takes f-o-r-e-v-e-r to manage by OpenGrok since OpenGrok's data model copies commit contents (dates + commit message) to every affected file separately — and FreeBSD commits and merges very often touch thousands of files. The branch is still a work-in-progress and idle for a year, but maybe I can extract the octopus handling from it, which would solve your issue too.

Originally posted by @idodeclare in #3166 (comment)

[vladak]

Do you mean initial history cache generation or incremental ?

[ChristopheBordieu]

Initial history cache. When done, when reindexing, it is ok.