i have never had my production site crash in this way and i have been running the no logging plugin on it, so that's why i made the suggestion.

Sorry guys , for replying late.( now a days I am not working on Elgg)

On my server , I am not runnig any cronjob. and I am using MariaDB, on centos7. 

And Yes I am using PHP7(You may not recommend it though)

If you are using MariaDB, add the line

max_delayed_threads = 0

to the [mysqld] section in my.cnf configuration file of the database server (on my server /etc.my.cnf).

You can also check if the archive engine of MariaDB gets even loaded (after an upgrade of MariaDB this engine wasn't loaded anymore on my server). I had to uncomment the line

plugin-load-add=archive=ha_archive.so

in the [server] section in /etc/my.cnf.d/default_plugins.cnf.

The archive engine is used by the system_log table. So, it's needed in any case. The problem is that the archive engine of MariaDB can't handle delayed queries and therefore setting max_delayed_threads to 0 is also necessary (at least for now - I think Elgg 2.3 won't use delayed queries for writing to the system_log table anymore).

I don't think that the problem I had with the private_settings table will happen for anyone else. I could fix it in the meantime. It was caused by a zero-size *.TMM file for the private_settings table. I don't know when and how this file got created. It caused the table to crash whenever OPTIMIZE TABLE was executed on the private_settings table by garbagecollector. Deleting the TMM file solved this issue.

This is worthy of a longer response. For now: Overall I agree UX around plugin discovery is seriously lacking and deserves more attention. Disagree that issue/feature mgmt should take place on community; stronger integration with GitHub, Packagist, and similar seem like the future.

ok with GIT for issue management.

two  more suggestion just stuck in my brain.

(8) currently few plugins are permanently siting in plugin home page. under the heading top rated. and top downloaded.   Even some of them are out dated now.   that dents Elggs reputation.  So atlist top 50 plugins need  to be reviewed.   and most importantly.  Show top rated or downloaded in last year. instead of lifetime.  that will encourage some developer to be on plugin homepage.

(9) comments per plugin release is not user friendly.  old style of comments was better. ( you can add filter for comments ) rather then totally different page.

currently few plugins are permanently siting in plugin home page. under the heading top rated. and top downloaded.   Even some of them are out dated now.   that dents Elggs reputation.  So atlist top 50 plugins need  to be reviewed.   and most importantly.  Show top rated or downloaded in last year. instead of lifetime.  that will encourage some developer to be on plugin homepage.

+1

comments per plugin release is not user friendly.  old style of comments was better. ( you can add filter for comments ) rather then totally different page.

I don't agree (i'm developer). It helps me to find out what version the user is using when reporting a bug (hoping the comment is on the version they use)