Memcached：你能用 `lru mode flat` 启动 Memcached 吗？

Question

• I wanted to experiment with using Memcached in the flat mode (as opposed to the default mode segmented )
• Right now all I see in the documentation is a runtime command for switching modes: lru mode flat
• I run most of my stuff in Kube.netes with Helm charts and so if there is a way to specify the mode at the start that would make my life easier

Can you start Memcached with lru mode flat ?

Answer 1

In a nutshell, no

• I checked at all the -h options for memcached
• none of the options set the mode to flat like the runtime command lru mode flat

Workaround: wait for the process to start then execute the runtime command

• wait for the process to come online by polling via te.net somehow (use the quit or stats te.net command.)
• use te.net to execute the command lru mode flat then quit ( printf "lru mode flat\r\nquit\r\n" | te.netlib3-client ${HOSTNAME} ${PORT} )

not as good workaround: turn off the hot and warm caches be similar to flat mode

This idea is from the memcached/doc/protocol.txt section lru mode flat where it says:

If switching from segmented to flat mode, the background thread will pull items from HOT|WARM into COLD queue.

• at the start use command line argument --extended hot_lru_pct=0,warm_lru_pct=0
• the idea is to use the --extended options to set the equivalent of lru tune 0 0 0.20 2.00 (current default is lru tune 20 40 0.20 2.00 i think)

update: i tested this command line option and the above command line errors out because of the values. the pct fields require the value to be >= 1. factor fields require the values to be > 0.0.

• here is the new command line: --extended hot_lru_pct=1,warm_lru_pct=1,hot_max_factor=0.0000000001,warm_max_factor=0.0000000001
• this command does not: turn off the hot/warm caches or change the mode to flat
• this command does: tells memcached to always move hot and warm items to cold