Redis.new(host, port, 0) gets Redis::ConnectionError

[chumaltd]

Hi, I've got Redis::ConnectionError on Redis.new() connecting to redis DB #0.

issue

I have 2 kubernetes clusters with mostly same configuration.
One cluster fails to connect redis DB #0, while the other has no problem.

• Cluster 1: Rails.new("rds", 6379, 0) gets Redis::ConnectionError
• Cluster 2: Rails.new("rds-dev", 6379, 0) and following commands work well.

I've watched requests with monitor on redis-cli, and got no log line on failure.
I've tested containers restart, and no luck.

workaround

Redis DB no.1 (or others) can be connected, and then switching to #0 works well.
So, I implemented a workaround to my mruby script as bellows:

redis = Rails.new("rds", 6379, 1)
redis.select 0

This works well.

configuration

• mruby-redis bundled with ngx_mruby master build. I've built docker image (ngx_mruby as nginx dynamic module).
  • https://github.com/uniqrn/docker-ruby/tree/2.7/ngx-mruby
  • I checked that md5sum of ngx_http_mruby_module.so on 2 clusters are identical. Actually, 2 docker images between clusters are the same.
• Redis v5.0.6. docker image built from bellows (mostly same as official docker image):
  • https://github.com/uniqrn/docker-redis/tree/v5.0