https://bugs.koha-community.org/bugzilla3/show_bug.cgi?id=27078 --- Comment #6 from Christian McDonald <rcmcdonald91@gmail.com> --- Well Koha doesn't really know it is part of a cluster, does it? It still talks to a single MariaDB instance (at localhost, just like a standalone instance), and the same can be applied to ES (again a single localhost:9200 ES node could be configured on each, just like a standalone deployment). Apache isn't aware it's part of a cluster. Plack/Starman aren't aware either. Really Koha is still "standalone" from the perspective of Koha itself, it just so happens that the DB, file-system and index are distributed. So what I mean about taking nodes offline is that, when all nodes are online and all services running, everything is very performant. As I would expect. However, when one node goes offline, the Koha application itself becomes very slow to respond to page loads...lots of spinning browser tabs waiting for a response...but it will eventually respond. My question is, why? Again, Koha as an application isn't aware that it is part of a cluster, it doesn't know that it's database, file system and index are replicated under-the-hood. Here's what's weird. Like I said, when all nodes and their services are online, everything is fine. However, say if I "systemctl stop" Maria, elastic, Apache, and memcached on a single node (say on Node A), everything still is fine when connecting to either of the remaining nodes (Nodes B and C). However, if I then power down Node A (remember, all it's koha-related services had been stopped) or pull node A's network connection, node B and C become very slow to serve page requests. Again, this isn't because of some performance degradation of Maria (3 nodes can withstand 1 node offline), Elastic (again, one node offline is okay). Also, when Apache is nuked, HAProxy immediately stops sending clients to that node. So in that regard, once Apache is hosed, that node isn't even going to get client requests. What can I do to monitor performance, or poke into Plack/Starman? The reason why I have a hunce Plack/Starman are involved here is because when I disable Plack on all nodes, the loss of a single node doesn't impact the performance of the remaining nodes... granted with Plack disabled they are all noticably slower, which is expected -- You are receiving this mail because: You are watching all bug changes. You are the assignee for the bug.