On Fri, Mar 27, 2015 at 11:04 PM, Michael Bayer <mike...@zzzcomputing.com> wrote: > Hi there - > > We are evaluating different ways of using the "stick match" and "backup" > options in order to achieve certain behaviors for failover, involving a > Galera cluster. For reference, we're picking and choosing from this blog > post: > http://blog.haproxy.com/2014/01/17/emulating-activepassing-application-clustering-with-haproxy/. > > We're basically looking to have all connections on only one server at all > times; as soon as a server is available, everyone should be kicked off and > blocked from any other servers in the backend. This is because while Galera > is a "multi-master" cluster, we're trying to have the application only use > one node as "master" at a time, at least for the moment. > > it seems like using just the "stick" table alone, as in: > > backend db-vms-galera > option httpchk > stick-table type ip size 1 > stick on dst > timeout server 90m > server rhos-node1 rhel7-1:3306 check inter 1s port 9200 > on-marked-down shutdown-sessions > server rhos-node2 rhel7-2:3306 check inter 1s port 9200 > on-marked-down shutdown-sessions > server rhos-node3 rhel7-3:3306 check inter 1s port 9200 > on-marked-down shutdown-sessions > > is not enough; from my observations running the "show table" socket command > and watching the logs, when a node goes down, its entry still remains in the > stick table for some period of time, and new connections, assuming they > continue to come in fast, have no choice but to skip stick match altogether > (I can provide logs and samples that show this happening). > > So we would then gather that the best configuration is this: > > backend db-vms-galera > option httpchk > stick-table type ip size 1 > stick on dst > timeout server 90m > server rhos-node1 rhel7-1:3306 check inter 1s port 9200 > on-marked-down shutdown-sessions > server rhos-node2 rhel7-2:3306 check inter 1s port 9200 > on-marked-down shutdown-sessions backup > server rhos-node3 rhel7-3:3306 check inter 1s port 9200 > on-marked-down shutdown-sessions backup > > this works a lot better; when I kill node1, all the connections go to node2 > unambiguously. Then, our galera cluster in an effort to bring node1 back up, > puts node2 into "Read only" mode, which bounces all connections to node3. At > this point node1 comes back and then the stick table does not appear to be > of any use; most connections continue to go to node3 and querying the stick > table shows that it's set to node3, however a handful of requests also go > back to node1. So again this is not a pure "active/passive" setup, multiple > nodes get hit at the same time. Was wondering if this behavior could be > clarified and how we can use the stick table as an absolute "gate" for all > requests, where no connections will fall through if a server goes down or > comes back up. > > I had hopes for the unusual setup of just making all three servers a > "backup" server: > > backend db-vms-galera > option httpchk > timeout server 90m > server rhos-node1 rhel7-1:3306 check inter 1s port 9200 > on-marked-down shutdown-sessions backup > server rhos-node2 rhel7-2:3306 check inter 1s port 9200 > on-marked-down shutdown-sessions backup > server rhos-node3 rhel7-3:3306 check inter 1s port 9200 > on-marked-down shutdown-sessions backup > > The idea being, no server is "official", so there's nothing to "fail back" > towards. This sort of seemed to work but still seems like it wants to "fail > back" up from node 3 to node2, to node 1; this approach seems to do the best > job of making sure all connections are all on one server, though; not > perfectly because it doesn't bump off connections still talking to the > being-replaced server, but still fairly well. > > Any insight on the usage of the stick table here would be appreciated! > >
Hi Michael, Can you add the 'nopurge' option on your stick-table statement and tell us if that fixes your issue? Baptiste
