DB Max Connections with Auto-Scaling Group

[Jerry Malcolm <te...@malcolms.com>]

I have a TC instance running on an EC2 in an AWS Autoscaling group.  I 
have a database with 500 max connections.  The default EC2 count is 2 
instances in the autoscaling group.  I guess that means that I should 
set the Tomcat resource config for this datasource to be maxTotal = 250, 
so if both instances max out we never exceed the 500 db max.  But sooner 
or later, the auto-scaling group is going to add a third and maybe a 
fourth instance at some crunch time, all still talking to the same 
database.  Now we have a maxTotal combined of 1000 connections talking 
to a database that can handle 500 which seems to be a recipe for 
disaster.  Yet I want to utilize all 500 available connections when I 
have one two EC2 instances running.

Is there something I can do inside TC to rebalance the maxTotal 
connections available to each TC instance as instances are added and 
removed?

Other suggestions?



---------------------------------------------------------------------
To unsubscribe, e-mail: users-unsubscribe@tomcat.apache.org
For additional commands, e-mail: users-help@tomcat.apache.org

Re: DB Max Connections with Auto-Scaling Group

[Christopher Schultz <ch...@christopherschultz.net>]

Jerry,

On 6/21/21 14:54, Jerry Malcolm wrote:
> I have a TC instance running on an EC2 in an AWS Autoscaling group.  I 
> have a database with 500 max connections.  The default EC2 count is 2 
> instances in the autoscaling group.  I guess that means that I should 
> set the Tomcat resource config for this datasource to be maxTotal = 250, 
> so if both instances max out we never exceed the 500 db max.  But sooner 
> or later, the auto-scaling group is going to add a third and maybe a 
> fourth instance at some crunch time, all still talking to the same 
> database.  Now we have a maxTotal combined of 1000 connections talking 
> to a database that can handle 500 which seems to be a recipe for 
> disaster.  Yet I want to utilize all 500 available connections when I 
> have one two EC2 instances running.
> 
> Is there something I can do inside TC to rebalance the maxTotal 
> connections available to each TC instance as instances are added and 
> removed?
> 
> Other suggestions?

You may be surprised at how few connections per node you can get away 
with. At $work, we usually have ~500 users per Tomcat node and they are 
each sharing a connection pool with maxTotal=20. Maybe you need more, 
but you might want to "work forward" from what you actually need on each 
node, rather than "working backward" from your database's limits.

Thanks,
-chris

---------------------------------------------------------------------
To unsubscribe, e-mail: users-unsubscribe@tomcat.apache.org
For additional commands, e-mail: users-help@tomcat.apache.org