> On 2/1/18 6:08 PM, Pawel Veselov wrote: >> On Thu, Feb 1, 2018 at 1:02 PM, Mark Thomas <ma...@apache.org> >> wrote: >>> On 01/02/18 20:57, Pawel Veselov wrote: >>>> Hello. >>>> >>>> It looks like in tomcat 8 (looking at master's HEAD), the >>>> minIdle support is broken. According to docs, minIdle supposed >>>> to do : "The minimum number of established connections that >>>> should be kept in the pool at all times. The connection pool >>>> can shrink below this number if validation queries fail." >>>> >>>> I see that pool cleaner thread checks if the minIdle is *less* >>>> than pool size, and only then invokes checkIdle(). checkIdle() >>>> then will remove(!) connections from idle pool until the value >>>> drops down to minIdle. But I don't see any code that will add >>>> connections when minIdle is not met, and the documentation >>>> suggests that that's the intent. >>>> >>>> Am I misunderstanding something? Is there a way to keep a level >>>> of connections in the pool? I don't want to have initialSize >>>> control that, as I need to at 0, to prevent failures during >>>> pool initialization... >>> But that is what initial size is for. >> >> Indisputably so. However, that would be the only other way to >> achieve this, as long as the database connection don't die. > > What is the problem with failures during pool initialization?
ConnectionPool.init() attempts to borrow initialSize worth of connections. Imagine your database server is having problems at this time. This will make init() fail, and the pool creation fail, and your webapp is dead in the water after that, it's unlikely that there are mechanisms to attempt to recreate the connection pool. This complicates automatic recovery. An existing pool can recover easily, once the database is back online after a failure, the connections will be vended normally. > If you > don't want the pool to make initialSize connections when it starts, > when DO you want the pool to create those connections? During the > first "cleaning"? I don't have strong expectations on exactly when the pool is to be inflated. minIdle suggests that it should happen at some point, may be that can be "cleaning", though this thread should probably then be renamed as "maintenance". If not inflated in time, then any requested connection will populate the pool, that's already what ends up going on in my case. In all cases, I think that either minIdle should be reimplemented, or at least the documentation should be changed from saying "The minimum number of established connections that should be kept in the pool at all times" to "Minimum idle connections that will remain in the pool after cleaning", with a note that idle connections are not created by the pool itself to fulfill that amount. The reason prefer the pool to auto-saturate, is that so sudden demand for high amount of database connections doesn't require a lot of new connections to be established, as that's the slowest part of the process. Thank you, Pawel. --------------------------------------------------------------------- To unsubscribe, e-mail: users-unsubscr...@tomcat.apache.org For additional commands, e-mail: users-h...@tomcat.apache.org
