On 31/03/2020 13:49, Aditya Kumar wrote: > Hi Mark, > > Sorry I'm not familiar with what a Selector is? However on one system I've > noticed 28000 such connections. Are these caused by client connections? I'm > not saying the connection originates from a client, but does the type of > socket get create because of client connections?
A selector is what a NIO Connector uses to "select" the socket connections that have data waiting to be processed out of all of the current connections. I'd expect a 1:1 mapping between Selectors and Tomcat Connectors. (It might be 2:1 to n+1:n I'd need to look at the code to be sure but it will be driven by listening sockets on Tomcat, not client connections. It looks like something is creating selectors but not destroying them. That might be Tomcat code but at those numbers I think the application is more likely. I recommend using a profiler to track the current number of Selectors and trying to work out what triggers the creation of a new one. Mark > > On Tue, Mar 31, 2020 at 1:20 PM Mark Thomas <ma...@apache.org> wrote: > >> On 31/03/2020 11:20, Aditya Kumar wrote: >>> Tomcat 9.0.30 on Windows Server 2012 / Java 1.8 >>> >>> I've noticed on a freshly installed version of tomcat 9, upon startup >> there >>> are several connections to and from localhost on different ports >>> >>> For example on my tomcat server there are 4 connections to and from >>> localhost (output from netstat) >>> >>> TCP 0.0.0.0:8080 0.0.0.0:0 LISTENING >> 3972 >>> TCP 127.0.0.1:55618 127.0.0.1:55619 ESTABLISHED >> 3972 >>> TCP 127.0.0.1:55619 127.0.0.1:55618 ESTABLISHED >> 3972 >>> TCP 127.0.0.1:55620 127.0.0.1:55621 ESTABLISHED >> 3972 >>> TCP 127.0.0.1:55621 127.0.0.1:55620 ESTABLISHED >> 3972 >>> TCP [::]:8080 [::]:0 LISTENING >> 3972 >>> >>> These can grow to a large number (several thousand) on a busy system. >> What >>> are these connections used for? What caused them? What thread are they >>> attributed to? >> >> The Java NIO implementation on Windows uses TCP for intra-process >> signalling. It opens a pair of self-connected sockets for every Selector. >> >> Mark >> >> --------------------------------------------------------------------- >> To unsubscribe, e-mail: users-unsubscr...@tomcat.apache.org >> For additional commands, e-mail: users-h...@tomcat.apache.org >> >> > --------------------------------------------------------------------- To unsubscribe, e-mail: users-unsubscr...@tomcat.apache.org For additional commands, e-mail: users-h...@tomcat.apache.org
