On 15/06/2016 12:03, Amit Pande wrote: > > > On 15/06/16 4:06 pm, "Mark Thomas" <ma...@apache.org> wrote: > >> On 15/06/2016 11:00, Amit Pande wrote: >>> We develop multiple web application which happen to share the same >>> stack (Spring, Hibernate,etc). >>> >>> Thinking of sharing these third party libraries instead of duplicating >>> in each web app war. >> >> Why? > To avoid jar duplication and improve memory footprint
Is memory footprint really that much of an issue? >>> IIUC, putting those in Tomcat (8)'s lib folder might cause issues since >>> the classes in there are loaded by a common loader. >> >> What issues? > Since loaded by a common class loader , the jars put in here will be > available to tomcat internal classes,even if not required , also need be > to thread safe. What is the harm in these classes being visible to Tomcat? I fail to see what thread-safety has to do with this. You do need to think about memory leaks though. >>> And sharing such libraries using the shared loader seems a better >>> approach. >> >> Why? > As loaded by shared loader which seems to be meant for sharing > libraries across web apps ŠI guess here also the thread safely concern > exists , need to validate though. As above, thread-safety is not a relevant concern. >>> Is my understanding correct ? >> >> No idea. You have not explained your understanding yet. > Hope it is explained now. It has. And your understanding, particularly around thread safety is not correct. >>> Does it have any further issues ? >> >> Further issues compared to what? > It was a general awareness question to get to know if people ran into > some issues after putting jars in tomcat¹s shared loader's path. It increases the risk of issues due to: - memory leaks since few libraries are written with a multi-class loader environment in mind - upgrades are harder since you have to take Tomcat down to upgrade any shared library - dependency management is harder since all webapps have to use the same set of dependencies >>> That said, I don't see much documentation around using shared loader. >>> Any documentation/help in this regard is highly appreciated. >> >> There isn't much call for the shared loader. You need to go back to the >> 5.5.x documentation for a diagram that includes the shared loader. >> >> http://tomcat.apache.org/tomcat-5.5-doc/class-loader-howto.html > > Thanks for this. In absence of clear documentation in recent release, I > was doubtful if it was deprecated. Not deprecated. Just rarely useful so disabled by default. Generally, it causes more problems than it solves so unless you are really under memory pressure it isn't worth the trouble. Mark --------------------------------------------------------------------- To unsubscribe, e-mail: users-unsubscr...@tomcat.apache.org For additional commands, e-mail: users-h...@tomcat.apache.org
