On 23/12/2011 02:05, hernan wrote: >> >>>>>> On 12/14/11 5:45 PM, hernan wrote: >>>>>>> I'm using Tomcat 7.0 for developing a new application. A key >>>>>>> component in the application have to run an external not >>>>>>> multithreaded application. >>>>>>> >>>>>>> Since I'm not an experienced user in Tomcat, I wonder which >>>>>>> implementation alternatives do you recommend for running my >>>>>>> external application. I'm trying to avoid launch a new os process >>>>>>> from java since I need the result of that process, so in this way >>>>>>> I've to deal communicating two processes (may be using serializable >>>>>>> objects using sockets). >>>>>> >>>>>> So, is this other program a Java program? Since you said >>>>>> "serializable" you probably are talking about running another Java >>>>>> "program". >>>>>> >>>>>> What makes this "external" "program" non-multithreaded? Is it actually >>>>>> not threadsafe? >>>>>> >>>>>> If you can't run it in the same process as Tomcat, then you'll have to >>>>>> either use Runtime.exec or some type of wrapper around it -- or have >>>>>> that process running completely separately (as a daemon) and connect >>>>>> to it via sockets. Anything else requires native code, which you >>>>>> definitely don't want. >>>>> >>>>> >>>>> My external application is a java application that uses java wrapper >>>> (using >>>>> JNI) for GLPK (written in ANSI C) (http://www.gnu.org/s/glpk/), and >>>> GLPK is >>>>> not threadsafe. Yes, I will consider those alternatives, executing a >> new >>>>> process when I receive the request (Runtime.exec) and a separated >> deamon >>>>> receiving requests launching those processes. >>>> >>>> Can you not import the application Jars and just interact with them >>>> directly then? Why do you have to interact with it via system process? >>>> >>> >>> If I do that, due to glpk is not threadsafe, a call to a method can crash >>> tomcat. >> >> I don't know what glpk does, can you explain? > > > glpk is a gnu library to solving some kind of mathematical problems > http://www.gnu.org/software/glpk/ > > You can use the library in c, and there exist wrappers for java, python and > other programming languages > > > >> >> I think you may be over thinking the thread safety issue. >> >> If multiple threads can't access the instances of the thing, thread >> safety is not an issue. >> >> If the entire code block was instantiated inside a Servlet doGet >> method with no external exposure or external scope, there is no >> problem. >> >> Do you know why it is not thread safe? > > I know about some problems related to process memory > allocation/deallocation because I've experienced them. The documentation > says that is not thread safe.
Yes, but thread-safety is a very broad topic. If the code does something weird like use a mmap'd file with a hard coded path, then starting up separate processes won't help either. > Why do you think that I'm over thinking thread safety issue? In Java for example, code that is not inherently thread-safe can be used safely in a multithreaded environment. The SimpleDateFormat class is a good example of this. Because it may be possible to use the code safely, if you take some precautions. Understanding exactly why it is deemed "not thread safe" would allow you do that. Warning that the code is not thread-safe usually just means that the author is telling you not to share use of that code *between* threads. If the code is utilised entirely within the scope of a single thread there is (usually) no issue. YMMV. p -- [key:62590808]
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