On 08/01/2017 22:04, Christopher Zinn wrote:
> Hello all,
> This is my first time posting to a mailing list so hopefully I'm doing
> this correctly.
Welcome to the Apache Tomcat community.
As problem reports go, this is pretty much perfect. And it includes a
simple test case. Many, many thanks.
> We are running into an issue where we have multiple copies of the same
> WAR loaded on a Tomcat instance each with its own context.xml.
> The initial problem I was trying to diagnose was A JNDI lookup to a
> Connection Pool in one of the WARs was returning the connection pool of one
> of the others.
> The problem only happens when the JNDI lookup is performed within a
> parallelStream().
>
> I was able to produce a very simple WAR with a single servlet and a
> context XML to reproduce the problem I'm having (See below).
>
> If you run the servlet from the first application, it works correctly.
> You will see that it only ever looks up 'Test 1'.
> When I run the servlet from the second application it will only return Test
> 1 in the first part (stream()) but a mix of 'Test 1' and 'Test 2' in the
> parallelStream() part.
>
> Thanks in advance for any advice or comments to our issue.
My initial comments are that this is rather odd. The correct JNDI
context is looked up via the thread context class loader. The class
loader from one web application should not be visible to another. I
wonder if when parallelStream() is first called some form of shared
thread-pool is set up that retains a reference to the current thread
context class loader?
A quick look at the JRE source code suggests this is handled correctly
but the code isn't the easiest to trace through. I'll set up the
provided test case and take a closer look. That may take an hour or two.
Mark
>
> -----------------------------------------------
> My Environment: (The problem happens to us on our CENTOS Linux
> environments as well)
> Server version: Apache Tomcat/8.5.9
> Server built: Dec 5 2016 20:18:12 UTC
> Server number: 8.5.9.0
> OS Name: Windows 10
> OS Version: 10.0
> Architecture: amd64
> JVM Version: 1.8.0_111-b14
> JVM Vendor: Oracle Corporation
>
> Runtime.getRuntime().availableProcessors() returns 12 on my machine.
> CPU: Intel i7-5820K
>
>
> My Test Servlet:
> @WebServlet(urlPatterns = "/test")
> public final class MyServlet extends HttpServlet
> {
> private static List<Integer> someNumbers = generateNonsense();
>
> @Override
> protected void doGet(HttpServletRequest request, HttpServletResponse
> response) throws ServletException, IOException
> {
> StringBuilder answerBuilder = new StringBuilder();
>
> // This should be okay.
> someNumbers.stream().forEach( number ->
> {
> answerBuilder.append(".stream() Looked up ")
> .append(lookupEnvironmentValue())
> .append("<br/>");
> });
>
> // This is most likely bad
> someNumbers.parallelStream().forEach( number ->
> {
> synchronized (MyServlet.class)
> {
> answerBuilder.append(".parallelStream() Looked up ")
> .append(lookupEnvironmentValue())
> .append("<br/>");
> }
> });
>
> response.setContentType("text/html");
> response.getWriter().write(answerBuilder.toString());
> }
>
> private String lookupEnvironmentValue()
> {
> try
> {
> Context context = new InitialContext();
> return (String) context.lookup("java:comp/env/testName");
> }
> catch(NamingException e)
> {
> e.printStackTrace();
> return e.getMessage();
> }
> }
>
> private static List<Integer> generateNonsense()
> {
> List<Integer> nonsense = new ArrayList<>();
> for(int n=0; n<1000; n++)
> nonsense.add(n);
>
> return nonsense;
> }
> }
>
>
> My test context.xml
> <Context path="/test1">
> <Environment name="testName" value="Test 1" type="java.lang.String"
> override="false"/>
> </Context>
>
>
> Preparing Tomcat:
> Step 1: Download the core.zip of Tomcat 8, 8.5 or 9
> Step 2: create a apache-tomcat-8.5.9/conf/Catalina/localhost directory
> Step 3: create two files in this directory with the contents of my
> context.xml: test1.xml and test2.xml and change the value and path in the
> second one to '2'
> Step 4: Create a WAR with just the sample servlet I have here. and then
> drop them in apache-tomcat-8.5.9/webapps directory / call them test1.war
> and test2.war
> Step 5: Go into apache-tomcat-8.5.9/bin and catalina start to start it up.
>
> The urls to test for me are:
> http://localhost:8080/test1/test
> http://localhost:8080/test2/test
>
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