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</o:shapelayout></xml><![endif]--></head><body lang=EN-CA link="#0563C1" vlink="#954F72" style='word-wrap:break-word'><div class=WordSection1><p class=MsoNormal>From <a href="https://openjdk.org/jeps/428">https://openjdk.org/jeps/428</a> and <a href="https://download.java.net/java/early_access/loom/docs/api/jdk.incubator.concurrent/jdk/incubator/concurrent/StructuredTaskScope.html">https://download.java.net/java/early_access/loom/docs/api/jdk.incubator.concurrent/jdk/incubator/concurrent/StructuredTaskScope.html</a><o:p></o:p></p><p class=MsoNormal><o:p> </o:p></p><p class=MsoNormal style='margin-left:36.0pt'><span class=modifiers>public</span> <span class=return-type>void</span> <span class=element-name>close</span>()<o:p></o:p></p><p class=MsoNormal style='margin-left:36.0pt'>Closes this task scope. <o:p></o:p></p><p style='margin-left:36.0pt'>This method first shuts down the task scope (as if by invoking the <a href="https://download.java.net/java/early_access/loom/docs/api/jdk.incubator.concurrent/jdk/incubator/concurrent/StructuredTaskScope.html#shutdown()"><code><span style='font-size:10.0pt;color:blue'>shutdown</span></code></a> method). <u>It then waits for the threads executing any unfinished tasks to finish.</u> If interrupted then this method <u>will continue to wait for the threads to finish</u> before completing with the interrupt status set. <o:p></o:p></p><p style='margin-left:36.0pt'>This method may only be invoked by the task scope owner. <o:p></o:p></p><p style='margin-left:36.0pt'>A StructuredTaskScope is intended to be used in a <em><span style='font-family:"Calibri",sans-serif'>structured manner</span></em>. If this method is called to close a task scope before nested task scopes are closed then it closes the underlying construct of each nested task scope (in the reverse order that they were created in), closes this task scope, and then throws <a href="https://download.java.net/java/early_access/loom/docs/api/jdk.incubator.concurrent/jdk/incubator/concurrent/StructureViolationException.html" title="class in jdk.incubator.concurrent"><code><span style='font-size:10.0pt;color:blue'>StructureViolationException</span></code></a>. Similarly, if called to close a task scope that <em><span style='font-family:"Calibri",sans-serif'>encloses</span></em> <a href="https://download.java.net/java/early_access/loom/docs/api/jdk.incubator.concurrent/jdk/incubator/concurrent/ExtentLocal.Carrier.html#run(java.lang.Runnable)">operations</a> with extent-local bindings then it also throws <code><span style='font-size:10.0pt'>StructureViolationException</span></code> after closing the task scope.<o:p></o:p></p><p class=MsoNormal>I am unclear on “It then waits for the threads executing any unfinished tasks to finish.”<o:p></o:p></p><p class=MsoNormal><o:p> </o:p></p><p class=MsoNormal><span style='font-size:10.0pt;font-family:"Courier New";mso-fareast-language:EN-CA'> Instant deadline = ...<o:p></o:p></span></p><p class=MsoNormal><span style='font-size:10.0pt;font-family:"Courier New";mso-fareast-language:EN-CA'><o:p> </o:p></span></p><p class=MsoNormal><span style='font-size:10.0pt;font-family:"Courier New";mso-fareast-language:EN-CA'> try (var scope = new StructuredTaskScope.ShutdownOnFailure()) {<o:p></o:p></span></p><p class=MsoNormal><span style='font-size:10.0pt;font-family:"Courier New";mso-fareast-language:EN-CA'><o:p> </o:p></span></p><p class=MsoNormal><span style='font-size:10.0pt;font-family:"Courier New";mso-fareast-language:EN-CA'> Future<String> future1 = scope.fork(() -> query(left));<o:p></o:p></span></p><p class=MsoNormal><span style='font-size:10.0pt;font-family:"Courier New";mso-fareast-language:EN-CA'> Future<String> future2 = scope.fork(() -> query(right));<o:p></o:p></span></p><p class=MsoNormal><span style='font-size:10.0pt;font-family:"Courier New";mso-fareast-language:EN-CA'><o:p> </o:p></span></p><p class=MsoNormal><span style='font-size:10.0pt;font-family:"Courier New";mso-fareast-language:EN-CA'> scope.joinUntil(deadline);<o:p></o:p></span></p><p class=MsoNormal><span style='font-size:10.0pt;font-family:"Courier New";mso-fareast-language:EN-CA'><o:p> </o:p></span></p><p class=MsoNormal><span style='font-size:10.0pt;font-family:"Courier New";mso-fareast-language:EN-CA'> scope.<a href="https://download.java.net/java/early_access/loom/docs/api/jdk.incubator.concurrent/jdk/incubator/concurrent/StructuredTaskScope.ShutdownOnFailure.html#throwIfFailed()"><span style='color:blue'>throwIfFailed</span></a>(e -> new WebApplicationException(e));<o:p></o:p></span></p><p class=MsoNormal><span style='font-size:10.0pt;font-family:"Courier New";mso-fareast-language:EN-CA'><o:p> </o:p></span></p><p class=MsoNormal><span style='font-size:10.0pt;font-family:"Courier New";mso-fareast-language:EN-CA'> // both tasks completed successfully<o:p></o:p></span></p><p class=MsoNormal><span style='font-size:10.0pt;font-family:"Courier New";mso-fareast-language:EN-CA'> String result = Stream.of(future1, future2)<o:p></o:p></span></p><p class=MsoNormal><span style='font-size:10.0pt;font-family:"Courier New";mso-fareast-language:EN-CA'> .map(<a href="https://download.java.net/java/early_access/loom/docs/api/java.base/java/util/concurrent/Future.html#resultNow()"><span style='color:blue'>Future::resultNow</span></a>)<o:p></o:p></span></p><p class=MsoNormal><span style='font-size:10.0pt;font-family:"Courier New";mso-fareast-language:EN-CA'> .collect(Collectors.joining(", ", "{ ", " }"));<o:p></o:p></span></p><p class=MsoNormal><span style='font-size:10.0pt;font-family:"Courier New";mso-fareast-language:EN-CA'><o:p> </o:p></span></p><p class=MsoNormal><span style='font-size:10.0pt;font-family:"Courier New";mso-fareast-language:EN-CA'> ...<o:p></o:p></span></p><p class=MsoNormal><span style='font-size:10.0pt;font-family:"Courier New";mso-fareast-language:EN-CA'> }<o:p></o:p></span></p><p class=MsoNormal><o:p> </o:p></p><ol style='margin-top:0cm' start=1 type=1><li class=MsoListParagraph style='margin-left:0cm;mso-list:l0 level1 lfo1'>Is there any scenario where close() waits forever?<o:p></o:p></li><ol style='margin-top:0cm' start=1 type=a><li class=MsoListParagraph style='margin-left:0cm;mso-list:l0 level2 lfo1'>Where it is implicit in this try block.<o:p></o:p></li><li class=MsoListParagraph style='margin-left:0cm;mso-list:l0 level2 lfo1'>I can imagine scenarios where subtasks don’t cancel properly or respond correctly to interrupts.<o:p></o:p></li></ol><li class=MsoListParagraph style='margin-left:0cm;mso-list:l0 level1 lfo1'>If there is, is there any programmatic way out of this?<o:p></o:p></li><ol style='margin-top:0cm' start=1 type=a><li class=MsoListParagraph style='margin-left:0cm;mso-list:l0 level2 lfo1'>Does the InterruptedException bypass close() and exit the try block?<o:p></o:p></li><li class=MsoListParagraph style='margin-left:0cm;mso-list:l0 level2 lfo1'>Is this guaranteed by the runtime?<o:p></o:p></li><li class=MsoListParagraph style='margin-left:0cm;mso-list:l0 level2 lfo1'>I assume it is, but I have made bad assumptions about the runtime before…<o:p></o:p></li></ol><li class=MsoListParagraph style='margin-left:0cm;mso-list:l0 level1 lfo1'>Personally, I would have thought that “<span style='font-size:10.0pt;font-family:"Courier New";mso-fareast-language:EN-CA'>scope.joinUntil(deadline);</span>” would guarantee this code exits the try block, but the documentation, as written, does not give me that confidence. There are two wait points…<o:p></o:p></li><ol style='margin-top:0cm' start=1 type=a><li class=MsoListParagraph style='margin-left:0cm;mso-list:l0 level2 lfo1'><span style='font-size:10.0pt;font-family:"Courier New";mso-fareast-language:EN-CA'>scope.joinUntil(deadline);</span><o:p></o:p></li><li class=MsoListParagraph style='margin-left:0cm;mso-list:l0 level2 lfo1'><span style='font-size:10.0pt;font-family:"Courier New";mso-fareast-language:EN-CA'>scope.close(); </span><o:p></o:p></li></ol><li class=MsoListParagraph style='margin-left:0cm;mso-list:l0 level1 lfo1'>While this may not be ambiguous to others, it is to me.<o:p></o:p></li><ol style='margin-top:0cm' start=1 type=a><li class=MsoListParagraph style='margin-left:0cm;mso-list:l0 level2 lfo1'>It would be nice if there was text that made this more explicit.<o:p></o:p></li></ol></ol><p class=MsoNormal><o:p> </o:p></p><p class=MsoNormal>Cheers, Eric<o:p></o:p></p></div></body></html>