Update Java Memory Assistant

Update Java Memory Assistant to version 0.4.0, which adds support for
the following JVMs:

- AdoptOpenJDK HotSpot 8.x
- AdoptOpenJDK HotSpot 11.x
- OpenJDK 11.x
- Oracle JVM 11.x
- Pivotal JDK 8.x
- SAP Machine 11.x

On Java 9+, an exception to the Java Module system must be added
(--add-opens jdk.management/com.sun.management.internal=ALL-UNNAMED)
to allow access to com.sun.management.HotSpotDiagnosticMXBean, which is
needed to created heapdumps in live mode.

[#789]

Signed-off-by: Ben Hale <[email protected]>

Author: mmanciop

docs/framework-java_memory_assistant.md

@@ -46,6 +46,13 @@ The timestamp pattern `%ts:yyyyMMdd'T'mmssSSSZ%` is equivalent to the `%FT%T%z`
 | Eden                   | `eden`             |
 | Survivor               | `survivor`         |
 | Old Generation         | `old_gen`          |
+| Tenured Gen            | `tenured_gen`      |
+| CodeHeap 'non-nmethods' | `code_heap.non_nmethods` |
+| CodeHeap 'profiled nmethods' | `code_heap.profiled_nmethods` |
+| CodeHeap 'non-profiled nmethods' | `code_heap.non_profiled_nmethods` |
+
+Different builds and versions of Java Virtual Machines offer different memory areas.
+The list of supported Java Virtual Machines and the respective memory areas can be found in the [Java Memory Assistant documentation](https://github.com/SAP/java-memory-assistant#supported-jvms).
 
 The default values can be found in the [`config/java_memory_assistant.yml`][] file.
 

lib/java_buildpack/framework/java_memory_assistant/agent.rb

@@ -42,6 +42,14 @@ def release
                 .add_system_property('jma.heap_dump_name', %("#{name_pattern}"))
                 .add_system_property 'jma.log_level', normalized_log_level
 
+        if @droplet.java_home.java_9_or_later?
+          # Enable access to com.sun.management.HotSpotDiagnosticMXBean to circumvent
+          # Java modules limitations in Java 9+
+          # See https://github.com/SAP/java-memory-assistant#running-the-java-memory-assistant-on-java-11
+          @droplet.java_opts
+                .add_preformatted_options('--add-opens jdk.management/com.sun.management.internal=ALL-UNNAMED')
+        end
+
         add_system_prop_if_config_present 'check_interval', 'jma.check_interval'
         add_system_prop_if_config_present 'max_frequency', 'jma.max_frequency'
 

spec/java_buildpack/framework/java_memory_assistant/agent_spec.rb

@@ -52,6 +52,8 @@
     it 'updates JAVA_OPTS with default values' do
       component.release
 
+      expect(java_opts).not_to include('--add-opens jdk.management/com.sun.management.internal=ALL-UNNAMED')
+
       expect(java_opts).to include('-javaagent:$PWD/.java-buildpack/java_memory_assistant_agent/' \
         'java-memory-assistant-1.2.3.jar')
       expect(java_opts).to include('-Djma.enabled=true')
@@ -61,6 +63,43 @@
 
       expect(java_opts).to include('-Djma.thresholds.heap=90')
       expect(java_opts).to include('-Djma.thresholds.old_gen=90')
+
+    end
+
+    context do
+
+      let(:java_home_delegate) do
+        delegate         = JavaBuildpack::Component::MutableJavaHome.new
+        delegate.root    = app_dir + '.test-java-home'
+        delegate.version = JavaBuildpack::Util::TokenizedVersion.new('1.8.0_55')
+    
+        delegate
+      end
+
+      it 'it does not add the --add-opens on Java 8' do
+        component.release
+  
+        expect(java_opts).not_to include('--add-opens jdk.management/com.sun.management.internal=ALL-UNNAMED')
+      end
+
+    end
+
+    context do
+
+      let(:java_home_delegate) do
+        delegate         = JavaBuildpack::Component::MutableJavaHome.new
+        delegate.root    = app_dir + '.test-java-home'
+        delegate.version = JavaBuildpack::Util::TokenizedVersion.new('9.0.1')
+    
+        delegate
+      end
+
+      it 'adds the --add-opens on Java 11' do
+        component.release
+  
+        expect(java_opts).to include('--add-opens jdk.management/com.sun.management.internal=ALL-UNNAMED')
+      end
+  
     end
 
   end
@@ -200,7 +239,7 @@
     end
 
     it 'falls back on JBP log_level when no log_level specified via configuration',
-       :enable_log_file, log_level: 'WARN' do
+        :enable_log_file, log_level: 'WARN' do
       component.release
 
       expect(java_opts).to include('-Djma.log_level=WARNING')