Configure Capsule/Driver to give Corda a relatively poxy 200mb heap by default: we don't seem to need more for development purposes. Switch to G1GC by default as well.

docs/source/node-administration.rst

@@ -56,9 +56,28 @@ Here are a few ways to build dashboards and extract monitoring data for a node:
 * *Java Mission Control* is a desktop app that can connect to a target JVM that has the right command line flags set
   (or always, if running locally). You can explore what data is available, create graphs of those metrics, and invoke
   management operations like forcing a garbage collection.
+* *VisualVM* is another desktop app that can do fine grained JVM monitoring and sampling. Very useful during development.
 * Cloud metrics services like New Relic also understand JMX, typically, by providing their own agent that uploads the
   data to their service on a regular schedule.
 
+Memory usage and tuning
+-----------------------
+
+All garbage collected programs can run faster if you give them more memory, as they need to collect less
+frequently. As a default JVM will happily consume all the memory on your system if you let it, Corda is
+configured with a relatively small 200mb Java heap by default. When other overheads are added, this yields
+a total memory usage of about 500mb for a node (the overheads come from things like compiled code, metadata,
+off-heap buffers, thread stacks, etc).
+
+If you want to make your node go faster and profiling suggests excessive GC overhead is the cause, or if your
+node is running out of memory, you can give it more by running the node like this:
+
+``java -Xmx1024m -jar corda.jar``
+
+The example command above would give a 1 gigabyte Java heap.
+
+.. note:: Unfortunately the JVM does not let you limit the total memory usage of Java program, just the heap size.
+
 Uploading and downloading attachments
 -------------------------------------
 

node/capsule/build.gradle

@@ -49,15 +49,25 @@ dependencies {
 }
 
 task buildCordaJAR(type: FatCapsule, dependsOn: ['buildCertSigningRequestUtilityJAR']) {
-    applicationClass 'net.corda.node.MainKt'
+    applicationClass 'net.corda.node.Corda'
     archiveName "corda-${corda_version}.jar"
     applicationSource = files(project.tasks.findByName('jar'), '../build/classes/main/CordaCaplet.class', 'config/dev/log4j2.xml')
 
     capsuleManifest {
         appClassPath = ["jolokia-agent-war-${project.rootProject.ext.jolokia_version}.war"]
         javaAgents = ["quasar-core-${quasar_version}-jdk8.jar"]
+        systemProperties['visualvm.display.name'] = 'Corda'
         minJavaVersion = '1.8.0'
+        // This version is known to work and avoids earlier 8u versions that have bugs.
+        minUpdateVersion['1.8'] = '102'
         caplets = ['CordaCaplet']
+
+        // JVM configuration:
+        // - Constrain to small heap sizes to ease development on low end devices.
+        // - Switch to the G1 GC which is going to be the default in Java 9 and gives low pause times/string dedup.
+        //
+        // If you change these flags, please also update Driver.kt
+        jvmArgs = ['-Xmx200m', '-XX:+UseG1GC']
     }
 }
 

node/src/main/kotlin/net/corda/node/Corda.kt

@@ -1,3 +1,4 @@
+@file:JvmName("Corda")
 package net.corda.node
 
 import com.typesafe.config.ConfigException

node/src/main/kotlin/net/corda/node/driver/Driver.kt

@@ -441,7 +441,6 @@ open class DriverDSL(
     }
 
     companion object {
-
         val name = arrayOf(
                 "Alice",
                 "Bob",
@@ -459,20 +458,28 @@ open class DriverDSL(
             // Write node.conf
             writeConfig(nodeConf.baseDirectory, "node.conf", nodeConf.config)
 
-            val className = "net.corda.node.MainKt" // cannot directly get class for this, so just use string
+            val className = "net.corda.node.Corda" // cannot directly get class for this, so just use string
             val separator = System.getProperty("file.separator")
             val classpath = System.getProperty("java.class.path")
             val path = System.getProperty("java.home") + separator + "bin" + separator + "java"
 
             val debugPortArg = if (debugPort != null)
-                listOf("-agentlib:jdwp=transport=dt_socket,server=y,suspend=n,address=$debugPort")
+                "-agentlib:jdwp=transport=dt_socket,server=y,suspend=n,address=$debugPort"
             else
-                emptyList()
+                ""
 
-            val javaArgs = listOf(path) +
+            val javaArgs = listOf(
-                    listOf("-Dname=${nodeConf.myLegalName}", "-javaagent:$quasarJarPath") + debugPortArg +
+                    path,
-                    listOf("-cp", classpath, className) +
+                    "-Dname=${nodeConf.myLegalName}",
+                    "-javaagent:$quasarJarPath",
+                    debugPortArg,
+                    "-Dvisualvm.display.name=Corda",
+                    "-Xmx200m",
+                    "-XX:+UseG1GC",
+                    "-cp", classpath,
+                    className,
                     "--base-directory=${nodeConf.baseDirectory}"
+            ).filter(String::isNotEmpty)
             val builder = ProcessBuilder(javaArgs)
             builder.redirectError(Paths.get("error.$className.log").toFile())
             builder.inheritIO()

samples/trader-demo/src/integration-test/kotlin/net/corda/traderdemo/TraderDemoTest.kt

@@ -12,7 +12,7 @@ import org.junit.Test
 
 class TraderDemoTest {
     @Test fun `runs trader demo`() {
-        driver(dsl = {
+        driver(isDebug = true) {
             val user = User("user1", "test", permissions = setOf(startFlowPermission<IssuerFlow.IssuanceRequester>()))
             val (nodeA, nodeB) = Futures.allAsList(
                 startNode("Bank A"),
@@ -23,6 +23,6 @@ class TraderDemoTest {
 
             assert(TraderDemoClientApi(nodeA.configuration.webAddress).runBuyer())
             assert(TraderDemoClientApi(nodeB.configuration.webAddress).runSeller(counterparty = nodeA.nodeInfo.legalIdentity.name))
-        }, isDebug = true)
+        }
     }
 }