Node startup minor refactor (#4342)

* Slight refactor

* Move side effect out of method

node/src/main/kotlin/net/corda/node/internal/NodeStartup.kt

@@ -126,7 +126,7 @@ open class NodeStartup : NodeStartupLogging {
 
         // Step 2. We do the single node check before we initialise logging so that in case of a double-node start it
         // doesn't mess with the running node's logs.
-        enforceSingleNodeIsRunning(cmdLineOptions.baseDirectory)
+        if (!isNodeRunningAt(cmdLineOptions.baseDirectory)) return ExitCodes.FAILURE
 
         // Step 3. Register all cryptography [Provider]s.
         // Required to install our [SecureRandom] before e.g., UUID asks for one.
@@ -253,7 +253,7 @@ open class NodeStartup : NodeStartupLogging {
         }
     }
 
-    internal fun enforceSingleNodeIsRunning(baseDirectory: Path) {
+    fun isNodeRunningAt(baseDirectory: Path): Boolean {
         // Write out our process ID (which may or may not resemble a UNIX process id - to us it's just a string) to a
         // file that we'll do our best to delete on exit. But if we don't, it'll be overwritten next time. If it already
         // exists, we try to take the file lock first before replacing it and if that fails it means we're being started
@@ -267,7 +267,7 @@ open class NodeStartup : NodeStartupLogging {
             if (pidFileLock == null) {
                 println("It appears there is already a node running with the specified data directory $baseDirectory")
                 println("Shut that other node down and try again. It may have process ID ${pidFile.readText()}")
-                System.exit(1)
+                return false
             }
             pidFile.deleteOnExit()
             // Avoid the lock being garbage collected. We don't really need to release it as the OS will do so for us
@@ -282,8 +282,9 @@ open class NodeStartup : NodeStartupLogging {
             val appUser = System.getProperty("user.name")
             println("Application user '$appUser' does not have necessary permissions for Node base directory '$baseDirectory'.")
             println("Corda Node process in now exiting. Please check directory permissions and try starting the Node again.")
-            System.exit(1)
+            return false
         }
+        return true
     }
 
     private fun lookupMachineNameAndMaybeWarn(): String {

node/src/test/kotlin/net/corda/node/internal/NodeStartupTest.kt

@@ -1,6 +1,7 @@
 package net.corda.node.internal
 
 import com.google.common.io.Files
+import org.assertj.core.api.Assertions.assertThat
 import org.junit.Test
 import java.nio.channels.OverlappingFileLockException
 import java.util.concurrent.CountDownLatch
@@ -16,7 +17,7 @@ class NodeStartupTest {
 
         thread(start = true) {
             val node = NodeStartup()
-            node.enforceSingleNodeIsRunning(dir)
+            assertThat(node.isNodeRunningAt(dir)).isTrue()
             latch.countDown()
         }
 
@@ -25,6 +26,6 @@ class NodeStartupTest {
 
         // Check that I can't start up another node in the same directory
         val anotherNode = NodeStartup()
-        assertFailsWith<OverlappingFileLockException> { anotherNode.enforceSingleNodeIsRunning(dir) }
+        assertFailsWith<OverlappingFileLockException> { anotherNode.isNodeRunningAt(dir) }
     }
 }

testing/node-driver/src/integration-test/kotlin/net/corda/testing/driver/DriverTests.kt

@@ -121,14 +121,8 @@ class DriverTests {
             baseDirectory
         }
 
-        if ((baseDirectory / "process-id").exists()) {
-            // The addShutdownHook call doesn't reliably get called on Windows (even on graceful node shutdown), so at least check
-            // that the lock has been released, to make sure the node has been killed
-            val pidFile = (baseDirectory / "process-id").toFile()
-            val pidFileRw = RandomAccessFile(pidFile, "rw")
-            pidFileRw.channel.tryLock()
-            pidFileRw.close()
-        }
+        // Should be able to start another node up in that directory
+        assertThat(NodeStartup().isNodeRunningAt(baseDirectory)).isTrue()
     }
 
     @Test