feat: add environment variables to tune async init without the need to recompile (#450)

Author: deki

aws-serverless-java-container-core/src/main/java/com/amazonaws/serverless/proxy/AsyncInitializationWrapper.java

@@ -38,11 +38,14 @@
  * seconds has already been used up.
  */
 public class AsyncInitializationWrapper extends InitializationWrapper {
-    private int INIT_GRACE_TIME_MS = 250;
+    private static final int DEFAULT_INIT_GRACE_TIME_MS = 150;
+    private static final String INIT_GRACE_TIME_ENVIRONMENT_VARIABLE_NAME = "AWS_SERVERLESS_JAVA_CONTAINER_INIT_GRACE_TIME";
+    private static final int INIT_GRACE_TIME_MS = Integer.parseInt(System.getProperty(
+            INIT_GRACE_TIME_ENVIRONMENT_VARIABLE_NAME, Integer.toString(DEFAULT_INIT_GRACE_TIME_MS)));
     private static final int LAMBDA_MAX_INIT_TIME_MS = 10_000;
 
     private CountDownLatch initializationLatch;
-    private long actualStartTime;
+    private final long actualStartTime;
     private Logger log = LoggerFactory.getLogger(AsyncInitializationWrapper.class);
 
     /**
@@ -60,7 +63,6 @@ public AsyncInitializationWrapper(long startTime) {
      */
     public AsyncInitializationWrapper() {
         actualStartTime = ManagementFactory.getRuntimeMXBean().getStartTime();
-        INIT_GRACE_TIME_MS = 150;
     }
 
     @Override
@@ -71,7 +73,7 @@ public void start(LambdaContainerHandler handler) throws ContainerInitialization
         initThread.start();
         try {
             long curTime = Instant.now().toEpochMilli();
-            // account for the time it took to call the various constructors with the actual start time + a grace of 500ms
+            // account for the time it took to call the various constructors with the actual start time + a grace time
             long awaitTime = (actualStartTime + LAMBDA_MAX_INIT_TIME_MS) - curTime - INIT_GRACE_TIME_MS;
             log.info("Async initialization will wait for " + awaitTime + "ms");
             if (!initializationLatch.await(awaitTime, TimeUnit.MILLISECONDS)) {

aws-serverless-java-container-core/src/main/java/com/amazonaws/serverless/proxy/model/ContainerConfig.java

@@ -26,7 +26,10 @@ public class ContainerConfig {
     public static final String DEFAULT_URI_ENCODING = "UTF-8";
     public static final String DEFAULT_CONTENT_CHARSET = "ISO-8859-1";
     private static final List<String> DEFAULT_FILE_PATHS = new ArrayList<String>() {{ add("/tmp"); add("/var/task"); }};
-    private static final int MAX_INIT_TIMEOUT_MS = 20_000;
+    private static final int DEFAULT_MAX_INIT_TIMEOUT_MS = 20_000;
+    private static final String MAX_INIT_TIMEOUT_ENVIRONMENT_VARIABLE_NAME = "AWS_SERVERLESS_JAVA_CONTAINER_MAX_INIT_TIMEOUT";
+    private static final int MAX_INIT_TIMEOUT_MS = Integer.parseInt(System.getProperty(
+            MAX_INIT_TIMEOUT_ENVIRONMENT_VARIABLE_NAME, Integer.toString(DEFAULT_MAX_INIT_TIMEOUT_MS)));
 
     public static ContainerConfig defaultConfig() {
         ContainerConfig configuration = new ContainerConfig();