Improve console exception messages

docs/changelog/87942.yaml

@@ -0,0 +1,5 @@
+pr: 87942
+summary: Improve console exception messages
+area: Infra/Core
+type: enhancement
+issues: []

server/src/main/java/org/elasticsearch/bootstrap/StartupException.java

@@ -27,7 +27,7 @@ public final class StartupException extends Exception {
     /** all lines from this package are RLE-compressed */
     static final String GUICE_PACKAGE = "org.elasticsearch.common.inject";
 
-    StartupException(Throwable cause) {
+    public StartupException(Throwable cause) {
         super(Objects.requireNonNull(cause));
     }
 

server/src/main/java/org/elasticsearch/common/logging/ConsoleThrowablePatternConverter.java

@@ -46,13 +46,27 @@ public void format(final LogEvent event, final StringBuilder toAppendTo) {
         }
         if (error instanceof StartupException e) {
             error = e.getCause();
+            toAppendTo.append("\n\nElasticsearch failed to startup normally.\n\n");
         }
-        toAppendTo.append("\n\nElasticsearch failed to startup normally.\n\n");
+        appendShortStacktrace(error, toAppendTo);
         if (error instanceof CreationException) {
             toAppendTo.append("There were problems initializing Guice. See log for more details.");
         } else {
-            toAppendTo.append(error.getMessage());
             toAppendTo.append("\n\nSee logs for more details.\n");
         }
     }
+
+    // prints a very truncated stack trace, leaving the rest of the details for the log
+    private static void appendShortStacktrace(Throwable error, StringBuilder toAppendTo) {
+        toAppendTo.append(error.getClass().getName());
+        toAppendTo.append(": ");
+        toAppendTo.append(error.getMessage());
+
+        var stacktrace = error.getStackTrace();
+        int len = Math.min(stacktrace.length, 5);
+        for (int i = 0; i < len; ++i) {
+            toAppendTo.append("\n\tat ");
+            toAppendTo.append(stacktrace[i].toString());
+        }
+    }
 }

server/src/test/java/org/elasticsearch/common/logging/ConsoleThrowablePatternConverterTests.java

@@ -0,0 +1,85 @@
+/*
+ * Copyright Elasticsearch B.V. and/or licensed to Elasticsearch B.V. under one
+ * or more contributor license agreements. Licensed under the Elastic License
+ * 2.0 and the Server Side Public License, v 1; you may not use this file except
+ * in compliance with, at your election, the Elastic License 2.0 or the Server
+ * Side Public License, v 1.
+ */
+
+package org.elasticsearch.common.logging;
+
+import org.apache.logging.log4j.core.LogEvent;
+import org.apache.logging.log4j.core.impl.Log4jLogEvent;
+import org.elasticsearch.bootstrap.StartupException;
+import org.elasticsearch.common.inject.CreationException;
+import org.elasticsearch.common.inject.spi.Message;
+import org.elasticsearch.test.ESTestCase;
+
+import java.util.Arrays;
+import java.util.List;
+
+import static org.hamcrest.Matchers.allOf;
+import static org.hamcrest.Matchers.containsString;
+import static org.hamcrest.Matchers.emptyString;
+import static org.hamcrest.Matchers.equalTo;
+import static org.hamcrest.Matchers.greaterThan;
+import static org.hamcrest.Matchers.not;
+
+public class ConsoleThrowablePatternConverterTests extends ESTestCase {
+    static final ConsoleThrowablePatternConverter converter = ConsoleThrowablePatternConverter.newInstance(null, null);
+
+    String format(Throwable e) {
+        LogEvent event = Log4jLogEvent.newBuilder().setThrown(e).build();
+        var builder = new StringBuilder();
+        converter.format(event, builder);
+        return builder.toString();
+    }
+
+    public void testNoException() {
+        assertThat(format(null), emptyString());
+    }
+
+    public void testStartupExceptionUnwrapped() {
+        var e = new StartupException(new RuntimeException("an error"));
+        assertThat(
+            format(e),
+            allOf(
+                containsString("Elasticsearch failed to startup normally"),
+                not(containsString("StartupException: ")),
+                containsString("RuntimeException: ")
+            )
+        );
+    }
+
+    public void testCreationException() {
+        var e = new CreationException(List.of(new Message("injection problem")));
+        assertThat(format(e), containsString("There were problems initializing Guice"));
+    }
+
+    public void testStackTruncation() {
+        var e = new NullPointerException();
+        var stacktrace = e.getStackTrace();
+        String output = format(e);
+        String[] lines = output.split("\n");
+        assertThat(lines.length, greaterThan(5));
+        assertThat(lines[0], equalTo("java.lang.NullPointerException: null"));
+        for (int i = 0; i < 5; ++i) {
+            assertThat(lines[i + 1], equalTo("\tat " + stacktrace[i]));
+        }
+        assertThat(lines[6], emptyString());
+    }
+
+    public void testShortStack() {
+        var e = new NullPointerException();
+        StackTraceElement[] stacktrace = Arrays.copyOf(e.getStackTrace(), randomIntBetween(1, 4));
+        e.setStackTrace(stacktrace);
+        String output = format(e);
+        String[] lines = output.split("\n");
+        assertThat(lines.length, greaterThan(stacktrace.length + 2));
+        assertThat(lines[0], equalTo("java.lang.NullPointerException: null"));
+        for (int i = 0; i < stacktrace.length; ++i) {
+            assertThat(lines[i + 1], equalTo("\tat " + stacktrace[i]));
+        }
+        assertThat(lines[stacktrace.length + 1], emptyString());
+    }
+}