Fix some possible NPEs in strange JVM configs

distribution/tools/server-cli/src/main/java/org/elasticsearch/server/cli/JvmErgonomics.java

@@ -64,28 +64,33 @@ static boolean tuneG1GCForSmallHeap(final long heapSize) {
     }
 
     static boolean tuneG1GCHeapRegion(final Map<String, JvmOption> finalJvmOptions, final boolean tuneG1GCForSmallHeap) {
-        JvmOption g1GCHeapRegion = finalJvmOptions.get("G1HeapRegionSize");
-        JvmOption g1GC = finalJvmOptions.get("UseG1GC");
-        return (tuneG1GCForSmallHeap && g1GC.getMandatoryValue().equals("true") && g1GCHeapRegion.isCommandLineOrigin() == false);
+        return tuneG1GCForSmallHeap && usingG1GcWithoutCommandLineOriginOption(finalJvmOptions, "G1HeapRegionSize");
     }
 
     static int tuneG1GCReservePercent(final Map<String, JvmOption> finalJvmOptions, final boolean tuneG1GCForSmallHeap) {
-        JvmOption g1GC = finalJvmOptions.get("UseG1GC");
-        JvmOption g1GCReservePercent = finalJvmOptions.get("G1ReservePercent");
-        if (g1GC.getMandatoryValue().equals("true")) {
-            if (g1GCReservePercent.isCommandLineOrigin() == false && tuneG1GCForSmallHeap) {
-                return 15;
-            } else if (g1GCReservePercent.isCommandLineOrigin() == false && tuneG1GCForSmallHeap == false) {
-                return 25;
-            }
+        if (usingG1GcWithoutCommandLineOriginOption(finalJvmOptions, "G1ReservePercent")) {
+            return tuneG1GCForSmallHeap ? 15 : 25;
         }
         return 0;
     }
 
     static boolean tuneG1GCInitiatingHeapOccupancyPercent(final Map<String, JvmOption> finalJvmOptions) {
-        JvmOption g1GC = finalJvmOptions.get("UseG1GC");
-        JvmOption g1GCInitiatingHeapOccupancyPercent = finalJvmOptions.get("InitiatingHeapOccupancyPercent");
-        return g1GCInitiatingHeapOccupancyPercent.isCommandLineOrigin() == false && g1GC.getMandatoryValue().equals("true");
+        return usingG1GcWithoutCommandLineOriginOption(finalJvmOptions, "InitiatingHeapOccupancyPercent");
+    }
+
+    private static boolean usingG1GcWithoutCommandLineOriginOption(Map<String, JvmOption> finalJvmOptions, String optionName) {
+        return getRequiredOption(finalJvmOptions, "UseG1GC").getMandatoryValue().equals("true")
+            && getRequiredOption(finalJvmOptions, optionName).isCommandLineOrigin() == false;
+    }
+
+    private static JvmOption getRequiredOption(final Map<String, JvmOption> finalJvmOptions, final String key) {
+        final var jvmOption = finalJvmOptions.get(key);
+        if (jvmOption == null) {
+            throw new IllegalStateException(
+                "JVM option [" + key + "] was unexpectedly missing. Elasticsearch requires this option to be present."
+            );
+        }
+        return jvmOption;
     }
 
     private static final Pattern SYSTEM_PROPERTY = Pattern.compile("^-D(?<key>[\\w+].*?)=(?<value>.*)$");

distribution/tools/server-cli/src/main/java/org/elasticsearch/server/cli/JvmOption.java

@@ -8,6 +8,8 @@
 
 package org.elasticsearch.server.cli;
 
+import org.elasticsearch.common.Strings;
+
 import java.io.BufferedReader;
 import java.io.IOException;
 import java.io.InputStream;
@@ -29,6 +31,11 @@ class JvmOption {
     private final String origin;
 
     JvmOption(String value, String origin) {
+        if (origin == null) {
+            throw new IllegalStateException(Strings.format("""
+                Elasticsearch could not determine the origin of JVM option [%s]. \
+                This indicates that it is running in an unsupported configuration.""", value));
+        }
         this.value = value;
         this.origin = origin;
     }

distribution/tools/server-cli/src/test/java/org/elasticsearch/server/cli/JvmErgonomicsTests.java

@@ -19,6 +19,7 @@
 import java.util.List;
 import java.util.Map;
 
+import static org.hamcrest.Matchers.allOf;
 import static org.hamcrest.Matchers.containsString;
 import static org.hamcrest.Matchers.equalTo;
 import static org.hamcrest.Matchers.everyItem;
@@ -179,4 +180,46 @@ public void testMaxDirectMemorySizeChoiceWhenSet() throws Exception {
         );
     }
 
+    @SuppressWarnings("ConstantConditions")
+    public void testMissingOptionHandling() {
+        final Map<String, JvmOption> g1GcOn = Map.of("UseG1GC", new JvmOption("true", ""));
+        final Map<String, JvmOption> g1GcOff = Map.of("UseG1GC", new JvmOption("", ""));
+
+        assertFalse(JvmErgonomics.tuneG1GCHeapRegion(Map.of(), false));
+        assertThat(
+            expectThrows(IllegalStateException.class, () -> JvmErgonomics.tuneG1GCHeapRegion(Map.of(), true)).getMessage(),
+            allOf(containsString("[UseG1GC]"), containsString("unexpectedly missing"))
+        );
+        assertThat(
+            expectThrows(IllegalStateException.class, () -> JvmErgonomics.tuneG1GCHeapRegion(g1GcOn, true)).getMessage(),
+            allOf(containsString("[G1HeapRegionSize]"), containsString("unexpectedly missing"))
+        );
+        assertFalse(JvmErgonomics.tuneG1GCHeapRegion(g1GcOff, randomBoolean()));
+
+        assertThat(
+            expectThrows(IllegalStateException.class, () -> JvmErgonomics.tuneG1GCReservePercent(Map.of(), randomBoolean())).getMessage(),
+            allOf(containsString("[UseG1GC]"), containsString("unexpectedly missing"))
+        );
+        assertThat(
+            expectThrows(IllegalStateException.class, () -> JvmErgonomics.tuneG1GCReservePercent(g1GcOn, randomBoolean())).getMessage(),
+            allOf(containsString("[G1ReservePercent]"), containsString("unexpectedly missing"))
+        );
+        assertEquals(0, JvmErgonomics.tuneG1GCReservePercent(g1GcOff, randomBoolean()));
+
+        assertThat(
+            expectThrows(IllegalStateException.class, () -> JvmErgonomics.tuneG1GCInitiatingHeapOccupancyPercent(Map.of())).getMessage(),
+            allOf(containsString("[UseG1GC]"), containsString("unexpectedly missing"))
+        );
+        assertThat(
+            expectThrows(IllegalStateException.class, () -> JvmErgonomics.tuneG1GCInitiatingHeapOccupancyPercent(g1GcOn)).getMessage(),
+            allOf(containsString("[InitiatingHeapOccupancyPercent]"), containsString("unexpectedly missing"))
+        );
+        assertFalse(JvmErgonomics.tuneG1GCInitiatingHeapOccupancyPercent(g1GcOff));
+
+        assertThat(
+            expectThrows(IllegalStateException.class, () -> new JvmOption("OptionName", null)).getMessage(),
+            allOf(containsString("could not determine the origin of JVM option [OptionName]"), containsString("unsupported"))
+        );
+    }
+
 }