feat: set limits for maximum memory use.

facades/PC/build.gradle.kts

@@ -60,6 +60,7 @@ logger.info("PC VERSION: {}", version)
 group = "org.terasology.facades"
 
 dependencies {
+    implementation(group = "net.java.dev.jna", name = "jna-platform", version = "5.6.0")
     implementation(group = "info.picocli", name = "picocli", version = "4.5.2")
     annotationProcessor("info.picocli:picocli-codegen:4.5.2")
 
@@ -68,6 +69,16 @@ dependencies {
 
     // TODO: Consider whether we can move the CR dependency back here from the engine, where it is referenced from the main menu
     implementation(group = "org.terasology.crashreporter", name = "cr-terasology", version = "4.1.0")
+
+    implementation(platform("org.junit:junit-bom:5.7.1")) {
+        // junit-bom will set version numbers for the other org.junit dependencies.
+    }
+    implementation("org.junit.jupiter:junit-jupiter-api")
+    implementation("org.junit.jupiter:junit-jupiter-params")
+    testRuntimeOnly("org.junit.jupiter:junit-jupiter-engine")
+
+    testImplementation("com.google.truth:truth:1.1.2")
+    testImplementation("com.google.truth.extensions:truth-java8-extension:1.1.2")
 }
 
 tasks.named<JavaCompile>("compileJava") {

facades/PC/src/main/java/org/terasology/engine/DataSizeConverter.java

@@ -0,0 +1,56 @@
+// Copyright 2021 The Terasology Foundation
+// SPDX-License-Identifier: Apache-2.0
+
+package org.terasology.engine;
+
+import picocli.CommandLine;
+
+import java.math.BigDecimal;
+import java.util.Locale;
+import java.util.regex.Matcher;
+import java.util.regex.Pattern;
+
+public class DataSizeConverter implements CommandLine.ITypeConverter<Long> {
+    protected final static Pattern pattern = Pattern.compile(
+            "(?<n>\\d+([.,]\\d*)?)" +
+            "\\s*" +
+            "(?<suffix>\\p{Alpha})?b?",
+            Pattern.CASE_INSENSITIVE
+    );
+
+    @SuppressWarnings("unused")  // used by Unit.valueOf
+    enum Unit {
+        B(1),
+        K(1 << 10),
+        M(1 << 20),
+        G(1 << 30),
+        T(1L << 40);
+
+        private final BigDecimal scale;
+
+        Unit(long scale) {
+            this.scale = BigDecimal.valueOf(scale);
+        }
+
+        BigDecimal multiply(BigDecimal n) {
+            return n.multiply(scale);
+        }
+    }
+
+    @Override
+    public Long convert(String value) {
+        if (value == null) {
+            throw new CommandLine.TypeConversionException("null input");
+        }
+        Matcher match = pattern.matcher(value);
+        if (!match.matches()) {
+            throw new CommandLine.TypeConversionException("JANK");
+        }
+        BigDecimal n = new BigDecimal(match.group("n"));
+        if (match.group("suffix") != null) {
+            Unit unit = Unit.valueOf(match.group("suffix").toUpperCase(Locale.ROOT));
+            n = unit.multiply(n);
+        }
+        return n.toBigInteger().longValueExact();
+    }
+}

facades/PC/src/main/java/org/terasology/engine/Terasology.java

@@ -2,6 +2,8 @@
 // SPDX-License-Identifier: Apache-2.0
 package org.terasology.engine;
 
+import com.sun.jna.Platform;
+import com.sun.jna.platform.unix.LibC;
 import org.slf4j.Logger;
 import org.slf4j.LoggerFactory;
 import org.terasology.crashreporter.CrashReporter;
@@ -10,7 +12,6 @@
 import org.terasology.engine.core.LoggingContext;
 import org.terasology.engine.core.PathManager;
 import org.terasology.engine.core.StandardGameStatus;
-import org.terasology.engine.core.TerasologyConstants;
 import org.terasology.engine.core.TerasologyEngine;
 import org.terasology.engine.core.TerasologyEngineBuilder;
 import org.terasology.engine.core.modes.StateLoading;
@@ -43,8 +44,10 @@
 
 import java.awt.GraphicsEnvironment;
 import java.io.IOException;
+import java.nio.file.Files;
 import java.nio.file.Path;
 import java.nio.file.Paths;
+import java.nio.file.StandardOpenOption;
 import java.util.List;
 import java.util.concurrent.Callable;
 import java.util.concurrent.CountDownLatch;
@@ -72,12 +75,25 @@ public final class Terasology implements Callable<Integer> {
     @CommandLine.Spec CommandLine.Model.CommandSpec spec;
 
     @SuppressWarnings("unused")
-    @Option(names = {"--help", "-help", "/help", "-h", "/h", "-?", "/?"}, usageHelp = true, description = "show help")
+    @Option(names = {"--help", "-help", "/help", "-h", "/h", "-?", "/?"}, usageHelp = true, description = "Show help")
     private boolean helpRequested;
 
     @Option(names = "--headless", description = "Start headless (no graphics)")
     private boolean isHeadless;
 
+    @Option(names = "--max-data-size",
+            description = "Set maximum process data size [Linux only]",
+            paramLabel = "<size>",
+            converter = DataSizeConverter.class
+    )
+    Long maxDataSize;
+
+    @Option(names = "--oom-score",
+            description = "Adjust out-of-memory score [Linux only]",
+            paramLabel = "<score>"
+    )
+    Integer outOfMemoryScore;
+
     @Option(names = "--crash-report", defaultValue = "true", negatable = true, description = "Enable crash reporting")
     private boolean crashReportEnabled;
 
@@ -208,6 +224,13 @@ private static void setupLogging() {
     }
 
     private void handleLaunchArguments() throws IOException {
+        if (outOfMemoryScore!= null) {
+            adjustOutOfMemoryScore(outOfMemoryScore);
+        }
+        if (maxDataSize != null) {
+            setMemoryLimit(maxDataSize);
+        }
+
         if (homeDir != null) {
             logger.info("homeDir is {}", homeDir);
             PathManager.getInstance().useOverrideHomePath(homeDir);
@@ -301,4 +324,27 @@ private static int getLastNumber(String str) {
         return Integer.parseInt(str.substring(positionOfLastDigit));
     }
 
+    private static void setMemoryLimit(long bytes) {
+        // Memory-limiting techniques are highly platform-specific.
+        if (Platform.isLinux()) {
+            final LibC.Rlimit dataLimit = new LibC.Rlimit();
+            dataLimit.rlim_cur = bytes;
+            dataLimit.rlim_max = bytes;
+            // Under Linux ≥ 4.7, we can limit the maximum size of the process's data segment, which includes its
+            // heap. Note we cannot directly limit its resident set size, see setrlimit(3).
+            LibC.INSTANCE.setrlimit(LibC.RLIMIT_DATA, dataLimit);
+        } else {
+            logger.warn("--max-data-size is not supported on platform {}", Platform.RESOURCE_PREFIX);
+        }
+    }
+
+    private static void adjustOutOfMemoryScore(int adjustment) {
+        Path procFile = Paths.get("/proc", "self", "oom_score_adj");
+        try {
+            Files.write(procFile, String.valueOf(adjustment).getBytes(),
+                    StandardOpenOption.WRITE, StandardOpenOption.TRUNCATE_EXISTING);
+        } catch (IOException e) {
+            logger.error("Failed to adjust out-of-memory score.", e);
+        }
+    }
 }

facades/PC/src/test/java/org/terasology/engine/DataSizeConverterTest.java

@@ -0,0 +1,41 @@
+// Copyright 2021 The Terasology Foundation
+// SPDX-License-Identifier: Apache-2.0
+
+package org.terasology.engine;
+
+import org.junit.jupiter.params.ParameterizedTest;
+import org.junit.jupiter.params.provider.CsvSource;
+import org.junit.jupiter.params.provider.NullAndEmptySource;
+import org.junit.jupiter.params.provider.ValueSource;
+import picocli.CommandLine;
+
+import static org.junit.jupiter.api.Assertions.assertEquals;
+import static org.junit.jupiter.api.Assertions.assertThrows;
+
+class DataSizeConverterTest {
+
+    @ParameterizedTest
+    @CsvSource({
+            "1, 1",
+            "16, 16b",
+            "126, 0.1234k",
+            "512, 0.5 k",
+            "11264, 11k",
+            "11264, 11Kb",
+            "44040192, 42 m",
+            "268435456, 256M",
+            "2684354560, 2.5g",
+            "8589934592, 8G",
+    })
+    void testValidInputs(long expected, String input) {
+        assertEquals(expected, new DataSizeConverter().convert(input));
+    }
+
+    @ParameterizedTest
+    @NullAndEmptySource
+    @ValueSource(strings = {"b", "mb", " mb", " ", "🆗", "-5m", "null", "NaN"})
+    void testBadInputs(String input) {
+        DataSizeConverter converter = new DataSizeConverter();
+        assertThrows(CommandLine.TypeConversionException.class, () -> converter.convert(input));
+    }
+}