Downgraded to Java 8. Java 11 is still required to build and run test due to Mockito dependency.

README.md

@@ -128,7 +128,7 @@ using [GraalVM Community Edition](https://github.com/graalvm/graalvm-ce-builds/r
 dependencies and can be run as is.
 
 A pure Java version in jar form (meshmonitor.jar) is also available. The Java version should work on 
-any platform with Java 17 or later installed (although it has only been tested on Linux).
+any platform with Java 8 or later installed (although it has only been tested on Linux).
 
 # Using Meshmonitor
 
@@ -230,11 +230,11 @@ Use the following command to run meshmonitor from the jar file:
 java -jar meshmonitor.jar <ARGS> 
 ```
 
-It requires at least Java 17 to run.
+Java 8 is enough to run it but Java 11 is required to build and execute tests.
 
 ## Building
 
-Java SDK is required to build and test the Meshmonitor. Version 17 or above.
+Java SDK is required to build and test the Meshmonitor. Version 11 or above.
 Maven is used as a build system but does not need to be installed locally.
 
 The `mvnw` script (or `mvnw.cmd` on Windows) is used to bootstrap the build

pom.xml

@@ -21,11 +21,11 @@
         <project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
         <project.reporting.outputEncoding>UTF-8</project.reporting.outputEncoding>
 
-        <maven.compiler.source>17</maven.compiler.source>
-        <maven.compiler.target>17</maven.compiler.target>
+        <maven.compiler.source>8</maven.compiler.source>
+        <maven.compiler.target>8</maven.compiler.target>
 
-        <maven.compiler.testSource>17</maven.compiler.testSource>
-        <maven.compiler.testTarget>17</maven.compiler.testTarget>
+        <maven.compiler.testSource>11</maven.compiler.testSource>
+        <maven.compiler.testTarget>11</maven.compiler.testTarget>
 
         <imageName>meshmonitor</imageName>
         <mainClass>org.voltdb.meshmonitor.cli.MeshMonitorCommand</mainClass>

src/main/java/org/voltdb/meshmonitor/ConsoleLogger.java

@@ -69,14 +69,14 @@ private void log(String hostAddress, LogLevel logLevel, String message, Object..
         String colourfulDateTime = CommandLine.Help.Ansi.AUTO.string(String.format("@|%s %s|@", logLevel, dateTime));
         String colourfulHostAddress = CommandLine.Help.Ansi.AUTO.string(String.format("@|%s [%15s]|@", logLevel, hostAddress));
 
-        out.println(colourfulDateTime + " " + colourfulHostAddress + " " + message.formatted(args));
+        out.println(colourfulDateTime + " " + colourfulHostAddress + " " + String.format(message, args));
     }
 
     public void debug(InetSocketAddress socketAddress, String format, Object... args) {
         String hostAddress = socketAddress.getAddress().getHostAddress();
 
         if (enableDebugLogging) {
-            log(hostAddress, LogLevel.INFO, format.formatted(args));
+            log(hostAddress, LogLevel.INFO, String.format(format, args));
         }
     }
 

src/main/java/org/voltdb/meshmonitor/GitPropertiesVersionProvider.java

@@ -59,15 +59,15 @@ public String getSimpleVersion() {
             String maybeCommitId = Objects.toString(properties.get(GIT_COMMIT_ID_PROPERTY), "");
 
             StringBuilder version = new StringBuilder();
-            if (!maybeTags.isBlank()) {
+            if (!maybeTags.trim().isEmpty()) {
                 version.append(maybeTags);
-            } else if (!maybeCommitId.isBlank()) {
+            } else if (!maybeCommitId.trim().isEmpty()) {
                 version.append(maybeCommitId);
             } else {
                 version.append(VERSION_UNKNOWN);
             }
 
-            if (!maybeBuildTime.isBlank()) {
+            if (!maybeBuildTime.trim().isEmpty()) {
                 version.append(" built on ").append(maybeBuildTime);
             }
 

src/main/java/org/voltdb/meshmonitor/HistogramLogger.java

@@ -53,11 +53,11 @@ private String format(Histogram deltaHistogram, long minHiccupSizeMicroseconds)
 
     private String getFormatWithColours(double value, double minHiccupSize) {
         if (value > 999.9) {
-            String formatted = "%4.1fs".formatted(value / 1000.0);
+            String formatted = String.format("%4.1fs", value / 1000.0);
             return CommandLine.Help.Ansi.AUTO.string("@|bold,red " + formatted + "|@");
         }
 
-        String formatted = "%5.1f".formatted(value);
+        String formatted = String.format("%5.1f", value);
         if (value > minHiccupSize) {
             return CommandLine.Help.Ansi.AUTO.string("@|bold,yellow " + formatted + "|@");
         }

src/main/java/org/voltdb/meshmonitor/MeshMonitorTimings.java

@@ -1,5 +1,5 @@
 /*
- * Copyright (C) 2024 Volt Active Data Inc.
+ * Copyright (C) 2024-2025 Volt Active Data Inc.
  *
  * Use of this source code is governed by an MIT
  * license that can be found in the LICENSE file or at
@@ -9,13 +9,24 @@
 
 import org.HdrHistogram.SynchronizedHistogram;
 
-public record MeshMonitorTimings(
-        HistogramWithDelta receiveHistogram,
-        HistogramWithDelta sendHistogram,
-        HistogramWithDelta deltaHistogram) {
+import java.util.Objects;
+
+public final class MeshMonitorTimings {
 
     public static final int NUMBER_OF_SIGNIFICANT_VALUE_DIGITS = 3;
     public static final long HIGHEST_TRACKABLE_VALUE = 24 * 60 * 60 * 1000 * 1000L;
+    private final HistogramWithDelta receiveHistogram;
+    private final HistogramWithDelta sendHistogram;
+    private final HistogramWithDelta deltaHistogram;
+
+    public MeshMonitorTimings(
+            HistogramWithDelta receiveHistogram,
+            HistogramWithDelta sendHistogram,
+            HistogramWithDelta deltaHistogram) {
+        this.receiveHistogram = receiveHistogram;
+        this.sendHistogram = sendHistogram;
+        this.deltaHistogram = deltaHistogram;
+    }
 
     public void pingReceived(long now, long lastReceiveTime, long timestampFromRemoteHost, long pingInterval) {
         long valueToRecord = now - lastReceiveTime;
@@ -41,4 +52,41 @@ public static MeshMonitorTimings createDefault(ConsoleLogger logger) {
                 new HistogramWithDelta(logger, "delta", defaultHistogram())
         );
     }
+
+    public HistogramWithDelta receiveHistogram() {
+        return receiveHistogram;
+    }
+
+    public HistogramWithDelta sendHistogram() {
+        return sendHistogram;
+    }
+
+    public HistogramWithDelta deltaHistogram() {
+        return deltaHistogram;
+    }
+
+    @Override
+    public boolean equals(Object obj) {
+        if (obj == this) return true;
+        if (obj == null || obj.getClass() != this.getClass())
+            return false;
+        MeshMonitorTimings that = (MeshMonitorTimings) obj;
+        return Objects.equals(this.receiveHistogram, that.receiveHistogram) &&
+               Objects.equals(this.sendHistogram, that.sendHistogram) &&
+               Objects.equals(this.deltaHistogram, that.deltaHistogram);
+    }
+
+    @Override
+    public int hashCode() {
+        return Objects.hash(receiveHistogram, sendHistogram, deltaHistogram);
+    }
+
+    @Override
+    public String toString() {
+        return "MeshMonitorTimings[" +
+               "receiveHistogram=" + receiveHistogram + ", " +
+               "sendHistogram=" + sendHistogram + ", " +
+               "deltaHistogram=" + deltaHistogram + ']';
+    }
+
 }

src/main/java/org/voltdb/meshmonitor/ServerManager.java

@@ -12,6 +12,7 @@
 import java.time.Duration;
 import java.util.ArrayList;
 import java.util.List;
+import java.util.stream.Collectors;
 
 public class ServerManager {
 
@@ -30,14 +31,14 @@ public ServerManager(ConsoleLogger consoleLogger, MonitorFactory monitorFactory,
     public synchronized List<Monitor> getMonitors() {
         return monitors.stream()
                 .filter(Monitor::isRunning)
-                .toList();
+                .collect(Collectors.toList());
     }
 
     public synchronized List<InetSocketAddress> getConnections() {
         return monitors.stream()
                 .filter(Monitor::isRunning)
                 .map(Monitor::getRemoteId)
-                .toList();
+                .collect(Collectors.toList());
     }
 
     public synchronized boolean createNewMonitorIfNotAlreadyPresent(SocketChannel channel, MeshMonitor meshMonitor, InetSocketAddress remoteId) {

src/main/java/org/voltdb/meshmonitor/cli/MeshMonitorCommand.java

@@ -121,14 +121,17 @@ public Integer call() {
 
         System.out.println(
                 CommandLine.Help.Ansi.AUTO.string(
-                        """
-                                @|green      __  ___          __                          _ __           \s
-                                    /  |/  /__  _____/ /_  ____ ___  ____  ____  (_) /_____  _____
-                                   / /|_/ / _ \\/ ___/ __ \\/ __ `__ \\/ __ \\/ __ \\/ / __/ __ \\/ ___/
-                                  / /  / /  __(__  ) / / / / / / / / /_/ / / / / / /_/ /_/ / /   \s
-                                 /_/  /_/\\___/____/_/ /_/_/ /_/ /_/\\____/_/ /_/_/\\__/\\____/_/ \s
-                                 |@                            %s
-                                """.formatted(new GitPropertiesVersionProvider().getSimpleVersion())));
+                        String.format(
+                                "@|green      __  ___          __                          _ __            \n" +
+                                "    /  |/  /__  _____/ /_  ____ ___  ____  ____  (_) /_____  _____\n" +
+                                "   / /|_/ / _ \\/ ___/ __ \\/ __ `__ \\/ __ \\/ __ \\/ / __/ __ \\/ ___/\n" +
+                                "  / /  / /  __(__  ) / / / / / / / / /_/ / / / / / /_/ /_/ / /    \n" +
+                                " /_/  /_/\\___/____/_/ /_/_/ /_/ /_/\\____/_/ /_/_/\\__/\\____/_/  \n" +
+                                " |@                            %s\n",
+                                new GitPropertiesVersionProvider().getSimpleVersion()
+                        )
+                )
+        );
 
         ConsoleLogger consoleLogger = new ConsoleLogger(spec.commandLine().getOut(), enableDebugLogging);
         ServerManager serverManager = new ServerManager(consoleLogger, Monitor::new, Duration.ofMillis(pingIntervalMilliseconds));

src/test/java/org/voltdb/meshmonitor/GitPropertiesVersionProviderTest.java

@@ -22,48 +22,36 @@ public class GitPropertiesVersionProviderTest {
     static Stream<Arguments> variousPropertiesContents() {
         return Stream.of(
                 Arguments.of(
-                        """
-                                git.tags=v1.0
-                                git.build.time=2024-01-01
-                                git.commit.id.abbrev=abc123
-                                """,
+                        "git.tags=v1.0\n" +
+                        "git.build.time=2024-01-01\n" +
+                        "git.commit.id.abbrev=abc123\n",
                         "version v1.0 built on 2024-01-01"
                 ),
                 Arguments.of(
-                        """
-                                git.tags=
-                                git.build.time=2024-01-01
-                                git.commit.id.abbrev=abc123
-                                """,
+                        "git.tags=\n" +
+                        "git.build.time=2024-01-01\n" +
+                        "git.commit.id.abbrev=abc123\n",
                         "version abc123 built on 2024-01-01"
                 ),
                 Arguments.of(
-                        """
-                                git.tags=
-                                git.build.time=2024-01-01
-                                git.commit.id.abbrev=
-                                """,
+                        "git.tags=\n" +
+                        "git.build.time=2024-01-01\n" +
+                        "git.commit.id.abbrev=\n",
                         "version unknown built on 2024-01-01"
                 ),
                 Arguments.of(
-                        """
-                                git.tags=
-                                git.build.time=
-                                git.commit.id.abbrev=
-                                """,
+                        "git.tags=\n" +
+                        "git.build.time=\n" +
+                        "git.commit.id.abbrev=\n",
                         "version unknown"
                 ),
                 Arguments.of(
-                        """
-                                git.build.time=2024-01-01
-                                git.commit.id.abbrev=abc123
-                                """,
+                        "git.build.time=2024-01-01\n" +
+                        "git.commit.id.abbrev=abc123\n",
                         "version abc123 built on 2024-01-01"
                 ),
                 Arguments.of(
-                        """
-                                git.build.time=2024-01-01
-                                """,
+                        "git.build.time=2024-01-01\n",
                         "version unknown built on 2024-01-01"
                 ),
                 Arguments.of(

src/test/java/org/voltdb/meshmonitor/e2e/ContainerTestBase.java

@@ -1,5 +1,5 @@
 /*
- * Copyright (C) 2024 Volt Active Data Inc.
+ * Copyright (C) 2024-2025 Volt Active Data Inc.
  *
  * Use of this source code is governed by an MIT
  * license that can be found in the LICENSE file or at
@@ -35,13 +35,12 @@ public class ContainerTestBase {
 
     private static final ImageFromDockerfile IMAGE_WITH_JAR = new ImageFromDockerfile()
             .withFileFromFile("/home/meshmonitor", new File(".").getAbsoluteFile().getParentFile())
-            .withFileFromString("/home/meshmonitor/meshmonitor", """
-                    #!/bin/bash
-
-                    java --enable-preview \\
-                         -cp "/home/meshmonitor/target/meshmonitor-1.0.0-jar-with-dependencies.jar" \\
-                         org.voltdb.meshmonitor.cli.MeshMonitorCommand -i 1 "$@"
-                    """)
+            .withFileFromString("/home/meshmonitor/meshmonitor",
+                    "#!/bin/bash\n" +
+                    "java \\\n" +
+                    "     -cp \"/home/meshmonitor/target/meshmonitor-1.0.0-jar-with-dependencies.jar\" \\\n" +
+                    "     org.voltdb.meshmonitor.cli.MeshMonitorCommand -i 1 \"$@\"\n"
+            )
             .withDockerfileFromBuilder(builder ->
                     builder
                             .from("ghcr.io/graalvm/graalvm-community:21.0.1-ol9-20231024")

src/test/java/org/voltdb/meshmonitor/testutils/ByteBufferReadableByteChannel.java

@@ -10,6 +10,8 @@
 import java.nio.ByteBuffer;
 import java.nio.channels.ReadableByteChannel;
 
+import static org.voltdb.meshmonitor.testutils.FileChannelUtils.byteBufferAbsolutePut;
+
 public class ByteBufferReadableByteChannel implements ReadableByteChannel {
 
     private final ByteBuffer data;
@@ -21,7 +23,8 @@ public class ByteBufferReadableByteChannel implements ReadableByteChannel {
     @Override
     public int read(ByteBuffer dst) {
         int remaining = dst.remaining();
-        dst.put(dst.position(), data, data.position(), remaining);
+
+        byteBufferAbsolutePut(dst, dst.position(), data, data.position(), remaining);
 
         dst.position(dst.position() + remaining);
         data.position(data.position() + remaining);

src/test/java/org/voltdb/meshmonitor/testutils/FakeWritableByteChannel.java

@@ -10,6 +10,8 @@
 import java.nio.ByteBuffer;
 import java.nio.channels.WritableByteChannel;
 
+import static org.voltdb.meshmonitor.testutils.FileChannelUtils.byteBufferAbsolutePut;
+
 public class FakeWritableByteChannel implements WritableByteChannel {
 
     private final boolean isSlow;
@@ -30,7 +32,7 @@ public int write(ByteBuffer src) {
             toBeWritten = 1;
         }
 
-        dataWritten.put(dataWritten.position(), src, src.position(), toBeWritten);
+        byteBufferAbsolutePut(dataWritten, dataWritten.position(), src, src.position(), toBeWritten);
         dataWritten.position(dataWritten.position() + toBeWritten);
         src.position(src.position() + toBeWritten);
 

src/test/java/org/voltdb/meshmonitor/testutils/FileChannelUtils.java

@@ -18,4 +18,24 @@ public static FakeWritableByteChannel newWritableChannel(boolean isSlowConnectio
     public static ByteBufferReadableByteChannel newReadableChannel(ByteBuffer data) {
         return new ByteBufferReadableByteChannel(data);
     }
+
+    /**
+     * It simulates put method that is available only since Java 16:
+     * <p>
+     * public ByteBuffer put(int index, ByteBuffer src, int offset, int length);
+     */
+    public static void byteBufferAbsolutePut(ByteBuffer dst, int index, ByteBuffer src, int offset, int length) {
+        if ((index < 0) || (offset < 0) || (length < 0) ||
+            (index > dst.limit() - length) ||
+            (offset > src.limit() - length)) {
+            throw new IndexOutOfBoundsException(
+                    String.format("dst.limit()=%d, index=%d, src.limit()=%d, offset=%d, length=%d",
+                            dst.limit(), index, src.limit(), offset, length)
+            );
+        }
+
+        for (int i = offset, j = index; i < offset + length; i++, j++) {
+            dst.put(j, src.get(i));
+        }
+    }
 }