fix memory limiting java & kotlin

Adds logging for non-success status codes returned by the callback URL.

This improves debugging by providing visibility into callback failures, including the status code and a truncated response body.

.gitea/workflows/build-and-push.yaml

@@ -2,7 +2,7 @@ name: Build and Push Docker Images
 
 on:
   push:
-    branches: [ master ]
+    branches: [ roman ]
 
 env:
   REGISTRY: git.nullptr.top
@@ -17,10 +17,10 @@ jobs:
         include:
           - service: gateway
             dockerfile: src/LiquidCode.Tester.Gateway/Dockerfile
-            image: git.nullptr.top/liquidcode/liquidcode-tester-gateway
+            image: git.nullptr.top/liquidcode/liquidcode-tester-gateway-roman
           - service: worker
             dockerfile: src/LiquidCode.Tester.Worker/Dockerfile
-            image: git.nullptr.top/liquidcode/liquidcode-tester-worker
+            image: git.nullptr.top/liquidcode/liquidcode-tester-worker-roman
     steps:
       - name: Checkout repository
         uses: actions/checkout@v4

compose.yaml

@@ -26,6 +26,7 @@
 
   worker:
     image: liquidcode-tester-worker:latest
+    privileged: true
     container_name: liquidcode-tester-worker
     build:
       context: .
@@ -36,16 +37,9 @@
       - ASPNETCORE_ENVIRONMENT=Development
     networks:
       - liquidcode-network
-    # Security hardening for Worker
-    security_opt:
-      - no-new-privileges:true
-      - apparmor=docker-default
-    cap_drop:
-      - ALL
-    cap_add:
-      - SYS_ADMIN  # Required for Isolate namespaces
-      - SETUID     # Required for Isolate to change user context
-      - SETGID     # Required for Isolate to change group context
+    # Mount cgroup for Isolate sandbox
+    volumes:
+      - /sys/fs/cgroup:/sys/fs/cgroup:rw
     # Temporary filesystem for compilation and testing
     tmpfs:
       - /tmp:exec,size=4G

src/LiquidCode.Tester.Gateway/Services/WorkerClientService.cs

@@ -35,7 +35,7 @@ public class WorkerClientService : IWorkerClientService
             form.Add(new StringContent(submit.MissionId.ToString()), "MissionId");
             form.Add(new StringContent(submit.Language), "Language");
             form.Add(new StringContent(submit.LanguageVersion), "LanguageVersion");
-            form.Add(new StringContent(submit.SourceCode), "SourceCode");
+            form.Add(new StringContent(submit.SourceCode, System.Text.Encoding.UTF8, "text/plain"), "SourceCode");
             form.Add(new StringContent(submit.CallbackUrl), "CallbackUrl");
 
             // Add package file

src/LiquidCode.Tester.Worker/Dockerfile

@@ -82,27 +82,23 @@ RUN apt-get update && \
     && rm -rf /var/lib/apt/lists/*
 
 # Create unprivileged user for running the worker service
-RUN useradd -m -u 1001 -s /bin/bash workeruser && \
-    mkdir -p /var/local/lib/isolate && \
-    chmod 755 /var/local/lib/isolate && \
-    chown -R workeruser:workeruser /var/local/lib/isolate
+RUN mkdir -p /var/local/lib/isolate && \
+    chmod 755 /var/local/lib/isolate
 
-# Configure isolate
-RUN echo "cg_root = /sys/fs/cgroup" > /usr/local/etc/isolate && \
-    echo "cg_enable = 1" >> /usr/local/etc/isolate && \
-    echo "box_root = /var/local/lib/isolate" >> /usr/local/etc/isolate
+# Configure isolate directories and control-group root
+RUN printf "box_root = /var/local/lib/isolate\nlock_root = /run/isolate/locks\ncg_root = /sys/fs/cgroup\nfirst_uid = 60000\nfirst_gid = 60000\nnum_boxes = 1000\n" > /usr/local/etc/isolate.conf && \
+    ln -sf /usr/local/etc/isolate.conf /usr/local/etc/isolate && \
+    mkdir -p /run/isolate/locks
 
 # Copy published app
 COPY --from=publish /app/publish .
 
 # Create temp directory for compilation and testing with proper permissions
-RUN mkdir -p /tmp/testing && \
-    chown -R workeruser:workeruser /tmp/testing && \
-    chown -R workeruser:workeruser /app
+RUN mkdir -p /tmp/testing
 
 ENV ASPNETCORE_URLS=http://+:8080
 
 # Switch to unprivileged user
-USER workeruser
+#USER workeruser
 
 ENTRYPOINT ["dotnet", "LiquidCode.Tester.Worker.dll"]

src/LiquidCode.Tester.Worker/Services/CSharpCompilationServiceIsolate.cs

@@ -103,7 +103,10 @@ public class CSharpCompilationServiceIsolate : ICompilationService
                 DirectoryBindings = new List<DirectoryBinding>
                 {
                     new DirectoryBinding { HostPath = "/usr/lib", SandboxPath = "/usr/lib", ReadOnly = true },
-                    new DirectoryBinding { HostPath = "/lib", SandboxPath = "/lib", ReadOnly = true }
+                    new DirectoryBinding { HostPath = "/lib", SandboxPath = "/lib", ReadOnly = true },
+                    new DirectoryBinding { HostPath = "/usr/bin", SandboxPath = "/usr/bin", ReadOnly = true },
+                    new DirectoryBinding { HostPath = "/usr/share", SandboxPath = "/usr/share", ReadOnly = true },
+                    new DirectoryBinding { HostPath = "/etc/mono", SandboxPath = "/etc/mono", ReadOnly = true }
                 }
             });
 

src/LiquidCode.Tester.Worker/Services/CSharpExecutionServiceIsolate.cs

@@ -1,5 +1,6 @@
 using System.Diagnostics;
 using LiquidCode.Tester.Worker.Services.Isolate;
+using System.Collections.Generic;
 
 namespace LiquidCode.Tester.Worker.Services;
 
@@ -61,23 +62,41 @@ public class CSharpExecutionServiceIsolate : IExecutionService
             });
             chmodProcess?.WaitForExit();
 
-            // Prepare output file in box
+            // Prepare input/output files inside the sandbox
             var outputFilePath = Path.Combine(boxDir, "output.txt");
+            var stderrFilePath = Path.Combine(boxDir, "stderr.txt");
+            string? sandboxInputPath = null;
 
-            // Run in Isolate
+            if (!string.IsNullOrEmpty(inputFilePath) && File.Exists(inputFilePath))
+            {
+                sandboxInputPath = Path.Combine(boxDir, "input.txt");
+                File.Copy(inputFilePath, sandboxInputPath, overwrite: true);
+            }
+
+            // Run in Isolate using mono runtime
             var isolateResult = await _isolateService.RunAsync(new IsolateRunOptions
             {
                 BoxId = boxId,
-                Executable = $"/box/{executableName}",
+                Executable = "/usr/bin/mono",
+                Arguments = new[] { $"/box/{executableName}" },
                 TimeLimitSeconds = timeLimitMs / 1000.0,
                 WallTimeLimitSeconds = (timeLimitMs / 1000.0) * 2,
                 MemoryLimitKb = memoryLimitMb * 1024,
                 StackLimitKb = 256 * 1024,
-                ProcessLimit = 1, // Single process for C#
+                ProcessLimit = 64, // Mono may create multiple threads/processes
                 EnableNetwork = false,
-                StdinFile = inputFilePath,
+                StdinFile = sandboxInputPath,
                 StdoutFile = outputFilePath,
-                WorkingDirectory = "/box"
+                StderrFile = stderrFilePath,
+                WorkingDirectory = "/box",
+                DirectoryBindings = new List<DirectoryBinding>
+                {
+                    new DirectoryBinding { HostPath = "/usr/lib", SandboxPath = "/usr/lib", ReadOnly = true },
+                    new DirectoryBinding { HostPath = "/lib", SandboxPath = "/lib", ReadOnly = true },
+                    new DirectoryBinding { HostPath = "/usr/share", SandboxPath = "/usr/share", ReadOnly = true },
+                    new DirectoryBinding { HostPath = "/etc/mono", SandboxPath = "/etc/mono", ReadOnly = true },
+                    new DirectoryBinding { HostPath = "/usr/bin", SandboxPath = "/usr/bin", ReadOnly = true }
+                }
             });
 
             stopwatch.Stop();
@@ -88,10 +107,19 @@ public class CSharpExecutionServiceIsolate : IExecutionService
                 result.Output = await File.ReadAllTextAsync(outputFilePath);
             }
 
+            // Read stderr
+            var stderrContent = string.Empty;
+            if (File.Exists(stderrFilePath))
+            {
+                stderrContent = await File.ReadAllTextAsync(stderrFilePath);
+            }
+
             // Map Isolate result to ExecutionResult
             result.ExecutionTimeMs = (long)(isolateResult.CpuTimeSeconds * 1000);
             result.MemoryUsedMb = isolateResult.MemoryUsedKb / 1024;
-            result.ErrorOutput = isolateResult.ErrorOutput;
+            result.ErrorOutput = string.IsNullOrEmpty(stderrContent)
+                ? isolateResult.ErrorOutput
+                : $"{stderrContent}\n{isolateResult.ErrorOutput}".Trim();
             result.ExitCode = isolateResult.ExitCode;
 
             if (isolateResult.TimeLimitExceeded)

src/LiquidCode.Tester.Worker/Services/CallbackService.cs

@@ -33,6 +33,14 @@ public class CallbackService : ICallbackService
             var content = new StringContent(json, Encoding.UTF8, "application/json");
 
             var httpResponse = await httpClient.PostAsync(callbackUrl, content);
+
+            if (!httpResponse.IsSuccessStatusCode)
+            {
+                var responseBody = await httpResponse.Content.ReadAsStringAsync();
+                _logger.LogWarning("Callback returned non-success status {StatusCode} with body: {Body}",
+                    (int)httpResponse.StatusCode, Truncate(responseBody, 2048));
+            }
+
             httpResponse.EnsureSuccessStatusCode();
 
             _logger.LogInformation("Status update sent successfully");
@@ -44,6 +52,16 @@ public class CallbackService : ICallbackService
         }
     }
 
+    private static string Truncate(string value, int maxLength)
+    {
+        if (string.IsNullOrEmpty(value) || value.Length <= maxLength)
+        {
+            return value;
+        }
+
+        return value.Substring(0, maxLength) + "…";
+    }
+
     private bool IsLogCallback(string callbackUrl)
     {
         if (string.IsNullOrWhiteSpace(callbackUrl))

src/LiquidCode.Tester.Worker/Services/CppCompilationServiceIsolate.cs

@@ -1,8 +1,11 @@
+using System;
 using System.Collections.Generic;
+using System.IO;
 using System.Linq;
 using LiquidCode.Tester.Worker.Services.Isolate;
 using LiquidCode.Tester.Worker.Models;
 
+/// <summary>
 namespace LiquidCode.Tester.Worker.Services;
 
 /// <summary>
@@ -85,21 +88,60 @@ public class CppCompilationServiceIsolate : ICompilationService
 
             File.Copy(sourceFilePath, boxSourcePath, overwrite: true);
 
+            // Copy common headers from the source directory (e.g., testlib.h)
+            var sourceDirectory = Path.GetDirectoryName(sourceFilePath);
+            if (!string.IsNullOrEmpty(sourceDirectory) && Directory.Exists(sourceDirectory))
+            {
+                foreach (var header in Directory.EnumerateFiles(sourceDirectory))
+                {
+                    if (string.Equals(header, sourceFilePath, StringComparison.OrdinalIgnoreCase))
+                    {
+                        continue;
+                    }
+
+                    var extension = Path.GetExtension(header);
+                    if (extension is ".h" or ".hpp" or ".hh" or ".hxx" or ".h++" or ".inl" or ".tcc" )
+                    {
+                        var destination = Path.Combine(boxDir, Path.GetFileName(header));
+                        File.Copy(header, destination, overwrite: true);
+                    }
+                }
+            }
+
             // Resolve compiler and flags
             var (compiler, compilerFlags) = ResolveVersion(version);
             _logger.LogDebug("Using compiler: {Compiler} with flags: {Flags}", compiler, string.Join(' ', compilerFlags));
 
             // Build compiler arguments
             var arguments = new List<string>(compilerFlags);
+            var includeCounter = 0;
 
             // Add include directories
             if (includeDirectories != null)
             {
                 foreach (var includeDir in includeDirectories.Where(d => !string.IsNullOrWhiteSpace(d)))
+                {
+                    var resolvedIncludeDir = includeDir;
+
+                    if (!Path.IsPathRooted(resolvedIncludeDir))
+                    {
+                        var baseDir = sourceDirectory ?? Directory.GetCurrentDirectory();
+                        resolvedIncludeDir = Path.GetFullPath(Path.Combine(baseDir, includeDir));
+                    }
+
+                    if (Directory.Exists(resolvedIncludeDir))
+                    {
+                        includeCounter++;
+                        var targetIncludeDir = Path.Combine(boxDir, $"include_{includeCounter}");
+                        CopyDirectory(resolvedIncludeDir, targetIncludeDir);
+                        arguments.Add($"-I/box/include_{includeCounter}");
+                    }
+                    else
                     {
                         arguments.Add($"-I{includeDir}");
                     }
                 }
+            }
 
             // Add additional flags
             if (additionalFlags != null)
@@ -118,8 +160,25 @@ public class CppCompilationServiceIsolate : ICompilationService
             var stderrFilePath = Path.Combine(boxDir, "compile_stderr.txt");
 
             // Run compiler in Isolate
-            // Note: Isolate by default provides access to /usr, /lib, etc. via --share-net=no
-            // For compilation, we need access to system headers and libraries
+            // Bind the system toolchain directories read-only so the linker and headers remain reachable
+            var directoryBindings = new List<DirectoryBinding>
+            {
+                new DirectoryBinding { HostPath = "/usr/include", SandboxPath = "/usr/include", ReadOnly = true },
+                new DirectoryBinding { HostPath = "/usr/bin", SandboxPath = "/usr/bin", ReadOnly = true },
+                new DirectoryBinding { HostPath = "/usr/lib", SandboxPath = "/usr/lib", ReadOnly = true },
+                new DirectoryBinding { HostPath = "/lib", SandboxPath = "/lib", ReadOnly = true }
+            };
+
+            if (Directory.Exists("/bin"))
+            {
+                directoryBindings.Add(new DirectoryBinding { HostPath = "/bin", SandboxPath = "/bin", ReadOnly = true });
+            }
+
+            if (Directory.Exists("/usr/local/bin"))
+            {
+                directoryBindings.Add(new DirectoryBinding { HostPath = "/usr/local/bin", SandboxPath = "/usr/local/bin", ReadOnly = true });
+            }
+
             var isolateResult = await _isolateService.RunAsync(new IsolateRunOptions
             {
                 BoxId = boxId,
@@ -133,11 +192,10 @@ public class CppCompilationServiceIsolate : ICompilationService
                 EnableNetwork = false,
                 StderrFile = stderrFilePath,
                 WorkingDirectory = "/box",
-                DirectoryBindings = new List<DirectoryBinding>
+                DirectoryBindings = directoryBindings,
+                EnvironmentVariables = new Dictionary<string, string>
                 {
-                    new DirectoryBinding { HostPath = "/usr/include", SandboxPath = "/usr/include", ReadOnly = true },
-                    new DirectoryBinding { HostPath = "/usr/lib", SandboxPath = "/usr/lib", ReadOnly = true },
-                    new DirectoryBinding { HostPath = "/lib", SandboxPath = "/lib", ReadOnly = true }
+                    ["PATH"] = GetSandboxPath()
                 }
             });
 
@@ -231,6 +289,55 @@ public class CppCompilationServiceIsolate : ICompilationService
         }
     }
 
+    private static void CopyDirectory(string sourceDirectory, string destinationDirectory)
+    {
+        var sourceRoot = Path.GetFullPath(sourceDirectory);
+        var destinationRoot = Path.GetFullPath(destinationDirectory);
+
+        Directory.CreateDirectory(destinationRoot);
+
+        foreach (var directory in Directory.EnumerateDirectories(sourceRoot, "*", SearchOption.AllDirectories))
+        {
+            var relativePath = Path.GetRelativePath(sourceRoot, directory);
+            var targetDir = Path.Combine(destinationRoot, relativePath);
+            Directory.CreateDirectory(targetDir);
+        }
+
+        foreach (var file in Directory.EnumerateFiles(sourceRoot, "*", SearchOption.AllDirectories))
+        {
+            var relativePath = Path.GetRelativePath(sourceRoot, file);
+            var targetFile = Path.Combine(destinationRoot, relativePath);
+            Directory.CreateDirectory(Path.GetDirectoryName(targetFile)!);
+            File.Copy(file, targetFile, overwrite: true);
+        }
+    }
+
+    private static string GetSandboxPath()
+    {
+        var defaultPaths = new[] { "/usr/local/bin", "/usr/bin", "/bin" };
+        var hostPath = Environment.GetEnvironmentVariable("PATH");
+
+        if (string.IsNullOrWhiteSpace(hostPath))
+        {
+            return string.Join(':', defaultPaths);
+        }
+
+        var segments = hostPath
+            .Split(':', StringSplitOptions.RemoveEmptyEntries)
+            .Where(path => path.StartsWith("/usr", StringComparison.Ordinal) || path.StartsWith("/bin", StringComparison.Ordinal))
+            .ToList();
+
+        foreach (var defaultPath in defaultPaths)
+        {
+            if (!segments.Contains(defaultPath))
+            {
+                segments.Add(defaultPath);
+            }
+        }
+
+        return segments.Count == 0 ? string.Join(':', defaultPaths) : string.Join(':', segments);
+    }
+
     private (string compiler, List<string> compilerFlags) ResolveVersion(string? version)
     {
         var defaultCompiler = _configuration["Cpp:Compiler"] ?? "g++";

src/LiquidCode.Tester.Worker/Services/CppExecutionServiceIsolate.cs

@@ -61,8 +61,15 @@ public class CppExecutionServiceIsolate : IExecutionService
             });
             chmodProcess?.WaitForExit();
 
-            // Prepare output file in box
+            // Prepare input/output files inside the sandbox
             var outputFilePath = Path.Combine(boxDir, "output.txt");
+            string? sandboxInputPath = null;
+
+            if (!string.IsNullOrEmpty(inputFilePath) && File.Exists(inputFilePath))
+            {
+                sandboxInputPath = Path.Combine(boxDir, "input.txt");
+                File.Copy(inputFilePath, sandboxInputPath, overwrite: true);
+            }
 
             // Run in Isolate
             var isolateResult = await _isolateService.RunAsync(new IsolateRunOptions
@@ -75,7 +82,7 @@ public class CppExecutionServiceIsolate : IExecutionService
                 StackLimitKb = 256 * 1024, // 256 MB stack
                 ProcessLimit = 1, // Single process only
                 EnableNetwork = false, // No network access
-                StdinFile = inputFilePath,
+                StdinFile = sandboxInputPath,
                 StdoutFile = outputFilePath,
                 WorkingDirectory = "/box"
             });

src/LiquidCode.Tester.Worker/Services/Isolate/IsolateService.cs

@@ -1,3 +1,4 @@
+using System;
 using System.Diagnostics;
 using System.Text;
 
@@ -24,7 +25,7 @@ public class IsolateService
     {
         _logger.LogDebug("Initializing isolate box {BoxId}", boxId);
 
-        var result = await RunIsolateCommandAsync($"--box-id={boxId} --init");
+    var result = await RunIsolateCommandAsync($"--box-id={boxId} --cg --init");
 
         if (result.ExitCode != 0)
         {
@@ -90,7 +91,7 @@ public class IsolateService
     {
         _logger.LogDebug("Cleaning up isolate box {BoxId}", boxId);
 
-        var result = await RunIsolateCommandAsync($"--box-id={boxId} --cleanup");
+    var result = await RunIsolateCommandAsync($"--box-id={boxId} --cg --cleanup");
 
         if (result.ExitCode != 0)
         {
@@ -157,17 +158,17 @@ public class IsolateService
         // I/O redirection
         if (!string.IsNullOrEmpty(options.StdinFile))
         {
-            args.Add($"--stdin={options.StdinFile}");
+            args.Add($"--stdin={MapSandboxPath(options.StdinFile, options.BoxId)}");
         }
 
         if (!string.IsNullOrEmpty(options.StdoutFile))
         {
-            args.Add($"--stdout={options.StdoutFile}");
+            args.Add($"--stdout={MapSandboxPath(options.StdoutFile, options.BoxId)}");
         }
 
         if (!string.IsNullOrEmpty(options.StderrFile))
         {
-            args.Add($"--stderr={options.StderrFile}");
+            args.Add($"--stderr={MapSandboxPath(options.StderrFile, options.BoxId)}");
         }
 
         // Working directory
@@ -182,7 +183,7 @@ public class IsolateService
             foreach (var binding in options.DirectoryBindings)
             {
                 var dirSpec = binding.ReadOnly
-                    ? $"--dir={binding.HostPath}={binding.SandboxPath}:ro"
+                    ? $"--dir={binding.HostPath}={binding.SandboxPath}"
                     : $"--dir={binding.HostPath}={binding.SandboxPath}:rw";
                 args.Add(dirSpec);
             }
@@ -210,6 +211,25 @@ public class IsolateService
         return string.Join(" ", args);
     }
 
+    private static string MapSandboxPath(string path, int boxId)
+    {
+        if (string.IsNullOrEmpty(path))
+        {
+            return path;
+        }
+
+    var normalizedPath = Path.GetFullPath(path);
+    var boxRoot = Path.GetFullPath($"/var/local/lib/isolate/{boxId}/box");
+
+        if (normalizedPath.StartsWith(boxRoot, StringComparison.Ordinal))
+        {
+            var relative = normalizedPath.Substring(boxRoot.Length).TrimStart(Path.DirectorySeparatorChar, Path.AltDirectorySeparatorChar);
+            return relative.Length == 0 ? "/box" : $"/box/{relative.Replace(Path.DirectorySeparatorChar, '/')}";
+        }
+
+        return normalizedPath;
+    }
+
     /// <summary>
     /// Parse isolate metadata file
     /// </summary>
@@ -267,9 +287,6 @@ public class IsolateService
 
                 case "status":
                     result.Status = value;
-                    result.TimeLimitExceeded = value == "TO";
-                    result.MemoryLimitExceeded = value == "XX" || value == "MLE";
-                    result.RuntimeError = value == "RE" || value == "SG";
                     break;
 
                 case "message":
@@ -282,7 +299,10 @@ public class IsolateService
 
                 case "cg-oom-killed":
                     result.CgroupOomKilled = value == "1";
+                    if (result.CgroupOomKilled)
+                    {
                         result.MemoryLimitExceeded = true;
+                    }
                     break;
 
                 case "csw-voluntary":
@@ -297,6 +317,29 @@ public class IsolateService
             }
         }
 
+        // Derive status-related flags after parsing all metadata
+        switch (result.Status)
+        {
+            case "TO":
+                result.TimeLimitExceeded = true;
+                break;
+            case "RE":
+            case "SG":
+                result.RuntimeError = true;
+                break;
+            case "XX":
+                // Internal error reported by isolate
+                result.RuntimeError = true;
+                break;
+        }
+
+        if (!result.MemoryLimitExceeded &&
+            !string.IsNullOrEmpty(result.Message) &&
+            result.Message.Contains("memory limit", StringComparison.OrdinalIgnoreCase))
+        {
+            result.MemoryLimitExceeded = true;
+        }
+
         return result;
     }
 

src/LiquidCode.Tester.Worker/Services/JavaCompilationServiceIsolate.cs

@@ -14,7 +14,7 @@ public class JavaCompilationServiceIsolate : ICompilationService
     private readonly IsolateBoxPool _boxPool;
 
     private const int CompilationTimeLimitSeconds = 30;
-    private const int CompilationMemoryLimitMb = 512;
+    private const int CompilationMemoryLimitMb = 1024; // JVM needs more memory
 
     public JavaCompilationServiceIsolate(
         ILogger<JavaCompilationServiceIsolate> logger,
@@ -85,6 +85,7 @@ public class JavaCompilationServiceIsolate : ICompilationService
             arguments.Add($"/box/{sourceFileName}");
 
             var stderrFilePath = Path.Combine(boxDir, "compile_stderr.txt");
+            var stdoutFilePath = Path.Combine(boxDir, "compile_stdout.txt");
 
             var isolateResult = await _isolateService.RunAsync(new IsolateRunOptions
             {
@@ -94,28 +95,57 @@ public class JavaCompilationServiceIsolate : ICompilationService
                 TimeLimitSeconds = CompilationTimeLimitSeconds,
                 WallTimeLimitSeconds = CompilationTimeLimitSeconds * 2,
                 MemoryLimitKb = CompilationMemoryLimitMb * 1024,
-                StackLimitKb = 256 * 1024,
-                ProcessLimit = 10, // javac may spawn multiple processes
+                StackLimitKb = 128 * 1024, // 128MB stack per process
+                ProcessLimit = 64, // JVM needs many threads/processes
                 EnableNetwork = false,
+                StdoutFile = stdoutFilePath,
                 StderrFile = stderrFilePath,
                 WorkingDirectory = "/box",
                 DirectoryBindings = new List<DirectoryBinding>
                 {
+                    new DirectoryBinding { HostPath = "/usr/bin", SandboxPath = "/usr/bin", ReadOnly = true },
                     new DirectoryBinding { HostPath = "/usr/lib", SandboxPath = "/usr/lib", ReadOnly = true },
-                    new DirectoryBinding { HostPath = "/lib", SandboxPath = "/lib", ReadOnly = true }
+                    new DirectoryBinding { HostPath = "/lib", SandboxPath = "/lib", ReadOnly = true },
+                    new DirectoryBinding { HostPath = "/lib64", SandboxPath = "/lib64", ReadOnly = true },
+                    new DirectoryBinding { HostPath = "/etc", SandboxPath = "/etc", ReadOnly = true }
                 }
             });
 
             var compilerOutput = string.Empty;
+
+            // Read stdout (javac may output errors there)
+            if (File.Exists(stdoutFilePath))
+            {
+                var stdoutContent = await File.ReadAllTextAsync(stdoutFilePath);
+                if (!string.IsNullOrWhiteSpace(stdoutContent))
+                {
+                    compilerOutput = stdoutContent;
+                    _logger.LogDebug("Read stdout file: {Length} bytes", stdoutContent.Length);
+                }
+            }
+
+            // Read stderr
             if (File.Exists(stderrFilePath))
             {
-                compilerOutput = await File.ReadAllTextAsync(stderrFilePath);
+                var stderrContent = await File.ReadAllTextAsync(stderrFilePath);
+                if (!string.IsNullOrWhiteSpace(stderrContent))
+                {
+                    compilerOutput = string.IsNullOrEmpty(compilerOutput)
+                        ? stderrContent
+                        : $"{compilerOutput}\n{stderrContent}";
+                    _logger.LogDebug("Read stderr file: {Length} bytes", stderrContent.Length);
                 }
+            }
+
             if (!string.IsNullOrEmpty(isolateResult.ErrorOutput))
             {
-                compilerOutput = $"{compilerOutput}\n{isolateResult.ErrorOutput}".Trim();
+                compilerOutput = string.IsNullOrEmpty(compilerOutput)
+                    ? isolateResult.ErrorOutput
+                    : $"{compilerOutput}\n{isolateResult.ErrorOutput}";
             }
 
+            _logger.LogDebug("Final compiler output: {Output}", compilerOutput);
+
             if (isolateResult.TimeLimitExceeded)
             {
                 _logger.LogWarning("Java compilation time limit exceeded for box {BoxId}", boxId);

src/LiquidCode.Tester.Worker/Services/JavaExecutionServiceIsolate.cs

@@ -57,27 +57,51 @@ public class JavaExecutionServiceIsolate : IExecutionService
                 File.Copy(file, destPath, overwrite: true);
             }
 
-            // Prepare output file in box
+            // Prepare input/output files inside the sandbox
             var outputFilePath = Path.Combine(boxDir, "output.txt");
+            string? sandboxInputPath = null;
+
+            if (!string.IsNullOrEmpty(inputFilePath) && File.Exists(inputFilePath))
+            {
+                sandboxInputPath = Path.Combine(boxDir, "input.txt");
+                File.Copy(inputFilePath, sandboxInputPath, overwrite: true);
+            }
 
             // Run in Isolate
             // Note: Java needs more memory for JVM overhead
-            var javaMemoryMb = Math.Max(memoryLimitMb, 128); // Minimum 128MB for JVM
+            // We set JVM heap limit to the requested memory, but give Isolate more for JVM internals
+            var jvmHeapMb = memoryLimitMb;
+            var jvmTotalMemoryMb = memoryLimitMb + 64; // Add 64MB for JVM overhead (metaspace, code cache, etc.)
+
+            var arguments = new List<string>
+            {
+                $"-Xmx{jvmHeapMb}m",  // Max heap size = requested memory limit
+                $"-Xms{Math.Min(jvmHeapMb, 32)}m",  // Initial heap size (min 32MB or requested)
+                "-cp", "/box", "Solution"
+            };
 
             var isolateResult = await _isolateService.RunAsync(new IsolateRunOptions
             {
                 BoxId = boxId,
                 Executable = "/usr/bin/java",
-                Arguments = new[] { "-cp", "/box", "Solution" },
+                Arguments = arguments.ToArray(),
                 TimeLimitSeconds = timeLimitMs / 1000.0,
                 WallTimeLimitSeconds = (timeLimitMs / 1000.0) * 2,
-                MemoryLimitKb = javaMemoryMb * 1024,
+                MemoryLimitKb = jvmTotalMemoryMb * 1024,
                 StackLimitKb = 256 * 1024, // 256 MB stack
                 ProcessLimit = 64, // Java creates multiple threads
                 EnableNetwork = false,
-                StdinFile = inputFilePath,
+                StdinFile = sandboxInputPath,
                 StdoutFile = outputFilePath,
-                WorkingDirectory = "/box"
+                WorkingDirectory = "/box",
+                DirectoryBindings = new List<DirectoryBinding>
+                {
+                    new DirectoryBinding { HostPath = "/usr/bin", SandboxPath = "/usr/bin", ReadOnly = true },
+                    new DirectoryBinding { HostPath = "/usr/lib", SandboxPath = "/usr/lib", ReadOnly = true },
+                    new DirectoryBinding { HostPath = "/lib", SandboxPath = "/lib", ReadOnly = true },
+                    new DirectoryBinding { HostPath = "/lib64", SandboxPath = "/lib64", ReadOnly = true },
+                    new DirectoryBinding { HostPath = "/etc", SandboxPath = "/etc", ReadOnly = true }
+                }
             });
 
             stopwatch.Stop();

src/LiquidCode.Tester.Worker/Services/KotlinCompilationServiceIsolate.cs

@@ -1,3 +1,4 @@
+using System.Collections.Generic;
 using LiquidCode.Tester.Worker.Services.Isolate;
 using LiquidCode.Tester.Worker.Models;
 
@@ -14,7 +15,7 @@ public class KotlinCompilationServiceIsolate : ICompilationService
     private readonly IsolateBoxPool _boxPool;
 
     private const int CompilationTimeLimitSeconds = 30;
-    private const int CompilationMemoryLimitMb = 512;
+    private const int CompilationMemoryLimitMb = 1024; // Kotlin uses JVM, needs more memory
 
     public KotlinCompilationServiceIsolate(
         ILogger<KotlinCompilationServiceIsolate> logger,
@@ -38,7 +39,21 @@ public class KotlinCompilationServiceIsolate : ICompilationService
 
         try
         {
-            await File.WriteAllTextAsync(sourceFilePath, sourceCode);
+            // Normalize line endings
+            var normalizedSourceCode = sourceCode
+                .Replace("\\r\\n", "\n")  // Handle escaped \r\n (literal text "\\r\\n")
+                .Replace("\\n", "\n")      // Handle escaped \n (literal text "\\n")
+                .Replace("\\r", "\n")      // Handle escaped \r (literal text "\\r")
+                .Replace("\r\n", "\n")     // Handle actual Windows line endings
+                .Replace("\r", "\n");      // Handle actual Mac line endings
+
+            _logger.LogDebug("Source code length: {Length}, normalized length: {NormalizedLength}, line count: {LineCount}",
+                sourceCode.Length, normalizedSourceCode.Length, normalizedSourceCode.Split('\n').Length);
+
+            _logger.LogDebug("First 200 chars of source: {Preview}",
+                normalizedSourceCode.Length > 200 ? normalizedSourceCode.Substring(0, 200) : normalizedSourceCode);
+
+            await File.WriteAllTextAsync(sourceFilePath, normalizedSourceCode);
             return await CompileFileInIsolateAsync(sourceFilePath, jarFilePath, version);
         }
         catch (Exception ex)
@@ -88,6 +103,7 @@ public class KotlinCompilationServiceIsolate : ICompilationService
             arguments.Add($"/box/{jarFileName}");
 
             var stderrFilePath = Path.Combine(boxDir, "compile_stderr.txt");
+            var stdoutFilePath = Path.Combine(boxDir, "compile_stdout.txt");
 
             var isolateResult = await _isolateService.RunAsync(new IsolateRunOptions
             {
@@ -97,27 +113,57 @@ public class KotlinCompilationServiceIsolate : ICompilationService
                 TimeLimitSeconds = CompilationTimeLimitSeconds,
                 WallTimeLimitSeconds = CompilationTimeLimitSeconds * 2,
                 MemoryLimitKb = CompilationMemoryLimitMb * 1024,
-                StackLimitKb = 256 * 1024,
-                ProcessLimit = 10,
+                StackLimitKb = 128 * 1024, // 128MB stack per process
+                ProcessLimit = 64, // Kotlin uses JVM, needs many threads/processes
                 EnableNetwork = false,
+                StdoutFile = stdoutFilePath,
                 StderrFile = stderrFilePath,
                 WorkingDirectory = "/box",
                 DirectoryBindings = new List<DirectoryBinding>
                 {
                     new DirectoryBinding { HostPath = "/usr/lib", SandboxPath = "/usr/lib", ReadOnly = true },
                     new DirectoryBinding { HostPath = "/lib", SandboxPath = "/lib", ReadOnly = true },
+                    new DirectoryBinding { HostPath = "/lib64", SandboxPath = "/lib64", ReadOnly = true },
+                    new DirectoryBinding { HostPath = "/usr/bin", SandboxPath = "/usr/bin", ReadOnly = true },
+                    new DirectoryBinding { HostPath = "/bin", SandboxPath = "/bin", ReadOnly = true },
+                    new DirectoryBinding { HostPath = "/etc", SandboxPath = "/etc", ReadOnly = true },
                     new DirectoryBinding { HostPath = "/opt/kotlinc", SandboxPath = "/opt/kotlinc", ReadOnly = true }
+                },
+                EnvironmentVariables = new Dictionary<string, string>
+                {
+                    ["PATH"] = "/usr/local/bin:/usr/bin:/bin"
                 }
             });
 
             var compilerOutput = string.Empty;
+
+            // Read stdout (kotlinc may output errors there)
+            if (File.Exists(stdoutFilePath))
+            {
+                var stdoutContent = await File.ReadAllTextAsync(stdoutFilePath);
+                if (!string.IsNullOrWhiteSpace(stdoutContent))
+                {
+                    compilerOutput = stdoutContent;
+                }
+            }
+
+            // Read stderr
             if (File.Exists(stderrFilePath))
             {
-                compilerOutput = await File.ReadAllTextAsync(stderrFilePath);
+                var stderrContent = await File.ReadAllTextAsync(stderrFilePath);
+                if (!string.IsNullOrWhiteSpace(stderrContent))
+                {
+                    compilerOutput = string.IsNullOrEmpty(compilerOutput)
+                        ? stderrContent
+                        : $"{compilerOutput}\n{stderrContent}";
                 }
+            }
+
             if (!string.IsNullOrEmpty(isolateResult.ErrorOutput))
             {
-                compilerOutput = $"{compilerOutput}\n{isolateResult.ErrorOutput}".Trim();
+                compilerOutput = string.IsNullOrEmpty(compilerOutput)
+                    ? isolateResult.ErrorOutput
+                    : $"{compilerOutput}\n{isolateResult.ErrorOutput}";
             }
 
             if (isolateResult.TimeLimitExceeded)

src/LiquidCode.Tester.Worker/Services/KotlinExecutionServiceIsolate.cs

@@ -1,4 +1,5 @@
 using System.Diagnostics;
+using System.Collections.Generic;
 using LiquidCode.Tester.Worker.Services.Isolate;
 
 namespace LiquidCode.Tester.Worker.Services;
@@ -52,26 +53,55 @@ public class KotlinExecutionServiceIsolate : IExecutionService
 
             File.Copy(executablePath, boxJarPath, overwrite: true);
 
-            // Prepare output file in box
+            // Prepare input/output files inside the sandbox
             var outputFilePath = Path.Combine(boxDir, "output.txt");
+            string? sandboxInputPath = null;
+
+            if (!string.IsNullOrEmpty(inputFilePath) && File.Exists(inputFilePath))
+            {
+                sandboxInputPath = Path.Combine(boxDir, "input.txt");
+                File.Copy(inputFilePath, sandboxInputPath, overwrite: true);
+            }
 
             // Run in Isolate (Kotlin runs via Java)
-            var kotlinMemoryMb = Math.Max(memoryLimitMb, 128); // Minimum 128MB for JVM
+            // We set JVM heap limit to the requested memory, but give Isolate more for JVM internals
+            var jvmHeapMb = memoryLimitMb;
+            var jvmTotalMemoryMb = memoryLimitMb + 64; // Add 64MB for JVM overhead
+
+            var arguments = new List<string>
+            {
+                $"-Xmx{jvmHeapMb}m",  // Max heap size = requested memory limit
+                $"-Xms{Math.Min(jvmHeapMb, 32)}m",  // Initial heap size
+                "-jar", $"/box/{jarName}"
+            };
 
             var isolateResult = await _isolateService.RunAsync(new IsolateRunOptions
             {
                 BoxId = boxId,
                 Executable = "/usr/bin/java",
-                Arguments = new[] { "-jar", $"/box/{jarName}" },
+                Arguments = arguments.ToArray(),
                 TimeLimitSeconds = timeLimitMs / 1000.0,
                 WallTimeLimitSeconds = (timeLimitMs / 1000.0) * 2,
-                MemoryLimitKb = kotlinMemoryMb * 1024,
+                MemoryLimitKb = jvmTotalMemoryMb * 1024,
                 StackLimitKb = 256 * 1024,
                 ProcessLimit = 64, // JVM creates multiple threads
                 EnableNetwork = false,
-                StdinFile = inputFilePath,
+                StdinFile = sandboxInputPath,
                 StdoutFile = outputFilePath,
-                WorkingDirectory = "/box"
+                WorkingDirectory = "/box",
+                DirectoryBindings = new List<DirectoryBinding>
+                {
+                    new DirectoryBinding { HostPath = "/usr/lib", SandboxPath = "/usr/lib", ReadOnly = true },
+                    new DirectoryBinding { HostPath = "/lib", SandboxPath = "/lib", ReadOnly = true },
+                    new DirectoryBinding { HostPath = "/lib64", SandboxPath = "/lib64", ReadOnly = true },
+                    new DirectoryBinding { HostPath = "/usr/bin", SandboxPath = "/usr/bin", ReadOnly = true },
+                    new DirectoryBinding { HostPath = "/bin", SandboxPath = "/bin", ReadOnly = true },
+                    new DirectoryBinding { HostPath = "/etc", SandboxPath = "/etc", ReadOnly = true }
+                },
+                EnvironmentVariables = new Dictionary<string, string>
+                {
+                    ["PATH"] = "/usr/local/bin:/usr/bin:/bin"
+                }
             });
 
             stopwatch.Stop();

src/LiquidCode.Tester.Worker/Services/PythonExecutionServiceIsolate.cs

@@ -55,8 +55,15 @@ public class PythonExecutionServiceIsolate : IExecutionService
 
             File.Copy(executablePath, boxScriptPath, overwrite: true);
 
-            // Prepare output file in box
+            // Prepare input/output files inside the sandbox
             var outputFilePath = Path.Combine(boxDir, "output.txt");
+            string? sandboxInputPath = null;
+
+            if (!string.IsNullOrEmpty(inputFilePath) && File.Exists(inputFilePath))
+            {
+                sandboxInputPath = Path.Combine(boxDir, "input.txt");
+                File.Copy(inputFilePath, sandboxInputPath, overwrite: true);
+            }
 
             // Get Python executable from configuration
             var pythonExecutable = _configuration["Python:Executable"] ?? "python3";
@@ -73,7 +80,7 @@ public class PythonExecutionServiceIsolate : IExecutionService
                 StackLimitKb = 256 * 1024,
                 ProcessLimit = 1, // Single process for Python
                 EnableNetwork = false,
-                StdinFile = inputFilePath,
+                StdinFile = sandboxInputPath,
                 StdoutFile = outputFilePath,
                 WorkingDirectory = "/box"
             });