Retention policy for cdb output files

Author: CapulusCodeNinja

nexus_engine/nexus_engine/Internal/CdbSession.cs

@@ -471,13 +471,77 @@ private string GetCdbSessionBasedLogPath(string sessionId)
         // Ensure the Sessions directory exists
         _ = Directory.CreateDirectory(sessionsDirectory);
 
+        var retentionDays = m_Settings.Get().Logging.RetentionDays;
+        if (retentionDays > 0)
+        {
+            CleanupOldCdbLogs(sessionsDirectory, retentionDays);
+        }
+
         var newFileNameWithoutExtension = $"cdb_{sessionId}";
         var newFileName = Path.ChangeExtension(newFileNameWithoutExtension, ".log");
         var newPath = Path.Combine(sessionsDirectory, newFileName);
 
         return newPath;
     }
 
+    /// <summary>
+    /// Cleans up CDB log files older than the configured retention period in the specified Sessions directory.
+    /// </summary>
+    /// <param name="sessionsDirectory">The directory containing the CDB log files.</param>
+    /// <param name="retentionDays">The retention period in days.</param>
+    protected void CleanupOldCdbLogs(string sessionsDirectory, int retentionDays)
+    {
+        if (retentionDays <= 0)
+        {
+            return;
+        }
+
+        try
+        {
+            var directoryInfo = m_FileSystem.GetDirectoryInfo(sessionsDirectory);
+            var files = directoryInfo.GetFiles("cdb_*.log");
+
+            if (files.Length == 0)
+            {
+                return;
+            }
+
+            var cutoff = DateTime.Now.AddDays(-retentionDays);
+            var deletedCount = 0;
+
+            foreach (var file in files)
+            {
+                if (file.CreationTime >= cutoff)
+                {
+                    continue;
+                }
+
+                try
+                {
+                    m_FileSystem.DeleteFile(file.FullName);
+                    deletedCount++;
+                }
+                catch (Exception ex)
+                {
+                    m_Logger.Warn(ex, "Failed to delete old CDB log file {CdbLogFile}", file.FullName);
+                }
+            }
+
+            if (deletedCount > 0)
+            {
+                m_Logger.Info(
+                    "Deleted {DeletedCount} CDB log files older than {RetentionDays} days in {SessionsDirectory}",
+                    deletedCount,
+                    retentionDays,
+                    sessionsDirectory);
+            }
+        }
+        catch (Exception ex)
+        {
+            m_Logger.Warn(ex, "Error while cleaning up old CDB log files in {SessionsDirectory}", sessionsDirectory);
+        }
+    }
+
     /// <summary>
     /// Builds the command line arguments for starting the CDB process.
     /// </summary>

unittests/nexus_engine/nexus_engine_unittests/Internal/CdbSessionTestAccessor.cs

@@ -183,6 +183,16 @@ public bool GetEffectiveProcessExitedForTesting()
         return CdbSession.CreateCommandWithSentinels(command);
     }
 
+    /// <summary>
+    /// Exposes the CleanupOldCdbLogs method for testing.
+    /// </summary>
+    /// <param name="sessionsDirectory">The directory containing the CDB log files.</param>
+    /// <param name="retentionDays">The retention period in days.</param>
+    public void CleanupOldCdbLogsForTesting(string sessionsDirectory, int retentionDays)
+    {
+        CleanupOldCdbLogs(sessionsDirectory, retentionDays);
+    }
+
     /// <summary>
     /// Sets the process exited state for testing purposes.
     /// </summary>

unittests/nexus_engine/nexus_engine_unittests/Internal/CdbSessionTests.cs

@@ -580,6 +580,53 @@ public void ProcessOutputLine_BeforeStartMarker_IgnoresLine()
         _ = output.ToString().Should().BeEmpty();
     }
 
+    /// <summary>
+    /// Verifies that CleanupOldCdbLogs deletes CDB log files older than the configured retention period
+    /// based on their creation time and leaves newer files intact.
+    /// </summary>
+    [Fact]
+    public void CleanupOldCdbLogs_DeletesFilesOlderThanRetentionDays()
+    {
+        // Arrange
+        var tempRoot = Path.Combine(Path.GetTempPath(), "MCPNexusCdbRetentionTests", Guid.NewGuid().ToString("N"));
+        var sessionsDirectory = Path.Combine(tempRoot, "Sessions");
+        _ = Directory.CreateDirectory(sessionsDirectory);
+
+        var oldFilePath = Path.Combine(sessionsDirectory, "cdb_old.log");
+        var recentFilePath = Path.Combine(sessionsDirectory, "cdb_recent.log");
+
+        File.WriteAllText(oldFilePath, "old");
+        File.WriteAllText(recentFilePath, "recent");
+
+        File.SetCreationTime(oldFilePath, DateTime.Now.AddDays(-10));
+        File.SetCreationTime(recentFilePath, DateTime.Now);
+
+        try
+        {
+            var directoryInfo = new DirectoryInfo(sessionsDirectory);
+            _ = m_MockFileSystem.Setup(fs => fs.GetDirectoryInfo(sessionsDirectory)).Returns(directoryInfo);
+            _ = m_MockFileSystem.Setup(fs => fs.DeleteFile(It.IsAny<string>()))
+                .Callback<string>(path => File.Delete(path));
+
+            var accessor = new CdbSessionTestAccessor(m_Settings.Object, m_MockFileSystem.Object, m_MockProcessManager.Object);
+
+            // Act
+            accessor.CleanupOldCdbLogsForTesting(sessionsDirectory, 7);
+
+            // Assert
+            _ = File.Exists(oldFilePath).Should().BeFalse();
+            _ = File.Exists(recentFilePath).Should().BeTrue();
+            m_MockFileSystem.Verify(fs => fs.DeleteFile(oldFilePath), Times.Once);
+        }
+        finally
+        {
+            if (Directory.Exists(tempRoot))
+            {
+                Directory.Delete(tempRoot, true);
+            }
+        }
+    }
+
     /// <summary>
     /// Verifies that ThrowIfDisposed throws when session is disposed.
     /// </summary>