Log DCP messages at Debug/Trace level in AppHost (#12533)

* Initial plan

* Map DCP log levels to Debug/Trace in AppHost

Co-authored-by: davidfowl <[email protected]>

* Update src/Aspire.Hosting/Dcp/DcpHost.cs

---------

Co-authored-by: copilot-swe-agent[bot] <[email protected]>
Co-authored-by: davidfowl <[email protected]>
Co-authored-by: David Fowler <[email protected]>

Author: Copilot

src/Aspire.Hosting/Dcp/DcpHost.cs

@@ -276,7 +276,7 @@ private async Task LogSocketOutputAsync(Socket socket, CancellationToken cancell
             if (!DcpLogParser.TryParseDcpLog(line, out var parsedMessage, out var logLevel, out var category))
             {
                 // If parsing fails, return a default logger and the line as-is
-                return (_logger, LogLevel.Information, Encoding.UTF8.GetString(line));
+                return (_logger, LogLevel.Debug, Encoding.UTF8.GetString(line));
             }
 
             var hash = new HashCode();
@@ -290,7 +290,12 @@ private async Task LogSocketOutputAsync(Socket socket, CancellationToken cancell
                 loggerCache[hashValue] = logger = _loggerFactory.CreateLogger($"Aspire.Hosting.Dcp.{category}");
             }
 
-            return (logger, logLevel, parsedMessage);
+            // Map DCP log levels to Debug/Trace to reduce noise in AppHost output.
+            // DCP errors are now flowing to resources and can be hidden from output,
+            // so we log them at Debug or Trace level instead of using the original DCP log level.
+            var appHostLogLevel = logLevel == LogLevel.Trace ? LogLevel.Trace : LogLevel.Debug;
+
+            return (logger, appHostLogLevel, parsedMessage);
         }
 
         try

tests/Aspire.Hosting.Tests/Dcp/DcpLogParserTests.cs

@@ -215,4 +215,26 @@ public void TryParseDcpLog_RealWorldExampleFromIssue_ParsesSuccessfully()
         Assert.Equal(LogLevel.Information, logLevel);
         Assert.Equal("dcpctrl.ExecutableReconciler", category);
     }
+
+    [Theory]
+    [InlineData("error", LogLevel.Error)]
+    [InlineData("warning", LogLevel.Warning)]
+    [InlineData("info", LogLevel.Information)]
+    [InlineData("debug", LogLevel.Debug)]
+    [InlineData("trace", LogLevel.Trace)]
+    public void TryParseDcpLog_ParsesAllLogLevels(string dcpLogLevel, LogLevel expectedLogLevel)
+    {
+        // Arrange
+        var logLine = $"2023-09-19T20:40:50.509-0700\t{dcpLogLevel}\tdcpctrl.TestReconciler\tTest message";
+        var bytes = Encoding.UTF8.GetBytes(logLine);
+
+        // Act
+        var result = DcpLogParser.TryParseDcpLog(bytes.AsSpan(), out var message, out var logLevel, out var category);
+
+        // Assert
+        Assert.True(result);
+        Assert.Equal("Test message", message);
+        Assert.Equal(expectedLogLevel, logLevel);
+        Assert.Equal("dcpctrl.TestReconciler", category);
+    }
 }