Part 1: adding better diagnostic messages for too-long TMPDIR on Linux (#5517)

Closes dotnet/runtime#111165

This PR adds better diagnostic messages in the scenario of too-long
TMPDIR values on Linux that cause the diagnostic socket to be absent or
incorrectly named.

---------

Co-authored-by: Rachel Jarvi <[email protected]>
Co-authored-by: Noah Falk <[email protected]>

Author: 3 people

src/Microsoft.Diagnostics.NETCore.Client/DiagnosticsIpc/IpcTransport.cs

@@ -239,10 +239,13 @@ internal class PidIpcEndpoint : IpcEndpoint
     {
         public static string IpcRootPath { get; } = RuntimeInformation.IsOSPlatform(OSPlatform.Windows) ? @"\\.\pipe\" : Path.GetTempPath();
         public static string DiagnosticsPortPattern { get; } = RuntimeInformation.IsOSPlatform(OSPlatform.Windows) ? @"^dotnet-diagnostic-(\d+)$" : @"^dotnet-diagnostic-(\d+)-(\d+)-socket$";
-
+        // Format strings as private const members
+        private const string _defaultAddressFormatWindows = "dotnet-diagnostic-{0}";
+        private const string _dsrouterAddressFormatWindows = "dotnet-diagnostic-dsrouter-{0}";
+        private const string _defaultAddressFormatNonWindows = "dotnet-diagnostic-{0}-{1}-socket";
+        private const string _dsrouterAddressFormatNonWindows = "dotnet-diagnostic-dsrouter-{0}-{1}-socket";
         private int _pid;
         private IpcEndpointConfig _config;
-
         /// <summary>
         /// Creates a reference to a .NET process's IPC Transport
         /// using the default rules for a given pid
@@ -289,11 +292,11 @@ private static bool TryGetDefaultAddress(int pid, out string defaultAddress)
 
             if (RuntimeInformation.IsOSPlatform(OSPlatform.Windows))
             {
-                defaultAddress = $"dotnet-diagnostic-{pid}";
+                defaultAddress = string.Format(_defaultAddressFormatWindows, pid);
 
                 try
                 {
-                    string dsrouterAddress = Directory.GetFiles(IpcRootPath, $"dotnet-diagnostic-dsrouter-{pid}").FirstOrDefault();
+                    string dsrouterAddress = Directory.GetFiles(IpcRootPath, string.Format(_dsrouterAddressFormatWindows, pid)).FirstOrDefault();
                     if (!string.IsNullOrEmpty(dsrouterAddress))
                     {
                         defaultAddress = dsrouterAddress;
@@ -305,11 +308,11 @@ private static bool TryGetDefaultAddress(int pid, out string defaultAddress)
             {
                 try
                 {
-                    defaultAddress = Directory.GetFiles(IpcRootPath, $"dotnet-diagnostic-{pid}-*-socket") // Try best match.
+                    defaultAddress = Directory.GetFiles(IpcRootPath, string.Format(_defaultAddressFormatNonWindows, pid, "*")) // Try best match.
                         .OrderByDescending(f => new FileInfo(f).LastWriteTime)
                         .FirstOrDefault();
 
-                    string dsrouterAddress = Directory.GetFiles(IpcRootPath, $"dotnet-diagnostic-dsrouter-{pid}-*-socket") // Try best match.
+                    string dsrouterAddress = Directory.GetFiles(IpcRootPath, string.Format(_dsrouterAddressFormatNonWindows, pid, "*")) // Try best match.
                         .OrderByDescending(f => new FileInfo(f).LastWriteTime)
                         .FirstOrDefault();
 
@@ -350,8 +353,15 @@ public static string GetDefaultAddress(int pid)
                 string msg = $"Unable to connect to Process {pid}.";
                 if (!RuntimeInformation.IsOSPlatform(OSPlatform.Windows))
                 {
+                    int total_length = IpcRootPath.Length + string.Format(_defaultAddressFormatNonWindows, pid, "##########").Length;
+                    if (total_length > 108) // This isn't perfect as we don't know the disambiguation key length. However it should catch most cases.
+                    {
+                        msg += "The total length of the diagnostic socket path may exceed 108 characters. " +
+                            "Try setting the TMPDIR environment variable to a shorter path";
+                    }
                     msg += $" Please verify that {IpcRootPath} is writable by the current user. "
                         + "If the target process has environment variable TMPDIR set, please set TMPDIR to the same directory. "
+                        + "Please also ensure that the target process has {TMPDIR}/dotnet-diagnostic-{pid}-{disambiguation_key}-socket shorter than 108 characters. "
                         + "Please see https://aka.ms/dotnet-diagnostics-port for more information";
                 }
                 throw new ServerNotAvailableException(msg);
@@ -367,7 +377,7 @@ public static bool IsDefaultAddressDSRouter(int pid, string address)
                 address = address.Substring(IpcRootPath.Length);
             }
 
-            string dsrouterAddress = $"dotnet-diagnostic-dsrouter-{pid}";
+            string dsrouterAddress = string.Format(_dsrouterAddressFormatWindows, pid);
             return address.StartsWith(dsrouterAddress, StringComparison.OrdinalIgnoreCase);
         }