Problem
Bugs and there handling are very important for each software developer. Often bugs are detected during internal test processes. But it’s also common that a bug appears the first time on a customer machine. In this case is important to log the exception / problem and to report this to the developer. Weiterhin ist das Schreiben von guten Logs nicht selbstverständlich, dies soll allerdings nicht Thema diesem Blogeintrag sein. It’s clear that good logs are important, but the technics to write good logs are not part of this blog entry.
An example of an log is the stack trace. A stack trace describes the last process steps if an unhandled exception is thrown.In this example we throw an exception in the method “test”. The log shows you the source code file and the line.
1 2 3 4 | bei System.Environment.GetStackTrace(Exception e, Boolean needFileInfo) bei System.Environment.get_StackTrace() bei ConsoleApp2.Program.test(Int32 wert) in C:\\Users\\lpl\\source\\repos\\ConsoleApp2\\ConsoleApp2\\Program.cs:Zeile 31. bei ConsoleApp2.Program.Main(String[] args) in C:\\Users\\lpl\\source\\repos\\ConsoleApp2\\ConsoleApp2\\Program.cs:Zeile 16. |
As you see in the stack trace above, the trace gives you a good hint where the error could be. But it’s not clear which parameter are used to call the method “test”, that this error appears. Also this used local variables and there values are not listed. These kind of information are often very important and gives you a better hint of that error. Often developers spent a lot of time to extract this kind of data. On technic is to reproduce that error, so that the developer is able to see the values with his debugger.
Soluction
Based on this, I started to search for option to get this information’s and values automatically, bevor a developer start to this about this issue. In my mind formed a tool that runs as a service on a client machine. And observes a process if any unhandled exceptions are thrown, so that this process is able to catch all needed information. Surly this kind of tool need to be fast and small, that it’s not blocking or interfering the main process.
I found the library MdbEngine. This library is a mobile debugger, like the debugger on a developer machine. This debugger is able to catch the same information’s as a developer with there debugger.
This code below shows you how to you the MdbEngine debugger. First of all you need to attach the debugger to a process. For that you need the process id. Additionally you need a workaround right after the start.
1 2 3 4 5 6 7 8 9 10 11 12 13 | _symbolPath = Uri.UnescapeDataString(symbolPath); _engine=new MDbgEngine(); _engine.Options.SymbolPath = _symbolPath; _process = _engine.Attach(processID); _process.SymbolPath = _symbolPath; _process.Go().WaitOne(); if (!(_process.StopReason is AttachCompleteStopReason)) throw new System.Exception("Unexpected"); _process.Go(); _process.PostDebugEvent += ProcessOnPostDebugEvent; |
With the PostDebugEvent we get a notification on a debug event. This means also on each exception.
1 2 3 4 5 6 7 8 9 10 11 | private void ProcessOnPostDebugEvent(object sender, CustomPostCallbackEventArgs e) { try { Process(sender, e); } catch (System.Exception) { } } |
In der eigentlichen Verarbeitung gibt es zunächst einen Filter auf den Debugeventtyp. Zusätzlich wird geprüft ob der Exceptionname nicht null ist.
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 | if (e.CallbackType != ManagedCallbackType.OnException2) return; CorException2EventArgs exception; exception = (CorException2EventArgs)e.CallbackArgs; if (exception.EventType == CorDebugExceptionCallbackType.DEBUG_EXCEPTION_FIRST_CHANCE || exception.EventType == CorDebugExceptionCallbackType.DEBUG_EXCEPTION_USER_FIRST_CHANCE) { MDbgThread thread; thread = _process.Threads.Lookup(exception.Thread); Exception exceptionResult = new Exception(); if (thread.CurrentException.Name != null) { exceptionResult.Name = thread.CurrentException.Name; exceptionResult.Value = thread.CurrentException.Value; } exceptionResult.TypeName = thread.CurrentException.TypeName; |
In a loop we read out all local variables and all parameters. We cut the stack trace after the first 10 frames. Normally the first 10 are enough, if you need more feel free to increase it. Just make sure that you do not ran into a performance issue, because your process is stopped at this point. Your process can only continue if you leave this method.
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 | var maxCount = 10; var count = 0; foreach (var frame in thread.Frames) { if (frame.Function == null) continue; if (count >= maxCount) break; count++; var frameResult = new Frame(); if (frame.SourcePosition != null) { frameResult.Path = frame.SourcePosition.Path; frameResult.Line = frame.SourcePosition.Line; } frameResult.FunctionName = frame.Function.FullName; if (frame.IsManaged && !frame.IsInfoOnly) { try { foreach (var argument in frame.Function.GetArguments(frame)) { var value = GetValue(argument); if (value != null) frameResult.Parameter.Add(value); } } catch (System.Exception) { } try { foreach (var variable in frame.Function.GetActiveLocalVars(frame)) { var value = GetValue(variable); if (value != null) frameResult.LocalVariables.Add(value); } } catch (System.Exception) { } } exceptionResult.Frames.Add(frameResult); } CreateTraceFile(thread.CurrentException.CorValue.Raw.GetHashCode() + "_" + thread.CurrentException.CorValue.Address, exceptionResult); |
We save all these values into a Json file. Additionally we need to define how we handle with complex types. We cannot use the object internal toString() method, because it’s not clear if the method is correctly implemented. What we get from the MdbEngine, is to print all members of an object. So that we roll out an object into their peace’s. we just need to define how deep we would like to go. Also make sure that you exclude some namespaces. Normally we do not need to roll out a foreign GUI object.
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 | private Value GetValue(MDbgValue aValue) { try { Value value = new Value(); value.Name = aValue.Name; if (aValue.IsNull) { value.TypeName = aValue.TypeName; value.ValueO = "null"; } else { value.TypeName = aValue.TypeName; value.ValueO = expandValue(aValue); } return value; } catch (System.Exception) { return null; } } private string expandValue(MDbgValue value) { if(value.TypeName.Contains("WebControls") || value.TypeName.Contains("ascx") || value.TypeName.Contains("ASP") || value.TypeName.Contains("System.Web")) return value.GetStringValue(0); int level = 0; string result = ""; while (level <= 3) { try { result = value.GetStringValue(level); level++; } catch (System.Exception) { return result; } } return result; } |
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 | class Options { [Value(0, Required = true, MetaName = "ProcessID", HelpText = "ID off Process")] public int ProcessID { get; set; } [Value(1, Required = true , MetaName = "FilePath", HelpText = @"Path to folder where debug files are saved. HttpRuntime.AppDomainAppPath + \"\\\\App_Data\\\\TraceFiles\\\\\" ")] public string FilePath { get; set; } [Value(2, Required = true, MetaName = "SymbolPath", HelpText = @"Path to folder where dlls and symbols are stored. HttpRuntime.AppDomainAppPath + \"\\\\bin\" ")] public string SymbolPath { get; set; } } static void Main(string[] args) { CommandLine.Parser.Default.ParseArguments <options>(args) .WithParsed <options>(Start);</options></options> AppDomain appDomain = AppDomain.CurrentDomain; appDomain.ProcessExit += new EventHandler(OnClose); while (true) { Thread.Sleep(1000); } } private static void Start(Options obj) { stackTrace = new StackTraceDataCollectorService(obj.ProcessID, obj.FilePath, obj.SymbolPath); } } |
Das Ergebnis sieht nun wie folgt aus.
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 | { "Name": null, "Value": null, "TypeName": "System.Exception", "Frames": [ { "Path": "source\\\\repos\\\\ConsoleApp2\\\\ConsoleApp2\\\\Program.cs", "Line": 35, "FunctionName": "ConsoleApp2.Program.test", "Parameter": [ { "Name": "wert", "TypeName": "N/A", "ValueO": "null" }, { "Name": "wert2", "TypeName": "System.Int32", "ValueO": "2" }, { "Name": "StringValue", "TypeName": "System.String", "ValueO": "\"myvalue\"" } ], "LocalVariables": [ { "Name": "b", "TypeName": "System.Int32", "ValueO": "1" } ] }, { "Path": "source\\\\repos\\\\ConsoleApp2\\\\ConsoleApp2\\\\Program.cs", "Line": 17, "FunctionName": "ConsoleApp2.Program.Main", "Parameter": [ { "Name": "args", "TypeName": "N/A", "ValueO": "null" } ], "LocalVariables": [] } ], "DateTime": "2019-10-29T09:41:18.8572539+01:00" } |
Weiter unten finden Sie die Sourcen.
Program.cs
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 | using System; using System.Collections.Generic; using System.Diagnostics; using System.Linq; using System.Text; using System.Threading; using System.Threading.Tasks; using System.Web; using Microsoft.Samples.Debugging.CorDebug; using Microsoft.Samples.Debugging.CorDebug.NativeApi; using Microsoft.Samples.Debugging.MdbgEngine; using CommandLine; namespace StackTraceApp { class Program { private static StackTrace stackTrace class Options { [Value(0, Required = true, MetaName = "ProcessID", HelpText = "ID off Process")] public int ProcessID { get; set; } [Value(1, Required = true , MetaName = "FilePath", HelpText = @"Path to folder where debug files are saved. HttpRuntime.AppDomainAppPath + \"\\\\App_Data\\\\TraceFiles\\\\\" ")] public string FilePath { get; set; } [Value(2, Required = true, MetaName = "SymbolPath", HelpText = @"Path to folder where dlls and symbols are stored. HttpRuntime.AppDomainAppPath + \"\\\\bin\" ")] public string SymbolPath { get; set; } } static void Main(string[] args) { CommandLine.Parser.Default.ParseArguments <options>(args) .WithParsed <options>(Start);</options></options> AppDomain appDomain = AppDomain.CurrentDomain; appDomain.ProcessExit += new EventHandler(OnClose); while (true) { Thread.Sleep(1000); } } private static void OnClose(object sender, EventArgs e) { stackTrace.Close(); } private static void Start(Options obj) { stackTrace = new StackTraceDataCollectorService(obj.ProcessID, obj.FilePath, obj.SymbolPath); } } } |
StackTraceService.cs
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 100 101 102 103 104 105 106 107 108 109 110 111 112 113 114 115 116 117 118 119 120 121 122 123 124 125 126 127 128 129 130 131 132 133 134 135 136 137 138 139 140 141 142 143 144 145 146 147 148 149 150 151 152 153 154 155 156 157 158 159 160 161 162 163 164 165 166 167 168 169 170 171 172 173 174 175 176 177 178 179 180 181 182 183 184 185 186 187 188 189 190 191 192 193 194 195 196 197 198 199 200 201 202 203 204 205 206 207 208 209 210 211 212 213 214 215 216 217 218 219 220 221 222 223 224 225 226 227 228 229 230 231 232 233 234 235 236 237 238 239 240 241 242 243 244 245 246 247 248 249 250 251 252 253 254 255 256 257 258 259 260 261 262 263 264 265 266 267 268 269 270 271 272 273 274 275 276 277 278 279 280 281 282 | using System; using System.Collections.Generic; using System.Diagnostics; using System.IO; using System.Linq; using System.Text; using System.Threading; using System.Threading.Tasks; using System.Timers; using System.Web; using Microsoft.Samples.Debugging.CorDebug; using Microsoft.Samples.Debugging.CorDebug.NativeApi; using Microsoft.Samples.Debugging.MdbgEngine; using Newtonsoft.Json; namespace StackTraceApp { public class StackTraceService { private MDbgEngine _engine; private MDbgProcess _process; private string _filePath; private string _symbolPath; public StackTraceService(int processID, string filePath, string symbolPath) { _filePath = Uri.UnescapeDataString(filePath); _symbolPath = Uri.UnescapeDataString(symbolPath); _engine = new MDbgEngine(); _engine.Options.SymbolPath = _symbolPath; _process = _engine.Attach(processID); _process.SymbolPath = _symbolPath; _process.Go().WaitOne(); if (!(_process.StopReason is AttachCompleteStopReason)) throw new System.Exception("Unexpected"); _process.Go(); _process.PostDebugEvent += ProcessOnPostDebugEvent; System.Timers.Timer aTimer = new System.Timers.Timer(); aTimer.Elapsed += new ElapsedEventHandler(CleanUp); aTimer.Interval = 60000; aTimer.Enabled = true; aTimer.AutoReset = true; AllCleanUp(); } public void Close() { _process.Detach(); } private void AllCleanUp() { if (!Directory.Exists(_filePath)) { Directory.CreateDirectory(_filePath); } System.IO.DirectoryInfo di = new DirectoryInfo(_filePath); foreach(FileInfo file in di.GetFiles()) { file.Delete(); } } private void CleanUp(object sender, ElapsedEventArgs e) { if (!Directory.Exists(_filePath)) { Directory.CreateDirectory(_filePath); } System.IO.DirectoryInfo di = new DirectoryInfo(_filePath); foreach(FileInfo file in di.GetFiles()) { if (file.CreationTime.AddMinutes(30) & lt; = DateTime.Now) { file.Delete(); } } } private void ProcessOnPostDebugEvent(object sender, CustomPostCallbackEventArgs e) { try { Process(sender, e); } catch (System.Exception) {} } private void Process(object sender, CustomPostCallbackEventArgs e) { if (e.CallbackType != ManagedCallbackType.OnException2) return; CorException2EventArgs exception; exception = (CorException2EventArgs) e.CallbackArgs; if (exception.EventType == CorDebugExceptionCallbackType.DEBUG_EXCEPTION_FIRST_CHANCE || exception.EventType == CorDebugExceptionCallbackType.DEBUG_EXCEPTION_USER_FIRST_CHANCE) { MDbgThread thread; thread = _process.Threads.Lookup(exception.Thread); Exception exceptionResult = new Exception(); if (thread.CurrentException.Name != null) { exceptionResult.Name = thread.CurrentException.Name; exceptionResult.Value = thread.CurrentException.Value; } exceptionResult.TypeName = thread.CurrentException.TypeName; var maxCount = 10; var count = 0; bool wasSPData = false; foreach(var frame in thread.Frames) { if (frame.Function == null) continue; if (!wasSPData & amp; & amp; frame.Function.FullName.Contains("SPData")) { wasSPData = true; maxCount = count + 3; } if (count & gt; = maxCount) break; count++; var frameResult = new Frame(); if (frame.SourcePosition != null) { frameResult.Path = frame.SourcePosition.Path; frameResult.Line = frame.SourcePosition.Line; } frameResult.FunctionName = frame.Function.FullName; if (frame.IsManaged & amp; & amp; !frame.IsInfoOnly) { try { foreach(var argument in frame.Function.GetArguments(frame)) { var value = GetValue(argument); if (value != null) frameResult.Parameter.Add(value); } } catch (System.Exception) { } try { foreach(var variable in frame.Function.GetActiveLocalVars(frame)) { var value = GetValue(variable); if (value != null) frameResult.LocalVariables.Add(value); } } catch (System.Exception) { } } exceptionResult.Frames.Add(frameResult); } CreateTraceFile(thread.CurrentException.CorValue.Raw.GetHashCode() + "_" + thread.CurrentException.CorValue.Address, exceptionResult); } } private struct ToPrint { public MDbgThread Thread; public Exception ExceptionResult; } private Value GetValue(MDbgValue aValue) { try { Value value = new Value(); value.Name = aValue.Name; if (aValue.IsNull) { value.TypeName = aValue.TypeName; value.ValueO = "null"; } else { value.TypeName = aValue.TypeName; value.ValueO = expandValue(aValue); } return value; } catch (System.Exception) { return null; } } private string expandValue(MDbgValue value) { if (value.TypeName.Contains("WebControls") || value.TypeName.Contains("ascx") || value.TypeName.Contains("ASP") || value.TypeName.Contains("System.Web")) return value.GetStringValue(0); int level = 0; string result = ""; while (level & lt; = 3) { try { result = value.GetStringValue(level); level++; } catch (System.Exception) { return result; } } return result; } private void CreateTraceFile(string ID, Exception exceptionResult) { if (!Directory.Exists(_filePath)) { Directory.CreateDirectory(_filePath); } string path = Path.Combine(_filePath, ID.ToString()); if (File.Exists(path)) { File.Delete(path); } byte[] bytes = Encoding.UTF8.GetBytes(JsonConvert.SerializeObject(exceptionResult)); FileStream fs = File.Create(path); fs.Write(bytes, 0, bytes.Length); fs.Close(); } private class Exception { public string Name { get; set; } public Object Value { get; set; } public string TypeName { get; set; } public List Frames { get; set; } = new List(); public DateTime DateTime { get; set; } = DateTime.Now; } private class Frame { public string Path { get; set; } public int Line { get; set; } public string FunctionName { get; set; } public List < value > Parameter { get; set; } = new List < value > (); < /value></value > public List < value > LocalVariables { get; set; } = new List < value > (); } < /value></value > private class Value { public string Name { get; set; } public string TypeName { get; set; } public Object ValueO { get; set; } } } } |