Update Self-Diagnostics instructions (#2271)

* Update Self-Diagnostics instructions

* Update Readme.md

* Update Readme.md

troubleshooting/ETW/Readme.md

@@ -116,21 +116,30 @@ StatusMonitor uses TraceEventSession to record ETW logs.
 - https://github.com/dotnet/roslyn/wiki/Recording-performance-traces-with-PerfView
 - https://github.com/microsoft/perfview/blob/master/src/TraceEvent/TraceEventSession.cs
 
-### Self Diagnostics
+### Self-Diagnostics
 
-As of version 2.18.0, this SDK also ships a "self-diagnostics feature", which
-helps troubleshooting.
-When enabled, internal events generated by ApplicationInsights SDK will be
-written to a log file.
+As of version 2.18.0, this SDK ships a "self-diagnostics feature" which captures internal events and writes to a log file in a specified directory.
 
-The self-diagnostics feature can be enabled/disabled while the process
-is running.
+The self-diagnostics feature can be enabled/changed/disabled while the process is running.
+The SDK will attempt to read the configuration file every 10 seconds, using a non-exclusive read-only mode.
+The SDK will create or overwrite a file with new logs according to the configuration. 
 
-To enable self-diagnostics, go to the
-[current working directory](https://en.wikipedia.org/wiki/Working_directory) of
-your process and create a configuration file named `ApplicationInsightsDiagnostics.json`
-with the following content:
+#### Configuration
 
+Configuration is controlled by a file named `ApplicationInsightsDiagnostics.json`.
+The configuration file must be no more than 4 KiB, otherwise only the first 4 KiB of content will be read.
+
+**To enable self-diagnostics**, go to the [current working directory](https://en.wikipedia.org/wiki/Working_directory) of your process and create a configuration file.
+In most cases, you could just drop the file along your application.
+On Windows, you can use [Process Explorer](https://docs.microsoft.com/sysinternals/downloads/process-explorer), 
+double click on the process to pop up Properties dialog, and find "Current directory" in "Image" tab.
+Internally, the SDK looks for the configuration file located in [GetCurrentDirectory](https://docs.microsoft.com/dotnet/api/system.io.directory.getcurrentdirectory),
+and then [AppContext.BaseDirectory](https://docs.microsoft.com/dotnet/api/system.appcontext.basedirectory).
+You can also find the exact directory by calling these methods from your code.
+
+**To disable self-diagnostics**, delete the configuration file.
+
+Example: 
 ```json
 {
     "LogDirectory": ".",
@@ -139,55 +148,22 @@ with the following content:
 }
 ```
 
-To disable self-diagnostics, delete the above file.
+#### Configuration Parameters
 
-Tip on finding the "current working directory":
-In most cases, you could just drop the file along your application.
-On Windows, you can use [Process Explorer](https://docs.microsoft.com/sysinternals/downloads/process-explorer),
-double click on the process to pop up Properties dialog and find "Current
-directory" in "Image" tab.
-Internally, it looks for the configuration file located in
-[GetCurrentDirectory](https://docs.microsoft.com/dotnet/api/system.io.directory.getcurrentdirectory),
-and then [AppContext.BaseDirectory](https://docs.microsoft.com/dotnet/api/system.appcontext.basedirectory).
-You can also find the exact directory by calling these methods from your code.
+A `FileSize`-KiB log file named as `ExecutableName.ProcessId.log` (e.g. `foobar.exe.12345.log`) will be generated at the specified directory `LogDirectory`.
 
-#### Configuration Parameters
+1. `LogDirectory` is the directory where the output log file will be stored. 
+It can be an absolute path or a relative path to the current directory.
+
+2. `FileSize` is a positive integer, which specifies the log file size in [KiB](https://en.wikipedia.org/wiki/Kibibyte).
+This value must be between 1 MiB and 128 MiB (inclusive), or it will be rounded to the closest upper or lower limit.
+
+3. `LogLevel` is the lowest level of the events to be captured. 
+This value must match one of the [fields](https://docs.microsoft.com/dotnet/api/system.diagnostics.tracing.eventlevel#fields) of the `EventLevel` enum.
+Lower severity levels encompass higher severity levels (e.g. `Warning` includes the `Error` and `Critical` levels).
 
-1. `LogDirectory` is the directory where the output log file will be stored. It
-   can be an absolute path or a relative path to the current directory.
-
-2. `FileSize` is a positive integer, which specifies the log file size in
-   [KiB](https://en.wikipedia.org/wiki/Kibibyte).
-
-3. `LogLevel` is the lowest level of the events to be captured. It has to be one
-   of the
-   [values](https://docs.microsoft.com/dotnet/api/system.diagnostics.tracing.eventlevel#fields)
-   of the [`EventLevel`
-   enum](https://docs.microsoft.com/dotnet/api/system.diagnostics.tracing.eventlevel).
-   The level signifies the severity of an event. Lower severity levels encompass
-   higher severity levels. For example, `Warning` includes the `Error` and
-   `Critical` levels.
-
-#### Remarks
-
-A `FileSize`-KiB log file named as `ExecutableName.ProcessId.log` (e.g.
-`foobar.exe.12345.log`) will be generated at the specified directory
-`LogDirectory`, into which logs are written to.
-
-The SDK will attempt to open the configuration file in non-exclusive read-only
-mode, read the file and parse it as the configuration file every 10 seconds. If
-the SDK fails to parse the `LogDirectory`, `FileSize` or `LogLevel` fields as
-the specified format, the configuration file will be treated as invalid and no
-log file would be generated. Otherwise, it will create or overwrite the log file
-as described above.
-
-Note that the `FileSize` has to be between 1 MiB and 128 MiB (inclusive), or it
-will be rounded to the closest upper or lower limit. When the `LogDirectory` or
-`FileSize` is found to be changed, the SDK will create or overwrite a file with
-new logs according to the new configuration. The configuration file has to be no
-more than 4 KiB. In case the file is larger than 4 KiB, only the first 4 KiB of
-content will be read.
+**Warning**: If the SDK fails to parse any of these fields, the configuration file will be treated as invalid and self-diagnostics will be disabled.
 
 ## References
 
-This document is referenced by: https://docs.microsoft.com/azure/azure-monitor/app/asp-net-troubleshoot-no-data#PerfView
+This document is referenced by: https://docs.microsoft.com/azure/azure-monitor/app/asp-net-troubleshoot-no-data#PerfView