Addressing reader and writer synchronization to the config file within the process.
This commit is contained in:
Mike Richmond
parent
b291e2006c
commit
6eb0f2d6c7
|
|
@ -137,6 +137,13 @@ namespace System.Management.Automation
|
|||
private const string configDirectoryName = "Configuration";
|
||||
private const string configFileName = "PowerShellProperties.json";
|
||||
|
||||
/// <summary>
|
||||
/// Lock used to enable multiple concurrent readers and singular write locks within a
|
||||
/// single process.
|
||||
/// TODO: This solution only works for IO from a single process. A more robust solution is needed to enable ReaderWriterLockSlim behavior between proceses.
|
||||
/// </summary>
|
||||
private ReaderWriterLockSlim fileLock = new ReaderWriterLockSlim();
|
||||
|
||||
internal JsonConfigFileAccessor()
|
||||
{
|
||||
//
|
||||
|
|
@ -328,6 +335,7 @@ namespace System.Management.Automation
|
|||
|
||||
private T ReadValueFromFile<T>(string fileName, string key)
|
||||
{
|
||||
fileLock.EnterReadLock();
|
||||
try
|
||||
{
|
||||
// Open file for reading, but allow multiple readers
|
||||
|
|
@ -343,9 +351,15 @@ namespace System.Management.Automation
|
|||
}
|
||||
}
|
||||
}
|
||||
// The file doesn't exist. Treat this the same way as if the
|
||||
// key was not present in the file.
|
||||
catch (FileNotFoundException) { }
|
||||
catch (FileNotFoundException)
|
||||
{
|
||||
// The file doesn't exist. Treat this the same way as if the
|
||||
// key was not present in the file.
|
||||
}
|
||||
finally
|
||||
{
|
||||
fileLock.ExitReadLock();
|
||||
}
|
||||
|
||||
return default(T);
|
||||
}
|
||||
|
|
@ -360,89 +374,97 @@ namespace System.Management.Automation
|
|||
/// <param name="addValue">Whether the key-value pair should be added to or removed from the file</param>
|
||||
private void UpdateValueInFile<T>(string fileName, string key, T value, bool addValue)
|
||||
{
|
||||
// Since multiple properties can be in a single file, replacement
|
||||
// is required instead of overwrite if a file already exists.
|
||||
// Handling the read and write operations within a single FileStream
|
||||
// prevents other processes from reading or writing the file while
|
||||
// the update is in progress. It also locks out readers during write
|
||||
// operations.
|
||||
using (FileStream fs = new FileStream(fileName, FileMode.OpenOrCreate, FileAccess.ReadWrite, FileShare.None))
|
||||
{
|
||||
JObject jsonObject = null;
|
||||
|
||||
// UTF8, BOM detection, and bufferSize are the same as the basic stream constructor.
|
||||
// The most important parameter here is the last one, which keeps the StreamReader
|
||||
// (and FileStream) open during Dispose so that it can be reused for the write
|
||||
// operation.
|
||||
using (StreamReader streamRdr = new StreamReader(fs, Encoding.UTF8, true, 1024, true))
|
||||
using (JsonTextReader jsonReader = new JsonTextReader(streamRdr))
|
||||
fileLock.EnterWriteLock();
|
||||
try
|
||||
{
|
||||
// Since multiple properties can be in a single file, replacement
|
||||
// is required instead of overwrite if a file already exists.
|
||||
// Handling the read and write operations within a single FileStream
|
||||
// prevents other processes from reading or writing the file while
|
||||
// the update is in progress. It also locks out readers during write
|
||||
// operations.
|
||||
using (FileStream fs = new FileStream(fileName, FileMode.OpenOrCreate, FileAccess.ReadWrite, FileShare.None))
|
||||
{
|
||||
// Safely determines whether there is content to read from the file
|
||||
bool isReadSuccess = jsonReader.Read();
|
||||
if (isReadSuccess)
|
||||
{
|
||||
// Read the stream into a root JObject for manipulation
|
||||
jsonObject = (JObject) JToken.ReadFrom(jsonReader);
|
||||
JProperty propertyToModify = jsonObject.Property(key);
|
||||
JObject jsonObject = null;
|
||||
|
||||
if (null == propertyToModify)
|
||||
// UTF8, BOM detection, and bufferSize are the same as the basic stream constructor.
|
||||
// The most important parameter here is the last one, which keeps the StreamReader
|
||||
// (and FileStream) open during Dispose so that it can be reused for the write
|
||||
// operation.
|
||||
using (StreamReader streamRdr = new StreamReader(fs, Encoding.UTF8, true, 1024, true))
|
||||
using (JsonTextReader jsonReader = new JsonTextReader(streamRdr))
|
||||
{
|
||||
// Safely determines whether there is content to read from the file
|
||||
bool isReadSuccess = jsonReader.Read();
|
||||
if (isReadSuccess)
|
||||
{
|
||||
// The property doesn't exist, so add it
|
||||
if (addValue)
|
||||
// Read the stream into a root JObject for manipulation
|
||||
jsonObject = (JObject) JToken.ReadFrom(jsonReader);
|
||||
JProperty propertyToModify = jsonObject.Property(key);
|
||||
|
||||
if (null == propertyToModify)
|
||||
{
|
||||
jsonObject.Add(new JProperty(key, value));
|
||||
// The property doesn't exist, so add it
|
||||
if (addValue)
|
||||
{
|
||||
jsonObject.Add(new JProperty(key, value));
|
||||
}
|
||||
// else the property doesn't exist so there is nothing to remove
|
||||
}
|
||||
// The property exists
|
||||
else
|
||||
{
|
||||
if (addValue)
|
||||
{
|
||||
propertyToModify.Replace(new JProperty(key, value));
|
||||
}
|
||||
else
|
||||
{
|
||||
propertyToModify.Remove();
|
||||
}
|
||||
}
|
||||
// else the property doesn't exist so there is nothing to remove
|
||||
}
|
||||
// The property exists
|
||||
else
|
||||
{
|
||||
// The file doesn't already exist and we want to write to it
|
||||
// or it exists with no content.
|
||||
// A new file will be created that contains only this value.
|
||||
// If the file doesn't exist and a we don't want to write to it, no
|
||||
// action is necessary.
|
||||
if (addValue)
|
||||
{
|
||||
propertyToModify.Replace(new JProperty(key, value));
|
||||
jsonObject = new JObject(new JProperty(key, value));
|
||||
}
|
||||
else
|
||||
{
|
||||
propertyToModify.Remove();
|
||||
return;
|
||||
}
|
||||
}
|
||||
}
|
||||
else
|
||||
|
||||
// Reset the stream position to the beginning so that the
|
||||
// changes to the file can be written to disk
|
||||
fs.Seek(0, SeekOrigin.Begin);
|
||||
|
||||
// Update the file with new content
|
||||
using (StreamWriter streamWriter = new StreamWriter(fs))
|
||||
using (JsonTextWriter jsonWriter = new JsonTextWriter(streamWriter))
|
||||
{
|
||||
// The file doesn't already exist and we want to write to it
|
||||
// or it exists with no content.
|
||||
// A new file will be created that contains only this value.
|
||||
// If the file doesn't exist and a we don't want to write to it, no
|
||||
// action is necessary.
|
||||
if (addValue)
|
||||
{
|
||||
jsonObject = new JObject(new JProperty(key, value));
|
||||
}
|
||||
else
|
||||
{
|
||||
return;
|
||||
}
|
||||
// The entire document exists within the root JObject.
|
||||
// I just need to write that object to produce the document.
|
||||
jsonObject.WriteTo(jsonWriter);
|
||||
|
||||
// This trims the file if the file shrank. If the file grew,
|
||||
// it is a no-op. The purpose is to trim extraneous characters
|
||||
// from the file stream when the resultant JObject is smaller
|
||||
// than the input JObject.
|
||||
fs.SetLength(fs.Position);
|
||||
}
|
||||
}
|
||||
|
||||
// Reset the stream position to the beginning so that the
|
||||
// changes to the file can be written to disk
|
||||
fs.Seek(0, SeekOrigin.Begin);
|
||||
|
||||
// Update the file with new content
|
||||
using (StreamWriter streamWriter = new StreamWriter(fs))
|
||||
using (JsonTextWriter jsonWriter = new JsonTextWriter(streamWriter))
|
||||
{
|
||||
// The entire document exists within the root JObject.
|
||||
// I just need to write that object to produce the document.
|
||||
jsonObject.WriteTo(jsonWriter);
|
||||
|
||||
// This trims the file if the file shrank. If the file grew,
|
||||
// it is a no-op. The purpose is to trim extraneous characters
|
||||
// from the file stream when the resultant JObject is smaller
|
||||
// than the input JObject.
|
||||
fs.SetLength(fs.Position);
|
||||
}
|
||||
}
|
||||
finally
|
||||
{
|
||||
fileLock.ExitWriteLock();
|
||||
}
|
||||
}
|
||||
|
||||
|
|
|
|||
Loading…
Reference in a new issue