Tuesday, March 3, 2015

Changing TransactionScope - Timeout at runtime

So... TransactionScope...

If you have worked with the TransactionScope in the past you might have noticed that it can be tricky, and even dangerous if you don't use it correctly.

So anyways, I have tried to change the TransactionScope timeout property at runtime and the thing still goes back to the default timeout of 10 minutes.

This is because the 'TransactionScope' uses the following object to get the maximum timeout for a transaction: TransactionManager.MaximumTimeout. If you decompile it you will see the following:

if (!TransactionManager._cachedMaxTimeout)
  lock (TransactionManager.ClassSyncObject)
    if (!TransactionManager._cachedMaxTimeout)
      TransactionManager._maximumTimeout = TransactionManager.MachineSettings.MaxTimeout;
      TransactionManager._cachedMaxTimeout = true;

Pay special attention to: TransactionManager.MachineSettings.MaxTimeout

It always reads from the machine settings defined on the machine.config (C:\Windows\Microsoft.NET\Framework64\v4.0.30319\Config\machine.config)

And this specific section is defined as follows:

<sectionGroup name="system.transactions" type="System.Transactions.Configuration.TransactionsSectionGroup, System.Transactions, Version=, Culture=neutral, PublicKeyToken=b77a5c561934e089, Custom=null">
   <section name="defaultSettings" type="System.Transactions.Configuration.DefaultSettingsSection, System.Transactions, Version=, Culture=neutral, PublicKeyToken=b77a5c561934e089, Custom=null"/>
   <section name="machineSettings" type="System.Transactions.Configuration.MachineSettingsSection, System.Transactions, Version=, Culture=neutral, PublicKeyToken=b77a5c561934e089, Custom=null" allowDefinition="MachineOnly" allowExeDefinition="MachineOnly"/>

Note that it's marked with: allowExeDefinition="MachineOnly" that's why we cannot override it in our config files - shame :(

So basically I can think in two options to increase the maximum transaction timeout:

Updating the machine.config file

You could do it although I wouldn't recommend it so I won't bother to show you how... well take a quick look

Hacking - using reflection

Or do it the Ninja way...

private void ConfigureTransactionTimeout(TimeSpan value)
    //initializing internal stuff
    // ReSharper disable once NotAccessedVariable
    var timespan = TransactionManager.MaximumTimeout;

    //initializing it again to be sure
    // ReSharper disable once RedundantAssignment
    timespan = TransactionManager.MaximumTimeout;

    SetTransactionManagerField("_cachedMaxTimeout", true);
    SetTransactionManagerField("_maximumTimeout", value);

    Condition.Ensures(TransactionManager.MaximumTimeout, "TransactionManager.MaximumTimeout").IsEqualTo(value);

private void SetTransactionManagerField(string fieldName, object value)
    var cacheField = typeof (TransactionManager).GetField(fieldName, BindingFlags.NonPublic | BindingFlags.Static);

    Condition.Ensures(cacheField, "cacheField").IsNotNull();

    cacheField.SetValue(null, value);

And use it like:


var timespan = TransactionManager.MaximumTimeout;

var transactionOptions = new TransactionOptions
    IsolationLevel = isolationLevel,
    Timeout = timespan

var ts = new TransactionScope(transactionScopeOption, transactionOptions);

There you go

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