Add an option to exclusively lock Transactional State

[scalalang2]

Motivation

The detailed motivation is described in #9898.

Changes.

The core idea in this PR is to change how isRead param is propagated when an exclusive lock is requested, in the ReaderWriterLock.cs

• Find(..., isRead, ...) -> Find(..., isRead && !exclusiveLock, ...)
• HasConflict(isRead, ...) -> HasConflict(isRead && !exclusiveLock, ...)

All other changes are made to support this behavior.

Example

Users attach UseExclusiveLockAttribute to acquire an exclusive lock.

[UseExclusiveLock]
[Transaction(TransactionOption.CreateOrJoin)]
Task<uint> GetBalance();

Since default value of UseExclusiveLock is false, this this change is backward-compatible, and existing code paths remain unaffected unless the attribute is explicitly attached.

DIsclamer

This change has not been fully tested and should not be merged into the main branch.

Microsoft Reviewers: Open in CodeFlow

[Copilot]

Pull request overview

This PR proposes an opt-in mechanism to acquire exclusive locks for transactional state even during read operations, aiming to reduce lock upgrade conflicts under high contention in Orleans Transactions.

Changes:

• Introduces [UseExclusiveLock] and propagates a UseExclusiveLock flag through transactional request/TransactionInfo.
• Adds useExclusiveLock overloads to ITransactionClient.RunTransaction(...) and plumbs the flag through TransactionClient.
• Updates ReaderWriterLock.EnterLock(...) call sites and adjusts conflict detection to treat reads as exclusive when requested.

Reviewed changes

Copilot reviewed 7 out of 7 changed files in this pull request and generated 3 comments.

Show a summary per file

File	Description
src/Orleans.Transactions/TransactionAttribute.cs	Adds [UseExclusiveLock] and request-side propagation into TransactionInfo.
src/Orleans.Transactions/TOC/TransactionCommitter.cs	Passes UseExclusiveLock into lock acquisition during commit/write path.
src/Orleans.Transactions/State/TransactionalState.cs	Passes UseExclusiveLock into lock acquisition for reads/updates.
src/Orleans.Transactions/State/ReaderWriterLock.cs	Adds exclusiveLock parameter and modifies how conflicts are computed.
src/Orleans.Transactions/ITransactionClient.cs	Adds RunTransaction(..., useExclusiveLock) overloads.
src/Orleans.Transactions/DistributedTM/TransactionInfo.cs	Adds UseExclusiveLock flag to serialized transaction context and copies it on fork.
src/Orleans.Transactions/DistributedTM/TransactionClient.cs	Implements new overloads and sets UseExclusiveLock when requested.

[ReubenBond]

The idea sounds good to me. I am not entirely sure of the benefit to using PerformRead+ExclusiveLock vs using PerformUpdate (other than avoiding the state copy + storage write). EDIT: I see you answered that in the issue thread.

[scalalang2]

I’ve added test code to verify that this proposal works as expected.

[scalalang2]

@copilot, please review again

[Copilot]

Pull request overview

Copilot reviewed 17 out of 17 changed files in this pull request and generated 3 comments.