Replace single global app lock with per-table scoped locks (#984)

[thecrockster]

Fixes #984

Replaces the single global application lock (_az_func_Trigger) with a two-level locking scheme so that functions monitoring different tables can process changes in parallel:

Global lock (_az_func_Trigger): Used only during startup for DDL operations (schema creation, GlobalState table creation)
Per-table lock (az_func_TT{userTableId}): Used for all runtime operations (change detection, lease management, metrics)
Previously, all trigger functions shared a single sp_getapplock resource (_az_func_Trigger), meaning functions monitoring completely independent tables would block each other. This change scopes runtime locks to the table level using the SQL Server OBJECT_ID, while keeping the global lock only for startup DDL that touches shared objects.

Files changed:

SqlTriggerConstants.cs — Replaced AppLockResource/AppLockStatements with GlobalAppLockResource/GlobalAppLockStatements + GetTableScopedAppLockStatements(int userTableId)
SqlTriggerListener.cs — CreateSchemaAsync and CreateGlobalStateTableAsync use global lock; InsertGlobalStateTableRowAsync and CreateLeasesTableAsync use table-scoped lock
SqlTableChangeMonitor.cs — All 7 runtime SQL command builders use pre-computed table-scoped lock
SqlTriggerMetricsProvider.cs — BuildGetUnprocessedChangesCommand uses table-scoped lock

Code Changes

• Unit tests are added, if possible
• Integration tests are added if the change is modifying existing behavior of one or more of the bindings
• New or changed code follows the C# style guidelines defined in .editorconfig
• All changes MUST be backwards compatible and changes to the shared az_func.GlobalState table must be compatible with all prior versions of the extension
• Use the ILogger instance to log relevant information, especially information useful for debugging or troubleshooting
• Use async and await for all long-running operations
• Ensure proper usage and propagation of CancellationToken
• T-SQL is safe from SQL Injection attacks through the use of SqlParameters and proper escaping/sanitization of input

Dependencies

• If updating dependencies, run dotnet restore --force-evaluate to update the lock files and ensure that there are NO major versions updates in either src/packages.lock.json or Worker.Extensions.Sql/src/packages.lock.json. If there are, contact the dev team for instructions.

Documentation

• Add samples if the change is modifying or adding functionality
• Update relevant documentation in the docs

[thecrockster]

@microsoft-github-policy-service agree

…

On Wed, Feb 11, 2026, 11:15 microsoft-github-policy-service[bot] < ***@***.***> wrote: *microsoft-github-policy-service[bot]* left a comment (Azure/azure-functions-sql-extension#1212) <#1212 (comment)> @thecrockster <https://github.com/thecrockster> please read the following Contributor License Agreement(CLA). If you agree with the CLA, please reply with the following information. @microsoft-github-policy-service agree [company="{your company}"] Options: - (default - no company specified) I have sole ownership of intellectual property rights to my Submissions and I am not making Submissions in the course of work for my employer. @microsoft-github-policy-service agree - (when company given) I am making Submissions in the course of work for my employer (or my employer has intellectual property rights in my Submissions by contract or applicable law). I have permission from my employer to make Submissions and enter into this Agreement on behalf of my employer. By signing below, the defined term “You” includes me and my employer. @microsoft-github-policy-service agree company="Microsoft" Contributor License Agreement Contribution License Agreement This Contribution License Agreement (*“Agreement”*) is agreed to by the party signing below (*“You”*), and conveys certain license rights to Microsoft Corporation and its affiliates (“Microsoft”) for Your contributions to Microsoft open source projects. This Agreement is effective as of the latest signature date below. 1. *Definitions*. *“Code”* means the computer software code, whether in human-readable or machine-executable form, that is delivered by You to Microsoft under this Agreement. *“Project”* means any of the projects owned or managed by Microsoft and offered under a license approved by the Open Source Initiative (www.opensource.org). *“Submit”* is the act of uploading, submitting, transmitting, or distributing code or other content to any Project, including but not limited to communication on electronic mailing lists, source code control systems, and issue tracking systems that are managed by, or on behalf of, the Project for the purpose of discussing and improving that Project, but excluding communication that is conspicuously marked or otherwise designated in writing by You as “Not a Submission.” *“Submission”* means the Code and any other copyrightable material Submitted by You, including any associated comments and documentation. 2. *Your Submission*. You must agree to the terms of this Agreement before making a Submission to any Project. This Agreement covers any and all Submissions that You, now or in the future (except as described in Section 4 below), Submit to any Project. 3. *Originality of Work*. You represent that each of Your Submissions is entirely Your original work. Should You wish to Submit materials that are not Your original work, You may Submit them separately to the Project if You (a) retain all copyright and license information that was in the materials as You received them, (b) in the description accompanying Your Submission, include the phrase “Submission containing materials of a third party:” followed by the names of the third party and any licenses or other restrictions of which You are aware, and (c) follow any other instructions in the Project’s written guidelines concerning Submissions. 4. *Your Employer*. References to “employer” in this Agreement include Your employer or anyone else for whom You are acting in making Your Submission, e.g. as a contractor, vendor, or agent. If Your Submission is made in the course of Your work for an employer or Your employer has intellectual property rights in Your Submission by contract or applicable law, You must secure permission from Your employer to make the Submission before signing this Agreement. In that case, the term “You” in this Agreement will refer to You and the employer collectively. If You change employers in the future and desire to Submit additional Submissions for the new employer, then You agree to sign a new Agreement and secure permission from the new employer before Submitting those Submissions. 5. *Licenses*. - *Copyright License*. You grant Microsoft, and those who receive the Submission directly or indirectly from Microsoft, a perpetual, worldwide, non-exclusive, royalty-free, irrevocable license in the Submission to reproduce, prepare derivative works of, publicly display, publicly perform, and distribute the Submission and such derivative works, and to sublicense any or all of the foregoing rights to third parties. - *Patent License*. You grant Microsoft, and those who receive the Submission directly or indirectly from Microsoft, a perpetual, worldwide, non-exclusive, royalty-free, irrevocable license under Your patent claims that are necessarily infringed by the Submission or the combination of the Submission with the Project to which it was Submitted to make, have made, use, offer to sell, sell and import or otherwise dispose of the Submission alone or with the Project. - *Other Rights Reserved*. Each party reserves all rights not expressly granted in this Agreement. No additional licenses or rights whatsoever (including, without limitation, any implied licenses) are granted by implication, exhaustion, estoppel or otherwise. 6. *Representations and Warranties*. You represent that You are legally entitled to grant the above licenses. You represent that each of Your Submissions is entirely Your original work (except as You may have disclosed under Section 3). You represent that You have secured permission from Your employer to make the Submission in cases where Your Submission is made in the course of Your work for Your employer or Your employer has intellectual property rights in Your Submission by contract or applicable law. If You are signing this Agreement on behalf of Your employer, You represent and warrant that You have the necessary authority to bind the listed employer to the obligations contained in this Agreement. You are not expected to provide support for Your Submission, unless You choose to do so. UNLESS REQUIRED BY APPLICABLE LAW OR AGREED TO IN WRITING, AND EXCEPT FOR THE WARRANTIES EXPRESSLY STATED IN SECTIONS 3, 4, AND 6, THE SUBMISSION PROVIDED UNDER THIS AGREEMENT IS PROVIDED WITHOUT WARRANTY OF ANY KIND, INCLUDING, BUT NOT LIMITED TO, ANY WARRANTY OF NONINFRINGEMENT, MERCHANTABILITY, OR FITNESS FOR A PARTICULAR PURPOSE. 7. *Notice to Microsoft*. You agree to notify Microsoft in writing of any facts or circumstances of which You later become aware that would make Your representations in this Agreement inaccurate in any respect. 8. *Information about Submissions*. You agree that contributions to Projects and information about contributions may be maintained indefinitely and disclosed publicly, including Your name and other information that You submit with Your Submission. 9. *Governing Law/Jurisdiction*. This Agreement is governed by the laws of the State of Washington, and the parties consent to exclusive jurisdiction and venue in the federal courts sitting in King County, Washington, unless no federal subject matter jurisdiction exists, in which case the parties consent to exclusive jurisdiction and venue in the Superior Court of King County, Washington. The parties waive all defenses of lack of personal jurisdiction and forum non-conveniens. 10. *Entire Agreement/Assignment*. This Agreement is the entire agreement between the parties, and supersedes any and all prior agreements, understandings or communications, written or oral, between the parties relating to the subject matter hereof. This Agreement may be assigned by Microsoft. — Reply to this email directly, view it on GitHub <#1212 (comment)>, or unsubscribe <https://github.com/notifications/unsubscribe-auth/AL4ARCEKIB3FGVAOGKKNEW34LMFNZAVCNFSM6AAAAACUXRP2SOVHI2DSMVQWIX3LMV43OSLTON2WKQ3PNVWWK3TUHMZTQOBTG43TKNZSGY> . You are receiving this because you were mentioned.Message ID: ***@***.***>

[Charles-Gagnon]

Thank you for submitting this @thecrockster !

The changes overall look reasonable, so there's no immediate concerns there.

But given the scope of this change we're going to hold off on fully reviewing & merging this until we have a bigger release planned. The app locking is a critical part of the app functionality, and so we want to make sure we're releasing in a way that will have the lowest risk for our users - likely as part of a major or minor release (instead of the patch releases we're currently doing).

[Copilot]

Pull request overview

This pull request addresses issue #984 by replacing the single global application lock with a two-level locking scheme that enables parallel processing of changes for functions monitoring different tables while maintaining deadlock prevention for functions monitoring the same table.

Changes:

• Introduced per-table scoped application locks using the table's SQL Server OBJECT_ID, allowing functions monitoring different tables to process changes concurrently
• Retained the global lock only for DDL operations during startup (schema creation, GlobalState table creation)
• Pre-computed table-scoped lock statements in SqlTableChangeMonitor for runtime efficiency

Reviewed changes

Copilot reviewed 6 out of 6 changed files in this pull request and generated no comments.

Show a summary per file

File	Description
src/TriggerBinding/SqlTriggerConstants.cs	Added GlobalAppLockResource, TableAppLockResourcePrefix constants and GetTableScopedAppLockStatements method to generate table-scoped lock SQL
src/TriggerBinding/SqlTriggerListener.cs	Updated DDL operations to use global lock, runtime operations to use table-scoped locks; added userTableId parameter to CreateLeasesTableAsync
src/TriggerBinding/SqlTableChangeMonitor.cs	Pre-computes table-scoped lock statements in constructor; uses cached statements in all 7 runtime SQL command builders
src/TriggerBinding/SqlTriggerMetricsProvider.cs	Updated BuildGetUnprocessedChangesCommand to use table-scoped lock
test/Unit/TriggerBinding/SqlTriggerConstantsTests.cs	Added comprehensive unit tests covering lock statement generation, resource name uniqueness, and separation of global vs table-scoped locks
docs/TriggerBinding.md	Updated documentation to explain the two-level locking scheme and provided guidance for custom synchronization

---

💡 Add Copilot custom instructions for smarter, more guided reviews. Learn how to get started.