AI Architecture

This document describes architecture shared by the GitLab Duo AI features. For historical motivation and goals of this architecture, see the AI Gateway Architecture blueprint.

Introduction

The following diagram shows a simplified view of how the different components in GitLab interact.

@startuml
!theme cloudscape-design
skinparam componentStyle rectangle

package Clients {
  [IDEs, Code Editors, Language Server] as IDE
  [GitLab Web Frontend] as GLWEB
}

[GitLab.com] as GLCOM
[Self-Managed/Dedicated] as SMI
[CustomersDot API] as CD
[AI Gateway] as AIGW

package Models {
  [3rd party models (Anthropic,VertexAI)] as THIRD
  [GitLab Native Models] as GLNM
}

Clients -down-> GLCOM : REST/Websockets
Clients -down-> SMI : REST/Websockets
SMI -right-> CD : License + JWT Sync
GLCOM -down-> AIGW : Prompts + Telemetry + JWT (REST)

SMI -down-> AIGW : Prompts + Telemetry + JWT (REST)
AIGW -up-> GLCOM : JWKS public key sync
AIGW -up-> CD : JWKS public key sync
AIGW -down-> Models : prompts
@enduml

• AI Abstraction layer - Every GitLab instance (Self-Managed, GitLab.com, ..) contains an AI Abstraction layer which provides a framework for implementing new AI features in the monolith. This layer adds contextual information to the request and does request pre/post processing.

Systems

• GitLab instances - GitLab monolith that powers all types of GitLab instances
• CustomersDot - Allows customers to buy and upgrade subscriptions by adding more seats and add/edit payment records. It also manages self-managed licenses.
• AI Gateway - System that provides unified interface for invoking models. Deployed in Google Cloud Run (using Runway).
• Extensions
  • Language Server (powers code suggestions in VS Code, Visual Studio 2022 for Windows, and Neovim)
  • VS Code
  • JetBrains
  • Visual Studio 2022 for Windows
  • Neovim

Difference between how GitLab.com and Self-Managed/Dedicated access AI Gateway

• GitLab.com
  • GitLab.com instances self-issue JWT Auth token signed with a private key.
• Other types of instances
  • Self-Managed and Dedicated regularly synchronise their licenses and AI Access tokens with CustomersDot.
  • Self-Managed and Dedicated instances route traffic to appropriate AI Gateway.

SaaS-based AI abstraction layer

GitLab currently operates a cloud-hosted AI architecture. We will allow access to it for licensed self managed instances using the AI-gateway. See the blueprint for details.

There are two primary reasons for this: the best AI models are cloud-based as they often depend on specialized hardware designed for this purpose, and operating self-managed infrastructure capable of AI at-scale and with appropriate performance is a significant undertaking. We are actively tracking self-managed customers interested in AI.

AI Gateway

The AI Gateway (formerly the model gateway) is a standalone-service that will give access to AI features to all users of GitLab, no matter which instance they are using: self-managed, dedicated or GitLab.com. The SaaS-based AI abstraction layer will transition to connecting to this gateway, rather than accessing cloud-based providers directly.

Calls to the AI-gateway from GitLab-rails can be made using the Abstraction Layer. By default, these actions are performed asynchronously via a Sidekiq job to prevent long-running requests in Puma. It should be used for non-latency sensitive actions due to the added latency by Sidekiq.

At the time of writing, the Abstraction Layer still directly calls the AI providers. Epic 11484 proposes to change this.

When a certain action is latency sensitive, we can decide to call the AI-gateway directly. This avoids the latency added by Sidekiq. We already do this for code_suggestions which get handled by API endpoints nested in /api/v4/code_suggestions. For any new endpoints added, we should nest them within the /api/v4/ai_assisted namespace. Doing this will automatically route the requests on GitLab.com to the ai-assisted fleet for GitLab.com, isolating the workload from the regular API and making it easier to scale if needed.

Supported technologies

As part of the AI working group, we have been investigating various technologies and vetting them. Below is a list of the tools which have been reviewed and already approved for use within the GitLab application.

It is possible to utilize other models or technologies, however they will need to go through a review process prior to use. Use the AI Project Proposal template as part of your idea and include the new tools required to support it.

Models

The following models have been approved for use:

• Google's Vertex AI and model garden
• Anthropic models
• Suggested reviewer

Vector stores

NOTE: There is a proposal to change vector stores for improving the quality of search results. See RAG for GitLab Duo for more information.

The following vector stores have been approved for use:

• pgvector is a Postgres extension adding support for storing vector embeddings and calculating ANN (approximate nearest neighbor).

Indexing Update

NOTE: There is a proposal to change indexing update for improving the quality of search results. See RAG for GitLab Duo for more information.

We are currently using sequential scan, which provides perfect recall. We are considering adding an index if we can ensure that it still produces accurate results, as noted in the pgvector indexing documentation.

Given that the table contains thousands of entries, indexing with these updated settings would likely improve search speed while maintaining high accuracy. However, more testing may be needed to verify the optimal configuration for this dataset size before deploying to production.

A draft MR has been created to update the index.

The index function has been updated to improve search quality. This was tested locally by setting the ivfflat.probes value to 10 with the following SQL command:

::Embedding::Vertex::GitlabDocumentation.connection.execute("SET ivfflat.probes = 10")

Setting the probes value for indexing improves results, as per the neighbor documentation.

For optimal probes and lists values:

• Use lists equal to rows / 1000 for tables with up to 1 million rows and sqrt(rows) for larger datasets.
• For probes start with lists / 10 for tables up to 1 million rows and sqrt(lists) for larger datasets.

Code Suggestions

Code Suggestions is being integrated as part of the GitLab-Rails repository which will unify the architectures between Code Suggestions and AI features that use the abstraction layer, along with offering self-managed support for the other AI features.

The following table documents functionality that Code Suggestions offers today, and what those changes will look like as part of the unification:

Self-managed support

Code Suggestions for self-managed users was introduced as part of the Cloud Connector MVC.

For more information on the technical solution for this project see the Cloud Connector architecture documentation.

The intention is to evolve this solution to service other AI features under the Cloud Connector product umbrella.

Code Suggestions Latency

Code Suggestions acceptance rates are highly sensitive to latency. While writing code with an AI assistant, a user will pause only for a short duration before continuing on with manually typing out a block of code. As soon as the user has pressed a subsequent keypress, the existing suggestion will be invalidated and a new request will need to be issued to the Code Suggestions endpoint. In turn, this request will also be highly sensitive to latency.

In a worst case with sufficient latency, the IDE could be issuing a string of requests, each of which is then ignored as the user proceeds without waiting for the response. This adds no value for the user, while still putting load on our services.

See our discussions here around how we plan to iterate on latency for this feature.

Future changes to the architecture

• We plan on deploying AI Gateway in different regions to improve latency (see the ed epic Multi-region support for AI Gateway).
• We would like to centralize telemetry. However, centralizing AI (or, Cloud Connector) telemetry is a difficult and unsolved problem as of now.