perf: Remove costly reduce operation for generating Engine context

MajorLift commented 4 days ago

Overview

Optimizes an expensive operation from the Engine initialization process.

A custom span for measuring this process was added in https://github.com/MetaMask/metamask-mobile/pull/11579.

Motivation

Currently, the Engine's context object is created using a Array.prototype.reduce() operation on a large controllers array. This reduce call is also written to create a temporary object on every iteration.

Benchmarks show that this particular implementation of reduce runs significantly slower than other means of creating an object, and compared to reduce calls that are written to re-use the output object the difference is in four orders of magnitude (1555.6 Ops/sec vs. 0.2 Ops/sec).

https://www.measurethat.net/Benchmarks/Show/21554/0/objectfromentries-vs-reduce-vs-assign

A simple fix would be to refactor the reduce operation so it doesn't rely on temporary objects and spreading:

diff --git a/app/core/Engine.ts b/app/core/Engine.ts
index decf28da51..1ba63ed106 100644
--- a/app/core/Engine.ts
+++ b/app/core/Engine.ts
@@ -1738,10 +1738,10 @@ export class Engine {
       this.controllerMessenger,
     );
     this.context = controllers.reduce<Partial<typeof this.context>>(
-      (context, controller) => ({
-        ...context,
-        [controller.name]: controller,
-      }),
+      (context, controller) => {
+        context[controller.name] = controller;
+        return context;
+      },
       {},
     ) as typeof this.context;

However, we can also avoid the cost of running reduce altogether simply by creating a controller name-keyed object to assign to the Engine's context field. This is also the approach taken in the Extension MetamaskController.

Description

Replaces controllers array in the Engine class with a corresponding object that is directly assigned to context.
Optimize Object.values for deriving ComposableController input with Object.keys and reduce (re-uses object).

https://www.measurethat.net/Benchmarks/Show/7173/0/objectvalues-vs-reduce
Removes for-loop that sets initial state for V1 controllers now that all mobile controllers have been updated to V2.

Related issues

Manual testing steps

Screenshots/Recordings

Pre-merge author checklist

[x] I’ve followed MetaMask Contributor Docs and MetaMask Mobile Coding Standards.
[x] I've completed the PR template to the best of my ability
[x] I’ve included tests if applicable
[x] I’ve documented my code using JSDoc format if applicable
[x] I’ve applied the right labels on the PR (see labeling guidelines). Not required for external contributors.

Pre-merge reviewer checklist

[ ] I've manually tested the PR (e.g. pull and build branch, run the app, test code being changed).
[ ] I confirm that this PR addresses all acceptance criteria described in the ticket it closes and includes the necessary testing evidence such as recordings and or screenshots.

github-actions[bot] commented 4 days ago

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github-actions[bot] commented 4 days ago

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codecov-commenter commented 4 days ago

Codecov Report

Attention: Patch coverage is 83.33333% with 1 line in your changes missing coverage. Please review.

Project coverage is 56.46%. Comparing base (22a4989) to head (0c662ae). Report is 29 commits behind head on main.

Files with missing lines	Patch %	Lines
app/core/Engine.ts	83.33%	0 Missing and 1 partial :warning:

Additional details and impacted files

```diff @@ Coverage Diff @@ ## main #12374 +/- ## ========================================== + Coverage 56.41% 56.46% +0.04% ========================================== Files 1797 1808 +11 Lines 40586 40724 +138 Branches 5097 5131 +34 ========================================== + Hits 22896 22993 +97 - Misses 16134 16159 +25 - Partials 1556 1572 +16 ```

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