fix: chunk fetchStatusByIds and updateAllUsersSince requests (MM-68226)

[ewwollesen]

Problem

On large teams fetchStatusByIds and updateAllUsersSince send all user IDs in a single POST body. This can exceed the server's MaximumPayloadSizeBytes. This can cause the app to return "Request body too large" on every app launch and WebSocket reconnect, breaking team switching entirely.

Solution

Fix (2 files, +8 / -2 lines)

1. app/constants/general.ts — Added MAX_IDS_PER_STATUS_REQUEST: 200 and MAX_IDS_PER_PROFILES_REQUEST: 100 (matching web client batch sizes)
2. app/actions/remote/user.ts:
   - fetchStatusByIds (line 366-368): Chunks userIds into batches of 200 before calling client.getStatusesByIds(), runs in parallel via Promise.all, flattens results
   - updateAllUsersSince (line 658-660): Chunks userIds into batches of 100 before calling client.getProfilesByIds(), same parallel + flatten pattern

The chunk utility from lodash was already imported. Existing tests pass unchanged since they use small ID arrays (single chunk).

[mm-cloud-bot]

@ewwollesen: Adding the "do-not-merge/release-note-label-needed" label because no release-note block was detected, please follow our release note process to remove it.

Details

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[coderabbitai]

📝 Walkthrough

Walkthrough

Two remote action functions were updated to split large ID lists into configured chunk sizes and fetch each chunk concurrently using Promise.allSettled, then flatten only fulfilled results before continuing with existing persistence logic. Two new constants define the chunk sizes.

Changes

Cohort / File(s)	Summary
Configuration Constants app/constants/general.ts	Added MAX_IDS_PER_STATUS_REQUEST = 200 and MAX_IDS_PER_PROFILES_REQUEST = 100 to the exported defaults.
Chunked Parallel Fetching app/actions/remote/user.ts	Replaced single large client.getStatusesByIds(userIds) and client.getProfilesByIds(userIds, {since}, groupLabel) calls with chunked requests using the new constants; batches are fetched via Promise.allSettled and only fulfilled results are flattened into statuses / userUpdates before existing batching/persistence.

Sequence Diagram(s)

sequenceDiagram
    participant RemoteAction as RemoteAction (user.ts)
    participant Config as Config (general.ts)
    participant Client as Client API
    participant Store as Persistence

    RemoteAction->>Config: read MAX_IDS_PER_* constants
    RemoteAction->>RemoteAction: split userIds into batches
    RemoteAction->>Client: send concurrent requests for each batch (allSettled)
    Client-->>RemoteAction: return settled results (fulfilled/rejected)
    RemoteAction->>RemoteAction: filter fulfilled, flatten results
    RemoteAction->>Store: continue with existing batching/persistence

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Estimated code review effort

🎯 3 (Moderate) | ⏱️ ~20 minutes

🚥 Pre-merge checks | ✅ 2 | ❌ 1

❌ Failed checks (1 warning)

Check name	Status	Explanation	Resolution
Docstring Coverage	⚠️ Warning	Docstring coverage is 0.00% which is insufficient. The required threshold is 80.00%.	Write docstrings for the functions missing them to satisfy the coverage threshold.

✅ Passed checks (2 passed)

Check name	Status	Explanation
Description check	✅ Passed	The description is well-detailed and directly related to the changeset, explaining both the problem and the solution with specific file and line references.
Title check	✅ Passed	The pull request title clearly and concisely summarizes the main change: implementing request chunking for fetchStatusByIds and updateAllUsersSince to resolve server payload size issues.

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✨ Finishing Touches

📝 Generate docstrings

• Create stacked PR
• Commit on current branch

🧪 Generate unit tests (beta)

• Create PR with unit tests
• Commit unit tests in branch fix/chunk-large-user-requests

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[github-actions]

Coverage Comparison Report

Generated on April 08, 2026 at 18:41:53 UTC

+-----------------+------------+------------+-----------+
| Metric          | Main       | This PR    | Diff      |
+-----------------+------------+------------+-----------+
| Lines           |     85.13% |     85.14% |     0.01% |
| Statements      |     85.00% |     85.00% |     0.00% |
| Branches        |     72.07% |     72.06% |    -0.01% |
| Functions       |     83.91% |     83.93% |     0.02% |
+-----------------+------------+------------+-----------+
| Total           |     81.52% |     81.53% |     0.01% |
+-----------------+------------+------------+-----------+

[ewwollesen]

https://mattermost.atlassian.net/browse/MM-68226