Slow GraphQL query getProjectMergeRequestsApprovalsEE causes high CPU duration and SLO violations

Impact

The getProjectMergeRequestsApprovalsEE GraphQL query is causing GraphQL Apdex SLO violations on GitLab Dedicated tenant outer_tomato_gull. 13.29% of these requests exceed the target duration of 5 seconds, and 2.5% exceed 10 seconds.

This contributes to recurring WebserviceServiceGraphqlQueryApdexSLOViolation alerts multiple times per week, directly degrading user experience in the merge request approvals workflow.

Summary

The getProjectMergeRequestsApprovalsEE GraphQL operation exhibits excessive CPU duration when fetching merge request approval data. While DB and Gitaly times are acceptable, the CPU time dominates the request duration, suggesting inefficient application-level processing.

Breakdown of requests over the week by duration bucket:

image

Problem

When users query merge request approvals for a project (e.g., listing 50 open MRs with approval status), the query takes 20-30+ seconds to complete. The CPU time is disproportionately high.

Example Log (sanitized)

{
  "path": "/api/graphql",
  "status": 200,
  "duration_s": 31.77,
  "target_duration_s": 5,
  "cpu_s": 21.72,
  "db_duration_s": 10.84,
  "gitaly_duration_s": 0.15,
  "redis_duration_s": 0.17,
  "queue_duration_s": 3.26,
  "graphql": {
    "operation_name": "getProjectMergeRequestsApprovalsEE",
    "complexity": 28,
    "depth": 6,
    "variables": {
      "fullPath": "<project_path>",
      "state": "opened",
      "firstPageSize": 50
    },
    "used_fields": [
      "Project.mergeRequests",
      "MergeRequest.approved",
      "MergeRequest.approvalsRequired",
      "MergeRequest.approvalsLeft",
      "MergeRequest.approvedBy",
      "UserCoreConnection.nodes"
    ]
  },
  "meta.feature_category": "code_review_workflow",
  "mem_bytes": 563962078,
  "mem_total_bytes": 1225005438
}

Observations

  • CPU duration (~21s) far exceeds DB + Gitaly + Redis combined (~11s)
  • Memory allocation is very high (563MB objects, 1.2GB total)
  • Feature category: code_review_workflow

Related

Environment

  • GitLab version: 18.8.6
  • Deployment: GitLab Dedicated - tenant outer_tomato_gull
  • Query parameters: 50 open MRs with approval fields
Edited by Konst Tchernov