Correlation page

performance/correlation/ — overlays one endpoint's latency against system resource usage on a shared time axis, so you can see whether a latency spike lined up with a CPU, memory or Celery-queue spike. This is the page for answering "why was it slow then?".

Controls

• Endpoint selector — the endpoints seen in the range, with static/media and asset paths (.css, .js, .png, .ico, …) filtered out so the list is real application endpoints. Defaults to the first available.
• Time window — an explicit start/end (ISO datetime) window rather than a preset range, so you can zoom into the exact incident. If start is after end, it falls back to the page's default range.

Correlation chart

Four series on one time axis for the selected endpoint and window:

Series	Source
p99 latency	PerformanceSummary.p99_ms for the endpoint
CPU %	web SystemResourceSnapshot.cpu_percent
RAM %	web SystemResourceSnapshot.ram_percent
Celery queued	celery_worker snapshots' celery_queued_tasks

When the p99 line rises at the same moment as CPU or the Celery queue, the latency is resource-driven; when p99 rises with flat resources, look at the code path or an external dependency instead.

Snapshot resolution limits correlation

Resource snapshots land every 15 minutes by default, so the resource series is coarse. For tight correlation, lower RESOURCE_SNAPSHOT_INTERVAL_MINUTES (and schedule the Celery snapshot tasks for non-web tiers) so there are enough points to line up against latency.

Request timeline

The 12 most recent requests to the selected endpoint in the window, with method, status, response time, DB query count, DB time and concurrency — and the captured headers/body drawer when capture is enabled. It lets you drop from "the chart shows a spike here" to the actual requests in that spike.

Admin correlation view

A parallel, simpler correlation view is injected into the Django admin at admin/performance/correlation/ when django.contrib.admin is installed. It takes endpoint, start and end query parameters and lists the matching API rows next to the resource snapshots for the same window — useful when you are already in the admin and do not need the full charted page.

Refresh endpoint

performance/api/correlation/ returns the page context as JSON, staff-only.