How to: Identify Hot Paths & Bottlenecks

[!TIP] A "Hot Path" is code that runs frequently or is critical for user experience. Optimizing here yields high ROI. Optimizing elsewhere is often a waste of time.

This guide outlines the standard procedures for identifying Hot Paths in WepNG using our available tooling.

1. Using Application Insights (Production/Staging)

Application Insights is our primary source of truth for real-world performance.

Procedure

1. Navigate: Azure Portal -> WepNG Resource -> Performance blade.
2. Sort: Sort the "Operation Name" list by Duration (95th percentile) to find slow requests, AND by Count to find high-frequency requests.
3. Identify:
   • High Count + Low Duration: Check for cumulative CPU usage. (e.g., a 10ms request called 1M times/hour).
   • High Duration: These are latency bottlenecks (e.g., ExportPDF).
4. Drill Down: Click Samples -> Select a slow request -> View End-to-End Transaction Details.
   • Look for Long Dependencies (SQL queries, HTTP calls).
   • Look for "Gaps" in the timeline (CPU heavy processing in C#).

2. Using MiniProfiler (Development)

MiniProfiler is active in the Staging and Dev environments (bottom-right corner overlay).

Procedure

1. Interact: Perform the action in the browser (e.g., "Load Student Profile").
2. Inspect: Click the specific interaction in the MiniProfiler overlay.
3. Analyze:
   • N+1 Queries: Look for valid SQL queries marked as DUPLICATE or a long list of identical SELECTs.
   • Slow SQL: Queries taking > 500ms are highlighted in red.
   • Controller Time: If "Controller" time is high but "SQL" is low, you have a CPU Hot Path (e.g., looping in C#, generating PDFs).

3. Using Visual Studio Diagnostic Tools (Local)

When you can reproduce the slowness locally.

Procedure

1. Start Debugging: F5 in Visual Studio.
2. Open Diagnostics: Debug -> Windows -> Show Diagnostic Tools.
3. Record CPU Profile:
   • Select CPU Usage tab.
   • Click Record CPU Profile.
   • Perform the action in the browser.
   • Stop Recording.
4. Analyze Call Tree:
   • Switch to Call Tree view.
   • Expand the "Hot Path" (marked with flame icons 🔥).
   • This shows exactly which C# method (e.g., String.Concat, DataFeeder.Calculate) is consuming the most CPU cycles.

4. Common WepNG Hot Paths (Known)

Component	Symptom	Tool to Verify
FinancialTransactionImporter	XML Parsing loop	VS CPU Profiler
WayTDFeeder	Loop calculating turnover	Application Insights (Duration)
HomeController.SolveFeeTitle	N+1 Query on Langs	MiniProfiler (Duplicate SQL)
WepEmailGenerator	SMTP Blocking	App Insights (Dependency Duration)