Multi Instance Runner for local clusters of n FHIR services (#5375)

* Add multi-instance FHIR server runner with NGINX proxy

- Add start-local-fhir-nginx.ps1 script to run multiple FHIR R4 instances behind NGINX
  - Configurable instance count, ports, and NGINX proxy settings
  - Automatic SQL database initialization and schema migration
  - Support for disabling security and persisting test environment variables
  - Log output redirection and process management
  
- Add comprehensive README.md documentation
  - Quick start guide and usage examples
  - Parameter reference with defaults
  - Instructions for running E2E tests against the cluster
  - Sample REST endpoints (health, metadata, Patient)
  - Visual Studio debugger attachment instructions for multi-instance debugging

* Add interactive scaling and management for FHIR instances in NGINX setup

Author: jestradaMS

.gitignore

@@ -300,4 +300,7 @@ install-aso/
 __*
 
 # For our Mac friends
-.DS_Store
+.DS_Store
+
+# For ignroing .local files from MultiInstanceRunner
+.local/

Tools/MultiInstanceRunner/README.md

@@ -0,0 +1,88 @@
+# Multi-instance local runner (NGINX proxy)
+
+Use `start-local-fhir-nginx.ps1` to spin up multiple local FHIR R4 instances behind an NGINX reverse proxy on a single port. Default settings start three instances on ports 5001-5003 and expose them via http://localhost:4343.
+
+## Prerequisites
+- PowerShell 7+
+- .NET SDK matching `global.json`
+- `sqlcmd` available on PATH (for optional DB creation)
+- Local SQL Server instance reachable by the provided connection string
+
+## Quick start
+```pwsh
+pwsh ./Tools/MultiInstanceRunner/start-local-fhir-nginx.ps1 -PersistTestEnvironment
+```
+This builds the R4 project (unless `-SkipBuild`), ensures the DB exists (unless `-SkipSchemaInitialization`), starts NGINX, and launches the configured number of instances.
+
+## Key parameters
+- `-InstanceCount` (default 3): number of FHIR processes; they bind sequentially starting at `-BasePort`.
+- `-BasePort` (default 5001): first backend port; instances use BasePort..BasePort+InstanceCount-1.
+- `-NginxListenPort` (default 4343): public listener forwarding to backends.
+- `-SqlConnectionString` / `-DatabaseName`: SQL connection; normalized to strip wrappers and ensure DB name.
+- `-ProjectPath` (default `src/Microsoft.Health.Fhir.R4.Web`): project to run.
+- `-Framework` (default `net9.0`): target framework for build/run.
+- `-SkipBuild`: reuse existing build outputs.
+- `-SkipSchemaInitialization`: skip schema manager apply.
+- `-DisableSecurity`: disable auth locally (default: on).
+- `-RedirectOutput`: write per-instance logs to `.local/logs`.
+- `-PersistTestEnvironment`: also write TestEnvironment* vars to the user profile.
+
+## Environment variables set per instance
+- `ASPNETCORE_URLS`, `ASPNETCORE_ENVIRONMENT`
+- `DataStore=SqlServer`, `SqlServer:ConnectionString`, `SqlServer:AllowDatabaseCreation=true`, `SqlServer:DeleteAllDataOnStartup=false`
+- `TaskHosting:*` tuned for fast background jobs
+- `FhirServer:CoreFeatures:SearchParameterCacheRefreshIntervalSeconds=1`, `SearchParameterCacheRefreshMaxInitialDelaySeconds=0`
+- Reindex/Export/ConvertData/Import enabled
+- Logging levels set to Debug for Microsoft.Health/Microsoft/System
+
+## Stopping
+- Press Ctrl+C in the PowerShell session to stop dotnet processes.
+- To stop NGINX manually:
+  ```pwsh
+  nginx -p $repoRoot/.local/nginx -s stop
+  ```
+
+## Logs
+When `-RedirectOutput` is set, stdout/stderr go to `.local/logs/fhir-r4-<port>.out.log` and `.err.log`. NGINX logs live under `.local/nginx/logs`.
+
+## Running E2E tests against the cluster
+1) Start the multi-instance cluster (example):
+```pwsh
+pwsh ./Tools/MultiInstanceRunner/start-local-fhir-nginx.ps1 -NoLaunchProfile -RedirectOutput -PersistTestEnvironment
+```
+2) In another shell from repo root, run the desired E2E suite pointing at the proxy (env vars are already set by the script):
+```pwsh
+dotnet test .\test\Microsoft.Health.Fhir.R4.Tests.E2E\Microsoft.Health.Fhir.R4.Tests.E2E.csproj -f net9.0 --no-build --filter "FullyQualifiedName~Microsoft.Health.Fhir.Tests.E2E.Rest.Reindex.ReindexTests&DisplayName~SqlServer" /p:CollectCoverage=false
+```
+Notes:
+- The script sets `TestEnvironmentUrl*` to http://localhost:4343 (via `-PersistTestEnvironment`).
+- Ensure the runner keeps running while tests execute; stop it after tests finish.
+
+## Sample endpoints (default proxy port 4343)
+- Health: http://localhost:4343/health/check
+- Metadata (capability statement): http://localhost:4343/metadata
+- Patient search: http://localhost:4343/Patient
+
+## Debugging with Visual Studio
+### Attach debugger to a running instance
+1) Open the solution in Visual Studio (e.g., `Microsoft.Health.Fhir.sln`)
+2) Go to **Debug → Attach to Process...** (or press **Ctrl+Alt+P**)
+  ![alt text](image.png)
+3) In the "Attach to Process" dialog:
+   - Confirm **Connection type** is set to "Local"
+   - In the process list, look for **Microsoft.Health.Fhir.R4.Web.exe** entries
+   - Each running instance will appear in the list with its PID
+   - Select the instance(s) you want to debug and click **Attach**
+  ![alt text](image-1.png)
+4) Set breakpoints in your code (e.g., in SearchParameterOperations.cs or SqlStoreClient.cs)
+5) Make requests via the proxy (http://localhost:4343) to hit the breakpoints
+
+### Debugging multiple instances
+- You can attach to multiple `Microsoft.Health.Fhir.R4.Web.exe` processes simultaneously
+- When a request comes through the NGINX proxy, it routes to one of the backends; use breakpoints to identify which instance handled it
+- Check the Visual Studio **Debug → Processes** window to see all attached processes
+
+### Tips
+- If you attached to instance on port 5001 and want to debug port 5002, use **Debug → Reattach to Microsoft.Health.Fhir.R4.Web.exe** (keyboard: **Shift+Alt+P**) as a shortcut
+- Ensure the solution is built before attaching so symbols are available
+- Use conditional breakpoints (right-click breakpoint → Filter) to target specific requests