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Career/Microlise/ESS ESP/ESP Applications.md

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+# What is ESP?
+
+ESP is a software suite built by ESS and sold to customers. It is deployed on a **per-customer basis** — similar to TMC (another internal product) but with fewer applications in the suite.
+
+Key traits:
+
+  - Customers only have the apps **they use** — not every customer gets everything
+  - Customers may have multiple environments (e.g. TEST and PROD)
+  - Test and PROD instances may live on the **same server** — this is a risk to be mindful of during deployment
+
+# Application Categories
+
+ESP applications fall into three categories:
+
+## 1\. Databases
+
+| Application | Type       | Notes                                       |
+| ----------- | ---------- | ------------------------------------------- |
+| EspBroker   | SQL Server | The core ESP database. Deployed via dacpac. |
+
+See [[ESP Database]] for Dacpac detail.
+
+## 2\. Windows Services
+
+[[Windows Services]] are background processes that run on a Windows server. They have no UI — they start, run, and are managed via the Windows Service Manager (or PowerShell commands like `Stop-Service`, `Start-Service`).
+
+| Service Name    | Notes                             |
+| --------------- | --------------------------------- |
+| DLService       | Unknown specific function (TBC)   |
+| EmailService    | Likely handles outbound emails    |
+| ExPlService     | Unknown specific function (TBC)   |
+| MISService      | Unknown specific function (TBC)   |
+| OutboundService | Likely handles outbound messaging |
+| ULService       | Unknown specific function (TBC)   |
+
+### Working with Windows Services in PowerShell
+
+``` powershell
+# Stop a service
+Stop-Service -Name "DLService" -Force
+
+# Start a service
+Start-Service -Name "DLService"
+
+# Check service status
+Get-Service -Name "DLService"
+
+# Wait for a service to stop
+(Get-Service -Name "DLService").WaitForStatus('Stopped', '00:01:00') 
+```
+
+### Why Services Must Be Stopped Before Deployment
+
+When deploying a new version, the old service process holds file locks on its [[DLL's]]. You cannot overwrite a locked file on Windows. Therefore the sequence is:
+
+1.  Stop the service
+2.  Swap the files (old → new)
+3.  Start the service
+
+## 3\. Citrix Applications
+
+Citrix is a technology that **streams desktop applications** to users remotely - the app runs on a server but the user sees it on their machine, similar to a remote desktop but on a per-app basis.
+
+| Application   | Notes                        |
+| ------------- | ---------------------------- |
+| VPlanner      | Main planning application    |
+| VPlannerAdmin | Admin interface for VPlanner |
+| ImportApp     | Data import application      |
+
+### Citrix Deployment Considerations
+
+Citrix apps are more complex to deploy than Windows Services because:
+
+  - **Active user sessions** may be running — you can't just swap files
+  - You must **notify users** of the upcoming upgrade and give a grace period
+  - After the grace period, **kill any remaining sessions**
+  - The actual upgrade mechanism is **still TBC** — believed to be a file copy with handling for locked executables built in
+  - Post-deploy **cycle checks** require navigating Citrix UI — hard to automate
+
+# Per-Customer App Lists
+
+Unlike TMC (where presumably all customers get everything), ESP is a subset deployment. This means:
+
+  - The manifest (see [[ESP Manifest]]) must define **which apps each customer has**
+  - The deployment scripts must skip apps not applicable to a given customer
+  - There is no universal "deploy everything" - each customer's list must be explicitly defined and maintained
+
+# Completeness of This List
+
+The handover document states this list is believed complete but **has not been confirmed**. Treat it as a working assumption, not a guarantee. Validate against actual customer environments when possible.