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Introduction To Windows Services

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The talk I'm giving at CodeStock this year

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Introduction To Windows Services

  1. 1. Introduction to Windows Services (Easier then you think) Josef Finsel AzureDBA.com
  2. 2. Who am I? <ul><li>Database Administrator </li></ul><ul><li>C# Programmer </li></ul><ul><li>Author/Maintainer of a half dozen Services used daily on my job </li></ul>
  3. 3. What’s a Service <ul><li>Long running program </li></ul><ul><li>Runs when computer starts </li></ul><ul><li>Can specify security context </li></ul>
  4. 4. Services Have Bad Rep <ul><li>Supposedly Services are: </li></ul><ul><ul><li>Hard to program </li></ul></ul><ul><ul><li>Hard to debug </li></ul></ul><ul><li>Only true if you let them be true </li></ul>
  5. 5. Windows Services the Easy Way <ul><li>Solution with three projects: </li></ul><ul><ul><li>Class Library that does all of the work </li></ul></ul><ul><ul><li>Win Form app for debugging </li></ul></ul><ul><ul><li>Actual service that is nothing more than a wrapper for the Class Library </li></ul></ul><ul><li>Every line of code excluded from the service is one less line to debug the hard way </li></ul>
  6. 6. Class Library Project <ul><li>Contains no Config information </li></ul><ul><li>Does no logging </li></ul><ul><ul><li>Offers a callback to communicate with calling program for logging </li></ul></ul><ul><li>Includes property for stopping long-running processes </li></ul><ul><li>Should handle all errors </li></ul>
  7. 7. Win Form Application Project <ul><li>App.Config contains all necessary configuration for the Class </li></ul><ul><li>Instantiates the class using only App.Config entries </li></ul><ul><li>Outputs all log information to screen </li></ul><ul><li>Has Timer, Checkbox to control Timer, Button to run without Timer and Button to test Stopping </li></ul>
  8. 8. Demo 1 <ul><li>Using the Win Form and the Class Library </li></ul>
  9. 9. Windows Service Project <ul><li>Supports Service Functions </li></ul><ul><li>App.Config contains all necessary configuration for the Class </li></ul><ul><li>Instantiates the class using only App.Config entries </li></ul><ul><li>Outputs all log information to screen </li></ul><ul><li>Has Timer </li></ul><ul><li>Copy of code from Win Form </li></ul>
  10. 10. Reviewing Service Code
  11. 11. Service Installer <ul><li>Class used for installing a service </li></ul><ul><li>Right-click on the Service Component Window and select Add Installer </li></ul><ul><li>Set the </li></ul><ul><ul><li>Description </li></ul></ul><ul><ul><li>Display name </li></ul></ul><ul><ul><li>Start type </li></ul></ul><ul><ul><li>Other service dependencies </li></ul></ul>
  12. 12. Service Process Installer <ul><li>Set Security Context </li></ul>
  13. 13. Installing the Service <ul><li>InstallUtil (Visual Studio Command Prompt) </li></ul><ul><li>Provide account context if required </li></ul>
  14. 14. Important Caveat <ul><li>Do not recompile after the Installer information has changed without uninstalling first! </li></ul><ul><li>Uninstall is same as install but with –u </li></ul><ul><li>Failure to Uninstall leads to RegEdit </li></ul>
  15. 15. Running and Debugging a Service Demo
  16. 16. Service States <ul><li>OnStart enable timer </li></ul><ul><li>OnStop disable timer </li></ul><ul><li>OnShutdown disable timer </li></ul><ul><li>OnPause disable timer </li></ul><ul><li>OnContinue enable timer </li></ul>
  17. 17. When is a Service Frozen? <ul><li>If Windows initiates a State Change and gets no response in 30 seconds, it’s frozen and may get killed </li></ul>
  18. 18. When a Service Fails <ul><li>When a service fails you can: </li></ul><ul><ul><li>Do nothing </li></ul></ul><ul><ul><li>Restart it </li></ul></ul><ul><ul><li>Run a program </li></ul></ul><ul><ul><li>Restart the computer </li></ul></ul>
  19. 19. Deploying a Service <ul><li>Deploy in stages: </li></ul><ul><ul><li>Running WinForm on Desktop in Debug mode to test stability </li></ul></ul><ul><ul><li>Running as a Service on your box with Debugger Attached </li></ul></ul><ul><ul><li>Deploying as real service </li></ul></ul>
  20. 20. Best Practices <ul><li>Service = Lightweight Wrapper around class </li></ul><ul><li>Class has callback for logging </li></ul><ul><li>Class has cancel mechanism </li></ul><ul><li>Most debugging done in WinForm </li></ul>
  21. 21. Questions?
  22. 22. Contact me <ul><li>http://www.azuredba.com </li></ul><ul><li>Twitter: @carpdeus </li></ul>

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