Application Starter: the entry point for your application
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ApplicationStarter is a tool that provides facilities to start applications from the command line. It handles parameter management, logging, and error handling. Developers define command line handlers by subclassing ApplicationStarterCommandLineHandler and specifying configuration parameters, activation logic, and other metadata. The starter then parses arguments and allows the application to access parameters. It is useful for containerized applications that need configurable startup.
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Application Starter: the entry point for your application
- 1. Application Starter The entrypoint for your application ba-st/ApplicationStarter
- 2. Hello! I am Inés Sosa I will present a talk because Julián Maestri was afraid. He sent a little girl instead. 2
- 3. What does it do? What is it? It’s a tool that provides facilities to start applications in from the command line. ◎ Parameter management ◎ Simple logging ◎ Startup error handling (Fuel) It’s especially useful in applications deployed with 3
- 4. Why/how does it help? ◎ Docker containers are ephemeral ◎ Not access to the running image to examine it ◎ Modifying configuration in a container can be annoying or complex 4
- 5. 1. How to use it 5
- 6. Defining the handler Load ApplicationStarter from ba-st/ApplicationStarter Subclass ApplicationStarterCommandLineHandler. Then define: 6 Class Side Instance Side #commandName #configurationDefinitions #description #basicActivate #logPrefix
- 7. #commandName (Class Side) Used to activate this handler from the command line. commandName ^ 'smalltalks2019' 7 ./pharo-ui Pharo.image smalltalks2019 --port=8080 ./pharo Pharo.image --list Currently installed Command Line Handlers: smalltalks2019 Example Command line handler for Smalltalks 2019, HI!
- 8. #description (Class Side) Describes the handler when using ./pharo <image> --list 8 ./pharo Pharo.image --list Currently installed Command Line Handlers: smalltalks2019 Example Command line handler for Smalltalks 2019, HI!
- 9. A string to prepend to the logs and fuel files. #logPrefix (Class Side) 9 Smalltalks 2019 Example-2019-11-08T002050.log Smalltalks 2019 Example-2019-11-08T002417.fuel
- 10. #configurationDefinitions (Instance Side) A collection of arguments available to the command line handler. These are logged to console when the application starts, and are accessible under self configuration on the command line handler. The arguments can be: Mandatory, Optional or Flags 10
- 12. #basicActivate (Instance Side) Contains the logic to actually start your application. It should use the parameters defined in the configurationDefinitions to start the application. 12
- 13. 2. Example 13
- 14. Defining only mandatory parameters 14 ./pharo Pharo.image smalltalks2019 --port=8080 [WARNING] format option not provided. Defaulting to 'text/plain' [INFO] format: text/plain [INFO] port: 8080
- 15. Without mandatory arguments 15 ./pharo Pharo.image smalltalks2019 [ERROR] port option not provided. You must provide one. port option not present
- 16. With all arguments 16 ./pharo Pharo.image smalltalks2019 --port=8080 --format=text/html [INFO] format: text/html [INFO] port: 8080
- 20. ◎ Graceful termination ◎ Use to CLAP ◎ Configuration from Environment Variables ◎ Support for sensitive parameters (passwords) ◎ Improved Logging Future Work 20
Editor's Notes
- It provides parameter management, logging and error handling (using fuel to serialize error stacks).
- NOTETS once finished, the context in which the application was executed is lost. You can’t raise a debugger in this context. It is easier to modify console parameters or environment variables.
- For this talk we’ve made an example, it’s a simple server that start up from the command line in a port (indicated through the command line) that calculates the factorial of a number sended by URL
- It beggins by… the following methods: that will be explain HEREINAFTER
- For easily recognize your logs It’s useful for when you have more than one application dumping logs on the same path
- Which declares… These arguments
- Here you define a collection of the argument that your application it’s going to recieve. Aas you can see, we defined a mandatory a
- It's wrapped in a block handling Error, to handle program termination on startup errors.
- Graceful Termination: Signal handling for pharo is not nice, the idea is to write a wrapper that helps with that. CLAP: Command Line Argument Parser Env Vars: currently this is achieved with a wrapper shell script. Helps for docker configuration. Sensitive Parameters: Do not display passwords on console Log: Integrate with an existing framework (suggestions accepted)