MCQs on Processes and Concurrency | Elixir
Elixir is known for its robust support for concurrency, allowing developers to build scalable and fault-tolerant applications. The language’s process-based model allows for easy parallel execution. In this set of 30 multiple-choice questions, we’ll explore managing processes with GenServer, handling state, process lifecycle, and the importance of supervision trees in fault tolerance.
30 Multiple-Choice Questions on Elixir Processes and Concurrency
1. What is the primary purpose of a GenServer in Elixir?
- A) To manage web requests
- B) To create a new thread for every request
- C) To manage state and handle asynchronous calls
- D) To handle HTTP routing
2. Which of the following is NOT a function provided by GenServer?
- A) handle_call
- B) handle_cast
- C) handle_event
- D) init
3. What does GenServer.start_link/3 do?
- A) Starts a new process and links it to the caller
- B) Starts a new process without linking it
- C) Creates a new GenServer but does not start it
- D) Initializes the state for a GenServer
4. In the GenServer lifecycle, what is the purpose of the init function?
- A) To terminate the process
- B) To initialize state and return the state
- C) To send messages to the client
- D) To handle synchronous calls
5. What does the handle_call/3 function in a GenServer do?
- A) Handles asynchronous messages
- B) Handles synchronous requests and returns a reply
- C) Initializes the state
- D) Sends messages to another process
6. Which function in GenServer is used for handling asynchronous requests?
- A) handle_cast
- B) handle_call
- C) handle_event
- D) handle_sync
7. What does the GenServer.stop/1 function do?
- A) Stops the process immediately
- B) Stops the process after handling pending messages
- C) Terminates the caller process
- D) Notifies all processes to stop
8. What type of communication model is used in GenServer for handling messages?
- A) Shared memory
- B) Message passing
- C) Direct function calls
- D) Blocking queues
9. What is the primary responsibility of the handle_cast/2 function in a GenServer?
- A) To handle synchronous messages
- B) To send a response back to the client
- C) To handle asynchronous messages and update state
- D) To initialize the state of the GenServer
10. What does the GenServer.call/2 function do?
- A) Sends an asynchronous message to a GenServer
- B) Sends a synchronous message and waits for a reply
- C) Starts a new process
- D) Calls an external API
11. What is the role of the state in GenServer?
- A) It holds the current process’s memory state
- B) It holds data that the GenServer processes use
- C) It is used to track the number of messages processed
- D) It holds global variables
12. In a GenServer, what does the :ok atom usually signify?
- A) Success, with no further action needed
- B) Failure, but continuing to handle the next request
- C) An unhandled error in the process
- D) Initialization of the GenServer
13. Which of the following statements is true about the init callback in GenServer?
- A) It can return an error to stop the GenServer
- B) It must return a
:stopresponse to shut down - C) It always starts a new process
- D) It is only called when the server is shutting down
14. What happens when a GenServer process crashes?
- A) The process automatically restarts
- B) The process stops without any intervention
- C) The system terminates the entire application
- D) The system ignores the failure and continues
15. What is a supervision tree in Elixir?
- A) A data structure for handling concurrency
- B) A collection of processes that manage the life cycle of other processes
- C) A way to handle database transactions
- D) A built-in tool for error handling
16. How does a supervisor handle a failing child process?
- A) It restarts the child process
- B) It sends an error notification to the parent
- C) It terminates the child process without taking any further action
- D) It ignores the failure
17. What is the purpose of the :restart strategy in a supervisor?
- A) To terminate the child process immediately
- B) To restart a child process if it crashes
- C) To restart the entire system
- D) To prevent the process from being restarted
18. In Elixir, what is the benefit of separating state and logic in processes?
- A) It improves performance
- B) It allows for better fault tolerance and scalability
- C) It reduces memory usage
- D) It simplifies code readability
19. What is the default behavior when a GenServer crashes?
- A) The parent process will terminate the application
- B) The process will automatically be restarted
- C) The process will continue running indefinitely
- D) The system will ignore the failure
20. What does the :temporary restart strategy in a supervisor indicate?
- A) The process should be restarted immediately after failure
- B) The process should not be restarted after it fails
- C) The process should be restarted after a delay
- D) The process should never fail
21. Which function is used to handle synchronous requests in GenServer?
- A) handle_sync
- B) handle_cast
- C) handle_call
- D) handle_message
22. What would happen if a GenServer state is not updated properly?
- A) The system will terminate immediately
- B) The GenServer will crash with an error
- C) The process will continue with outdated state
- D) A new state will be generated automatically
23. How do you handle an error in a GenServer’s handle_call or handle_cast function?
- A) By using the
tryandcatchblocks - B) By returning
{:error, reason} - C) By letting the error propagate to the caller
- D) By raising a custom exception
24. Which of the following is true about a process in Elixir?
- A) A process is a lightweight thread with its own memory space
- B) Processes in Elixir share memory space for better performance
- C) Processes in Elixir are always created by a supervisor
- D) A process in Elixir can run only on a single core
25. What is the key difference between handle_call and handle_cast?
- A)
handle_callis used for synchronous requests, whilehandle_castis for asynchronous requests - B)
handle_callis for terminating the process, andhandle_castis for initialization - C)
handle_callhandles messages, whilehandle_casthandles errors - D) There is no difference between them
26. What is a “supervisor” in the context of Elixir?
- A) A process that manages other processes, ensuring they restart on failure
- B) A process that handles all incoming requests
- C) A monitor that tracks system performance
- D) A utility for managing databases
27. What happens if a child process in a supervisor tree crashes?
- A) It is ignored and continues running
- B) The supervisor will restart the child process
- C) The parent process will automatically be killed
- D) The entire system will shut down
28. How can a process in Elixir be isolated from other processes?
- A) By using shared memory
- B) By using process-based concurrency
- C) By using threads
- D) By using external services
29. What would happen if a GenServer fails to handle an incoming call or cast?
- A) The system will ignore the error
- B) The error will cause the process to crash
- C) The caller will receive a default response
- D) The error will be logged and then handled later
30. What is the significance of start_link in GenServer?
- A) It starts a process and links it to the calling process
- B) It initializes the state for a GenServer
- C) It stops the GenServer process
- D) It terminates the calling process
Answer Key
| Qno | Answer (Option with the text) |
|---|---|
| 1 | C) To manage state and handle asynchronous calls |
| 2 | C) handle_event |
| 3 | A) Starts a new process and links it to the caller |
| 4 | B) To initialize state and return the state |
| 5 | B) Handles synchronous requests and returns a reply |
| 6 | A) handle_cast |
| 7 | B) Stops the process after handling pending messages |
| 8 | B) Message passing |
| 9 | C) To handle asynchronous messages and update state |
| 10 | B) Sends a synchronous message and waits for a reply |
| 11 | B) It holds data that the GenServer processes use |
| 12 | A) Success, with no further action needed |
| 13 | A) It can return an error to stop the GenServer |
| 14 | A) The process automatically restarts |
| 15 | B) A collection of processes that manage the life cycle of other processes |
| 16 | A) It restarts the child process |
| 17 | B) To restart a child process if it crashes |
| 18 | B) It allows for better fault tolerance and scalability |
| 19 | B) The process will automatically be restarted |
| 20 | B) The process should not be restarted after it fails |
| 21 | C) handle_call |
| 22 | C) The process will continue with outdated state |
| 23 | B) By returning {:error, reason} |
| 24 | A) A process is a lightweight thread with its own memory space |
| 25 | A) handle_call is used for synchronous requests, while handle_cast is for asynchronous requests |
| 26 | A) A process that manages other processes, ensuring they restart on failure |
| 27 | B) The supervisor will restart the child process |
| 28 | B) By using process-based concurrency |
| 29 | B) The error will cause the process to crash |
| 30 | A) It starts a process and links it to the calling process |