45 lines
3.0 KiB
Markdown
45 lines
3.0 KiB
Markdown
|
# Hints
|
||
|
|
|
||
|
|
## General
|
||
|
|
|
||
|
|
- Read about links and tasks in the official [Getting Started guide][getting-started-links].
|
||
|
|
- Take a look at the [documentation of the `Task` module][task].
|
||
|
|
- Read ["Demystifying processes in Elixir" on blog.appsignal.com][appsignal-processes].
|
||
|
|
- Read ["Understanding Exit Signals in Erlang/Elixir" on crypt.codemancers.com][codemancers-exit-signals].
|
||
|
|
|
||
|
|
## 1. Start a reliability check for a single input
|
||
|
|
|
||
|
|
- You don't need a task for this step, a regular linked process is enough.
|
||
|
|
- There is a [built-in function][spawn-link] that runs a given anonymous function in a new process and links it to the current process.
|
||
|
|
|
||
|
|
## 2. Interpret the results of a reliability check
|
||
|
|
|
||
|
|
- To receive a single message, call [`receive`][receive] once. It will read the first message that matches any of the given patterns, leaving other messages in the process inbox.
|
||
|
|
- Either a guard or [the pin operator][pin-operator] can be used to ensure that only messages from a process whose PID matches the PID given to `await_reliability_check_result/2` as an argument will be received.
|
||
|
|
- [`receive`][receive] accepts an `after` clause to handle timeouts.
|
||
|
|
|
||
|
|
## 3. Run a concurrent reliability check for many inputs
|
||
|
|
|
||
|
|
- The current process must start trapping exits before any new linked processes are spawned.
|
||
|
|
- Trapping exits in a process is achieved by setting a flag on that process.
|
||
|
|
- There is a [built-in function][process-flag] that sets a flag on a process and returns the old value of that flag.
|
||
|
|
- The flag for trapping exits is called `:trap_exit` and accepts a boolean value.
|
||
|
|
- Make use of `Enum` functions to first start a process for each input, and then await messages from each process. Use the functions implemented in the two previous steps. Note that the map returned by `start_reliability_check/2` matches the map that `await_reliability_check_result/2` expects as the first argument.
|
||
|
|
|
||
|
|
## 4. Run a concurrent correctness check for many inputs
|
||
|
|
|
||
|
|
- Use an asynchronous task for this step.
|
||
|
|
- There is a [built-in function][task-async] that starts an asynchronous task.
|
||
|
|
- There is a [built-in function][task-await] that waits for an asynchronous task to finish executing and returns its result. It accepts a timeout as a second argument.
|
||
|
|
- Make use of `Enum` functions to first start a task for each input, and then wait for each task.
|
||
|
|
|
||
|
|
[spawn-link]: https://hexdocs.pm/elixir/Kernel.html#spawn_link/1
|
||
|
|
[pin-operator]: https://hexdocs.pm/elixir/Kernel.SpecialForms.html#%5E/1
|
||
|
|
[receive]: https://hexdocs.pm/elixir/Kernel.SpecialForms.html#receive/1
|
||
|
|
[process-flag]: https://hexdocs.pm/elixir/Process.html#flag/2
|
||
|
|
[task-async]: https://hexdocs.pm/elixir/Task.html#async/1
|
||
|
|
[task-await]: https://hexdocs.pm/elixir/Task.html#await/2
|
||
|
|
[task]: https://hexdocs.pm/elixir/Task.html
|
||
|
|
[appsignal-processes]: https://blog.appsignal.com/2017/05/18/elixir-alchemy-demystifying-processes-in-elixir.html
|
||
|
|
[getting-started-links]: https://hexdocs.pm/elixir/processes.html#links
|
||
|
|
[codemancers-exit-signals]: https://crypt.codemancers.com/posts/2016-01-24-understanding-exit-signals-in-erlang-slash-elixir/
|