nelson687
Difference between Task.await and Task.yield
Been reading the Hex docs but it’s still not very clear to me.
I can see this
Task.yield/2 is an alternative to await/2 where the caller will temporarily block, waiting until the task replies or crashes. If the result does not arrive within the timeout, it can be called again at a later moment. This allows checking for the result of a task multiple times. If a reply does not arrive within the desired time, Task.shutdown/2 can be used to stop the task.
When is that “later” moment? Is that the only difference between await and yield ?
I’m also lost with the caller being temporarily blocked - Does this mean that the the processes will not run in parallel? or am I missing something?
Also this snippet that is the in the docs for yield confuses me
case Task.yield(task, timeout) || Task.shutdown(task) do
{:ok, result} ->
result
nil ->
Logger.warn "Failed to get a result in #{timeout}ms"
nil
end
When the timeout happens, what’s gonna happen? is it gonna log the warning because it returned nil or execute Task.shutdown(task)
thanks!
Most Liked
peerreynders
Yes - so typically you would decrement a counter and take drastic action once it gets to 0.
If the timeout is exceeded, then the current process will exit. If the task process is linked to the current process which is the case when a task is started with async, then the task process will also exit.
So Task.await/2 will automatically take drastic action after the first timeout. Task.yield/2 leaves the response to a timeout entirely up to you.
peerreynders
Pretty much.
You could also immediately issue Task.shutdown/2 for the runaway task, simply to keep your current process alive (an option which Task.await/2 doesn’t give you but given that the current process potentially provided faulty startup data to the task also terminating the current process may be a reasonable approach).
Qqwy
It means that the caller process will wait (AKA be blocked) until:
- the task completed, or
- the timeout has passed. In this case you could call
Task.yieldagain (this is ‘later’).
So yes, it will not run in parallel during this time, which is exactly the point of this call: Waiting until a result is available. Obviously, by using a low timeout, we only check if there currently is a value without really ‘waiting’ in the meantime.
Last Post!
nelson687
Popular in Questions
Other popular topics
Latest on Elixir Forum
Sponsor Spotlight
Practical resources that improve the lives of professional developers.
Categories:
Sub Categories:
Forums
Popular Tags
- #ecto
- #liveview
- #troubleshooting
- #learning-elixir
- #deployment
- #library
- #erlang
- #testing
- #genserver
- #mix
- #absinthe
- #remote-other
- #otp
- #plug
- #how-to-question
- #macros
- #postgres
- #channels
- #elixirconf
- #exunit
- #discussion
- #code-sync
- #javascript
- #podcasts
- #onsite
- #dialyzer
- #docker
- #authentication
- #umbrella
- #full-time-contract
- #podcasts-by-brainlid
- #ecto-query
- #elixir-ls
- #phoenix_html
- #iex
- #blog-post
- #graphql
- #genstage
- #ai
- #websockets
- #supervisor
- #elixirconf-us
- #advent-of-code
- #distillery
- #processes
- #api
- #forms
- #metaprogramming
- #security
- #hex
Our Sponsors
Build Elixir applications with speed and confidence.
Supporting innovation across the BEAM ecosystem.
We build reliable cloud platforms for business-critical systems.
Catch errors, track performance, monitor hosts and more.
Error tracking for Elixir devs who love to ship. Start your free account.
Practical resources that improve the lives of professional developers.
Develop your skills with books, videos, and courses.
The deployment platform built for Elixir: PaaS ease, VPS control.
The team behind Membrane, Popcorn, LiveDebugger. Available for hire.
Courses that'll move you from confusion to "Aha, now I get it!"