“Is it secret Frodo? Is it SAFE?” So I have this piece of code (first serious coroutine hacking I’ve done) where I have a map associating names with lists of data. The main thread will allow clients to access the lists while a daily background thread will update the data. Main thread is read-only, Background thread is write-only. I think, from an app perspective, that this code is safe even if not predictable. So am I correct?

only threadsafe if

data

is thread safe, I think. if

data

is accessed concurrently with a non-thread-safe-map like HashMap, it's likely to to throw ConcurrentModificationException or worse, fail silently. reason being is that you are accessing

data

on two threads, the

<http://Disp.IO|Disp.IO>

threads and your main threads. even if it's not writing on both, it's still problematic for HashMap.

You should share the data by communicating, not by sharing mutable data. I think you should use an

actor

.

@marstran do you have a link handy?

You could check out Roman's talk from Kotlinconf last year:

https://kotlin.github.io/kotlinx.coroutines/kotlinx-coroutines-core/kotlinx.coroutines.channels/actor.html for current API, to be phased out

And I just came across

actor

in the link @octylFractal sent.

@octylFractal Yes, but there will be a replacement. Actors as a concept is not obsolete.

mhm. I only meant the specific API point

Yes, it is very clear from https://github.com/Kotlin/kotlinx.coroutines/issues/87 that the

actor

model is useful but could be better (support a more complex model). So it looks like a decent choice to fix my issue.

Sharing

MutableMap

in this way is not safe.