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Add note regarding synchronous communication between too many isolates #6182

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merged 12 commits into from
Nov 8, 2024
Merged

Add note regarding synchronous communication between too many isolates #6182

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a654eca
Add note regarding synchronous communication between too many isolates
aam Oct 30, 2024
6f18be3
Clean up
aam Oct 30, 2024
434eeb4
Concurrent vs parallel, added 'unless...'
aam Oct 31, 2024
335c807
Fix url links
aam Oct 31, 2024
8a902ad
Use site variable
aam Oct 31, 2024
1766a28
Fix url links again
aam Oct 31, 2024
89162f2
Move text around
aam Nov 4, 2024
250255c
Merge branch 'main' into comment-on-limit-concurrency
aam Nov 4, 2024
beed89f
rewrite/restructure
MaryaBelanger Nov 7, 2024
c0c61bc
Merge branch 'main' into comment-on-limit-concurrency
MaryaBelanger Nov 7, 2024
a578081
fix typos, links
MaryaBelanger Nov 7, 2024
473bf61
aam reviews
MaryaBelanger Nov 7, 2024
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6 changes: 6 additions & 0 deletions src/content/language/isolates.md
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Expand Up @@ -39,6 +39,12 @@ but here are some more situations where they can be useful:
- Performing I/O, such as communicating with a database.
- Handling a large volume of network requests.

Also note a caveat due to a limit to the number of isolates running in parallel:

- The limit is not hardcoded to a particular number, it is calculated based on the Dart VM heap size available to the Dart application, can be considered to be between 8 and 32 depending on the platform.
- This limit doesn't affect asynchronous communction between isolates via messages - you can have hundreds of isolates running and making progress. The isolates are scheduled on the CPU in round-robin fashion and yield to each other often.
- Attempts to do *synchronous* communication between isolates over the limit though may result in a deadlock unless special care is taken (the C code that does synchronous communication would need to leave the current isolate before it blocks and re-enter it before returning to dart, see [`Dart_EnterIsolate`]({{site.repo.dart.sdk}}/blob/c9a8bbd8d6024e419b5e5f26b5131285eb19cc93/runtime/include/dart_api.h#L1254) and [`Dart_ExitIsolate`]({{site.repo.dart.sdk}}/blob/c9a8bbd8d6024e419b5e5f26b5131285eb19cc93/runtime/include/dart_api.h#L1455).

[Flutter]: {{site.flutter-docs}}/perf/isolates

## Implementing a simple worker isolate
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