Use EventLoop provided by SwiftNIO's MultiThreadedEventLoopGroup.singleton

[tkrajacic]

Since SwiftNIO provides a global EventLoopGroup singleton, you can now create a PostgresConnection without explicitly providing an EventLoop. In such a case, an eventLoop from this singleton will be used.

// Uses the MultiThreadedEventLoopGroup.singleton.any() eventLoop
let connection = try await PostgresConnection.connect(
  configuration: config,
  id: 1,
  logger: logger
)

Fixes #388

[fabianfett]

Two small nits.

[weissi]

We're still figuring out the patterns here so I don't know if this is a good suggestion but maybe a defaulted parameter on eventLoop: EventLoop = MultiThreadedEventLoopGroup.singleton.any() could work?

[fabianfett]

Not sure about this in the context of NIOTS... If we can import NIOTS, I would love to use the NIOTS EventLoop in the future for those cases. Defaulting inside the API might prove problematic then.

[weissi]

Once NIOTS is supported, I'd suggest to go down the route of my AHC PR: https://github.com/swift-server/async-http-client/pull/697/files#diff-914333008acc7684e7d98c700381a134ecdf49f095ce644e5898e857a16feabfR880

Then PostgresNIO could provide a PostgresNIO.defaultEventLoopGroup which would return either MTELG.singleton or NIOTSELG.singleton. And apart from the default value nothing needs to change.

If you don't want to "leak" that we're using MTELG.singleton today, then I'd suggest to add the static var defaultEventLoopGroup to PostgresNIO with this PR.

[fabianfett]

@weissi Lovely! @tkrajacic can you take ti from here?

[fabianfett]

@tkrajacic Just discussed this a bit further with @weissi:

extension PostgresConnection {
     /// Returns the default `EventLoopGroup` singleton, automatically selecting the best for the platform.
     ///
     /// This will select the concrete `EventLoopGroup` depending which platform this is running on.
     public static var defaultEventLoopGroup: EventLoopGroup {
 #if canImport(Network)
         if #available(OSX 10.14, iOS 12.0, tvOS 12.0, watchOS 6.0, *) {
             return NIOTSEventLoopGroup.singleton
         } else {
             return MultiThreadedEventLoopGroup.singleton
         }
 #else
         return MultiThreadedEventLoopGroup.singleton
 #endif
     }
 }

And then we should default the existing connect method to . defaultEventLoopGroup, instead of creating a separate connect method.

[tkrajacic]

@fabianfett I have all that locally staged, but I was waiting until I could use the new NIOTS default eventloop group. So I am waiting for that to get released

[fabianfett]

@tkrajacic sounds great!

[codecov-commenter]

Codecov Report

Merging #389 (352965b) into main (220eb50) will decrease coverage by 0.04%.
Report is 1 commits behind head on main.
The diff coverage is 0.00%.

❗ Current head 352965b differs from pull request most recent head 6eba762. Consider uploading reports for the commit 6eba762 to get more accurate results

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #389      +/-   ##
==========================================
- Coverage   46.02%   45.98%   -0.04%     
==========================================
  Files         110      110              
  Lines        8833     8840       +7     
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  Hits         4065     4065              
- Misses       4768     4775       +7     

Files Changed	Coverage Δ
...es/PostgresNIO/Connection/PostgresConnection.swift	34.87% <0.00%> (-0.68%)	⬇️

[fabianfett]

Looks great! Thanks @tkrajacic