[example] Add example for Swift Service Lifecycle #522
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Pull Request Overview
This PR adds a comprehensive example demonstrating Swift Service Lifecycle integration with AWS Lambda and PostgreSQL RDS, along with minor fixes to Docker command references and local server implementation.
- Adds a complete ServiceLifecycle+Postgres example with AWS infrastructure setup
- Fixes Docker command references in format checking scripts
- Updates local server implementation to handle return values properly
Reviewed Changes
Copilot reviewed 18 out of 18 changed files in this pull request and generated 3 comments.
Show a summary per file
| File | Description |
|---|---|
| scripts/check-format-linux.sh | Fixed Docker command references from 'container' to 'docker' |
| Sources/AWSLambdaRuntime/Lambda+LocalServer.swift | Updated return type handling and error management in local server |
| Examples/Streaming/samconfig.toml | Added SAM configuration for streaming example |
| Examples/ServiceLifecycle+Postgres/* | Complete new example with PostgreSQL integration, infrastructure templates, and documentation |
| .licenseignore | Added .toml files to license ignore list |
| .github/workflows/pull_request.yml | Added new example to CI workflow |
| @@ -106,7 +106,7 @@ internal struct LambdaHTTPServer { | |||
| eventLoopGroup: MultiThreadedEventLoopGroup = .singleton, | |||
| logger: Logger, | |||
| _ closure: sending @escaping () async throws -> Result | |||
| ) async throws -> Result { | |||
| ) async throws -> Swift.Result<Result, any Error> { | |||
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The return type change from Result to Swift.Result<Result, any Error> appears to be a breaking change that could affect API consumers. This should be carefully considered for backward compatibility.
| ) async throws -> Swift.Result<Result, any Error> { | |
| ) async throws -> Result { |
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So when does this function throw an error and when does it return the error as a Result?
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Out of interest what was causing the shutdown error, that you are ignoring now
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So when does this function throw an error and when does it return the error as a Result?
when the user types CTRL-C to stop the server and the server is part of a service lifecycle group
Out of interest what was causing the shutdown error, that you are ignoring now
The reported error is Channel I/O by an attempt to read/write on a closed channel.
I don't know the root cause.
Because this happens on the local server, just used for testing, and at the time of shutdown. I think it's sfe to ignore the error and let the app terminate.
|
@adam-fowler This is a new example. The rest is "just" a PostgreSQL + service lifecycle example. I provide a SAM template to setup the database in a secure way (private network, restrictive security groups, password stored in secret manager) |
| // TODO: ideally, I want to do this once, after serviceGroup.run() is done | ||
| // but before the handler is called | ||
| logger.trace("Checking database") | ||
| try await prepareDatabase() |
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For Hummingbird I created a wrapper service for a service which called a closure before running the wrapped service. This allowed me to have prelude code like your prepareDatabase. You could use this to wrap the lambda runtime and run the prepareDatabase beforehand
/// Wrap another service to run after a prelude closure has completed
struct PreludeService<S: Service>: Service, CustomStringConvertible {
let prelude: @Sendable () async throws -> Void
let service: S
var description: String {
"PreludeService<\(S.self)>"
}
init(service: S, prelude: @escaping @Sendable () async throws -> Void) {
self.service = service
self.prelude = prelude
}
func run() async throws {
try await self.prelude()
try await self.service.run()
}
}
extension Service {
/// Build existential ``PreludeService`` from an existential `Service`
func withPrelude(_ prelude: @escaping @Sendable () async throws -> Void) -> Service {
PreludeService(service: self, prelude: prelude)
}
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Using the PostgresNIO driver, can we run a prelude code (that will send SQL commands on the connection) before service.run() ?
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I just tried it and the answer is "yes" :-)
| @@ -106,7 +106,7 @@ internal struct LambdaHTTPServer { | |||
| eventLoopGroup: MultiThreadedEventLoopGroup = .singleton, | |||
| logger: Logger, | |||
| _ closure: sending @escaping () async throws -> Result | |||
| ) async throws -> Result { | |||
| ) async throws -> Swift.Result<Result, any Error> { | |||
There was a problem hiding this comment.
So when does this function throw an error and when does it return the error as a Result?
| @@ -106,7 +106,7 @@ internal struct LambdaHTTPServer { | |||
| eventLoopGroup: MultiThreadedEventLoopGroup = .singleton, | |||
| logger: Logger, | |||
| _ closure: sending @escaping () async throws -> Result | |||
| ) async throws -> Result { | |||
| ) async throws -> Swift.Result<Result, any Error> { | |||
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Out of interest what was causing the shutdown error, that you are ignoring now
|
@adam-fowler Thank you for the initial review. I added |
Now that task cancellation works, re publishing this PR with a new example for Swift Service Lifecycle