Handle remote HTTP errors

async-http-faraday.gemspec

@@ -25,6 +25,6 @@ Gem::Specification.new do |spec|
 
 	spec.required_ruby_version = ">= 3.3"
 
-	spec.add_dependency "async-http", "~> 0.42"
+	spec.add_dependency "async-http", "~> 0.99"
 	spec.add_dependency "faraday"
 end

context/getting-started.md

@@ -48,6 +48,21 @@ connection = Faraday.new(...) do |builder|
 end
 ~~~
 
+### Retrying Remote Failures
+
+When a remote endpoint fails while processing a request, the adapter raises {ruby Faraday::ConnectionFailed}. You can use the `faraday-retry` middleware to retry idempotent requests:
+
+~~~ruby
+require "faraday/retry"
+
+connection = Faraday.new(...) do |builder|
+	builder.request :retry, exceptions: [Faraday::ConnectionFailed]
+	builder.adapter :async_http
+end
+~~~
+
+By default, `faraday-retry` only retries idempotent methods. Configure its retry policy explicitly before retrying other methods.
+
 The value of isolation cannot be overstated - if you can design you program using a share-nothing (between threads) architecture, you will have a much easier time debugging and reasoning about your program, however this comes at the cost of increased resource usage.
 
 Alternatively, if you do not want to cache client connections, you can use the `Async::HTTP::Faraday::Clients` interface, which closes the connection after each request:

gems.rb

@@ -28,6 +28,7 @@
 	gem "bake-test-external"
 
 	gem "faraday-multipart"
+	gem "faraday-retry"
 
 	gem "sus-fixtures-async"
 	gem "sus-fixtures-async-http"

lib/async/http/faraday/adapter.rb

@@ -105,6 +105,7 @@ def self.setup_parallel_manager(**options)
 
 				# The exceptions that are considered connection errors and result in a `Faraday::ConnectionFailed` exception.
 				CONNECTION_EXCEPTIONS = [
+					::Protocol::HTTP::RemoteError,
 					Errno::EADDRNOTAVAIL,
 					Errno::ECONNABORTED,
 					Errno::ECONNREFUSED,

test/async/http/faraday/adapter.rb

@@ -16,6 +16,7 @@
 
 require "faraday"
 require "faraday/multipart"
+require "faraday/retry"
 
 require "protocol/http/body/file"
 require "protocol/multipart"
@@ -268,6 +269,42 @@ def get_response(url = bound_url, path = "/index", adapter_options: {})
 		end
 	end
 
+	with "a remote failure" do
+		it "can retry using Faraday middleware" do
+			attempts = 0
+			client = Object.new
+			client.define_singleton_method(:call) do |request|
+				attempts += 1
+
+				if attempts == 1
+					body = Protocol::HTTP::Body::Writable.new
+					body.close_write(Protocol::HTTP::RemoteError.new("The remote endpoint failed!"))
+					Protocol::HTTP::Response[200, {}, body]
+				else
+					Protocol::HTTP::Response[200, {}, ["Hello World"]]
+				end
+			end
+
+			clients = Object.new
+			clients.define_singleton_method(:with_client) do |endpoint, &block|
+				block.call(client)
+			end
+			clients.define_singleton_method(:close){}
+
+			connection = Faraday.new("https://example.com") do |builder|
+				builder.request :retry, max: 1, exceptions: [Faraday::ConnectionFailed]
+				builder.adapter :async_http, clients: proc{clients}
+			end
+
+			response = connection.get("/")
+
+			expect(response.body).to be == "Hello World"
+			expect(attempts).to be == 2
+		ensure
+			connection&.close
+		end
+	end
+
 	with "a multi-part post body" do
 		include Sus::Fixtures::Async::HTTP::ServerContext