fix: retry HTTP requests on 5xx status codes (502, 503, 504)

toby676 · YOU54F · commit 2174a318c475 · 2026-02-23T15:30:19.000Z
Add RetriableHttpStatusError class that raises on 502/503/504 responses,
which triggers automatic retry via the existing Retry.until_true mechanism.
Add comprehensive tests with stderr output mocked to avoid noisy test output.

This ensures transient server errors don't cause pact publication/verification
to fail immediately.
diff --git a/lib/pact/hal/http_client.rb b/lib/pact/hal/http_client.rb
@@ -6,6 +6,18 @@
 
 module Pact
   module Hal
+    class RetriableHttpStatusError < StandardError
+      RETRIABLE_STATUS_CODES = [502, 503, 504].freeze
+
+      attr_reader :status_code, :response_body
+
+      def initialize status_code, response_body
+        @status_code = status_code
+        @response_body = response_body
+        super("HTTP #{status_code} error: #{response_body}")
+      end
+    end
+
     class HttpClient
       attr_accessor :username, :password, :verbose, :token
 
@@ -65,9 +77,15 @@ def perform_request request, uri
             end
             http.verify_mode = OpenSSL::SSL::VERIFY_NONE
           end
-          http.start do |http|
+          result = http.start do |http|
             http.request request
           end
+
+          # Raise error on specific 5xx status codes to trigger retry
+          status_code = result.code.to_i
+          raise RetriableHttpStatusError.new(status_code, result.body) if RetriableHttpStatusError::RETRIABLE_STATUS_CODES.include?(status_code)
+
+          result
         end
         Response.new(response)
       end
diff --git a/spec/lib/pact/hal/http_client_spec.rb b/spec/lib/pact/hal/http_client_spec.rb
@@ -82,6 +82,109 @@ module Hal
         it "returns a response" do
           expect(do_get.body).to eq({"some" => "json"})
         end
+
+        context "when server returns 502 Bad Gateway" do
+          before do
+            allow(Retry).to receive(:until_true).and_call_original
+            allow($stderr).to receive(:puts)
+          end
+
+          let!(:request) do
+            stub_request(:get, "http://example.org/").
+              to_return(status: 502, body: "<html>Bad Gateway</html>").then.
+              to_return(status: 200, body: response_body, headers: {'Content-Type' => 'application/json'})
+          end
+
+          it "retries and succeeds on second attempt" do
+            expect(do_get.body).to eq({"some" => "json"})
+            expect(request).to have_been_made.times(2)
+          end
+        end
+
+        context "when server returns 503 Service Unavailable" do
+          before do
+            allow(Retry).to receive(:until_true).and_call_original
+            allow($stderr).to receive(:puts)
+          end
+
+          let!(:request) do
+            stub_request(:get, "http://example.org/").
+              to_return(status: 503, body: "<html>Service Unavailable</html>").then.
+              to_return(status: 200, body: response_body, headers: {'Content-Type' => 'application/json'})
+          end
+
+          it "retries and succeeds on second attempt" do
+            expect(do_get.body).to eq({"some" => "json"})
+            expect(request).to have_been_made.times(2)
+          end
+        end
+
+        context "when server returns 504 Gateway Timeout" do
+          before do
+            allow(Retry).to receive(:until_true).and_call_original
+            allow($stderr).to receive(:puts)
+          end
+
+          let!(:request) do
+            stub_request(:get, "http://example.org/").
+              to_return(status: 504, body: "<html>Gateway Timeout</html>").then.
+              to_return(status: 200, body: response_body, headers: {'Content-Type' => 'application/json'})
+          end
+
+          it "retries and succeeds on second attempt" do
+            expect(do_get.body).to eq({"some" => "json"})
+            expect(request).to have_been_made.times(2)
+          end
+        end
+
+        context "when server returns 500 Internal Server Error" do
+          before do
+            allow(Retry).to receive(:until_true).and_call_original
+          end
+
+          let!(:request) do
+            stub_request(:get, "http://example.org/").
+              to_return(status: 500, body: '{"error": "internal server error"}', headers: {'Content-Type' => 'application/json'})
+          end
+
+          it "does not retry on 500 status code" do
+            expect(do_get.body).to eq({"error" => "internal server error"})
+            expect(request).to have_been_made.times(1)
+          end
+        end
+
+        context "when server returns 404 Not Found" do
+          before do
+            allow(Retry).to receive(:until_true).and_call_original
+          end
+
+          let!(:request) do
+            stub_request(:get, "http://example.org/").
+              to_return(status: 404, body: '{"error": "not found"}', headers: {'Content-Type' => 'application/json'})
+          end
+
+          it "does not retry on 4xx status codes" do
+            expect(do_get.body).to eq({"error" => "not found"})
+            expect(request).to have_been_made.times(1)
+          end
+        end
+
+        context "when server returns 502 three times" do
+          before do
+            allow(Retry).to receive(:until_true).and_call_original
+            allow($stderr).to receive(:puts)
+          end
+
+          let!(:request) do
+            stub_request(:get, "http://example.org/").
+              to_return(status: 502, body: "<html>Bad Gateway</html>")
+          end
+
+          it "raises RetriableHttpStatusError after max retries" do
+            expect { do_get }.to raise_error(Pact::Hal::RetriableHttpStatusError, /HTTP 502 error/)
+            expect(request).to have_been_made.times(3)
+          end
+        end
       end
 
       describe "post" do
