FEATURE: Add basic connection check to DNS SRV resources (#563)
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@ -11,7 +11,7 @@ module DiscourseAi
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.fetch("dns_srv_lookup:#{domain}", expires_in: 5.minutes) do
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resources = dns_srv_lookup_for_domain(domain)
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select_server(resources)
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server_election(resources)
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end
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end
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@ -36,9 +36,29 @@ module DiscourseAi
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return resource if random_weight < 0
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end
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end
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# fallback
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resources.first
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def self.server_available?(server)
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begin
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conn = Faraday.new { |f| f.adapter FinalDestination::FaradayAdapter }
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conn.head("https://#{server.target}:#{server.port}")
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true
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rescue StandardError
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false
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end
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end
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def self.server_election(resources)
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return nil if resources.empty?
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return resources.first if resources.length == 1
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candidate = select_server(resources)
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if server_available?(candidate)
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candidate
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else
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server_election(resources - [candidate])
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end
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end
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end
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end
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@ -5,10 +5,10 @@ describe DiscourseAi::Utils::DnsSrv do
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let(:weighted_dns_results) do
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[
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Resolv::DNS::Resource::IN::SRV.new(1, 1, 443, "service1.example.com"),
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Resolv::DNS::Resource::IN::SRV.new(1, 2, 443, "service2.example.com"),
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Resolv::DNS::Resource::IN::SRV.new(1, 2, 443, "service3.example.com"),
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Resolv::DNS::Resource::IN::SRV.new(2, 1, 443, "service4.example.com"),
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Resolv::DNS::Resource::IN::SRV.new(2, 1, 443, "service5.example.com"),
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Resolv::DNS::Resource::IN::SRV.new(2, 2, 443, "service2.example.com"),
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Resolv::DNS::Resource::IN::SRV.new(2, 2, 443, "service3.example.com"),
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Resolv::DNS::Resource::IN::SRV.new(3, 1, 443, "service4.example.com"),
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Resolv::DNS::Resource::IN::SRV.new(3, 1, 443, "service5.example.com"),
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]
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end
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@ -17,6 +17,10 @@ describe DiscourseAi::Utils::DnsSrv do
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Resolv::DNS.any_instance.stubs(:getresources).returns(weighted_dns_results)
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Discourse.cache.delete("dns_srv_lookup:#{domain}")
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(1..5).each do |i|
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stub_request(:head, "https://service#{i}.example.com/").to_return(status: 200)
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end
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end
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it "picks a server" do
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@ -31,4 +35,52 @@ describe DiscourseAi::Utils::DnsSrv do
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expect(weighted_dns_results.filter { |r| r.priority == 1 }).to include(selected_server)
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end
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end
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context "when the first server is not available" do
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before do
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Resolv::DNS.any_instance.stubs(:getresources).returns(weighted_dns_results)
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Discourse.cache.delete("dns_srv_lookup:#{domain}")
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stub_request(:head, "https://service1.example.com/").to_raise(Faraday::SSLError)
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(2..5).each do |i|
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stub_request(:head, "https://service#{i}.example.com/").to_return(status: 200)
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end
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end
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it "picks another server" do
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selected_server = DiscourseAi::Utils::DnsSrv.lookup(domain)
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expect(weighted_dns_results).to include(selected_server)
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expect(selected_server.port).to eq(443)
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expect(selected_server.target.to_s).to_not eq("service1.example.com")
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end
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end
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context "when the multiple servers are not available" do
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before do
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Resolv::DNS.any_instance.stubs(:getresources).returns(weighted_dns_results)
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Discourse.cache.delete("dns_srv_lookup:#{domain}")
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(1..3).each do |i|
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stub_request(:head, "https://service#{i}.example.com/").to_raise(Faraday::SSLError)
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end
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(4..5).each do |i|
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stub_request(:head, "https://service#{i}.example.com/").to_return(status: 200)
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end
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end
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it "picks another server" do
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selected_server = DiscourseAi::Utils::DnsSrv.lookup(domain)
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expect(weighted_dns_results).to include(selected_server)
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expect(selected_server.port).to eq(443)
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expect(selected_server.target.to_s).to_not eq("service1.example.com")
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expect(selected_server.target.to_s).to_not eq("service2.example.com")
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expect(selected_server.target.to_s).to_not eq("service3.example.com")
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end
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end
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end
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