From 3ebb46320a4b47af1405bd413dee9c8937dfd88c Mon Sep 17 00:00:00 2001 From: Ricardo Katz Date: Wed, 15 Jul 2020 14:59:45 -0300 Subject: [PATCH] Improve gRPC Plugin when backend is not available (#3966) * Improve gRPC Plugin when backend is not available Signed-off-by: Ricardo Pchevuzinske Katz * Improve gRPC Plugin when backend is not available Signed-off-by: Ricardo Pchevuzinske Katz --- plugin/grpc/grpc.go | 22 +++++++++++++++++----- 1 file changed, 17 insertions(+), 5 deletions(-) diff --git a/plugin/grpc/grpc.go b/plugin/grpc/grpc.go index 3dda225df..2ecf29597 100644 --- a/plugin/grpc/grpc.go +++ b/plugin/grpc/grpc.go @@ -3,6 +3,7 @@ package grpc import ( "context" "crypto/tls" + "errors" "time" "github.com/coredns/coredns/plugin" @@ -36,10 +37,10 @@ func (g *GRPC) ServeDNS(ctx context.Context, w dns.ResponseWriter, r *dns.Msg) ( } var ( - span, child ot.Span - ret *dns.Msg - err error - i int + span, child ot.Span + ret *dns.Msg + upstreamErr, err error + i int ) span = ot.SpanFromContext(ctx) list := g.list() @@ -73,6 +74,8 @@ func (g *GRPC) ServeDNS(ctx context.Context, w dns.ResponseWriter, r *dns.Msg) ( child.Finish() } + upstreamErr = err + // Check if the reply is correct; if not return FormErr. if !state.Match(ret) { debug.Hexdumpf(ret, "Wrong reply for id: %d, %s %d", ret.Id, state.QName(), state.QType()) @@ -87,7 +90,11 @@ func (g *GRPC) ServeDNS(ctx context.Context, w dns.ResponseWriter, r *dns.Msg) ( return 0, nil } - return 0, nil + if upstreamErr != nil { + return dns.RcodeServerFailure, upstreamErr + } + + return dns.RcodeServerFailure, ErrNoHealthy } // NewGRPC returns a new GRPC. @@ -129,3 +136,8 @@ func (g *GRPC) isAllowedDomain(name string) bool { func (g *GRPC) list() []*Proxy { return g.p.List(g.proxies) } const defaultTimeout = 5 * time.Second + +var ( + // ErrNoHealthy means no healthy proxies left. + ErrNoHealthy = errors.New("no healthy gRPC proxies") +)