repo: Initial commit

Dockerfile

@@ -0,0 +1,18 @@
+FROM golang:alpine as builder
+
+ENV GO111MODULE on
+RUN apk update && apk add git && apk add ca-certificates
+RUN adduser -D -g '' unprivileged
+COPY . $GOPATH/src/github.com/joa/jawlb/
+WORKDIR $GOPATH/src/github.com/joa/jawlb/
+RUN go get -d -v
+RUN go generate main.go
+RUN CGO_ENABLED=0 GOOS=linux GOARCH=amd64 go build -a -installsuffix cgo -ldflags="-w -s" -o /go/bin/app
+
+FROM scratch
+COPY --from=builder /etc/ssl/certs/ca-certificates.crt /etc/ssl/certs/
+COPY --from=builder /etc/passwd /etc/passwd
+COPY --from=builder /go/bin/app /go/bin/app
+USER unprivileged
+EXPOSE 8000
+ENTRYPOINT ["/go/bin/app"]

README.md

@@ -0,0 +1,120 @@
+### Jawlb
+Jawlb (pronounced jolp) is an unsophisticated grpclb implementation for things running in Kubernetes talking to gRPC 
+services within that same Kubernetes cluster.
+
+This load balancer performs  service discovery via the Kubernetes API and announces any changes it sees
+via the grpclb protocol to its clients.
+
+### Building
+You'll want to push the result of `docker build -f Dockerfile .` into your registry.
+
+### grpclb
+The grpclb Go implementation (others maybe too) requires you to define a SRV record for the loadbalancer. 
+The easy solution is to define a Kubernetes service with a port named `grpclb` and you're all set.
+
+### Example
+The example shows a load balancer setup that'll forward requests to `myservice:grpc`. 
+We assume that RBAC isn't required.
+
+#### Load Balancer Deployment
+```yaml
+apiVersion: apps/v1
+kind: Deployment
+metadata:
+  name: myservice-lb
+spec:
+  selector:
+    matchLabels:
+      app: jawlb
+      service: myservice
+  replicas: 1
+  template:
+    metadata:
+      labels:
+        app: jawlb
+        service: myservice
+    spec:
+      restartPolicy: Always
+      containers:
+      - image: "your.regist.ry/jawlb:yolo"
+        name: jawlb
+        ports:
+        - containerPort: 8000
+          name: grpclb
+        env:
+        # The name of the upstream service we want
+        # to balance
+        - name: JAWLB_SERVICE
+          value: "myservice"
+        # The name of the port exposed by this service
+        # which we want to forward to
+        - name: JAWLB_TARGETPORT
+          value: "grpc"
+        # The namespace in which jawlb performs the lookup
+        # and we use the current one simply
+        - name: JAWLB_NAMESPACE
+          valueFrom:
+            fieldRef:
+              fieldPath: metadata.namespace
+```
+
+#### Load Balancer Service
+```yaml
+apiVersion: v1
+kind: Service
+metadata:
+  name: myservice-lb
+  labels:
+    app: jawlb
+    service: myservice
+spec:
+  # Make this a headless service because we'll have to use
+  # the dns:// resolver in the Go client
+  clusterIP: None
+  ports:
+  # The port MUST be named grpclb in order to create
+  # the proper DNS SRV entry
+  - name: grpclb
+    port: 8000
+    targetPort: grpclb
+  selector:
+    app: jawlb
+    service: myservice
+```
+
+#### gRPC Client
+```go
+import 	_ "google.golang.org/grpc/balancer/grpclb"
+
+// When dialing, gRPC's DNS resolver will issue a SRV lookup and
+// because we're so nice to provide the grpclb entry, everything
+// works as expected
+
+conn, err := grpc.Dial(
+	"dns:///myservice-lb:8000",        // must use the dns resolver and port exposed at the balancer
+    grpc.WithBalancerName("grpclb"),   // select the grpclb balancer strat
+	grpc.WithInsecure())
+
+// ... magic 🧙‍♀️
+```
+
+### Configuration
+Everything is passed via environment variables.
+
+- `JAWLB_NAMESPACE` in which namespace service lookup is performed, default `"default"`
+- `JAWLB_SERVICE` the name of the Kubernetes service to balance, required
+- `JAWLB_TARGETPORT` the name(!) of the target port on that service, default `"grpc"`
+- `JAWLB_LABELSELECTOR` an additional label selector, default `""`
+- `JAWLB_HOST` the hostname to listen on, default`""`
+- `JAWLB_PORT` port to listen on, default `8000`
+- `JAWLB_SHUTDOWNGRACEPERIOD` Grace period for open connections during shutdown, default `"25s"`
+
+### What's missing
+- Potentially some actual load balancing
+- Implementation of [LoadReporter](https://github.com/grpc/grpc/blob/master/src/proto/grpc/lb/v1/load_reporter.proto) service
+- Readiness Probe 
+- Health Check
+
+### Resources
+- [grpclb spec](https://github.com/grpc/grpc/tree/master/src/proto/grpc/lb/v1)
+- [Load Balancing in gRPC](https://github.com/grpc/grpc/blob/master/doc/load-balancing.md)

broadcast.go

@@ -0,0 +1,63 @@
+package main
+
+import (
+	"context"
+)
+
+type Listener chan<- ServerList
+
+type broadcast struct {
+	ctx   context.Context
+	src   <-chan ServerList
+	state ServerList
+	tgts  map[Listener]bool
+	add   chan Listener
+	rem   chan Listener
+}
+
+func newBroadcast(ctx context.Context, src <-chan ServerList) *broadcast {
+	b := &broadcast{
+		ctx:  ctx,
+		src:  src,
+		tgts: make(map[Listener]bool),
+		add:  make(chan Listener),
+		rem:  make(chan Listener),
+	}
+
+	go b.run()
+
+	return b
+}
+
+func (b *broadcast) addListener(listener Listener) {
+	b.add <- listener
+
+	// send initial state if present once on registration
+	if len(b.state) > 0 {
+		go func() { listener <- b.state }()
+	}
+}
+
+func (b *broadcast) remListener(listener Listener) {
+	b.rem <- listener
+}
+
+func (b *broadcast) run() {
+	for {
+		select {
+		case <-b.ctx.Done():
+			close(b.add)
+			close(b.rem)
+			return
+		case l := <-b.add:
+			b.tgts[l] = true
+		case l := <-b.rem:
+			delete(b.tgts, l)
+		case state := <-b.src:
+			b.state = state
+			for tgt := range b.tgts {
+				go func() { tgt <- state }()
+			}
+		}
+	}
+}

go.mod

@@ -0,0 +1,26 @@
+module github.com/joa/jawlb
+
+require (
+	github.com/gogo/protobuf v1.1.1 // indirect
+	github.com/google/btree v0.0.0-20180813153112-4030bb1f1f0c // indirect
+	github.com/google/gofuzz v0.0.0-20170612174753-24818f796faf // indirect
+	github.com/googleapis/gnostic v0.2.0 // indirect
+	github.com/gregjones/httpcache v0.0.0-20181110185634-c63ab54fda8f // indirect
+	github.com/imdario/mergo v0.3.6 // indirect
+	github.com/json-iterator/go v1.1.5 // indirect
+	github.com/kelseyhightower/envconfig v1.3.0
+	github.com/modern-go/concurrent v0.0.0-20180306012644-bacd9c7ef1dd // indirect
+	github.com/modern-go/reflect2 v1.0.1 // indirect
+	github.com/peterbourgon/diskv v2.0.1+incompatible // indirect
+	github.com/spf13/pflag v1.0.3 // indirect
+	golang.org/x/crypto v0.0.0-20181127143415-eb0de9b17e85 // indirect
+	golang.org/x/time v0.0.0-20181108054448-85acf8d2951c // indirect
+	google.golang.org/grpc v1.16.0
+	gopkg.in/inf.v0 v0.9.1 // indirect
+	gopkg.in/yaml.v2 v2.2.1 // indirect
+	k8s.io/api v0.0.0-20181121071145-b7bd5f2d334c
+	k8s.io/apimachinery v0.0.0-20181126191516-4a9a8137c0a1
+	k8s.io/client-go v9.0.0+incompatible
+	k8s.io/klog v0.1.0 // indirect
+	sigs.k8s.io/yaml v1.1.0 // indirect
+)

go.sum

@@ -0,0 +1,69 @@
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lb.go

@@ -0,0 +1,60 @@
+package main
+
+import (
+	grpclb "google.golang.org/grpc/balancer/grpclb/grpc_lb_v1"
+	"google.golang.org/grpc/codes"
+	"google.golang.org/grpc/status"
+)
+
+type lb struct {
+	b *broadcast
+}
+
+func (l *lb) BalanceLoad(req grpclb.LoadBalancer_BalanceLoadServer) error {
+	if in, err := req.Recv(); err != nil {
+		return err
+	} else if init := in.GetInitialRequest(); init != nil {
+		err := req.Send(&grpclb.LoadBalanceResponse{
+			LoadBalanceResponseType: &grpclb.LoadBalanceResponse_InitialResponse{
+				InitialResponse: &grpclb.InitialLoadBalanceResponse{},
+			},
+		})
+
+		if err != nil {
+			return err
+		}
+	} else {
+		return status.Error(codes.InvalidArgument, "expected initial request")
+	}
+
+	ch := make(chan ServerList)
+	defer close(ch)
+
+	l.b.addListener(ch)
+	defer l.b.remListener(ch)
+
+	for {
+		select {
+		case <-req.Context().Done():
+			return nil
+		case msg := <-ch:
+			var servers []*grpclb.Server
+
+			for _, server := range msg {
+				servers = append(servers, &grpclb.Server{IpAddress: server.IP, Port: server.Port})
+			}
+
+			err := req.Send(&grpclb.LoadBalanceResponse{
+				LoadBalanceResponseType: &grpclb.LoadBalanceResponse_ServerList{
+					ServerList: &grpclb.ServerList{
+						Servers: servers,
+					},
+				},
+			})
+
+			if err != nil {
+				return err
+			}
+		}
+	}
+}