Add an example of a simple storage server

examples/.gitignore

@@ -0,0 +1 @@
+storage/storage

examples/Makefile

@@ -0,0 +1,29 @@
+proto_include := $(shell go list -m -f {{.Dir}} github.com/relab/gorums)
+proto_src := $(shell find . -type f -name '*.proto')
+proto_go := $(proto_src:%.proto=%.pb.go)
+gorums_go := $(proto_src:%.proto=%_gorums.pb.go)
+binaries := storage/storage
+
+.PHONY: all debug protos download tools $(binaries)
+
+all: $(binaries)
+
+debug: GCFLAGS += -gcflags='all=-N -l'
+debug: $(binaries)
+
+$(binaries): protos
+	@go build -o ./$@ $(GCFLAGS) ./$(dir $@)
+
+protos: tools download $(proto_go) $(gorums_go)
+
+download:
+	@go mod download
+
+tools: download
+	@cat tools.go | grep _ | awk -F'"' '{print $$2}' | xargs -I % go install %
+
+%.pb.go %_gorums.pb.go : %.proto
+	@protoc -I=$(proto_include):. \
+		--go_out=paths=source_relative:. \
+		--gorums_out=paths=source_relative:. \
+		$<

examples/README.md

@@ -0,0 +1,30 @@
+# Gorums examples
+
+This folder contains examples of services implemented with Gorums.
+If you want a detailed walkthrough of how to get started with Gorums, read the [user guide](../doc/userguide.md).
+
+## Prerequisites
+
+Requires Go 1.13 or later and you must have `$GOPATH/bin` in your `$PATH`.
+See <https://github.com/golang/go/wiki/SettingGOPATH> for more details.
+
+## Interactive Storage service
+
+The `storage` example implements a simple key-value storage service.
+The client features an interactive command line interface that allows you to send RPCs and quorum calls to different configurations of servers, called Nodes.
+Both the client and the server are included in the same binary, and four local servers will be started automatically.
+
+Install:
+
+`go get github.com/relab/gorums/examples/storage`
+
+Run:
+
+`storage`
+
+## (Optional) Compile examples with Make
+
+Run `make` in this folder to compile all examples.
+Requires a recent `protoc` version 3.
+
+If you need to recompile the proto files, you can run `make -B`.

examples/go.mod

@@ -0,0 +1,14 @@
+module github.com/relab/gorums/examples
+
+go 1.14
+
+require (
+	github.com/golang/protobuf v1.4.2
+	github.com/google/shlex v0.0.0-20191202100458-e7afc7fbc510
+	github.com/relab/gorums v0.2.0
+	golang.org/x/crypto v0.0.0-20191011191535-87dc89f01550
+	golang.org/x/net v0.0.0-20200301022130-244492dfa37a
+	golang.org/x/sys v0.0.0-20200223170610-d5e6a3e2c0ae // indirect
+	google.golang.org/grpc v1.30.0
+	google.golang.org/protobuf v1.25.0
+)

examples/go.sum

@@ -0,0 +1,100 @@
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examples/storage/client.go

@@ -0,0 +1,97 @@
+package main
+
+import (
+	"log"
+	"time"
+
+	"github.com/relab/gorums/examples/storage/proto"
+	"google.golang.org/grpc"
+)
+
+func RunClient(addresses []string) {
+	if len(addresses) < 1 {
+		log.Fatalln("No addresses provided!")
+	}
+
+	// init gorums manager
+	mgr, err := proto.NewManager(addresses,
+		proto.WithDialTimeout(1*time.Second),
+		proto.WithGrpcDialOptions(
+			grpc.WithInsecure(), // disable TLS
+			grpc.WithBlock(),    // block until connections are made
+		),
+	)
+	if err != nil {
+		log.Fatalf("Failed to create manager: %v\n", err)
+	}
+
+	nodeIDs := mgr.NodeIDs()
+	// create configuration containing all nodes
+	cfg, err := mgr.NewConfiguration(nodeIDs, &qspec{cfgSize: len(nodeIDs)})
+	if err != nil {
+		log.Fatalf("Failed to create configuration: %v\n", err)
+	}
+
+	Repl(mgr, cfg)
+}
+
+type qspec struct {
+	cfgSize int
+}
+
+// ReadQCQF is the quorum function for the ReadQC
+// ordered quorum call method. The in parameter is the request object
+// supplied to the ReadQC method at call time, and may or may not
+// be used by the quorum function. If the in parameter is not needed
+// you should implement your quorum function with '_ *ReadRequest'.
+func (q qspec) ReadQCQF(_ *proto.ReadRequest, replies []*proto.ReadResponse) (*proto.ReadResponse, bool) {
+	// wait until at least half of the replicas have responded
+	if len(replies) <= q.cfgSize/2 {
+		return nil, false
+	}
+	// return the value with the most recent timestamp
+	return newestValue(replies), true
+}
+
+// WriteQCQF is the quorum function for the WriteQC
+// ordered quorum call method. The in parameter is the request object
+// supplied to the WriteQC method at call time, and may or may not
+// be used by the quorum function. If the in parameter is not needed
+// you should implement your quorum function with '_ *WriteRequest'.
+func (q qspec) WriteQCQF(in *proto.WriteRequest, replies []*proto.WriteResponse) (*proto.WriteResponse, bool) {
+	// wait until at least half of the replicas have responded and have updated their value
+	if numUpdated(replies) <= q.cfgSize/2 {
+		// if all replicas have responded, the write must have failed
+		if len(replies) == q.cfgSize {
+			return &proto.WriteResponse{New: false}, true
+		}
+		return nil, false
+	}
+	// return true
+	return &proto.WriteResponse{New: true}, true
+}
+
+// newestValue returns the reply that had the most recent timestamp
+func newestValue(values []*proto.ReadResponse) *proto.ReadResponse {
+	if len(values) < 1 {
+		return nil
+	}
+	newest := values[0]
+	for _, v := range values[1:] {
+		if v.GetTime().AsTime().After(newest.GetTime().AsTime()) {
+			newest = v
+		}
+	}
+	return newest
+}
+
+// numUpdated returns the number of replicas that updated their value
+func numUpdated(replies []*proto.WriteResponse) int {
+	count := 0
+	for _, r := range replies {
+		if r.GetNew() {
+			count++
+		}
+	}
+	return count
+}

examples/storage/main.go

@@ -0,0 +1,40 @@
+package main
+
+import (
+	"flag"
+	"log"
+	"strings"
+
+	"github.com/relab/gorums/examples/storage/proto"
+)
+
+func main() {
+	server := flag.String("server", "", "Start as a server on given address.")
+	remotes := flag.String("connect", "", "Comma-separated list of servers to connect to.")
+	flag.Parse()
+
+	if *server != "" {
+		RunServer(*server)
+		return
+	}
+
+	addrs := strings.Split(*remotes, ",")
+	// start local servers if no remote servers were specified
+	if len(addrs) == 1 && addrs[0] == "" {
+		addrs = nil
+		srvs := make([]*proto.GorumsServer, 0, 4)
+		for i := 0; i < 4; i++ {
+			srv, addr := StartServer("127.0.0.1:0")
+			srvs = append(srvs, srv)
+			addrs = append(addrs, addr)
+			log.Printf("Started storage server on %s\n", addr)
+		}
+		defer func() {
+			for _, srv := range srvs {
+				srv.Stop()
+			}
+		}()
+	}
+
+	RunClient(addrs)
+}