diff --git a/README.md b/README.md index 4c1433f..e0e6b92 100644 --- a/README.md +++ b/README.md @@ -46,6 +46,7 @@ if err := upg.Ready(); err != nil { ``` Please see the more elaborate [graceful shutdown with net/http](http_example_test.go) example. +For gRPC servers, see the [graceful gRPC server example](examples/grpc-server). ## Integration with `systemd` diff --git a/examples/grpc-server/README.md b/examples/grpc-server/README.md new file mode 100644 index 0000000..e4c20bc --- /dev/null +++ b/examples/grpc-server/README.md @@ -0,0 +1,24 @@ +# Graceful gRPC server upgrades + +This example transfers the listening socket to a new process while the old gRPC server finishes its active RPCs. It registers the standard gRPC health service and server reflection, so no generated service code is required. + +Build and start the server: + +```sh +go build -o tableflip-grpc . +./tableflip-grpc -pid-file ./tableflip-grpc.pid +``` + +With [`grpcurl`](https://github.com/fullstorydev/grpcurl) installed, check the server: + +```sh +grpcurl -plaintext localhost:8080 grpc.health.v1.Health/Check +``` + +Start an upgrade by sending `SIGHUP` to the current process: + +```sh +kill -HUP "$(cat tableflip-grpc.pid)" +``` + +The replacement process inherits the listening socket and calls `Ready` before the old process stops accepting connections. The old gRPC server then calls `GracefulStop`, which lets active RPCs finish. If they do not finish within `-shutdown-timeout`, the server calls `Stop` and terminates them. diff --git a/examples/grpc-server/go.mod b/examples/grpc-server/go.mod new file mode 100644 index 0000000..fd95c06 --- /dev/null +++ b/examples/grpc-server/go.mod @@ -0,0 +1,10 @@ +module github.com/cloudflare/tableflip/examples/grpc-server + +go 1.14 + +require ( + github.com/cloudflare/tableflip v0.0.0 + google.golang.org/grpc v1.45.0 +) + +replace github.com/cloudflare/tableflip => ../.. diff --git a/examples/grpc-server/go.sum b/examples/grpc-server/go.sum new file mode 100644 index 0000000..8f18201 --- /dev/null +++ b/examples/grpc-server/go.sum @@ -0,0 +1,121 @@ +cloud.google.com/go v0.26.0/go.mod h1:aQUYkXzVsufM+DwF1aE+0xfcU+56JwCaLick0ClmMTw= +cloud.google.com/go v0.34.0/go.mod h1:aQUYkXzVsufM+DwF1aE+0xfcU+56JwCaLick0ClmMTw= +github.com/BurntSushi/toml v0.3.1/go.mod h1:xHWCNGjB5oqiDr8zfno3MHue2Ht5sIBksp03qcyfWMU= +github.com/antihax/optional v1.0.0/go.mod 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h1:rf3lG4BRIbNafJWhAfAdb/ePZxsR/4RtNHQocxwk9r4= +honnef.co/go/tools v0.0.0-20190523083050-ea95bdfd59fc/go.mod h1:rf3lG4BRIbNafJWhAfAdb/ePZxsR/4RtNHQocxwk9r4= diff --git a/examples/grpc-server/main.go b/examples/grpc-server/main.go new file mode 100644 index 0000000..fe9971d --- /dev/null +++ b/examples/grpc-server/main.go @@ -0,0 +1,104 @@ +package main + +import ( + "flag" + "fmt" + "log" + "os" + "os/signal" + "syscall" + "time" + + "github.com/cloudflare/tableflip" + "google.golang.org/grpc" + "google.golang.org/grpc/health" + healthpb "google.golang.org/grpc/health/grpc_health_v1" + "google.golang.org/grpc/reflection" +) + +var ( + listenAddr = flag.String("listen", "localhost:8080", "address to listen on") + pidFile = flag.String("pid-file", "", "path to the tableflip PID file") + shutdownTimeout = flag.Duration("shutdown-timeout", 30*time.Second, "maximum time to drain active RPCs") +) + +func main() { + flag.Parse() + log.SetPrefix(fmt.Sprintf("%d ", os.Getpid())) + + upg, err := tableflip.New(tableflip.Options{PIDFile: *pidFile}) + if err != nil { + log.Fatal(err) + } + defer upg.Stop() + + go upgradeOnSignal(upg) + + ln, err := upg.Listen("tcp", *listenAddr) + if err != nil { + log.Fatal(err) + } + + server := grpc.NewServer() + healthServer := health.NewServer() + healthServer.SetServingStatus("", healthpb.HealthCheckResponse_SERVING) + healthpb.RegisterHealthServer(server, healthServer) + reflection.Register(server) + + serveErr := make(chan error, 1) + go func() { + serveErr <- server.Serve(ln) + }() + + if err := upg.Ready(); err != nil { + log.Fatal(err) + } + log.Printf("serving gRPC on %s", *listenAddr) + + select { + case <-upg.Exit(): + healthServer.SetServingStatus("", healthpb.HealthCheckResponse_NOT_SERVING) + if !gracefulStop(server, *shutdownTimeout) { + log.Printf("graceful shutdown timed out after %s; stopped active RPCs", *shutdownTimeout) + } + case err := <-serveErr: + if err != nil { + log.Fatal(err) + } + } +} + +func upgradeOnSignal(upg *tableflip.Upgrader) { + signals := make(chan os.Signal, 1) + signal.Notify(signals, syscall.SIGHUP) + for range signals { + if err := upg.Upgrade(); err != nil { + log.Printf("upgrade failed: %v", err) + } + } +} + +type gracefulServer interface { + GracefulStop() + Stop() +} + +// gracefulStop waits for active RPCs and force-stops them after the deadline. +func gracefulStop(server gracefulServer, timeout time.Duration) bool { + done := make(chan struct{}) + go func() { + server.GracefulStop() + close(done) + }() + + timer := time.NewTimer(timeout) + defer timer.Stop() + + select { + case <-done: + return true + case <-timer.C: + server.Stop() + return false + } +} diff --git a/examples/grpc-server/main_test.go b/examples/grpc-server/main_test.go new file mode 100644 index 0000000..86913bf --- /dev/null +++ b/examples/grpc-server/main_test.go @@ -0,0 +1,60 @@ +package main + +import ( + "sync" + "testing" + "time" +) + +type testServer struct { + releaseGraceful chan struct{} + stopCalled chan struct{} + stopOnce sync.Once +} + +func newTestServer() *testServer { + return &testServer{ + releaseGraceful: make(chan struct{}), + stopCalled: make(chan struct{}), + } +} + +func (server *testServer) GracefulStop() { + <-server.releaseGraceful +} + +func (server *testServer) Stop() { + server.stopOnce.Do(func() { + close(server.stopCalled) + close(server.releaseGraceful) + }) +} + +func TestGracefulStopCompletesBeforeDeadline(t *testing.T) { + server := newTestServer() + close(server.releaseGraceful) + + if !gracefulStop(server, time.Second) { + t.Fatal("expected graceful shutdown") + } + + select { + case <-server.stopCalled: + t.Fatal("Stop called after GracefulStop completed") + default: + } +} + +func TestGracefulStopForcesShutdownAtDeadline(t *testing.T) { + server := newTestServer() + + if gracefulStop(server, time.Millisecond) { + t.Fatal("expected forced shutdown") + } + + select { + case <-server.stopCalled: + default: + t.Fatal("Stop was not called") + } +}