packer/rpc: set keep-alive on all RPC connections [GH-416]

CHANGELOG.md

@@ -14,6 +14,8 @@ IMPROVEMENTS:
 
 BUG FIXES:
 
+* core: Set TCP KeepAlives on internally created RPC connections so that
+  they don't die. [GH-416]
 * builder/amazon/all: While waiting for AMI, will detect "failed" state.
 * builder/amazon/all: Waiting for state will detect if the resource (AMI,
   instance, etc.) disappears from under it.

packer/rpc/build.go

@@ -52,7 +52,7 @@ func (b *build) Run(ui packer.Ui, cache packer.Cache) ([]packer.Artifact, error)
 
 	artifacts := make([]packer.Artifact, len(result))
 	for i, addr := range result {
-		client, err := rpc.Dial("tcp", addr)
+		client, err := rpcDial(addr)
 		if err != nil {
 			return nil, err
 		}
@@ -92,7 +92,7 @@ func (b *BuildServer) Prepare(v map[string]string, reply *error) error {
 }
 
 func (b *BuildServer) Run(args *BuildRunArgs, reply *[]string) error {
-	client, err := rpc.Dial("tcp", args.UiRPCAddress)
+	client, err := rpcDial(args.UiRPCAddress)
 	if err != nil {
 		return err
 	}

packer/rpc/builder.go

@@ -5,7 +5,6 @@ import (
 	"fmt"
 	"github.com/mitchellh/packer/packer"
 	"log"
-	"net"
 	"net/rpc"
 )
 
@@ -95,7 +94,7 @@ func (b *builder) Run(ui packer.Ui, hook packer.Hook, cache packer.Cache) (packe
 		return nil, nil
 	}
 
-	client, err := rpc.Dial("tcp", response.RPCAddress)
+	client, err := rpcDial(response.RPCAddress)
 	if err != nil {
 		return nil, err
 	}
@@ -119,12 +118,12 @@ func (b *BuilderServer) Prepare(args *BuilderPrepareArgs, reply *error) error {
 }
 
 func (b *BuilderServer) Run(args *BuilderRunArgs, reply *interface{}) error {
-	client, err := rpc.Dial("tcp", args.RPCAddress)
+	client, err := rpcDial(args.RPCAddress)
 	if err != nil {
 		return err
 	}
 
-	responseC, err := net.Dial("tcp", args.ResponseAddress)
+	responseC, err := tcpDial(args.ResponseAddress)
 	if err != nil {
 		return err
 	}

packer/rpc/command.go

@@ -66,7 +66,7 @@ func (c *CommandServer) Help(args *interface{}, reply *string) error {
 }
 
 func (c *CommandServer) Run(args *CommandRunArgs, reply *int) error {
-	client, err := rpc.Dial("tcp", args.RPCAddress)
+	client, err := rpcDial(args.RPCAddress)
 	if err != nil {
 		return err
 	}

packer/rpc/communicator.go

@@ -177,7 +177,7 @@ func (c *CommunicatorServer) Start(args *CommunicatorStartArgs, reply *interface
 
 	toClose := make([]net.Conn, 0)
 	if args.StdinAddress != "" {
-		stdinC, err := net.Dial("tcp", args.StdinAddress)
+		stdinC, err := tcpDial(args.StdinAddress)
 		if err != nil {
 			return err
 		}
@@ -187,7 +187,7 @@ func (c *CommunicatorServer) Start(args *CommunicatorStartArgs, reply *interface
 	}
 
 	if args.StdoutAddress != "" {
-		stdoutC, err := net.Dial("tcp", args.StdoutAddress)
+		stdoutC, err := tcpDial(args.StdoutAddress)
 		if err != nil {
 			return err
 		}
@@ -197,7 +197,7 @@ func (c *CommunicatorServer) Start(args *CommunicatorStartArgs, reply *interface
 	}
 
 	if args.StderrAddress != "" {
-		stderrC, err := net.Dial("tcp", args.StderrAddress)
+		stderrC, err := tcpDial(args.StderrAddress)
 		if err != nil {
 			return err
 		}
@@ -208,7 +208,7 @@ func (c *CommunicatorServer) Start(args *CommunicatorStartArgs, reply *interface
 
 	// Connect to the response address so we can write our result to it
 	// when ready.
-	responseC, err := net.Dial("tcp", args.ResponseAddress)
+	responseC, err := tcpDial(args.ResponseAddress)
 	if err != nil {
 		return err
 	}
@@ -234,7 +234,7 @@ func (c *CommunicatorServer) Start(args *CommunicatorStartArgs, reply *interface
 }
 
 func (c *CommunicatorServer) Upload(args *CommunicatorUploadArgs, reply *interface{}) (err error) {
-	readerC, err := net.Dial("tcp", args.ReaderAddress)
+	readerC, err := tcpDial(args.ReaderAddress)
 	if err != nil {
 		return
 	}
@@ -250,7 +250,7 @@ func (c *CommunicatorServer) UploadDir(args *CommunicatorUploadDirArgs, reply *e
 }
 
 func (c *CommunicatorServer) Download(args *CommunicatorDownloadArgs, reply *interface{}) (err error) {
-	writerC, err := net.Dial("tcp", args.WriterAddress)
+	writerC, err := tcpDial(args.WriterAddress)
 	if err != nil {
 		return
 	}

packer/rpc/dial.go

@@ -0,0 +1,33 @@
+package rpc
+
+import (
+	"net"
+	"net/rpc"
+)
+
+// rpcDial makes a TCP connection to a remote RPC server and returns
+// the client. This will set the connection up properly so that keep-alives
+// are set and so on and should be used to make all RPC connections within
+// this package.
+func rpcDial(address string) (*rpc.Client, error) {
+	tcpConn, err := tcpDial(address)
+	if err != nil {
+		return nil, err
+	}
+
+	// Create an RPC client around our connection
+	return rpc.NewClient(tcpConn), nil
+}
+
+// tcpDial connects via TCP to the designated address.
+func tcpDial(address string) (*net.TCPConn, error) {
+	conn, err := net.Dial("tcp", address)
+	if err != nil {
+		return nil, err
+	}
+
+	// Set a keep-alive so that the connection stays alive even when idle
+	tcpConn := conn.(*net.TCPConn)
+	tcpConn.SetKeepAlive(true)
+	return tcpConn, nil
+}

packer/rpc/environment.go

@@ -28,7 +28,7 @@ func (e *Environment) Builder(name string) (b packer.Builder, err error) {
 		return
 	}
 
-	client, err := rpc.Dial("tcp", reply)
+	client, err := rpcDial(reply)
 	if err != nil {
 		return
 	}
@@ -43,7 +43,7 @@ func (e *Environment) Cache() packer.Cache {
 		panic(err)
 	}
 
-	client, err := rpc.Dial("tcp", reply)
+	client, err := rpcDial(reply)
 	if err != nil {
 		panic(err)
 	}
@@ -64,7 +64,7 @@ func (e *Environment) Hook(name string) (h packer.Hook, err error) {
 		return
 	}
 
-	client, err := rpc.Dial("tcp", reply)
+	client, err := rpcDial(reply)
 	if err != nil {
 		return
 	}
@@ -80,7 +80,7 @@ func (e *Environment) PostProcessor(name string) (p packer.PostProcessor, err er
 		return
 	}
 
-	client, err := rpc.Dial("tcp", reply)
+	client, err := rpcDial(reply)
 	if err != nil {
 		return
 	}
@@ -96,7 +96,7 @@ func (e *Environment) Provisioner(name string) (p packer.Provisioner, err error)
 		return
 	}
 
-	client, err := rpc.Dial("tcp", reply)
+	client, err := rpcDial(reply)
 	if err != nil {
 		return
 	}
@@ -109,7 +109,7 @@ func (e *Environment) Ui() packer.Ui {
 	var reply string
 	e.client.Call("Environment.Ui", new(interface{}), &reply)
 
-	client, err := rpc.Dial("tcp", reply)
+	client, err := rpcDial(reply)
 	if err != nil {
 		panic(err)
 	}

packer/rpc/hook.go

@@ -46,7 +46,7 @@ func (h *hook) Cancel() {
 }
 
 func (h *HookServer) Run(args *HookRunArgs, reply *interface{}) error {
-	client, err := rpc.Dial("tcp", args.RPCAddress)
+	client, err := rpcDial(args.RPCAddress)
 	if err != nil {
 		return err
 	}

packer/rpc/post_processor.go

@@ -57,7 +57,7 @@ func (p *postProcessor) PostProcess(ui packer.Ui, a packer.Artifact) (packer.Art
 		return nil, false, nil
 	}
 
-	client, err := rpc.Dial("tcp", response.RPCAddress)
+	client, err := rpcDial(response.RPCAddress)
 	if err != nil {
 		return nil, false, err
 	}
@@ -75,7 +75,7 @@ func (p *PostProcessorServer) Configure(args *PostProcessorConfigureArgs, reply
 }
 
 func (p *PostProcessorServer) PostProcess(address string, reply *PostProcessorProcessResponse) error {
-	client, err := rpc.Dial("tcp", address)
+	client, err := rpcDial(address)
 	if err != nil {
 		return err
 	}

packer/rpc/provisioner.go

@@ -65,7 +65,7 @@ func (p *ProvisionerServer) Prepare(args *ProvisionerPrepareArgs, reply *error)
 }
 
 func (p *ProvisionerServer) Provision(args *ProvisionerProvisionArgs, reply *interface{}) error {
-	client, err := rpc.Dial("tcp", args.RPCAddress)
+	client, err := rpcDial(args.RPCAddress)
 	if err != nil {
 		return err
 	}