Merge pull request #7 from athos/feature/retry-connection

Retry on connection

README.md

@@ -23,6 +23,7 @@ Unlike ordinary Clojure REPLs, it starts up instantly as it just connects to a r
 - [Usage](#usage)
   - [Connecting to a server](#connecting-to-a-server)
     - [Port file](#port-file)
+    - [Retry on connection](#retry-on-connection)
   - [Evaluation](#evaluation)
     - [Evaluating an expression (`-e`)](#evaluating-an-expression--e)
     - [Evaluating a file (`-f`)](#evaluating-a-file--f)
@@ -62,19 +63,21 @@ Trenchman does not have `readline` support at this time. If you want to use feat
 usage: trench [<flags>] [<args>...]
 
 Flags:
-      --help               Show context-sensitive help (also try --help-long and --help-man).
-  -p, --port=PORT          Connect to the specified port.
-      --port-file=FILE     Specify port file that specifies port to connect to. Defaults to .nrepl-port.
-  -P, --protocol=nrepl     Use the specified protocol. Possible values: n[repl], p[repl]. Defaults to nrepl.
+      --help                    Show context-sensitive help (also try --help-long and --help-man).
+  -p, --port=PORT               Connect to the specified port.
+      --port-file=FILE          Specify port file that specifies port to connect to. Defaults to .nrepl-port.
+  -P, --protocol=nrepl          Use the specified protocol. Possible values: n[repl], p[repl]. Defaults to nrepl.
   -s, --server=[(nrepl|prepl)://]host[:port]
-                           Connect to the specified URL (e.g. prepl://127.0.0.1:5555).
-  -i, --init=FILE          Load a file before execution.
-  -e, --eval=EXPR          Evaluate an expression.
-  -f, --file=FILE          Evaluate a file.
-  -m, --main=NAMESPACE     Call the -main function for a namespace.
-      --init-ns=NAMESPACE  Initialize REPL with the specified namespace. Defaults to "user".
-  -C, --color=auto         When to use colors. Possible values: always, auto, none. Defaults to auto.
-      --version            Show application version.
+                                Connect to the specified URL (e.g. prepl://127.0.0.1:5555).
+      --retry-timeout=DURATION  Timeout after which retries are aborted. By default, Trenchman never retries connection.
+      --retry-interval=1s       Interval between retries when connecting to the server.
+  -i, --init=FILE               Load a file before execution.
+  -e, --eval=EXPR               Evaluate an expression.
+  -f, --file=FILE               Evaluate a file.
+  -m, --main=NAMESPACE          Call the -main function for a namespace.
+      --init-ns=NAMESPACE       Initialize REPL with the specified namespace. Defaults to "user".
+  -C, --color=auto              When to use colors. Possible values: always, auto, none. Defaults to auto.
+      --version                 Show application version.
 
 Args:
   [<args>]  Arguments to pass to -main. These will be ignored unless -m is specified.
@@ -138,6 +141,23 @@ $ cat my-port-file
 $ trench --port-file my-port-file
 ```
 
+#### Retry on connection
+
+When connecting to a server that is starting up, it's useful to be able to automatically retry the connection if it fails.
+
+The `--retry-timeout` and `--retry-interval` options control connection retries.
+`--retry-timeout DURATION` specifies the amount of time before connection retries are aborted and `--retry-interval DURATION` specifies the time interval between each retry (`DURATION` can be specified in the format accepted by [Go's duration parser](https://pkg.go.dev/time#ParseDuration), like `500ms`, `10s` or `1m`).
+
+For example, the following command will retry the connection every 5 seconds for up to 30 seconds:
+
+```sh
+$ trench --retry-timeout 30s --retry-interval 5s
+```
+
+If the connection fails after retrying the connection until the timeout, Trenchman will print the error and exit.
+
+If `--retry-timeout` is not specified, Trenchman will not retry the connection.
+
 ### Evaluation
 
 By default, Trenchman starts a new REPL session after the connection is established:

client/client.go

@@ -9,7 +9,7 @@ type (
 	Request  interface{}
 	Response interface{}
 
-	Conn interface {
+	Transport interface {
 		io.Closer
 		Send(req Request) error
 		Recv() (Response, error)
@@ -60,9 +60,9 @@ func (e *RuntimeError) Error() string {
 	return e.err
 }
 
-func StartLoop(conn Conn, handler Handler, done chan struct{}) {
+func StartLoop(transport Transport, handler Handler, done chan struct{}) {
 	for {
-		resp, err := conn.Recv()
+		resp, err := transport.Recv()
 		if err != nil {
 			select {
 			case <-done:

client/conn_builder.go

@@ -0,0 +1,48 @@
+package client
+
+import (
+	"fmt"
+	"net"
+	"time"
+)
+
+type ConnBuilder interface {
+	Connect() (net.Conn, error)
+}
+
+type TCPConnBuilder struct {
+	Host string
+	Port int
+}
+
+func (conn *TCPConnBuilder) Connect() (net.Conn, error) {
+	return net.Dial("tcp", fmt.Sprintf("%s:%d", conn.Host, conn.Port))
+}
+
+type ConnBuilderFunc func() (net.Conn, error)
+
+func (f ConnBuilderFunc) Connect() (net.Conn, error) {
+	return f()
+}
+
+func NewRetryConnBuilder(connBuilder ConnBuilder, timeout time.Duration, interval time.Duration) ConnBuilder {
+	if interval > timeout {
+		interval = timeout
+	}
+	return ConnBuilderFunc(func() (conn net.Conn, err error) {
+		end := time.Now().Add(timeout)
+		for {
+			conn, err = connBuilder.Connect()
+			if err == nil {
+				return conn, nil
+			}
+			if time.Now().After(end) {
+				return
+			}
+			time.Sleep(interval)
+			if time.Now().After(end) {
+				return
+			}
+		}
+	})
+}

cmd/trench/helper.go

@@ -42,11 +42,10 @@ func readPortFromFile(protocol, portFile string) (int, bool, error) {
 	return port, false, nil
 }
 
-func (h setupHelper) nReplFactory(host string, port int, initNS string) func(client.OutputHandler) client.Client {
+func (h setupHelper) nReplFactory(connBuilder client.ConnBuilder, initNS string) func(client.OutputHandler) client.Client {
 	return func(outHandler client.OutputHandler) client.Client {
 		c, err := nrepl.NewClient(&nrepl.Opts{
-			Host:          host,
-			Port:          port,
+			ConnBuilder:   connBuilder,
 			InitNS:        initNS,
 			OutputHandler: outHandler,
 			ErrorHandler:  h.errHandler,
@@ -58,11 +57,10 @@ func (h setupHelper) nReplFactory(host string, port int, initNS string) func(cli
 	}
 }
 
-func (h setupHelper) pReplFactory(host string, port int, initNS string) func(client.OutputHandler) client.Client {
+func (h setupHelper) pReplFactory(connBuilder client.ConnBuilder, initNS string) func(client.OutputHandler) client.Client {
 	return func(outHandler client.OutputHandler) client.Client {
 		c, err := prepl.NewClient(&prepl.Opts{
-			Host:          host,
-			Port:          port,
+			ConnBuilder:   connBuilder,
 			InitNS:        initNS,
 			OutputHandler: outHandler,
 			ErrorHandler:  h.errHandler,
@@ -74,22 +72,24 @@ func (h setupHelper) pReplFactory(host string, port int, initNS string) func(cli
 	}
 }
 
-func (h setupHelper) setupRepl(protocol string, host string, port int, initNS string, opts *repl.Opts) *repl.Repl {
+func (h setupHelper) setupRepl(protocol string, connBuilder client.ConnBuilder, initNS string, opts *repl.Opts) *repl.Repl {
 	opts.In = os.Stdin
 	opts.Out = os.Stdout
 	opts.Err = os.Stderr
 	opts.ErrHandler = h.errHandler
 	var factory func(client.OutputHandler) client.Client
 	if protocol == "nrepl" {
-		factory = h.nReplFactory(host, port, initNS)
+		factory = h.nReplFactory(connBuilder, initNS)
 	} else {
-		factory = h.pReplFactory(host, port, initNS)
+		factory = h.pReplFactory(connBuilder, initNS)
 	}
 	return repl.NewRepl(opts, factory)
 }
 
-func (h setupHelper) arbitrateServerInfo(args *cmdArgs) (protocol string, host string, port int) {
+func (h setupHelper) resolveConnection(args *cmdArgs) (protocol string, connBuilder client.ConnBuilder) {
 	server := *args.server
+	var host string
+	var port int
 	if server != "" {
 		match := urlRegex.FindStringSubmatch(server)
 		if match == nil {
@@ -127,5 +127,9 @@ func (h setupHelper) arbitrateServerInfo(args *cmdArgs) (protocol string, host s
 		}
 		port = p
 	}
+	connBuilder = &client.TCPConnBuilder{Host: host, Port: port}
+	if *args.retryTimeout > 0 {
+		connBuilder = client.NewRetryConnBuilder(connBuilder, *args.retryTimeout, *args.retryInterval)
+	}
 	return
 }

cmd/trench/main.go

@@ -4,6 +4,7 @@ import (
 	"fmt"
 	"os"
 	"strings"
+	"time"
 
 	"github.com/athos/trenchman/client"
 	"github.com/athos/trenchman/repl"
@@ -21,17 +22,19 @@ const (
 )
 
 type cmdArgs struct {
-	port        *int
-	portfile    *string
-	protocol    *string
-	server      *string
-	init        *string
-	eval        *string
-	file        *string
-	mainNS      *string
-	initNS      *string
-	colorOption *string
-	args        *[]string
+	port          *int
+	portfile      *string
+	protocol      *string
+	server        *string
+	retryTimeout  *time.Duration
+	retryInterval *time.Duration
+	init          *string
+	eval          *string
+	file          *string
+	mainNS        *string
+	initNS        *string
+	colorOption   *string
+	args          *[]string
 }
 
 type errorHandler struct {
@@ -51,17 +54,19 @@ func (h errorHandler) HandleErr(err error) {
 }
 
 var args = cmdArgs{
-	port:        kingpin.Flag("port", "Connect to the specified port.").Short('p').Int(),
-	portfile:    kingpin.Flag("port-file", "Specify port file that specifies port to connect to. Defaults to .nrepl-port.").PlaceHolder("FILE").String(),
-	protocol:    kingpin.Flag("protocol", "Use the specified protocol. Possible values: n[repl], p[repl]. Defaults to nrepl.").Default("nrepl").Short('P').Enum("n", "nrepl", "p", "prepl"),
-	server:      kingpin.Flag("server", "Connect to the specified URL (e.g. prepl://127.0.0.1:5555).").Default("127.0.0.1").Short('s').PlaceHolder("[(nrepl|prepl)://]host[:port]").String(),
-	init:        kingpin.Flag("init", "Load a file before execution.").Short('i').PlaceHolder("FILE").String(),
-	eval:        kingpin.Flag("eval", "Evaluate an expression.").Short('e').PlaceHolder("EXPR").String(),
-	file:        kingpin.Flag("file", "Evaluate a file.").Short('f').String(),
-	mainNS:      kingpin.Flag("main", "Call the -main function for a namespace.").Short('m').PlaceHolder("NAMESPACE").String(),
-	initNS:      kingpin.Flag("init-ns", "Initialize REPL with the specified namespace. Defaults to \"user\".").PlaceHolder("NAMESPACE").String(),
-	colorOption: kingpin.Flag("color", "When to use colors. Possible values: always, auto, none. Defaults to auto.").Default(COLOR_AUTO).Short('C').Enum(COLOR_NONE, COLOR_AUTO, COLOR_ALWAYS),
-	args:        kingpin.Arg("args", "Arguments to pass to -main. These will be ignored unless -m is specified.").Strings(),
+	port:          kingpin.Flag("port", "Connect to the specified port.").Short('p').Int(),
+	portfile:      kingpin.Flag("port-file", "Specify port file that specifies port to connect to. Defaults to .nrepl-port.").PlaceHolder("FILE").String(),
+	protocol:      kingpin.Flag("protocol", "Use the specified protocol. Possible values: n[repl], p[repl]. Defaults to nrepl.").Default("nrepl").Short('P').Enum("n", "nrepl", "p", "prepl"),
+	server:        kingpin.Flag("server", "Connect to the specified URL (e.g. prepl://127.0.0.1:5555).").Default("127.0.0.1").Short('s').PlaceHolder("[(nrepl|prepl)://]host[:port]").String(),
+	retryTimeout:  kingpin.Flag("retry-timeout", "Timeout after which retries are aborted. By default, Trenchman never retries connection.").PlaceHolder("DURATION").Duration(),
+	retryInterval: kingpin.Flag("retry-interval", "Interval between retries when connecting to the server.").Default("1s").Duration(),
+	init:          kingpin.Flag("init", "Load a file before execution.").Short('i').PlaceHolder("FILE").String(),
+	eval:          kingpin.Flag("eval", "Evaluate an expression.").Short('e').PlaceHolder("EXPR").String(),
+	file:          kingpin.Flag("file", "Evaluate a file.").Short('f').String(),
+	mainNS:        kingpin.Flag("main", "Call the -main function for a namespace.").Short('m').PlaceHolder("NAMESPACE").String(),
+	initNS:        kingpin.Flag("init-ns", "Initialize REPL with the specified namespace. Defaults to \"user\".").PlaceHolder("NAMESPACE").String(),
+	colorOption:   kingpin.Flag("color", "When to use colors. Possible values: always, auto, none. Defaults to auto.").Default(COLOR_AUTO).Short('C').Enum(COLOR_NONE, COLOR_AUTO, COLOR_ALWAYS),
+	args:          kingpin.Arg("args", "Arguments to pass to -main. These will be ignored unless -m is specified.").Strings(),
 }
 
 func colorized(colorOption string) bool {
@@ -95,7 +100,7 @@ func main() {
 	printer := repl.NewPrinter(colorized(*args.colorOption))
 	errHandler := errorHandler{printer}
 	helper := setupHelper{errHandler}
-	protocol, host, port := helper.arbitrateServerInfo(&args)
+	protocol, connBuilder := helper.resolveConnection(&args)
 	initFile := strings.TrimSpace(*args.init)
 	filename := strings.TrimSpace(*args.file)
 	initNS := strings.TrimSpace(*args.initNS)
@@ -105,7 +110,7 @@ func main() {
 		Printer:  printer,
 		HidesNil: filename != "" || mainNS != "" || code != "",
 	}
-	repl := helper.setupRepl(protocol, host, port, initNS, opts)
+	repl := helper.setupRepl(protocol, connBuilder, initNS, opts)
 	defer repl.Close()
 
 	if initFile != "" {

nrepl/client.go

@@ -2,7 +2,6 @@ package nrepl
 
 import (
 	"fmt"
-	"net"
 	"path/filepath"
 	"strings"
 	"sync"
@@ -28,13 +27,11 @@ type (
 	}
 
 	Opts struct {
-		Host          string
-		Port          int
 		InitNS        string
 		Oneshot       bool
 		OutputHandler client.OutputHandler
 		ErrorHandler  client.ErrorHandler
-		connBuilder   func(host string, port int) (net.Conn, error)
+		ConnBuilder   client.ConnBuilder
 		idGenerator   func() string
 	}
 )
@@ -52,7 +49,7 @@ func NewClient(opts *Opts) (*Client, error) {
 		pending:       map[string]chan client.EvalResult{},
 		idGenerator:   opts.idGenerator,
 	}
-	conn, err := Connect(&ConnOpts{opts.Host, opts.Port, opts.connBuilder})
+	conn, err := Connect(&ConnOpts{opts.ConnBuilder})
 	if err != nil {
 		return nil, err
 	}

nrepl/nrepl.go

@@ -24,9 +24,7 @@ type (
 	}
 
 	ConnOpts struct {
-		Host        string
-		Port        int
-		connBuilder func(host string, port int) (net.Conn, error)
+		ConnBuilder client.ConnBuilder
 	}
 
 	SessionInfo struct {
@@ -36,13 +34,8 @@ type (
 )
 
 func Connect(opts *ConnOpts) (conn *Conn, err error) {
-	connBuilder := opts.connBuilder
-	if connBuilder == nil {
-		connBuilder = func(host string, port int) (net.Conn, error) {
-			return net.Dial("tcp", fmt.Sprintf("%s:%d", host, port))
-		}
-	}
-	socket, err := connBuilder(opts.Host, opts.Port)
+	connBuilder := opts.ConnBuilder
+	socket, err := connBuilder.Connect()
 	if err != nil {
 		return
 	}

nrepl/nrepl_test.go

@@ -79,9 +79,9 @@ func setupClient(mock *client.MockServer) (*Client, error) {
 	return NewClient(&Opts{
 		OutputHandler: mock,
 		ErrorHandler:  mock,
-		connBuilder: func(_ string, _ int) (net.Conn, error) {
+		ConnBuilder: client.ConnBuilderFunc(func() (net.Conn, error) {
 			return mock, nil
-		},
+		}),
 		idGenerator: func() string { return EXEC_ID },
 	})
 }

prepl/prepl.go

@@ -34,23 +34,16 @@ type (
 	}
 
 	Opts struct {
-		Host          string
-		Port          int
 		InitNS        string
 		OutputHandler client.OutputHandler
 		ErrorHandler  client.ErrorHandler
-		connBuilder   func(host string, port int) (net.Conn, error)
+		ConnBuilder   client.ConnBuilder
 	}
 )
 
 func NewClient(opts *Opts) (*Client, error) {
-	connBuilder := opts.connBuilder
-	if connBuilder == nil {
-		connBuilder = func(host string, port int) (net.Conn, error) {
-			return net.Dial("tcp", fmt.Sprintf("%s:%d", host, port))
-		}
-	}
-	socket, err := connBuilder(opts.Host, opts.Port)
+	connBuilder := opts.ConnBuilder
+	socket, err := connBuilder.Connect()
 	if err != nil {
 		return nil, err
 	}