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client.go
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client.go
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package rtreq
import (
"fmt"
"math/rand"
"time"
pb "github.com/anancds/rtreq/msg"
"github.com/bbengfort/x/stats"
"github.com/gogo/protobuf/proto"
zmq "github.com/pebbe/zmq4"
)
// NewClient creates a new rtreq.Client. If context is nil, it also creates
// a context that will be managed by the sever.
func NewClient(addr, name string, context *zmq.Context) (c *Client, err error) {
if context == nil {
if context, err = zmq.NewContext(); err != nil {
return nil, WrapError("could not create zmq context", err)
}
}
c = new(Client)
c.Init(addr, name, context)
return c, nil
}
//===========================================================================
// Client Transporter
//===========================================================================
// Client communicates a server.
type Client struct {
Transporter
messages uint64 // number of messages sent to measure throughput
latency time.Duration // total time to send messages for throughput
stats *stats.Statistics // distribution of message latency
identity string // the identity being sent to the server
}
// Connect to the remote peer
func (c *Client) Connect() (err error) {
// Create the socket
if c.sock, err = c.context.NewSocket(zmq.REQ); err != nil {
return err
}
// Create an identity for the client
// NOTE: the identity must be unique - do not rely on randomness since
// parallel instantiation may result in the same seed!
c.identity = fmt.Sprintf("%s-%04X", c.name, rand.Intn(0x10000))
c.sock.SetIdentity(c.identity)
// Connect to the server
ep := c.addr
if err = c.sock.Connect(ep); err != nil {
return err
}
info("connected to %s\n", ep)
return nil
}
// Reset the socket by setting the linger to 0, closing it, then reconnecting.
func (c *Client) Reset() error {
// Close the socket
if err := c.Close(); err != nil {
return err
}
// And reconnect
return c.Connect()
}
//===========================================================================
// Transport Methods
//===========================================================================
// Send a message to the remote peer in a safe fashion, specifying the # of
// retries and the timeout to wait on.
func (c *Client) Send(message string, retries int, timeout time.Duration) error {
if err := c.send(message); err != nil {
return err
}
for {
// Poll socket for a reply, with timeout
poller := zmq.NewPoller()
poller.Add(c.sock, zmq.POLLIN)
sockets, err := poller.PollAll(timeout)
if err != nil {
return err
}
// Process a reply and exit if the reply is valid. Otherwise clsoe
// socket and retry the message for num retries. Abandon after we
// exhaust the number of allocated retries.
if sock := sockets[0]; sock.Events&zmq.POLLIN != 0 {
data, err := sock.Socket.RecvBytes(0)
if err != nil {
return err
}
reply := new(pb.BasicMessage)
if err := proto.Unmarshal(data, reply); err != nil {
return err
}
info("received: %s\n", reply.String())
return nil
} else if retries--; retries == 0 {
warn("connection to %s is offline, message dropped", c.addr)
if err := c.Reset(); err != nil {
return err
}
return nil
} else {
warn("no response from server, retrying send")
// Old socket is confused, reset it.
if err := c.Reset(); err != nil {
return err
}
// Resend the original message
if err := c.send(message); err != nil {
return err
}
}
}
}