// initBalancer takes hosts from cfg.ChainedServers and it uses them to create a
// balancer.
func (client *Client) initBalancer(cfg *ClientConfig) (*balancer.Balancer, error) {
if len(cfg.ChainedServers) == 0 {
return nil, fmt.Errorf("No chained servers configured, not initializing balancer")
}
// The dialers slice must be large enough to handle all chained
// servers.
dialers := make([]*balancer.Dialer, 0, len(cfg.ChainedServers))
// Add chained (CONNECT proxy) servers.
log.Debugf("Adding %d chained servers", len(cfg.ChainedServers))
for _, s := range cfg.ChainedServers {
dialer, err := s.Dialer(cfg.DeviceID)
if err == nil {
dialers = append(dialers, dialer)
} else {
log.Errorf("Unable to configure chained server. Received error: %v", err)
}
}
bal := balancer.New(dialers...)
var oldBal *balancer.Balancer
var ok bool
ob, ok := client.bal.Get(0 * time.Millisecond)
if ok {
oldBal = ob.(*balancer.Balancer)
}
log.Trace("Publishing balancer")
client.bal.Set(bal)
if oldBal != nil {
// Close old balancer on a goroutine to avoid blocking here
go func() {
oldBal.Close()
log.Debug("Closed old balancer")
}()
}
return bal, nil
}
// newReverseProxy creates a reverse proxy that uses the client's balancer to
// dial out.
func (client *Client) newReverseProxy(bal *balancer.Balancer) *httputil.ReverseProxy {
transport := &http.Transport{
TLSHandshakeTimeout: 40 * time.Second,
}
// TODO: would be good to make this sensitive to QOS, which
// right now is only respected for HTTPS connections. The
// challenge is that ReverseProxy reuses connections for
// different requests, so we might have to configure different
// ReverseProxies for different QOS's or something like that.
transport.Dial = client.proxiedDialer(bal.Dial)
allAuthTokens := bal.AllAuthTokens()
return &httputil.ReverseProxy{
// We need to set the authentication tokens for all servers that we might
// connect to because we don't know which one the dialer will actually
// pick. We also need to strip out X-Forwarded-For that reverseproxy adds
// because it confuses the upstream servers with the additional 127.0.0.1
// field when upstream servers are trying to determine the client IP.
// We need to add also the X-Lantern-Device-Id field.
Director: func(req *http.Request) {
// Add back the Host header which was stripped by the ReverseProxy. This
// is needed for sites that do virtual hosting.
req.Header.Set("Host", req.Host)
req.Header.Set("X-LANTERN-DEVICE-ID", client.cfg().DeviceID)
for _, authToken := range allAuthTokens {
req.Header.Add("X-LANTERN-AUTH-TOKEN", authToken)
}
},
Transport: &errorRewritingRoundTripper{
&noForwardedForRoundTripper{withDumpHeaders(false, transport)},
},
// Set a FlushInterval to prevent overly aggressive buffering of
// responses, which helps keep memory usage down
FlushInterval: 250 * time.Millisecond,
ErrorLog: log.AsStdLogger(),
}
}