// Copyright (c) 2015-2021 MinIO, Inc.//// This file is part of MinIO Object Storage stack//// This program is free software: you can redistribute it and/or modify// it under the terms of the GNU Affero General Public License as published by// the Free Software Foundation, either version 3 of the License, or// (at your option) any later version.//// This program is distributed in the hope that it will be useful// but WITHOUT ANY WARRANTY; without even the implied warranty of// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the// GNU Affero General Public License for more details.//// You should have received a copy of the GNU Affero General Public License// along with this program. If not, see <http://www.gnu.org/licenses/>.package httpimport ( "context" "net" "time" "github.com/rs/dnscache")// DialContextWithDNSCache is a helper function which returns `net.DialContext` function.// It randomly fetches an IP from the DNS cache and dials it by the given dial// function. It dials one by one and returns first connected `net.Conn`.// If it fails to dial all IPs from cache it returns first error. If no baseDialFunc// is given, it sets default dial function.//// You can use returned dial function for `http.Transport.DialContext`.//// In this function, it uses functions from `rand` package. To make it really random,// you MUST call `rand.Seed` and change the value from the default in your applicationfunc DialContextWithDNSCache(resolver *dnscache.Resolver, baseDialCtx DialContext) DialContext { if baseDialCtx == nil { // This is same as which `http.DefaultTransport` uses. baseDialCtx = (&net.Dialer{ Timeout: 30 * time.Second, KeepAlive: 30 * time.Second, }).DialContext } return func(ctx context.Context, network, addr string) (conn net.Conn, err error) { host, port, err := net.SplitHostPort(addr) if err != nil { return nil, err } if net.ParseIP(host) != nil { // For IP only setups there is no need for DNS lookups. return baseDialCtx(ctx, "tcp", addr) } ips, err := resolver.LookupHost(ctx, host) if err != nil { return nil, err } for _, ip := range ips { conn, err = baseDialCtx(ctx, "tcp", net.JoinHostPort(ip, port)) if err == nil { break } } return }}
// Copyright (c) 2015-2021 MinIO, Inc.
//
// This file is part of MinIO Object Storage stack
//
// This program is free software: you can redistribute it and/or modify
// it under the terms of the GNU Affero General Public License as published by
// the Free Software Foundation, either version 3 of the License, or
// (at your option) any later version.
//
// This program is distributed in the hope that it will be useful
// but WITHOUT ANY WARRANTY; without even the implied warranty of
// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
// GNU Affero General Public License for more details.
//
// You should have received a copy of the GNU Affero General Public License
// along with this program. If not, see <http://www.gnu.org/licenses/>.
package http
import (
"context"
"net"
"time"
"github.com/rs/dnscache"
)
// DialContextWithDNSCache is a helper function which returns `net.DialContext` function.
// It randomly fetches an IP from the DNS cache and dials it by the given dial
// function. It dials one by one and returns first connected `net.Conn`.
// If it fails to dial all IPs from cache it returns first error. If no baseDialFunc
// is given, it sets default dial function.
//
// You can use returned dial function for `http.Transport.DialContext`.
//
// In this function, it uses functions from `rand` package. To make it really random,
// you MUST call `rand.Seed` and change the value from the default in your application
func DialContextWithDNSCache(resolver *dnscache.Resolver, baseDialCtx DialContext) DialContext {
if baseDialCtx == nil {
// This is same as which `http.DefaultTransport` uses.
baseDialCtx = (&net.Dialer{
Timeout: 30 * time.Second,
KeepAlive: 30 * time.Second,
}).DialContext
}
return func(ctx context.Context, network, addr string) (conn net.Conn, err error) {
host, port, err := net.SplitHostPort(addr)
if err != nil {
return nil, err
}
if net.ParseIP(host) != nil {
// For IP only setups there is no need for DNS lookups.
return baseDialCtx(ctx, "tcp", addr)
}
ips, err := resolver.LookupHost(ctx, host)
if err != nil {
return nil, err
}
for _, ip := range ips {
conn, err = baseDialCtx(ctx, "tcp", net.JoinHostPort(ip, port))
if err == nil {
break
}
}
return
}
}