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