mirror of
https://github.com/minio/minio
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e37c4efc6e
DNS refresh() in-case of MinIO can safely re-use the previous values on bare-metal setups, since bare-metal arrangements do not change DNS in any manner commonly. This PR simplifies that, we only ever need DNS caching on bare-metal setups. - On containerized setups do not enable DNS caching at all, as it may have adverse effects on the overall effectiveness of k8s DNS systems. k8s DNS systems are dynamic and expect applications to avoid managing DNS caching themselves, instead provide a cleaner container native caching implementations that must be used. - update IsDocker() detection, including podman runtime - move to minio/dnscache fork for a simpler package
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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