-
Notifications
You must be signed in to change notification settings - Fork 0
/
kubernetes-service-iii.html
1437 lines (586 loc) · 52.7 KB
/
kubernetes-service-iii.html
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
350
351
352
353
354
355
356
357
358
359
360
361
362
363
364
365
366
367
368
369
370
371
372
373
374
375
376
377
378
379
380
381
382
383
384
385
386
387
388
389
390
391
392
393
394
395
396
397
398
399
400
401
402
403
404
405
406
407
408
409
410
411
412
413
414
415
416
417
418
419
420
421
422
423
424
425
426
427
428
429
430
431
432
433
434
435
436
437
438
439
440
441
442
443
444
445
446
447
448
449
450
451
452
453
454
455
456
457
458
459
460
461
462
463
464
465
466
467
468
469
470
471
472
473
474
475
476
477
478
479
480
481
482
483
484
485
486
487
488
489
490
491
492
493
494
495
496
497
498
499
500
501
502
503
504
505
506
507
508
509
510
511
512
513
514
515
516
517
518
519
520
521
522
523
524
525
526
527
528
529
530
531
532
533
534
535
536
537
538
539
540
541
542
543
544
545
546
547
548
549
550
551
552
553
554
555
556
557
558
559
560
561
562
563
564
565
566
567
568
569
570
571
572
573
574
575
576
577
578
579
580
581
582
583
584
585
586
587
588
589
590
591
592
593
594
595
596
597
598
599
600
601
602
603
604
605
606
607
608
609
610
611
612
613
614
615
616
617
618
619
620
621
622
623
624
625
626
627
628
629
630
631
632
633
634
635
636
637
638
639
640
641
642
643
644
645
646
647
648
649
650
651
652
653
654
655
656
657
658
659
660
661
662
663
664
665
666
667
668
669
670
671
672
673
674
675
676
677
678
679
680
681
682
683
684
685
686
687
688
689
690
691
692
693
694
695
696
697
698
699
700
701
702
703
704
705
706
707
708
709
710
711
712
713
714
715
716
717
718
719
720
721
722
723
724
725
726
727
728
729
730
731
732
733
734
735
736
737
738
739
740
741
742
743
744
745
746
747
748
749
750
751
752
753
754
755
756
757
758
759
760
761
762
763
764
765
766
767
768
769
770
771
772
773
774
775
776
777
778
779
780
781
782
783
784
785
786
787
788
789
790
791
792
793
794
795
796
797
798
799
800
801
802
803
804
805
806
807
808
809
810
811
812
813
814
815
816
817
818
819
820
821
822
823
824
825
826
827
828
829
830
831
832
833
834
835
836
837
838
839
840
841
842
843
844
845
846
847
848
849
850
851
852
853
854
855
856
857
858
859
860
861
862
863
864
865
866
867
868
869
870
871
872
873
874
875
876
877
878
879
880
881
882
883
884
885
886
887
888
889
890
891
892
893
894
895
896
897
898
899
900
901
902
903
904
905
906
907
908
909
910
911
912
913
914
915
916
917
918
919
920
921
922
923
924
925
926
927
928
929
930
931
932
933
934
935
936
937
938
939
940
941
942
943
944
945
946
947
948
949
950
951
952
953
954
955
956
957
958
959
960
961
962
963
964
965
966
967
968
969
970
971
972
973
974
975
976
977
978
979
980
981
982
983
984
985
986
987
988
989
990
991
992
993
994
995
996
997
998
999
1000
<!DOCTYPE html>
<html class="theme-next pisces use-motion" lang="en">
<head>
<meta charset="UTF-8"/>
<meta http-equiv="X-UA-Compatible" content="IE=edge"/>
<meta name="viewport" content="width=device-width, initial-scale=1, maximum-scale=2"/>
<meta name="theme-color" content="#222"/>
<link rel="stylesheet" href="/lib/font-awesome/css/font-awesome.min.css?v=4.6.2"/>
<link rel="stylesheet" href="/css/main.css?v=7.0.1"/>
<link rel="apple-touch-icon" sizes="180x180" href="/images/apple-touch-icon-next.png?v=7.0.1">
<link rel="icon" type="image/png" sizes="32x32" href="/images/favicon-32x32-next.png?v=7.0.1">
<link rel="icon" type="image/png" sizes="16x16" href="/images/favicon-16x16-next.png?v=7.0.1">
<link rel="mask-icon" href="/images/logo.svg?v=7.0.1" color="#222">
<script id="hexo.configurations">
var NexT = window.NexT || {};
var CONFIG = {
root: '/',
scheme: 'Pisces',
version: '7.0.1',
sidebar: {"position":"left","display":"post","offset":12,"onmobile":false,"dimmer":false},
back2top: true,
back2top_sidebar: false,
fancybox: false,
fastclick: false,
lazyload: false,
tabs: true,
motion: {"enable":true,"async":false,"transition":{"post_block":"fadeIn","post_header":"slideDownIn","post_body":"slideDownIn","coll_header":"slideLeftIn","sidebar":"slideUpIn"}},
algolia: {
applicationID: '',
apiKey: '',
indexName: '',
hits: {"per_page":10},
labels: {"input_placeholder":"Search for Posts","hits_empty":"We didn't find any results for the search: ${query}","hits_stats":"${hits} results found in ${time} ms"}
}
};
</script>
<meta name="description" content="在前述中我們已經學過了什麼是 kubernetes service 以及如何實現 ClusterIP 這種類型的 service. 透過對 iptables 的探討與研究, 我們可以理解到 ClusterIP 本身會提供一個虛擬的 IP 地址,接下來只要跟這個地址有關的封包,都會透過 DNAT 的方式進行轉換找到最後的 Endpoint IP. 至於如何選擇的部分,則是透過機率的方式去尋找. 接下">
<meta name="keywords" content="Kubernetes,Service,Linux,k8s,iptables,NodePort">
<meta property="og:type" content="article">
<meta property="og:title" content="[Kubernetes] How to Implement Kubernetes Service - NodePort">
<meta property="og:url" content="https://www.hwchiu.com/kubernetes-service-iii.html">
<meta property="og:site_name" content="Hwchiu Learning Note">
<meta property="og:description" content="在前述中我們已經學過了什麼是 kubernetes service 以及如何實現 ClusterIP 這種類型的 service. 透過對 iptables 的探討與研究, 我們可以理解到 ClusterIP 本身會提供一個虛擬的 IP 地址,接下來只要跟這個地址有關的封包,都會透過 DNAT 的方式進行轉換找到最後的 Endpoint IP. 至於如何選擇的部分,則是透過機率的方式去尋找. 接下">
<meta property="og:locale" content="en">
<meta property="og:image" content="https://i.imgur.com/xoPvipq.png">
<meta property="og:image" content="https://i.imgur.com/9amwybH.png">
<meta property="og:image" content="https://i.imgur.com/9amwybH.png">
<meta property="og:updated_time" content="2018-09-27T17:54:31.507Z">
<meta name="twitter:card" content="summary">
<meta name="twitter:title" content="[Kubernetes] How to Implement Kubernetes Service - NodePort">
<meta name="twitter:description" content="在前述中我們已經學過了什麼是 kubernetes service 以及如何實現 ClusterIP 這種類型的 service. 透過對 iptables 的探討與研究, 我們可以理解到 ClusterIP 本身會提供一個虛擬的 IP 地址,接下來只要跟這個地址有關的封包,都會透過 DNAT 的方式進行轉換找到最後的 Endpoint IP. 至於如何選擇的部分,則是透過機率的方式去尋找. 接下">
<meta name="twitter:image" content="https://i.imgur.com/xoPvipq.png">
<link rel="alternate" href="/atom.xml" title="Hwchiu Learning Note" type="application/atom+xml"/>
<link rel="canonical" href="https://www.hwchiu.com/kubernetes-service-iii.html"/>
<script id="page.configurations">
CONFIG.page = {
sidebar: "",
};
</script>
<title>[Kubernetes] How to Implement Kubernetes Service - NodePort | Hwchiu Learning Note</title>
<script>
window.fbAsyncInit = function() {
FB.init({
appId : '',
xfbml : true,
version: 'v2.10'
});
};
(function(d, s, id) {
var js, fjs = d.getElementsByTagName(s)[0];
if (d.getElementById(id)) {return;}
js = d.createElement(s); js.id = id;
js.src = "//connect.facebook.net/en/sdk.js";
fjs.parentNode.insertBefore(js, fjs);
}(document, 'script', 'facebook-jssdk'));
</script>
<script async src="//www.googletagmanager.com/gtag/js?id=UA-54006186-1"></script>
<script>
var host = window.location.hostname;
if (host !== "localhost" || !true) {
window.dataLayer = window.dataLayer || [];
function gtag(){dataLayer.push(arguments);}
gtag('js', new Date());
gtag('config', 'UA-54006186-1');
}
</script>
<noscript>
<style>
.use-motion .motion-element,
.use-motion .brand,
.use-motion .menu-item,
.sidebar-inner,
.use-motion .post-block,
.use-motion .pagination,
.use-motion .comments,
.use-motion .post-header,
.use-motion .post-body,
.use-motion .collection-title { opacity: initial; }
.use-motion .logo,
.use-motion .site-title,
.use-motion .site-subtitle {
opacity: initial;
top: initial;
}
.use-motion .logo-line-before i { left: initial; }
.use-motion .logo-line-after i { right: initial; }
</style>
</noscript>
<script async src="//pagead2.googlesyndication.com/pagead/js/adsbygoogle.js"></script>
<script>
(adsbygoogle = window.adsbygoogle || []).push({
google_ad_client: "ca-pub-1100711228720990",
enable_page_level_ads: true
});
</script>
</head>
<body itemscope itemtype="http://schema.org/WebPage" lang="en">
<div class="container sidebar-position-left page-post-detail">
<div class="headband"></div>
<header id="header" class="header" itemscope itemtype="http://schema.org/WPHeader">
<div class="header-inner"><div class="site-brand-wrapper">
<div class="site-meta">
<div class="custom-logo-site-title">
<a href="/" class="brand" rel="start">
<span class="logo-line-before"><i></i></span>
<span class="site-title">Hwchiu Learning Note</span>
<span class="logo-line-after"><i></i></span>
</a>
</div>
<h1 class="site-subtitle" itemprop="description">kubernetes, sdn, linux,devops</h1>
</div>
<div class="site-nav-toggle">
<button aria-label="Toggle navigation bar">
<span class="btn-bar"></span>
<span class="btn-bar"></span>
<span class="btn-bar"></span>
</button>
</div>
</div>
<nav class="site-nav">
<ul id="menu" class="menu">
<li class="menu-item menu-item-home">
<a href="/" rel="section"><i class="menu-item-icon fa fa-fw fa-home"></i> <br/>Home</a>
</li>
<li class="menu-item menu-item-about">
<a href="/about/" rel="section"><i class="menu-item-icon fa fa-fw fa-user"></i> <br/>About</a>
</li>
<li class="menu-item menu-item-tags">
<a href="/tags/" rel="section"><i class="menu-item-icon fa fa-fw fa-tags"></i> <br/>Tags</a>
</li>
<li class="menu-item menu-item-archives">
<a href="/archives/" rel="section"><i class="menu-item-icon fa fa-fw fa-archive"></i> <br/>Archives</a>
</li>
<li class="menu-item menu-item-sitemap">
<a href="/sitemap.xml" rel="section"><i class="menu-item-icon fa fa-fw fa-sitemap"></i> <br/>Sitemap</a>
</li>
</ul>
</nav>
</div>
</header>
<a href="https://github.com/hwchiu" class="github-corner" title="Follow me on GitHub" aria-label="Follow me on GitHub" rel="noopener" target="_blank"><svg width="80" height="80" viewBox="0 0 250 250" style="fill: #222; color: #fff; position: absolute; top: 0; border: 0; right: 0;" aria-hidden="true"><path d="M0,0 L115,115 L130,115 L142,142 L250,250 L250,0 Z"></path><path d="M128.3,109.0 C113.8,99.7 119.0,89.6 119.0,89.6 C122.0,82.7 120.5,78.6 120.5,78.6 C119.2,72.0 123.4,76.3 123.4,76.3 C127.3,80.9 125.5,87.3 125.5,87.3 C122.9,97.6 130.6,101.9 134.4,103.2" fill="currentColor" style="transform-origin: 130px 106px;" class="octo-arm"></path><path d="M115.0,115.0 C114.9,115.1 118.7,116.5 119.8,115.4 L133.7,101.6 C136.9,99.2 139.9,98.4 142.2,98.6 C133.8,88.0 127.5,74.4 143.8,58.0 C148.5,53.4 154.0,51.2 159.7,51.0 C160.3,49.4 163.2,43.6 171.4,40.1 C171.4,40.1 176.1,42.5 178.8,56.2 C183.1,58.6 187.2,61.8 190.9,65.4 C194.5,69.0 197.7,73.2 200.1,77.6 C213.8,80.2 216.3,84.9 216.3,84.9 C212.7,93.1 206.9,96.0 205.4,96.6 C205.1,102.4 203.0,107.8 198.3,112.5 C181.9,128.9 168.3,122.5 157.7,114.1 C157.9,116.9 156.7,120.9 152.7,124.9 L141.0,136.5 C139.8,137.7 141.6,141.9 141.8,141.8 Z" fill="currentColor" class="octo-body"></path></svg></a>
<main id="main" class="main">
<div class="main-inner">
<div class="content-wrap">
<div id="content" class="content">
<div id="posts" class="posts-expand">
<article class="post post-type-normal" itemscope itemtype="http://schema.org/Article">
<div class="post-block">
<link itemprop="mainEntityOfPage" href="https://www.hwchiu.com/kubernetes-service-iii.html"/>
<span hidden itemprop="author" itemscope itemtype="http://schema.org/Person">
<meta itemprop="name" content="Hwchiu"/>
<meta itemprop="description" content="kubernetes/SDN/DevOps"/>
<meta itemprop="image" content="/images/avatar.jpg"/>
</span>
<span hidden itemprop="publisher" itemscope itemtype="http://schema.org/Organization">
<meta itemprop="name" content="Hwchiu Learning Note"/>
</span>
<header class="post-header">
<h2 class="post-title" itemprop="name headline">[Kubernetes] How to Implement Kubernetes Service - NodePort
</h2>
<div class="post-meta">
<span class="post-time">
<span class="post-meta-item-icon">
<i class="fa fa-calendar-o"></i>
</span>
<span class="post-meta-item-text">Posted on</span>
<time title="Created: 2018-08-25 01:17:08" itemprop="dateCreated datePublished" datetime="2018-08-25T01:17:08+00:00">2018-08-25</time>
<span class="post-meta-divider">|</span>
<span class="post-meta-item-icon">
<i class="fa fa-calendar-check-o"></i>
</span>
<span class="post-meta-item-text">Edited on</span>
<time title="Modified: 2018-09-27 17:54:31" itemprop="dateModified" datetime="2018-09-27T17:54:31+00:00">2018-09-27</time>
</span>
<span class="post-comments-count">
<span class="post-meta-divider">|</span>
<span class="post-meta-item-icon">
<i class="fa fa-comment-o"></i>
</span>
<span class="post-meta-item-text">Comments: </span>
<a href="/kubernetes-service-iii.html#comments" itemprop="discussionUrl">
<span class="post-comments-count disqus-comment-count" data-disqus-identifier="kubernetes-service-iii.html" itemprop="commentCount"></span>
</a>
</span>
<div class="post-description">在前述中我們已經學過了什麼是 kubernetes service 以及如何實現 ClusterIP 這種類型的 service. 透過對 iptables 的探討與研究, 我們可以理解到 ClusterIP 本身會提供一個虛擬的 IP 地址,接下來只要跟這個地址有關的封包,都會透過 DNAT 的方式進行轉換找到最後的 Endpoint IP. 至於如何選擇的部分,則是透過機率的方式去尋找. 接下來我們要來探討另外一個也是很常使用的 kubernetes service 類型, 也就是 NodePort. NodePort 本身包含了 ClusterIP 的所有功能, 此外也額外開啟了一個新的存取方式. 透過直接存取節點的 IP 地址配上一個設定好的 Port, 也可以將該封包直接送到最後面的容器應用程式. 因此本文也要延續上一篇的思路,繼續研究 iptables 的規則來探討 NodePort 到底是如何實現的</div>
</div>
</header>
<div class="post-body" itemprop="articleBody">
<h1 id="Preface"><a href="#Preface" class="headerlink" title="Preface"></a>Preface</h1><p>本文章是屬於 <code>kubernetes</code> service 系列文之一,該系列文希望能夠與大家討論下列兩個觀念</p>
<ol>
<li>什麼是 <code>Kubernetes Service</code>, 為什麼我們需要它? 它能夠幫忙解決什麼問題</li>
<li><code>Kubernetes Service</code> 是怎麼實現的?, 讓我們用 iptables 來徹徹底底的理解他</li>
</ol>
<p>相關文章:<br><a href="https://www.hwchiu.com/kubernetes-service-i.html">[Kubernetes] What is Service</a><br><a href="https://www.hwchiu.com/kubernetes-service-ii.html">[Kubernetes] How To Implement Kubernetes Service - ClusterIP</a><br><a href="https://www.hwchiu.com/kubernetes-service-iiii.html">[Kubernetes] How To Implement Kubernetes Service - SessionAffinity</a></p>
<p>本文銜接上篇文章,繼續透過對 <code>iptables</code> 的分析來研究 <code>kubernetes service</code> 中 <code>NodePort</code> 的實作原理。</p>
<a id="more"></a>
<p><code>NodePort</code> 的功能就如同字面上的意思一樣,<code>Node Port</code>, 提供了一種透過存取叢集節點上事先定義好的<code>Port Number</code> 就可以輾轉存取到後端的真正服務。</p>
<p>作為一個靠腦力生存的人,每次遇到全新概念的時候,都要問問自己幾個問題</p>
<ol>
<li>這個概念是想要解決什麼問題?</li>
<li>什麼時候會用到?</li>
<li>如果是我,我會怎麼實作?</li>
</ol>
<h1 id="Why-We-Need-NortPort"><a href="#Why-We-Need-NortPort" class="headerlink" title="Why We Need NortPort"></a>Why We Need NortPort</h1><p><code>NodePort</code> 本身是屬於 <code>kubernetes service</code>的一環,自然就是要提供一個方式可以讓外部來存取集群內的服務,而且可以不用去理會後面這些容器們的真實<code>IP</code>地址。</p>
<p>既然已經有前面的 <code>ClusterIP</code> 提供了一種叢集內存取的方式,什麼情況下我們會需要 <code>NodePort</code> 這種透過存取節點的方式?</p>
<p>這邊使用一個下列的範例來解釋可能的情況 </p>
<div class="note danger">
<p>以下只是一種範例,但是未必是最佳解</p>
</div>
<p>假設今天有一個試驗環境,在<code>Cloud Provider(Google/Azure/AWS...etc)</code>中架設了一個<code>kubernetes</code>叢集,裡面透過 <code>nginx</code> 的方式部屬了一個網頁伺服器。<br>與此同時,我希望該叢集能夠提供下列的特性供我使用</p>
<ul>
<li>我希望管理人員可以不需要去擔心該 <code>nginx</code> 的狀態,其網頁服務能夠一直正常運作。</li>
<li>我可以在任意地方直接連接到該 <code>nginx</code> 提供的網頁伺服器服務</li>
</ul>
<p>為了滿足第一個條件,我們可以透過 <code>kubernetes deployment</code> 的方式去確保 <code>nginx</code> 的容器處於一種運行的狀態。<br>為了滿足第二個條件,我們可以透過 <code>kubernetes service</code> 的方式去連接上述的 <code>nginx</code> 容器們並且提供一種接口讓外部存取<br>在這種情況下,只要<code>kubernetes</code>叢集內的節點擁有一個固定的對外<code>IP</code>地址,同時 <code>kubernetes server</code> 透過 <code>NodePorts</code> 的方式提供該<code>nginx</code>往外存取的能力。<br>這種情況下,我們就可以在任何地方,透過直接存取該節點的對外<code>IP</code>地址,然後間接透過<code>NodePort</code>的功能存取到集群內的<code>nginx</code>服務。</p>
<h1 id="How-It-Works"><a href="#How-It-Works" class="headerlink" title="How It Works"></a>How It Works</h1><p>已經有了前述關於 <code>ClusterIP</code> 運作的概念後,其實要探討 <code>NodePort</code> 是如何實現的就非常簡單了。</p>
<p>我們先快速複習一下 <code>ClusterIP</code> 的運作流程<br><img src="https://i.imgur.com/xoPvipq.png" alt="Imgur"></p>
<ol>
<li>封包若來自叢集上的應用程式/節點,則跳到 `KUBE-SVC</li>
<li>如果封包的目標<code>IP</code>地址是 <code>ClusterIP</code> 所提供的虛擬<code>IP</code>地址, 則跳到 <code>KUBE-SVC-XXXX</code></li>
<li><code>KUBE-SVC-XXX</code> 裡面根據機率的方式,選到一個 <code>Endpoints</code>,最後跳到 <code>KUBE-SEP-XXX</code></li>
<li><code>KUBE-SEP-XXX</code> 裡面執行 <code>DNAT</code>, 將封包的目標地址改成真正的容器地址,然後轉發</li>
</ol>
<p>有了上述的概念,我們如果要支援 <code>NodePort</code> 這種能夠透過<code>節點IP</code>的方式存取的話。<br>想了一下,其實就是把上述的(1)/(2)改掉就好,能夠跳到 <code>KUBE-SVC-XXX</code>的話,後續就完全一致了。</p>
<p>接下來,我們繼續使用<a href="https://github.com/hwchiu/kubeDemo" target="_blank" rel="noopener">kubeDemo</a>來進行相關的服務部屬以及<code>iptables</code>規則研究。</p>
<p>首先,我們先在環境內部署相關的 <code>nginx</code> 以及 <code>kubernetes service(NodePort)</code></p>
<figure class="highlight bash"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br></pre></td><td class="code"><pre><span class="line">vortex-dev:06:36:12 [~/go/src/github.com/hwchiu/kubeDemo/services](master)vagrant</span><br><span class="line"><span class="variable">$kubectl</span> apply -f deployment/nginx.yml</span><br><span class="line">deployment.apps/k8s-nginx created</span><br><span class="line"></span><br><span class="line">vortex-dev:06:36:18 [~/go/src/github.com/hwchiu/kubeDemo/services](master)vagrant</span><br><span class="line"><span class="variable">$kubectl</span> apply -f service/nginx-node.yml</span><br><span class="line">service/k8s-nginx-node created</span><br></pre></td></tr></table></figure>
<p>這邊就不再敘述太多跟 <code>service/endpoints</code> 相關的資訊與位置,直接從 <code>iptables</code> 的角度出發。</p>
<p>我個人非常喜歡 <code>kubernetes</code>的一點就是所有的 <code>iptables</code> 的規則都會下註解,所以其實可以很輕易的透過 <code>grep</code> 的方式找到相關的規則。<br>以上述的範例來說,我們在 <code>default</code> namespace 中部屬了一個 <code>k8s-nginx-node</code> 的 <code>kubernetes service</code>.<br>所以透過 <code>grep default/k8s-nginx-node</code> 的方式就可以過濾出所有跟這個<code>Service</code>有關的所有規則。</p>
<figure class="highlight bash"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br><span class="line">10</span><br><span class="line">11</span><br><span class="line">12</span><br><span class="line">13</span><br><span class="line">14</span><br><span class="line">15</span><br></pre></td><td class="code"><pre><span class="line">vortex-dev:03:17:35 [~]vagrant</span><br><span class="line"><span class="variable">$sudo</span> iptables-save | grep default/k8s-nginx-node</span><br><span class="line">-A KUBE-NODEPORTS -p tcp -m comment --comment <span class="string">"default/k8s-nginx-node:"</span> -m tcp --dport 30136 -j KUBE-MARK-MASQ</span><br><span class="line">-A KUBE-NODEPORTS -p tcp -m comment --comment <span class="string">"default/k8s-nginx-node:"</span> -m tcp --dport 30136 -j KUBE-SVC-RD5DSC6PXE26GCYZ</span><br><span class="line">-A KUBE-SEP-VRKO3GZ2XUCPVWY5 -s 10.244.0.115/32 -m comment --comment <span class="string">"default/k8s-nginx-node:"</span> -j KUBE-MARK-MASQ</span><br><span class="line">-A KUBE-SEP-VRKO3GZ2XUCPVWY5 -p tcp -m comment --comment <span class="string">"default/k8s-nginx-node:"</span> -m tcp -j DNAT --to-destination 10.244.0.115:80</span><br><span class="line">-A KUBE-SEP-YNJKNN6SS5424R7C -s 10.244.0.113/32 -m comment --comment <span class="string">"default/k8s-nginx-node:"</span> -j KUBE-MARK-MASQ</span><br><span class="line">-A KUBE-SEP-YNJKNN6SS5424R7C -p tcp -m comment --comment <span class="string">"default/k8s-nginx-node:"</span> -m tcp -j DNAT --to-destination 10.244.0.113:80</span><br><span class="line">-A KUBE-SEP-ZGMDZ7UNNV74OV5B -s 10.244.0.114/32 -m comment --comment <span class="string">"default/k8s-nginx-node:"</span> -j KUBE-MARK-MASQ</span><br><span class="line">-A KUBE-SEP-ZGMDZ7UNNV74OV5B -p tcp -m comment --comment <span class="string">"default/k8s-nginx-node:"</span> -m tcp -j DNAT --to-destination 10.244.0.114:80</span><br><span class="line">-A KUBE-SERVICES ! -s 10.244.0.0/16 -d 10.98.128.179/32 -p tcp -m comment --comment <span class="string">"default/k8s-nginx-node: cluster IP"</span> -m tcp --dport 80 -j KUBE-MARK-MASQ</span><br><span class="line">-A KUBE-SERVICES -d 10.98.128.179/32 -p tcp -m comment --comment <span class="string">"default/k8s-nginx-node: cluster IP"</span> -m tcp --dport 80 -j KUBE-SVC-RD5DSC6PXE26GCYZ</span><br><span class="line">-A KUBE-SVC-RD5DSC6PXE26GCYZ -m comment --comment <span class="string">"default/k8s-nginx-node:"</span> -m statistic --mode random --probability 0.33332999982 -j KUBE-SEP-YNJKNN6SS5424R7C</span><br><span class="line">-A KUBE-SVC-RD5DSC6PXE26GCYZ -m comment --comment <span class="string">"default/k8s-nginx-node:"</span> -m statistic --mode random --probability 0.50000000000 -j KUBE-SEP-ZGMDZ7UNNV74OV5B</span><br><span class="line">-A KUBE-SVC-RD5DSC6PXE26GCYZ -m comment --comment <span class="string">"default/k8s-nginx-node:"</span> -j KUBE-SEP-VRKO3GZ2XUCPVWY5</span><br></pre></td></tr></table></figure>
<p>我們快速的掃過所有的規則,根據 <code>custom chain</code> 來看,分成四個部分</p>
<ol>
<li>KUBE-NODEPORTS</li>
<li>KUBE-SEP-XXXX</li>
<li>KUBE-SERVICES</li>
<li>KUBE-SVC-XXXX</li>
</ol>
<p>這邊目前只有 <code>KUBE-NODEPORTS</code> 還沒有看過,剩下的都跟 <code>ClusterIP</code> 是一樣的功能的。</p>
<div class="note danger">
<p>NodePort 的功能基於 ClusterIP 之上再添加新功能,所以本來 Cluster 該有的規則對於 NodePort 來說都不會少 </p>
</div>
<h1 id="KUBE-NODEPORTS"><a href="#KUBE-NODEPORTS" class="headerlink" title="KUBE-NODEPORTS"></a>KUBE-NODEPORTS</h1><p>我們仔細觀察 <code>KUBE-NODEPORTS</code> 相關的兩條規則<br><figure class="highlight bash"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br></pre></td><td class="code"><pre><span class="line">-A KUBE-NODEPORTS -p tcp -m comment --comment <span class="string">"default/k8s-nginx-node:"</span> -m tcp --dport 30136 -j KUBE-MARK-MASQ</span><br><span class="line">-A KUBE-NODEPORTS -p tcp -m comment --comment <span class="string">"default/k8s-nginx-node:"</span> -m tcp --dport 30136 -j KUBE-SVC-RD5DSC6PXE26GCYZ</span><br></pre></td></tr></table></figure></p>
<p>第一條規則的目標是 <code>-j KUBE-MARK-MASQ</code>, 這部份是跟 <code>SNAT</code> 有關的,這個之後有機會再寫額外的文章來介紹 <code>SNAT</code> 相關的功能以及處理方式。<br>這邊只要知道這是修改封包的來源<code>IP</code>位址即可<br>第二條規則比較重要,我們可以觀察到</p>
<ol>
<li>其比對條件是 <code>-m tcp --dport 30136</code>.</li>
<li>符合條件後執行的行為是 <code>-j KUBE-SVC-RD5DSC6PXE26GCYZ</code></li>
</ol>
<figure class="highlight bash"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br></pre></td><td class="code"><pre><span class="line">vortex-dev:03:34:14 [~]vagrant</span><br><span class="line"><span class="variable">$kubectl</span> get svc</span><br><span class="line">NAME TYPE CLUSTER-IP EXTERNAL-IP PORT(S) AGE</span><br><span class="line">k8s-nginx-node NodePort 10.98.128.179 <none> 80:30136/TCP 1d</span><br></pre></td></tr></table></figure>
<p>根據查詢 <code>kubernetes svc</code> 的結果,我們可以觀察到透過存取 <code>30136/TCP</code> 的方式就可以存取 <code>NodePOrt</code>.<br>而這個資訊與我們前面看到的 <code>KUBE-NODEPORTS</code> 這邊的規則完全一樣<br>最後可以發現當規則一致時,就會跳到 <code>KUBE-SVC-XXX</code> 去進行 <code>endpoints</code> 的挑選以及相關的 <code>DNAT</code> 功能。</p>
<p>哪接下來的問題只剩下一個<br>到底封包什麼時候會進入到 <code>KUBE-NODEPORTS</code> ? 只要釐清這個問題,剩下的處理方式就都跟 <code>ClusterIP</code> 完全一樣了。<br>這時候我們就要一條一條 <code>iptables</code> 的規則來慢慢查詢</p>
<p>我偷懶直接使用 <code>-j KUBE-NODEPORTS</code> 的方式來查詢,到底誰會跳入 <code>KUBE-NODEPORT</code><br><figure class="highlight bash"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br></pre></td><td class="code"><pre><span class="line">vortex-dev:03:43:42 [~]vagrant</span><br><span class="line"><span class="variable">$sudo</span> iptables-save | grep <span class="string">"\-j KUBE-NODEPORTS"</span></span><br><span class="line">-A KUBE-SERVICES -m comment --comment <span class="string">"kubernetes service nodeports; NOTE: this must be the last rule in this chain"</span> -m addrtype --dst-type LOCAL -j KUBE-NODEPORTS</span><br></pre></td></tr></table></figure></p>
<p>這個規則非常有趣,首先我們可以觀察到,他在 <code>KUBE-SERVICES</code> 這個 <code>custom chain</code> 裡面。 接下來可以觀察他的註解<br><figure class="highlight plain"><table><tr><td class="gutter"><pre><span class="line">1</span><br></pre></td><td class="code"><pre><span class="line">kubernetes service nodeports; NOTE: this must be the last rule in this chain</span><br></pre></td></tr></table></figure></p>
<p>然後看一下比對條件以及執行目標</p>
<ol>
<li>-m addrtype –dst-type LOCAL</li>
<li>-j KUBE-NODEPORTS</li>
</ol>
<p>第一個比對條件我們從文字上來解讀,只要封包的目標<code>IP</code>地址是屬於本節點上的任何網卡<code>IP</code>。<br>只要符合上述規則,就會跳到 <code>KUBE-NODEPORT</code> 裡面進行比對,然後就按照前述的去處理了。</p>
<div class="note danger">
<p>對於 –dst-type LOCAL 有興趣的人可以嘗試閱讀下列這個檔案<br><a href="https://elixir.bootlin.com/linux/v4.7.8/source/net/netfilter/xt_addrtype.c#L119" target="_blank" rel="noopener">https://elixir.bootlin.com/linux/v4.7.8/source/net/netfilter/xt_addrtype.c#L119</a><br><a href="https://elixir.bootlin.com/linux/v4.7.8/source/include/uapi/linux/rtnetlink.h#L203" target="_blank" rel="noopener">https://elixir.bootlin.com/linux/v4.7.8/source/include/uapi/linux/rtnetlink.h#L203</a><br>看看 kernel 內大致上是怎麼處理這系列操作的</p>
</div>
<p>到這邊我們整理一下所有的思路。</p>
<ol>
<li>NodePort 也是倚賴 <code>KUBE-SERVICES</code>,當封包目標是本地端的 <code>IP</code> 位置的時候,就會跳到 <code>KUBE-NODEPORT</code> 裡面去比對 <code>protocol/port</code> 來進行後續跟 <code>ClusterIP</code> 相同的處理</li>
<li>所有的 <code>kubernetes NodePort service</code> 都會共用同一個 <code>KUBE-NODEPORT</code>, 因此所有的 <code>NodePort</code> 使用的 <code>Port</code> 都不能一樣</li>
</ol>
<p>我們用下列這張圖來總結 <code>NodePort</code> 的運作</p>
<p><img src="https://i.imgur.com/9amwybH.png" alt="Imgur"></p>
<h1 id="PortBinding"><a href="#PortBinding" class="headerlink" title="PortBinding"></a>PortBinding</h1><p>由於 <code>NodePort</code> 會使用到節點上面的 <code>Port</code> 來提供服務<br>但從 <code>iptables</code> 的規則觀察下,其實 <code>NodePort</code> 所用到的 <code>Port</code> 就是一個虛擬的 <code>Port</code>,譬如上述範例的 <code>30136</code>。<br>為了避免有任何應用程式之後將 <code>NodePort</code> 要用到的 <code>Port</code> 給拿去使用,導致整個有任何非預期的行為出現</p>
<ul>
<li>譬如某服務想要用 30136 port, 但是所有的封包都被 iptables 導走了,導致該服務一直沒有辦法接收到真正的連線</li>
</ul>
<p>為了解決這個問題就是不要讓任何應用程式有機會使用到 <code>30136</code> 的連接埠,因此每個節點上面的 <code>kube-proxy</code> 就會幫忙做這件事情。</p>
<p>一旦 <code>NodePort</code> 成功建立後,就會將該 <code>Port</code> 給使用走,讓其他的應用程式沒有機會使用。</p>
<p>這部份我們可以透過 <code>netstat</code> 的指令來觀察<br><figure class="highlight bash"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br></pre></td><td class="code"><pre><span class="line">vortex-dev:04:08:18 [~]vagrant</span><br><span class="line"><span class="variable">$sudo</span> netstat -ltpn | grep 30136</span><br><span class="line">tcp6 0 0 :::30136 :::* LISTEN 10181/kube-proxy</span><br></pre></td></tr></table></figure></p>
<p>這點跟 <code>docker</code> 的想法是很類似的,不過 <code>docker</code> 所啟用的 <code>docker-proxy</code> 其實也會幫忙 <code>forward</code> 這些封包,而不是單純的搶占避免服務失效而已。<br><figure class="highlight bash"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br></pre></td><td class="code"><pre><span class="line">vortex-dev:01:08:39 [~/go/src/github.com/linkernetworks/vortex/vendor](hwchiu/VX-62)vagrant</span><br><span class="line"><span class="variable">$sudo</span> docker run -d -p 5566:80 nginx</span><br><span class="line">f4b6b72ad82c170a92cd6ea272fc8d665b69835b8508d20e1ac2b220b2ba5b31</span><br><span class="line">vortex-dev:01:08:43 [~/go/src/github.com/linkernetworks/vortex/vendor](hwchiu/VX-62)vagrant</span><br><span class="line"><span class="variable">$ps</span> axuw | grep docker-p</span><br><span class="line">root 21499 0.0 0.0 59068 2852 ? Sl 01:08 0:00 /usr/bin/docker-proxy -proto tcp -host-ip 0.0.0.0 -host-port 5566 -container-ip 172.18.0.2 -container-port 80</span><br></pre></td></tr></table></figure></p>
<h1 id="Summary"><a href="#Summary" class="headerlink" title="Summary"></a>Summary</h1><p>本章節我們仔細的討論了 <code>NodePort</code> 各種面向的概念,最後發現其實 <code>NodePort</code> 的規則非常簡單,建立於 <code>ClusterIP</code> 之上。<br>只要能夠掌握 <code>ClusterIP</code> 是如何運作的,回過頭來看 <code>NodePort</code> 就不難理解這整個過程。</p>
<p>最後繼續使用這張圖作為總結,希望大家這時候都能夠順利的看懂這張圖要表達的一切概念<br><img src="https://i.imgur.com/9amwybH.png" alt="Imgur"></p>
</div>
<div class="popular-posts-header">Related Posts</div>
<ul class="popular-posts">
<li class="popular-posts-item">
<div class="popular-posts-title"><a href="/kubernetes-service-ii.html" rel="bookmark">[Kubernetes] How to Implement Kubernetes Service - ClusterIP</a></div>
</li>
<li class="popular-posts-item">
<div class="popular-posts-title"><a href="/kubernetes-service-iiii.html" rel="bookmark">[Kubernetes] How to Implement Kubernetes Service - SessionAffinity</a></div>
</li>
<li class="popular-posts-item">
<div class="popular-posts-title"><a href="/kubernetes-dns-iiii.html" rel="bookmark">[Kubernetes] DNS Setting with Dockerd(原始碼分析下)</a></div>
</li>
<li class="popular-posts-item">
<div class="popular-posts-title"><a href="/introduce-cni-iii.html" rel="bookmark">[Container Network Interface] Implement Your CNI In Golang</a></div>
</li>
<li class="popular-posts-item">
<div class="popular-posts-title"><a href="/k8s-security-11tips-i.html" rel="bookmark">11個保護你 Kubernetes 集群的技巧與觀念(上)</a></div>
</li>
</ul>
<footer class="post-footer">
<div class="post-tags">
<a href="/tags/Linux/" rel="tag"># Linux</a>
<a href="/tags/Kubernetes/" rel="tag"># Kubernetes</a>
<a href="/tags/Iptables/" rel="tag"># Iptables</a>
</div>
<div class="post-nav">
<div class="post-nav-next post-nav-item">
<a href="/kubernetes-service-ii.html" rel="next" title="[Kubernetes] How to Implement Kubernetes Service - ClusterIP">
<i class="fa fa-chevron-left"></i> [Kubernetes] How to Implement Kubernetes Service - ClusterIP
</a>
</div>
<span class="post-nav-divider"></span>
<div class="post-nav-prev post-nav-item">
<a href="/kubernetes-service-iiii.html" rel="prev" title="[Kubernetes] How to Implement Kubernetes Service - SessionAffinity">
[Kubernetes] How to Implement Kubernetes Service - SessionAffinity <i class="fa fa-chevron-right"></i>
</a>
</div>
</div>
</footer>
</div>
</article>
</div>
</div>
<div class="comments" id="comments">
<div id="disqus_thread">
<noscript>Please enable JavaScript to view the comments powered by Disqus.</noscript>
</div>
</div>
</div>
<div class="sidebar-toggle">
<div class="sidebar-toggle-line-wrap">
<span class="sidebar-toggle-line sidebar-toggle-line-first"></span>
<span class="sidebar-toggle-line sidebar-toggle-line-middle"></span>
<span class="sidebar-toggle-line sidebar-toggle-line-last"></span>
</div>
</div>
<aside id="sidebar" class="sidebar">
<div class="sidebar-inner">
<ul class="sidebar-nav motion-element">
<li class="sidebar-nav-toc sidebar-nav-active" data-target="post-toc-wrap">
Table of Contents
</li>
<li class="sidebar-nav-overview" data-target="site-overview-wrap">
Overview
</li>
</ul>
<div class="site-overview-wrap sidebar-panel">
<div class="site-overview">
<div class="site-author motion-element" itemprop="author" itemscope itemtype="http://schema.org/Person">
<img class="site-author-image" itemprop="image"
src="/images/avatar.jpg"
alt="Hwchiu"/>
<p class="site-author-name" itemprop="name">Hwchiu</p>
<div class="site-description motion-element" itemprop="description">kubernetes/SDN/DevOps</div>
</div>
<nav class="site-state motion-element">
<div class="site-state-item site-state-posts">
<a href="/archives/">
<span class="site-state-item-count">157</span>
<span class="site-state-item-name">posts</span>
</a>
</div>
<div class="site-state-item site-state-tags">
<a href="/tags/">
<span class="site-state-item-count">91</span>
<span class="site-state-item-name">tags</span>
</a>
</div>
</nav>
<div class="feed-link motion-element">
<a href="/atom.xml" rel="alternate">
<i class="fa fa-rss"></i>
RSS
</a>
</div>
<div class="links-of-author motion-element">
<span class="links-of-author-item">