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AWS 提供 Hybrid Cloud 環境下 DNS 管理的說明

不知道為什麼出現在 browser tab 上,不知道是哪邊看到的... AWS 放出了一份文件,在講 hybrid cloud 環境下當你同時有一般 IDC 機房,而且使用內部 domain 在管理時,網路與 AWS 打通後要怎麼解決 DNS resolver 的問題:「Hybrid Cloud DNS Solutions for Amazon VPC」。

有些東西在官方的說明文件內都寫過,但是是 AWS 的特殊設計,這邊就會重複說明 XDDD

像是這份文件裡提到 Amazon DNS Server 一定會在 VPC 的 base 位置加二 (舉例來說,10.0.0.0/16 的 VPC,Amazon DNS Server 會在 10.0.0.2):

Amazon DNS Server
The Amazon DNS Server in a VPC provides full public DNS resolution, with additional resolution for internal records for the VPC and customer-defined Route 53 private DNS records.4 The AmazonProvidedDNS maps to a DNS server running on a reserved IP address at the base of the VPC network range, plus two. For example, the DNS Server on a 10.0.0.0/16 network is located at 10.0.0.2. For VPCs with multiple CIDR blocks, the DNS server IP address is located in the primary CIDR block.

在官方文件裡,則是在「DHCP Options Sets」這邊提到一樣的事情:

When you create a VPC, we automatically create a set of DHCP options and associate them with the VPC. This set includes two options: domain-name-servers=AmazonProvidedDNS, and domain-name=domain-name-for-your-region. AmazonProvidedDNS is an Amazon DNS server, and this option enables DNS for instances that need to communicate over the VPC's Internet gateway. The string AmazonProvidedDNS maps to a DNS server running on a reserved IP address at the base of the VPC IPv4 network range, plus two. For example, the DNS Server on a 10.0.0.0/16 network is located at 10.0.0.2. For VPCs with multiple IPv4 CIDR blocks, the DNS server IP address is located in the primary CIDR block.

另外也還是有些東西在官方的說明文件內沒看過,像是講到 Elastic Network Interface (ENI) 對 Amazon DNS Server 是有封包數量限制的;這點我沒在官方文件上找到,明顯在量太大的時候會中獎,然後開 Support Ticket 才會發現的啊 XDDD:

Each network interface in an Amazon VPC has a hard limit of 1024 packets that it can send to the Amazon Provided DNS server every second.

Anyway... 這份文件裡面提供三種解法:

  • Secondary DNS in a VPC,直接用程式抄一份到 Amazon Route 53 上,這樣 Amazon DNS Server 就可以直接看到了,這也是 AWS 在一般情況下比較推薦的作法。
  • Highly Distributed Forwarders,每台 instance 都跑 Unbound,然後針對不同的 domain 導開,這樣可以有效避開單一 ENI 對 Amazon DNS Server 的封包數量限制,但缺點是這樣的設計通常會需要像是 Puppet 或是 Chef 之類的軟體管理工具才會比較好設定。
  • Zonal Forwarders Using Supersede,就是在上面架設一組 Unbound 伺服器集中管理,透過 DHCP 設定讓 instance 用。但就要注意量不能太大,不然 ENI 對 Amazon DNS Server 的限制可能會爆掉 XD

都可以考慮看看...

AWS CodeDeploy 支援單機測試模式

AWS CodeDeploy 本來是個 client-server 服務架構,但現在讓你方便在本機測試,支援直接在本機下指令 deploy (不需要 server) 看看發生什麼狀況:「AWS CodeDeploy Supports Local Testing and Debugging」。

Previously, if you wanted to test and debug your deployment, you had to fully configure AWS CodeDeploy. This includes installing the agent on the target host, creating a CodeDeploy Application, and creating a CodeDeploy Deployment Group.

Now, you can execute a deployment directly on a local machine or instance where the CodeDeploy agent is installed. If your deployment has errors, you can easily find and view the error logs by accessing the agent with your terminal. This makes it faster and easier to find and fix bugs before configuring CodeDeploy for production.

是有很多人一直中獎然後跟 AWS 反應嗎... XD

HAProxy 1.8 多了好多東西...

雖然大家都在用 nginx,但 HAProxy 還是在努力:「What’s New in HAProxy 1.8」。

這個版本多了好多東西...

  • 支援 HTTP/2。(終於...)
  • Multithreading 架構。(health check 總算是一隻了 XD 不會開八隻就打八次...)
  • DNS 的 Service Discovery。
  • TLS 1.3 0-RTT。(居然支援了...)

有種突然醒過來的感覺...

被告了就把證據滅掉... XD

這個好讚,在告知安全漏洞後還是不更新選舉用伺服器,於是就被告了,而在被告以後選舉單位就把證據給幹掉 XD:「Georgia election server wiped after lawsuit filed」。

The lawsuit, filed on July 3 by a diverse group of election reform advocates, aims to force Georgia to retire its antiquated and heavily criticized election technology. The server in question, which served as a statewide staging location for key election-related data, made national headlines in June after a security expert disclosed a gaping security hole that wasn’t fixed six months after he reported it to election authorities.

然後現在還找不到是誰下令幹掉的...

It’s not clear who ordered the server’s data irretrievably erased.

執政者用的方法都差不多...

Heimdall Data:自動 Cache RDBMS 資料增加效能

看到 AWS 的「Automating SQL Caching for Amazon ElastiCache and Amazon RDS」這篇裡面介紹了 Heimdall Data – SQL caching and performance optimization 這個產品。

從官網的介紹也可以看出來是另外疊一層 proxy,但自動幫你處理 cache invalidation 的問題:

But what makes Heimdall Data unique in industry is its auto-cache AND auto-invalidation capability. Our machine learning algorithms determine what queries to cache while invalidating to ensure maximum performance and data integrity.

看起來支援了四個蠻常見的 RDBMS:

Heimdall Data supports most all relational database (e.g. MySQL, Postgres, Amazon RDS, Oracle, SQL Server, MariaDB).

看起來是一個花錢直接買效能的方案... 不過 cache invalidation 的部分不知道要怎麼跨機器做,在 FAQ 沒看到 cluster 情況下會怎麼解決。

Apache 的 Optionsbleed

Apache 也出了類似 Heartbleed 的包:「Apache bug leaks contents of server memory for all to see—Patch now」,原文出自「Optionsbleed - HTTP OPTIONS method can leak Apache's server memory」。

這掛上 CVE-2017-9798 了,影響版本包括了:

This affects the Apache HTTP Server through 2.2.34 and 2.4.x through 2.4.27.

發生在對 OPTIONS 處理出問題:

Optionsbleed is a use after free error in Apache HTTP that causes a corrupted Allow header to be constructed in response to HTTP OPTIONS requests. This can leak pieces of arbitrary memory from the server process that may contain secrets. The memory pieces change after multiple requests, so for a vulnerable host an arbitrary number of memory chunks can be leaked.

就... 更新吧 @_@

Google 放棄對海外伺服器搜索票的抵抗了...

先前美國政府透過搜索票,要求各雲端廠商提供海外伺服器的資料而引起話題 (像是先前 Microsoft 往上打官司抵抗:「Does US have right to data on overseas servers? We’re about to find out」),而現在看起來 Google 打算放棄掙扎了:「Google stops challenging most US warrants for data on overseas servers」。

Google has quietly stopped challenging most search warrants from US judges in which the data requested is stored on overseas servers, according to the Justice Department.

Microsoft 這邊有些不錯的進展,成功在巡迴庭擋下:

Microsoft convinced the New York-based 2nd US Circuit Court of Appeals—which has jurisdiction over Connecticut, New York, and Vermont—that US search-and-seizure law does not require compliance with a warrant to turn over e-mail stored on its servers in Ireland.

不過沒看到 AWS 相關的消息,感覺不妙...

Cloudflare 的 F-Root

Cloudflare 從三月底開始跟 ISC 簽約合作,服務 F-Root 這個 DNS Service (f.root-servers.net):「Delivering Dot」。

Since March 30, 2017, Cloudflare has been providing DNS Anycast service as additional F-Root instances under contract with ISC (the F-Root operator).

Linode 東京的機器上面可以看出來 www.cloudflare.com 走的路徑跟 f.root-server.net 相同:

gslin@one [~] [22:49] mtr -4 --report www.cloudflare.com
Start: Tue Sep 12 22:49:29 2017
HOST: one.abpe.org                Loss%   Snt   Last   Avg  Best  Wrst StDev
  1.|-- 139.162.65.2               0.0%    10    0.6   0.6   0.5   0.6   0.0
  2.|-- 139.162.64.5               0.0%    10    2.0   1.1   0.6   2.5   0.5
  3.|-- 139.162.64.8               0.0%    10    0.7   1.0   0.7   2.1   0.3
  4.|-- 218.100.6.62               0.0%    10    0.8   0.8   0.8   1.0   0.0
  5.|-- 198.41.215.162             0.0%    10    0.7   0.7   0.7   0.8   0.0
gslin@one [~] [22:49] mtr -4 --report f.root-servers.net
Start: Tue Sep 12 22:49:46 2017
HOST: one.abpe.org                Loss%   Snt   Last   Avg  Best  Wrst StDev
  1.|-- 139.162.65.3               0.0%    10    0.5   0.6   0.5   0.6   0.0
  2.|-- 139.162.64.7               0.0%    10    0.7   0.7   0.6   0.8   0.0
  3.|-- 139.162.64.8               0.0%    10    0.7   0.7   0.6   0.8   0.0
  4.|-- 218.100.6.62               0.0%    10    0.8   0.8   0.8   0.8   0.0
  5.|-- f.root-servers.net         0.0%    10    0.8   0.8   0.7   0.8   0.0

而且也可以從監控發現,f.root-servers.net 的效能變好:

Using RIPE atlas probe measurements, we can see an immediate performance benefit to the F-Root server, from 8.24 median RTT to 4.24 median RTT.

DNS query 的量也大幅增加:

而且之後也會隨著 Cloudflare 的 PoP 增加而愈來愈快... 在原文的 comment 也提到了 Cloudflare 也有打算跟其他的 Root Server 合作,所以看起來會讓整個 infrastructure 愈來愈快而且穩定。

另外這也代表台灣在本島也會直接連到 F-Root 了,不過 HiNet 自己也有 F-Root,所以 HiNet 的部份就沒什麼差...

InnoDB 與 MyRocks 之間的取捨

MyRocks 的主要作者 Mark Callaghan 整理了一篇關於大台機器下,資料可以放到記憶體內的效能比較:「In-memory sysbench, a larger server and contention - part 1」。

這其實才是一般會遇到的情況:當事業夠大時,直接花錢買 1TB RAM + 數片 PCI-E SSD 的機器用錢換效能... (主要應該會在記憶體花不少錢,剛剛查了一下,現在白牌的 server 一台大約七十萬就可以擺平?兩台做 HA 也才一百四十萬,對有這個規模的單位來說通常不是大問題...)

而三種不同的 case 裡面,最後這個應該是最接近真實情況的:

可以看到 InnoDB 在幾乎所有項目都還是超越 MyRocks (只有 random-points 與 insert-only 輸)。

不知道後續的開發能量還會有多少... (因為 Facebook 的用法跟一般情況不一樣)

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