Apple 要求六月開始的 iOS 程式都必須能在 IPv6-only network 運作

Apple 對 iOS 程式的新政策:「Supporting IPv6-only Networks」。

也就是說,在 ISP 提供 NAT64 的環境下 client 想要連 210.61.183.31 時會連 IPv6 的位置 ::d23d:b71f,ISP 會幫忙 NAT 出去。而client 端的應用程式要能夠在這樣的網路環境下正常運作。

這測試環境沒建過,不知道會遇到什麼問題... @_@

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在 Android 上傳蘋果的 iMessage

PieMessage 是個讓 Android 的人可以傳 iMessage 的專案,不過目前看起來弄得好複雜,需要四個元件:

  • messages.applescript
  • Java Web Server (JWS)
  • OSX Client
  • Android Client

看起來不是 hack protocol,而是一路堆出來的東西 (透過 Apple 的機器 relay),好複雜啊...

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用 Lambda 做 DynamoDB 的 Auto Scaling

AWS Lambda 可以跑 cron job 後應該就不怎麼意外出現了:「Autoscale DynamoDB provisioned capacity using Lambda」。

不像 EC2Auto Scaling,或是 ELB 自己會成長或縮小,DynamoDB 跟其他 AWS 服務不同,雖然可以 scale,但需要自己手動設定 capacity 伸縮。

於是就有人寫了程式 (也就是這個專案),判斷目前的 r/w 用量來決定策略... 有點像是我在處理自家 bandwidth 的搞法,達到某個警戒值就自動增加導去 CDN 的量,或是降低回來 :o

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Blogger (Blogspot) 全面提供 HTTPS 版本

Google 主動啟用了 HTTPS 版本:「Bringing HTTPS to all blogspot domain blogs」,預設會將 HTTPS 開起來:

As part of this launch, we're removing the HTTPS Availability setting. Even if you did not previously turn on this setting, your blogs will have an HTTPS version enabled.

另外提供 HTTPS Redirect 的選項,可以將訪客自動轉到 HTTPS 上:

custom domain 的部份不知道會怎麼提供...

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VENUE Act 對專利蟑螂的反擊

EFF 的「We Can't Keep Waiting: Pass the VENUE Act This Year」這篇寫的還蠻清楚的,VENUE Act (S. 2733) 是一個看起來頗有效的 workaround,先上這個 workaround 降低專利蟑螂的攻勢。

專利蟑螂 (通常是原告) 可以選擇任意一個聯邦法庭提出控告:

As the law stands now, patent owners have almost complete control over which federal district to file a case in. That’s a major problem.

而專利蟑螂會挑選對原告最有利的地區來提出控告,也就是美國德克薩斯東區聯邦地區法院 (U.S. District Court for the Eastern District of Texas),這對被告方很不利:

According to the Mercatus Center and George Mason University, nearly half of all patent cases are filed in the U.S. District Court for the Eastern District of Texas. That’s more than 70 times the average number of patent cases heard in other federal judicial districts.

Respected academics have identified evidence that procedures in the Eastern District of Texas unnecessarily favor plaintiffs and impose significant, unnecessary costs on companies and individuals accused of infringement, however questionable the patents and demands may be.

而 VENUE Act 則是拔掉這個武器,必須在與被告相關的主要地區提告。

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在網頁行動版的 Twitter 上增加快速鍵

現在 Twitter 的網頁版愈做愈慢,於是有不少人在桌機上是用提供給行動裝置的版本瀏覽 (也就是 mobile.twitter.com 這個站),但這個站的功能其實頗陽春。

sindresorhus/refined-twitter 這個專案則在行動版本上面增加了許多快速鍵,在 Google Chrome 上可以透過 Store 安裝:「Refined Twitter」。

之前沒用過行動版的網站,這速度快好多啊...

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Percona 宣佈把 Galera Cluster 納入 Enterprise 與 Premium Support 內

Percona 的「MySQL High Availability: The Road Ahead for Percona and XtraDB Cluster」這篇文章的前面講了很多東西,最主要就是要宣佈把 Galera Cluster 納入 Enterprise/Premium Support:

Today we’re taking the next natural step – we will no longer require customers to purchase Percona XtraDB Cluster as a separate add-on. Percona will include support for XtraDB Cluster and other Galera-based replication technologies in our Enterprise and Premier support levels, as well as our Percona Care and Managed Services subscriptions.

先前是分開賣的,現在包進去了。

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調整 MySQL 的記憶體用量

Percona 的「Best Practices for Configuring Optimal MySQL Memory Usage」這篇給了個蠻不錯的建議:

Don’t allow the mysqld process VSZ exceed 90% of the system memory

ps ax -O vsz | grep mysqld 可以看到 mysqld 吃了多少 VSZ,然後自己除整台機器的記憶體大小,就可以算出來目前吃了多少,然後調整 innodb_buffer_pool_size 的數字。

另外 performance schema 也會有不少影響:

MySQL is workload related – if you have many connections active at the same time that run heavy selects using a lot of memory for sorting or temporary tables, you might need a lot of memory (especially if Performance Schema is enabled). In other cases this amount of memory is minimal. You’ll generally need somewhere between 1 and 10GB for this purpose.

記憶體碎裂問題應該是在調整時就會考慮進去:

Another thing you need to account for is memory fragmentation. Depending on the memory allocation library you’re using (glibc, TCMalloc, jemalloc, etc.), the operating system settings such as Transparent Huge Pages (THP) and workload may show memory usage to grow over time (until it reaches some steady state). Memory fragmentation can also account for 10% or more of additional memory usage.

其實就是沒有一定的定論,在不同的系統上會有不同的反應...

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WordPress.com 的 Elasticsearch

在「State of WordPress.com Elasticsearch Systems 2016」這邊描述他們 Elasticsearch 的架構。

有五個 cluster 打散,有跑 1.3.x 也有 1.7.x。把一般使用者與 VIP 分開,而全站的資料又是一組。另外在 2.3.x 的測試機上跑 en.support.wordpress.com 的資料 (看起來是短時間炸掉沒關係?XD)。

由於是自己生機器出來,所以機器的選擇上用大量的記憶體與 SSD 硬碟來換各種效能:

Typical data server config:
* 96GB RAM with 31GB for ES heap. Remaining gets used for file system caching
* 1-3 TB of SSD per server. In our testing SSDs are very worthwhile.

另外上面還是有疊 cache:

memcache timeouts vary from 30 seconds to 36 hours depending on use case

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CloudFlare 的 Origin CA:保護 CloudFlare 到 Origin 這段的傳輸過程

CloudFlare 推出的 Origin CA 用來保護從 CloudFlare 到 Origin Server 這段的過程:「Introducing CloudFlare Origin CA」,也就是右半部這段:

CloudFlare 把這個新功能包裝得很神,但實際上只是弄個 CA 出來跑而已,僅此而已。

當然,由於他不需要處理 Public CA 的問題,所以有很多在一般 TLS 連線需要做的檢查步驟可以被簡化,藉此達到效能改善,包括了省掉 intermediate certificates、OCSP 以及 SCTs:

With Origin CA certificates, we’ve stripped everything that’s extraneous to communication between our servers and yours to produce the smallest possible certificate and handshake. For example, we have no need to bundle intermediate certificates to assist browsers in building paths to trusted roots; no need to include signed certificate timestamps (SCTs) for purposes of certificate transparency and EV treatment; no need to include links to Certification Practice Statements or other URLs; and no need to listen to Online Certificate Status Protocol (OCSP) responses from third-parties.

進而省下大量的連線成本:

Eliminating these unnecessary components typically found in certificates from public CAs has allowed us to reduce the size of the handshake by up to 70%, from over 4500 bytes in some cases to under 1300.

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