Tag Archives: cache

Quotient filter

Posted on August 9, 2017 by Gea-Suan Lin

之前有提過「Cuckoo Filter：比 Bloom Filter 多了 Delete」，最近在「A general purpose counting filter: making every bit count」這邊看到 Quotient filter，也是類似 Bloom filter 的資料結構，但想要解決更多問題。 一般的 Bloom filter (BF) 會有這些問題： The inability to delete items Poor scaling out of RAM The inability to resize dynamically The … Continue reading →

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Telegram 使用 CDN 加速下載

Posted on July 25, 2017 by Gea-Suan Lin

Telegram 說明他們將會使用 CDN 加速：「More Speed and Security!」。 資料在 CDN 的節點上是加密的，金鑰需要透過 Telegram 的 key server 提供： While these caching nodes are only used to temporarily store public media (imagine Telegram versions of superpopular YouTube hits), all data that goes through them … Continue reading →

Posted in CDN, Computer, Murmuring, Network, Privacy, Security, Service, Software, WWW | Tagged , , , , , , , , , , , , , | 1 Comment

除了 DNS 的 TTL 外，還有瀏覽器本身的 cache time...

Posted on July 1, 2017 by Gea-Suan Lin

在看「Reviewing Fastly’s New Approach To Load Balancing In The Cloud」這篇的時候被提醒： However, most browsers have implemented their own caching layer that can override the TTL specified by the server. In fact, some browsers cache for 5-10 minutes, which is an eternity … Continue reading →

Posted in Browser, Computer, DNS, Firefox, GoogleChrome, IE, Murmuring, Network, Software, WWW | Tagged , , , , | 1 Comment

Web Cache Deception Attack

Posted on June 9, 2017 by Gea-Suan Lin

在「How (Not) to Control Your CDN」這邊看到了「Web Cache Deception Attack」這個攻擊方式。 攻擊的手法是利用網站會把 /user/personal-info/foo.css 與 /user/personal-info 視為一樣的內容時，配合 CDN 或是 reverse proxy server 會把 .css 設定無差異 cache 時，就可以在 cache server (cache edge) 取得使用者的敏感資料。 這主要是 url routing 的條件放太寬造成的。 另外 Mark Nottingham 還建議 cache 應該在 origin … Continue reading →

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MySQL 總算要拔掉 mysql_query_cache 了

Posted on May 31, 2017 by Gea-Suan Lin

半官方的 MySQL blog 上宣佈了拔掉 mysql_query_cache 的計畫：「MySQL 8.0: Retiring Support for the Query Cache」。 作者開頭引用了 ProxySQL 的人對 MySQL Query Cache 的說明： Although MySQL Query Cache was meant to improve performance, it has serious scalability issues and it can easily become a … Continue reading →

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Reddit 在處理 Page View 的方式

Posted on May 28, 2017 by Gea-Suan Lin

Reddit 說明了他們如何處理 pageview：「View Counting at Reddit」。 以 Reddit 的規模有提到兩個重點，第一個在善用 Redis 的 HyperLogLog 這個資料結構，當量大的時候其實可以允許有微小的誤差： The amount of memory varies per implementation, but in the case of this implementation, we could count over 1 million IDs using just 12 kilobytes of space, … Continue reading →

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超越線性成長的資料庫架構

Posted on April 25, 2017 by Gea-Suan Lin

標題取自 Percona 的「Better Than Linear Scaling」。 其實是因為機器數量增加，而且有妥善規劃，使得 cache 的 hit rate 上升而讓整體效率變好 (也就是 1 + 1 > 2)。 不只在 database 上會發生，在其他系統上其實會有類似的情況，剛好看到覺得很懷念 XD

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Amazon DynamoDB Accelerator (DAX)

Posted on April 20, 2017 by Gea-Suan Lin

DynamoDB 推出的新架構，在系統上幫忙處理 cache：「Amazon DynamoDB Accelerator (DAX) – In-Memory Caching for Read-Intensive Workloads」。 DAX 跟現有的 DynamoDB API 相容： DAX is a fully managed caching service that sits (logically) in front of your DynamoDB tables. It operates in write-through mode, and is … Continue reading →

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eBay 把 MongoDB 當 cache layer 的用法...

Posted on February 2, 2017 by Gea-Suan Lin

在「How eBay’s Shopping Cart used compression techniques to solve network I/O bottlenecks」這邊 eBay 描述了他們怎麼解決在 MongoDB 上遇到的問題，不過我看的是他們怎麼用 MongoDB，而不是這次解決的問題： It’s easier to think of the MongoDB layer as a “cache” and the Oracle store as the persistent copy. If there’s a cache … Continue reading →

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kernel.org 將要關閉 FTP 服務

Posted on January 30, 2017 by Gea-Suan Lin

kernel.org 將關閉 FTP 服務：「Shutting down FTP services」。 三月將關閉 ftp://ftp.kernel.org/，而 12 月將關閉 ftp://mirrors.kernel.org/。現在透過 HTTP 更新已經是主流了，對於 firewall 設定與 cache 都有比較好的支援。

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