Tag Archives: cache

imgproxy:自動處理圖片的工具

看到「imgproxy: Resize your images instantly and securely」這篇文章,介紹「DarthSim/imgproxy」這個專案,想起很久以前的同事在 PIXNET 弄的 *.pimg.tw 系列服務... imgproxy 可以 resizing,也可以 croping,然後也支援 signature token 機制,感覺是每個大一點的站台都會自己刻一次的服務 XD 整個專案以 Golang 為主,效能應該是不錯... 不過一般前面還是會放 cache 機制 (像是 CDN 之類的服務),而不會把 loading 直接打進來,避免同樣的圖片一直重複計算。

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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 … Continue reading

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Mozilla 的提案「HTTP Immutable Responses」

狀態已經是 Category: Standards Track 了,RFC 8246 的「HTTP Immutable Responses」: The immutable HTTP response Cache-Control extension allows servers to identify resources that will not be updated during their freshness lifetime. This ensures that a client never needs to revalidate a cached … Continue reading

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Quotient filter

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

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

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除了 DNS 的 TTL 外,還有瀏覽器本身的 cache time...

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

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

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

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

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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