跟讀練習: Top 5 Redis Use Cases - 通過影片學習英語口語

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In this video, we discover the versatility of Redis.
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We'll talk about the top use cases that have been better tested in production at various companies and at various scales.
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Get insights into how Redis solves interesting scalability challenges for us
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and learn why it is a great tool to know well in our system design toolset.
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Let's dive right into it.
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First of all, what is Redis and why do people use it?
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Redis is an in -memory data structure store.
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It is most commonly used as a cache.
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It supports many data structures such as strings, hashes, lists, sets, and sorted sets.
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Redis is known for its speed.
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We made a video to explain why Redis is so fast.
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Look for the link in the description if you would like to watch that video.
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Now let's dive into the top use cases of Redis.
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The number one use case of Redis is caching objects to speed up web applications.
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In this use case, Redis stores frequently requested data in memory.
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It allows the web servers to return frequently accessed data quickly.
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This reduces the load on the database and improves the response time for the application.
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At scale, the cache is distributed among a cluster of Redis servers.
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Sharding is a common technique to distribute and caching load evenly across the cluster.
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Other topics to consider when deploying Redis as a distributed cache include setting a correct TTL
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and handling thundering hurt on cold start.
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Another common use case is to use Redis as a session store to share session data among stateless servers.
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When a user logs into a web application, the session data is stored in Redis,
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along with a unique session ID that is returned to the client as a cookie.
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When a user makes a request to the application, the session ID is included in the request,
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and the stateless web server retrieves the session data from Redis using the ID.
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It is important to note that Redis is an in -memory database.
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The session data stored in Redis will be lost if the Redis server restarts.
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Even though Redis provides persistent options like a snapshot and AOF or append -only file,
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they allow session data to be saved to disk and reloaded into memory in the event of a restart.
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These options often take too long to load to be practical.
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In production, replication is usually used instead.
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In this case, data is replicated to a backup instance.
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In the event of a crash of the main instance, the backup instance is quickly promoted to take over the traffic.
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The next use case is distributed log.
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Distributed logs are used when multiple nodes in an application need to coordinate access to some shared resource.
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Redis is used as a distributed log with its atomic commands like set -nx or set -if -not -exists.
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It allows a caller to set a key only if it does not already exist.
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Here's how it works at a high level.
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Client 1 tries to acquire the log by setting a key with a unique value
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and a timeout using the set -nx command.
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If the key was not already set, the set -nx command returns 1, indicating that the log has been acquired by client 1.
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Client 1 finishes its work and releases the log by deleting the key.
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Now if the key was already set, the set -annex command returns 0, indicating that the log has already been held by another client.
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In this case, client 1 waits and retries the set -annex operation until the log is released by the other client.
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Note that this simple implementation might be good enough for many use cases, but it is not completely fault -tolerant.
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For production use, there are many Redis client libraries that provide high -quality distributed log implementation built right off the box.
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Next up is Ray Limiter.
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Redis can be used as a Ray Limiter by using its increment command on some counters
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and setting expiration times on those counters.
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A very basic
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Ray Limiting algorithm works this way.
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For each incoming request, the request IP or user ID is used as a key.
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The number of requests for the key is incremented using the increment command in Redis.
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The current count is compared to the allowed rate limit.
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If the count is within the rate limit, the request is processed.
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If the count is over the limit, the request is rejected.
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The keys are set to expire after a specific time window, for example, a minute, to reset the cans for the next time window.
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More sophisticated rate limiters, like the leaky bucket algorithm, can also be implemented using Redis.
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The last use case we would like to talk about is gaming leaderboard.
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For most games that are not super high scale, Redis is a delightful way to implement various types of gaming leaderboards.
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Sort of sets are the fundamental data structure that enables this.
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A sort of set is a collection of unique elements, each with a score associated with it.
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The elements are sorted by score.
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This allows for quick retrieval of the elements by score in logarithmic time.
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That's it for our top Redis use cases.
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Redis is very versatile.
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There are many different ways to use it.
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Some features are more better tested than others.
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Our creativity is the limit.
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Use it with care and have fun with it.
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本課的詞彙與口語要點

這節口語課以影片“Top 5 Redis Use Cases”為素材。 影片中反覆出現的詞有:Redis, log, client, session, key。 這段影片共有 75 個句子、937 個單詞可供跟讀。 講話部分時長為 6:16。 說話人語速平穩,每分鐘約 149 個詞,很適合跟讀。 只有 77% 的單詞屬於英語最常用的 3,000 詞,詞彙難度較高。

影片中的重點詞彙

影片中 15 個值得學習的單詞,附發音和釋義:

單詞發音釋義
distribute 動詞/dɪˈstɹɪbjuːt/分配
server 名詞/ˈsɝvɚ/伺服器 /伺服器, 伺服器
cache 名詞/kæʃ/快取 /快取, 快取
element 名詞/ˈɛləmənt/要素
topic 名詞/ˈtɑpɪk/主題 /主題, 話題 /話題
log 名詞/lɔɡ/圓木 /圓木
indicate 動詞/ˈɪndɪˌkeɪt/表明, 表示
database 名詞/ˈdeɪtəˌbeɪs/資料庫 /資料庫
implementation 名詞/ˌɪmplɪmənˈteɪʃən/履行
backup 名詞/ˈbækˌʌp/備份 /備份
implement 動詞/ˈɪmpləmənt/實施 /實施, 執行 /執行
acquire 動詞/əˈkwaɪɚ/獲得 /獲得, 取得
dive 動詞/daɪv/潛水 /潛水
algorithm 名詞/ˈælɡəɹɪðm̩/演算法, 演算法
cluster 名詞/ˈklʌstɚ/串, 叢 /叢

影片中出現的短語動詞

單詞發音釋義
speed up 動詞/spiːdˈʌp/加速, 加快
take over 動詞接管, 接手

影片中的語法

說話人最常用的結構,並附上影片中的原話:

結構影片中的用法
被動語態 be + 過去分詞 — 強調發生了什麼,而不是誰做的is known · is distributed · is stored
現在完成時 have/has + 過去分詞 — 過去發生但與現在仍有關聯的事have been · has been acquired · has already been held

需要注意的發音

  • “th” 音: algorithm /ˈælɡəɹɪðm̩/, thunder /ˈθʌndɚ/, logarithmic /ˌlɒɡəˈɹɪðmɪk/
  • “sh” 和 “zh” 音: cache /kæʃ/, implementation /ˌɪmplɪmənˈteɪʃən/, associate /əˈsoʊʃi.ət/, hash /ˈhæʃ/, expiration /ˌɛk.spɚˈeɪ̯.ʃən/
  • 長單詞——注意重音位置: implementation /ˌɪmplɪmənˈteɪʃən/, associate /əˈsoʊʃi.ət/, fundamental /ˌfʌn.dəˈmɛn.təl/, creativity /kri.eɪˈtɪv.ᵻ.ti/, coordinate /koʊˈɔɹ.dəˌneɪt/

中文母語者容易讀錯的音:

  • /v/ — 不要讀成 /w/,上齒輕觸下唇: server /ˈsɝvɚ/, dive /daɪv/, solve /sɒlv/, discover /dɪˈskʌvə/, creativity /kri.eɪˈtɪv.ᵻ.ti/
  • 詞尾子音 — 要讀清楚,後面不要加母音: distribute /dɪˈstɹɪbjuːt/, cache /kæʃ/, element /ˈɛləmənt/, topic /ˈtɑpɪk/, log /lɔɡ/
  • /r/ 和 /l/ 的區別: algorithm /ˈælɡəɹɪðm̩/, practical /ˈpɹæk.tɪ.kəl/, tolerant /ˈtɑːləɹənt/, replicate /ˈɹɛplɪkeɪt/, logarithmic /ˌlɒɡəˈɹɪðmɪk/

如何用這段影片練習

  1. 先完整聽一遍影片,不要開口,記下不認識的單詞。
  2. 用正常速度逐句跟讀,每句重複到你的節奏與說話人一致為止。
  3. 錄下自己的聲音並與原聲對比,特別注意 distribute, server, cache 這類單詞。

什麼是跟讀法?

跟讀法 (Shadowing) 是一種有科學依據的語言學習技巧,最初開發用於專業口譯員的培訓,並由多語言者Alexander Arguelles博士普及。這個方法簡單而強大:您在聽英語母語原聲的同時立即大聲重複——就像是一個延遲1-2秒緊跟說話者的影子。與被動聽力或語法練習不同,跟讀法強迫您的大腦和口腔肌肉同時處理並模模擬實的講話模式。研究表明它能顯著提高發音準確性,語調,節奏,連讀,聽力理解和口語流利度——使其成為雅思口語備考和真實英語交流最有效的方法之一。

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