大綱
- 同步
- 網(wǎng)絡(luò)
- 數(shù)據(jù)庫
- 分布式
- 性能
- 估算
- 面向?qū)ο?/li>
案例
- 社交網(wǎng)站信息流
- 日志統(tǒng)計
- 網(wǎng)絡(luò)爬蟲
- 電商產(chǎn)品頁面
Concurrency
Thread vs. Process
Consumer and Producer
Blockingqueue
Tracking:（log記錄）
Synchronized（同步）：每次請求直接寫入磁盤
Asynchronized（異步）：先放入緩沖區(qū)闺鲸，每隔一段時間刷新到磁盤上
Network
OSI模型（上到下封包）
- Application Layer（*http1.0/1.1協(xié)議，應(yīng)用層）
- Presentaation Layer（應(yīng)用層）
- Session Layer（會話層）
- Transport Layer（*TCP,UDP協(xié)議禽篱，傳輸層）
- Network Layer（網(wǎng)絡(luò)層）
- Data Link Layer（數(shù)據(jù)連接層）
- Physical Layer（物理層）
Visit URL
What happens after you typed a URL in your browser and pressed return key?
（*尋址與建立鏈接是關(guān)鍵）
- 訪問DNS
- DNS返回網(wǎng)頁服務(wù)器IP地址
- 與網(wǎng)頁服務(wù)器建立連接（三次無首惊完，80端口）
- 瀏覽器與服務(wù)器建立http會話（接受數(shù)據(jù)）
- 瀏覽器解析數(shù)據(jù)，渲染網(wǎng)頁
- 關(guān)閉瀏覽器褒侧，終止http會話
Database
Relational DB vs. KV Store（關(guān)系型數(shù)據(jù)庫VS.KeyValue存儲）
Sharding vs. Clustering（分片VS.集群）
TinyURL：
Store the mapping from shortlink code to full URL.
document:
- code:varchar(8)
- url:varchar(1000)
- created_at:timestamp
- We also need to store the reverse mapping from URL back to code.
Distribute System
How to scala Tiny URL service?(規(guī)亩范簦化Tiny URL服務(wù))
- Stateless frontend servers behind a load balancer（負(fù)載均衡）
- Sharded/replicated database(on shortlink code)（數(shù)據(jù)庫備份化）
- Memcached to scala read traffic（逐層加cache提高性能）
- Spread write load（平分化）
- Locally buffered evevt tracking + async flush to high-throughput messagequeue
- Use a distributed unique IDgenerator(64-bit)
Performance
Cache is KEY!
- Numbers Everyone Should Know
- L1 cache reference 0.5ns
- Branch mispredict 5ns
- L2 cache reference 7ns
- Mutex lock/unlock 25ns
- Main memory reference 100ns
- Compress 1K bytes with Zippy 3,000ns
- Send 2K bytes over 1 Gbps network 20,000ns
- Read 1 MB sequentially from memory 250,000ns
- Round trip within same datacenter 500,000ns
- Disk seek 10,000,000ns
- Read 1 MB sequentially from disk 20,000,000ns
- Send packet CA->Netherlands->CA 150,000,000ns
Estimation
How many piano tuners are there in the entire world?
Tiny URL:How much is total storage?
- URL Length 10-1000 chars.
- Total accumulated URL number 100M
- New URL registrations are on the order 100,000/day(1/sec)
- Redirect requests are on the order of 100M/day(1000/sec)
Design Pattern
23patterns
- MVC(前后端分離坞笙，中間件連接)
- Singleton（保證只有一個實例）
- Factory（工業(yè)框架，生成一系列子類）
- Iterator（迭代器碎赢，提供方法順序訪問聚合對象并且不暴露內(nèi)部特征）
- Decorator（裝飾器低剔，為對象添加額外職責(zé)）
- Facade
