BookNote

17 Creating confusion with octal literals In Go, an integer literal starting with 0 is considered an octal integer (base 8). Note the integer literal representations in Golang: Binary - Uses a 0b or 0B prefix (for example, 0b100 is equal to 4 in base 10) Octal - Uses a 0 or 0o prefix (for example, 0o10 is equal 8 in base 10) Hexadecimal - Uses an 0x or 0X prefix (for example, 0xF is equal to 15 in base 10) Imaginary - Uses an i suffix (for example, 3i) 20 Not understanding slice length and capacity In Go, a slice is backed by an array. That means the slice’s data is stored contiguously in an array data structure. A slice also handles the logic of adding an element if the backing array is full or shrinking the backing array if it’s almost empty. ...

30: Ignoring the fact that elements are copied in range loops type account struct { balance float32 } accounts := []account{ {balance: 100.}, {balance: 200.}, {balance: 300.}, } for _, a := range accounts { a.balance += 1000 } // Output: [{100} {200} {300}] In this example, the range loop does not affect the slice’s content. In Go, everything we assign is a copy: If we assign the result of a function returning a struct, it performs a copy of that struct. If we assign the result of a function returning a pointer, it performs a copy of the memory address (an address is 64 bits long on a 64-bit architecture). Solutions: ...

Explore Rust Chapter 3 Types Arrays 不支持动态开数组： // an array of 100 int32 elements, all set to 1 let mut arr1 = [1;100]; // correct let n = 100; let mur arr2 = [1;c]; // error Vectors let mut arr = vec![0,6,4,8,1]; arr.sort() // increasing order arr.sort_by(|a,b| b.cmp(a)) // decreasing order If you know the number of elements a vector will need in advance, instead of Vec::new you can call Vec::with_capacity to create a vector with a buffer large enough to hold them all, right from the start. ...

本章是这本书最酣畅淋漓的一章，涉及到了一致性和共识问题的方方面面，知识点多而不失条理。第一部分先讲了 Linearizability, 为后面的知识点做铺垫。到了 “Ordering Guarantees” 这一小节，从因果关系的带来的 “Happened Before” 的关系开始讲起，讲到了序列号和 Lamport Timestamp，提出来 Lamport Timestamp 的一个缺点：无法在某事件发生时判断是否有冲突，然后引出了全序关系广播，在全序关系广播中又讲到了和 Linearizable 之间的等价关系，最后引出共识算法。太精彩了，值得反复阅读！ Consistency Guarantees Most replicated databases provide at least eventual consistency, which means that if you stop writing to the database and wait for some unspecified length of time, then eventually all read requests will return the same value. A better name for eventual consistency may be convergence, as we expect all replicas to eventually converge to the same value. ...

Faults and Partial Failures An individual computer with good software is usually either fully functional or entirely broken, but not something in between. Thus, computers hide the fuzzy physical reality on which they are implemented and present an idealized system model that operates with mathematical perfection. In a distributed system, there may well be some parts of the system that are broken in some unpredictable way, even though other parts of the system are working fine. This is known as a partial failure. The difficulty is that partial failures are nondeterministic: if you try to do anything involving multiple nodes and the network, it may sometimes work and sometimes unpredictably fail. ...