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crazylion lee

GitHub - jtesta/ssh-mitm: SSH man-in-the-middle tool - 0 views

github.com/ssh-mitm

ssh MIT

shared by crazylion lee on 06 Nov 17 - No Cached
  • crazylion lee on 06 Nov 17
     
    "SSH man-in-the-middle tool"
crazylion lee

GitHub - atech/postal: - 0 views

github.com/postal

mail

shared by crazylion lee on 06 Nov 17 - No Cached
  • crazylion lee on 06 Nov 17
     
    "
crazylion lee

Server.js - server.js - 0 views

serverjs.io

nodejs express framework

shared by crazylion lee on 05 Nov 17 - No Cached
  • crazylion lee on 05 Nov 17
     
    "server.js for Node"
crazylion lee

GitHub - tidwall/evio: Fast event-loop networking for Go - 0 views

github.com/evio

go network io

shared by crazylion lee on 05 Nov 17 - No Cached
  • crazylion lee on 05 Nov 17
     
    "evio is an event loop networking framework that is fast and small. It makes direct epoll and kqueue syscalls rather than using the standard Go net package, and works in a similar manner as libuv and libevent."
張 旭

plataformatec/simple_form - 0 views

github.com/...simple_form

rails gem form html

shared by 張 旭 on 29 Aug 16 - No Cached
  • The basic goal of Simple Form is to not touch your way of defining the layout
  • by default contains label, hints, errors and the input itself
  • Simple Form acts as a DSL and just maps your input type (retrieved from the column definition in the database) to a specific helper method.
  • ...68 more annotations...
  • can overwrite the default label by passing it to the input method
  • configure the html of any of them
  • disable labels, hints or error
  • add a hint, an error, or even a placeholder
  • add an inline label
  • pass any html attribute straight to the input, by using the :input_html option
  • use the :defaults option in simple_form_fo
  • Simple Form generates a wrapper div around your label and input by default, you can pass any html attribute to that wrapper as well using the :wrapper_html option,
  • By default all inputs are required
  • the required property of any input can be overwritten
  • Simple Form will look at the column type in the database and use an appropriate input for the column
  • lets you overwrite the default input type it creates
  • can also render boolean attributes using as: :select to show a dropdown.
  • give the :disabled option to Simple Form, and it'll automatically mark the wrapper as disabled with a CSS class
  • Simple Form accepts same options as their corresponding input type helper in Rails
  • Any extra option passed to these methods will be rendered as html option.
  • use label, hint, input_field, error and full_error helpers
  • to strip away all the div wrappers around the <input> field
  • is to use f.input_field
  • changing boolean_style from default value :nested to :inline
  • overriding the :collection option
  • Collections can be arrays or ranges, and when a :collection is given the :select input will be rendered by default
  • Other types of collection are :radio_buttons and :check_boxes
  • label_method
  • value_method
  • Both of these options also accept lambda/procs
  • define a to_label method on your model as Simple Form will search for and use :to_label as a :label_method first if it is found
  • create grouped collection selects, that will use the html optgroup tags
  • Grouped collection inputs accept the same :label_method and :value_method options
  • group_method
  • group_label_method
  • configured with a default value to be used on the site through the SimpleForm.country_priority and SimpleForm.time_zone_priority helpers.
  • association
  • association
  • render a :select input for choosing the :company, and another :select input with :multiple option for the :roles
  • all options available to :select, :radio_buttons and :check_boxes are also available to association
  • declare different labels and values
  • the association helper is currently only tested with Active Record
  • f.input
  • f.select
  • create a <button> element
  • simple_fields_for
  • Creates a collection of radio inputs with labels associated
  • Creates a collection of checkboxes with labels associated
  • collection_radio_buttons
  • collection_check_boxes
  • associations in your model
  • Role.all
  • the html element you will get for each attribute according to its database definition
  • redefine existing Simple Form inputs by creating a new class with the same name
  • Simple Form uses all power of I18n API to lookup labels, hints, prompts and placeholders
  • specify defaults for all models under the 'defaults' key
  • Simple Form will always look for a default attribute translation under the "defaults" key if no specific is found inside the model key
  • Simple Form will fallback to default human_attribute_name from Rails when no other translation is found for labels.
  • Simple Form will only do the lookup for options if you give a collection composed of symbols only.
  • "Add %{model}"
  • translations for labels, hints and placeholders for a namespaced model, e.g. Admin::User, should be placed under admin_user, not under admin/user
  • This difference exists because Simple Form relies on object_name provided by Rails' FormBuilder to determine the translation path for a given object instead of i18n_key from the object itself.
  • configure how your components will be rendered using the wrappers API
  • optional
  • unless_blank
  • By default, Simple Form will generate input field types and attributes that are supported in HTML5
  • The HTML5 extensions include the new field types such as email, number, search, url, tel, and the new attributes such as required, autofocus, maxlength, min, max, step.
  • If you want to have all other HTML 5 features, such as the new field types, you can disable only the browser validation
  • add novalidate to a specific form by setting the option on the form itself
  • the Simple Form configuration file
  • passing the html5 option
  • as: :date, html5: true
張 旭

循序漸進理解 HTTP Cache 機制 | TechBridge 技術共筆部落格 - 0 views

blog.techbridge.cc/...cache-introduction

http web cache performance

shared by 張 旭 on 25 Sep 17 - No Cached
  • 減少資源的損耗
  • Cache，台灣翻譯叫做快取，中國翻譯叫做緩存
  • 用到這些資訊的時候，都可以用極快的速度撈出來，而不是再到資料庫裡面重新算一次
  • ...9 more annotations...
  • Server side 的 Cache，藉由把 Database 的資料撈出來之後存到別的地方達成。
  • Server 跟瀏覽器之間的 Cache 機制
  • 瀏覽器會檢視「現在的時間」是否有超過這個 Expires
  • HTTP 1.1 有一個新的 header 出現了，叫做：Cache-Control
  • max-age設定成31536000秒，也就是 365 天的意思
  • max-age會蓋過Expires。因此現在的快取儘管兩個都會放，但其實真正會用到的是max-age。
  • 過期了不代表不能用
  • 在 Server 傳送 Response 的時候，可以多加一個Last-Modified的 Header，表示這個檔案上一次更改是什麼時候。
  • 用If-Modified-Since來跟 Server 指定拿取：某個時間點以後有更改的資料。
crazylion lee

GitHub - joyieldInc/predixy: A high performance and full features proxy for redis, supp... - 0 views

github.com/predixy

redis proxy

shared by crazylion lee on 29 Aug 17 - No Cached
  • crazylion lee on 29 Aug 17
     
    "A high performance and full features proxy for redis, support redis sentinel and redis cluster"
張 旭

Deploying Rails Apps, Part 6: Writing Capistrano Tasks - Vladi Gleba - 0 views

vladigleba.com/...art-6-writing-capistrano-tasks

rails capistrano deploy ruby docker devops

shared by 張 旭 on 23 Aug 17 - No Cached
  • we can write our own tasks to help us automate various things.
  • organizing all of the tasks here under a namespace
  • upload a file from our local computer.
  • ...27 more annotations...
  • learn about is SSHKit and the various methods it provides
  • SSHKit was actually developed and released with Capistrano 3, and it’s basically a lower-level tool that provides methods for connecting and interacting with remote servers
  • on(): specifies the server to run on
  • within(): specifies the directory path to run in
  • with(): specifies the environment variables to run with
  • run on the application server
  • within the path specified
  • with certain environment variables set
  • execute(): the workhorse that runs the commands on your server
  • upload(): uploads a file from your local computer to your remote server
  • capture(): executes a command and returns its output as a string
    • 張 旭
      張 旭 on 23 Aug 17
       
      capture 是跑在遠端伺服器上
  • upload() has the bang symbol (!) because that’s how it’s defined in SSHKit, and it’s just a convention letting us know that the method will block until it finishes.
  • But in order to ensure rake runs with the proper environment variables set, we have to use rake as a symbol and pass db:seed as a string
  • This format will also be necessary whenever you’re running any other Rails-specific commands that rely on certain environment variables being set
  • I recommend you take a look at SSHKit’s example page to learn more
  • make sure we pushed all our local changes to the remote master branch
  • run this task before Capistrano runs its own deploy task
  • actually creates three separate tasks
  • I created a namespace called deploy to contain these tasks since that’s what they’re related to.
  • we’re using the callbacks inside a namespace to make sure Capistrano knows which tasks the callbacks are referencing.
  • custom recipe (a Capistrano term meaning a series of tasks)
  • /shared: holds files and directories that persist throughout deploys
  • When you run cap production deploy, you’re actually calling a Capistrano task called deploy, which then sequentially invokes other tasks
  • your favorite browser (I hope it’s not Internet Explorer)
  • Deployment is hard and takes a while to sink in.
  • the most important thing is to not get discouraged
  • I didn’t want other people going through the same thing
張 旭

elabs/pundit: Minimal authorization through OO design and pure Ruby classes - 0 views

github.com/pundit

authorization rails ruby gem library

shared by 張 旭 on 20 Mar 16 - No Cached
  • The class implements some kind of query method
  • Pundit will call the current_user method to retrieve what to send into this argumen
  • put these classes in app/policies
  • ...49 more annotations...
  • in leveraging regular Ruby classes and object oriented design patterns to build a simple, robust and scaleable authorization system
  • map to the name of a particular controller action
  • In the generated ApplicationPolicy, the model object is called record.
  • record
  • authorize
  • authorize would have done something like this: raise "not authorized" unless PostPolicy.new(current_user, @post).update?
  • pass a second argument to authorize if the name of the permission you want to check doesn't match the action name.
  • you can chain it
  • authorize returns the object passed to it
  • the policy method in both the view and controller.
  • have some kind of view listing records which a particular user has access to
  • ActiveRecord::Relation
  • Instances of this class respond to the method resolve, which should return some kind of result which can be iterated over.
  • scope.where(published: true)
    • 張 旭
      張 旭 on 29 Aug 16
       
      我想大概的意思就是：如果是 admin 可以看到全部 post，如果不是只能看到 published = true 的 post
  • use this class from your controller via the policy_scope method:
  • PostPolicy::Scope.new(current_user, Post).resolve
  • policy_scope(@user.posts).each
  • This method will raise an exception if authorize has not yet been called.
  • verify_policy_scoped to your controller. This will raise an exception in the vein of verify_authorized. However, it tracks if policy_scope is used instead of authorize
  • need to conditionally bypass verification, you can use skip_authorization
  • skip_policy_scope
  • Having a mechanism that ensures authorization happens allows developers to thoroughly test authorization scenarios as units on the policy objects themselves.
  • Pundit doesn't do anything you couldn't have easily done yourself. It's a very small library, it just provides a few neat helpers.
  • all of the policy and scope classes are just plain Ruby classes
  • rails g pundit:policy post
  • define a filter that redirects unauthenticated users to the login page
  • fail more gracefully
  • raise Pundit::NotAuthorizedError, "must be logged in" unless user
  • having rails handle them as a 403 error and serving a 403 error page.
  • config.action_dispatch.rescue_responses["Pundit::NotAuthorizedError"] = :forbidden
  • with I18n to generate error messages
  • retrieve a policy for a record outside the controller or view
  • define a method in your controller called pundit_user
  • Pundit strongly encourages you to model your application in such a way that the only context you need for authorization is a user object and a domain model that you want to check authorization for.
  • Pundit does not allow you to pass additional arguments to policies
  • authorization is dependent on IP address in addition to the authenticated user
  • create a special class which wraps up both user and IP and passes it to the policy.
  • set up a permitted_attributes method in your policy
  • policy(@post).permitted_attributes
  • permitted_attributes(@post)
  • Pundit provides a convenient helper method
  • permit different attributes based on the current action,
  • If you have defined an action-specific method on your policy for the current action, the permitted_attributes helper will call it instead of calling permitted_attributes on your controller
  • If you don't have an instance for the first argument to authorize, then you can pass the class
  • restart the Rails server
  • Given there is a policy without a corresponding model / ruby class, you can retrieve it by passing a symbol
  • after_action :verify_authorized
  • It is not some kind of failsafe mechanism or authorization mechanism.
  • Pundit will work just fine without using verify_authorized and verify_policy_scoped
  • crazylion lee on 20 Mar 16
     
    "Minimal authorization through OO design and pure Ruby classes"
張 旭

我必须得告诉大家的MySQL优化原理 - 简书 - 0 views

www.jianshu.com/d7665192aaaf

mysql performance system

shared by 張 旭 on 19 Aug 17 - No Cached
  • 很多的查询优化工作实际上就是遵循一些原则让MySQL的优化器能够按照预想的合理方式运行而已
  • MySQL客户端/服务端通信协议是“半双工”的：在任一时刻，要么是服务器向客户端发送数据，要么是客户端向服务器发送数据，这两个动作不能同时发生。
  • 当查询语句很长的时候，需要设置max_allowed_packet参数。
  • ...70 more annotations...
  • 如果查询实在是太大，服务端会拒绝接收更多数据并抛出异常
  • 服务器响应给用户的数据通常会很多，由多个数据包组成
  • 减小通信间数据包的大小和数量是一个非常好的习惯
  • 查询中尽量避免使用SELECT *以及加上LIMIT限制
  • 在解析一个查询语句前，如果查询缓存是打开的，那么MySQL会检查这个查询语句是否命中查询缓存中的数据。
  • 两个查询在任何字符上的不同（例如：空格、注释），都会导致缓存不会命中。
  • MySQL将缓存存放在一个引用表
  • 如果查询中包含任何用户自定义函数、存储函数、用户变量、临时表、mysql库中的系统表，其查询结果 都不会被缓存。
  • MySQL的查询缓存系统会跟踪查询中涉及的每个表，如果这些表（数据或结构）发生变化，那么和这张表相关的所有缓存数据都将失效。
  • 在任何的写操作时，MySQL必须将对应表的所有缓存都设置为失效。
  • 查询缓存对系统的额外消耗也不仅仅在写操作，读操作也不例外
  • 任何的查询语句在开始之前都必须经过检查，即使这条SQL语句永远不会命中缓存
  • 如果查询结果可以被缓存，那么执行完成后，会将结果存入缓存，也会带来额外的系统消耗
  • 并不是什么情况下查询缓存都会提高系统性能，缓存和失效都会带来额外消耗
  • 用多个小表代替一个大表
  • 批量插入代替循环单条插入
  • 合理控制缓存空间大小
  • 可以通过SQL_CACHE和SQL_NO_CACHE来控制某个查询语句是否需要进行缓存
  • 不要轻易打开查询缓存，特别是写密集型应用
  • 将query_cache_type设置为DEMAND，这时只有加入SQL_CACHE的查询才会走缓存，其他查询则不会，这样可以非常自由地控制哪些查询需要被缓存。
  • 预处理则会根据MySQL规则进一步检查解析树是否合法。比如检查要查询的数据表和数据列是否存在等等。
  • 一条查询可以有很多种执行方式，最后都返回相应的结果。优化器的作用就是找到这其中最好的执行计划。
  • 查询当前会话的last_query_cost的值来得到其计算当前查询的成本。
  • 尝试预测一个查询使用某种执行计划时的成本
  • 有非常多的原因会导致MySQL选择错误的执行计划
  • MySQL值选择它认为成本小的，但成本小并不意味着执行时间短
  • 提前终止查询（比如：使用Limit时，查找到满足数量的结果集后会立即终止查询）
  • 找某列的最小值，如果该列有索引，只需要查找B+Tree索引最左端，反之则可以找到最大值
  • 在完成解析和优化阶段以后，MySQL会生成对应的执行计划，查询执行引擎根据执行计划给出的指令逐步执行得出结果。
  • 查询过程中的每一张表由一个handler实例表示。
  • MySQL在查询优化阶段就为每一张表创建了一个handler实例，优化器可以根据这些实例的接口来获取表的相关信息
  • 即使查询不到数据，MySQL仍然会返回这个查询的相关信息，比如改查询影响到的行数以及执行时间等等。
  • 结果集返回客户端是一个增量且逐步返回的过程
  • 整型就比字符操作代价低，因而会使用整型来存储ip地址，使用DATETIME来存储时间，而不是使用字符串。
  • 如果计划在列上创建索引，就应该将该列设置为NOT NULL
  • UNSIGNED表示不允许负值，大致可以使正数的上限提高一倍。
  • 没有太大的必要使用DECIMAL数据类型。即使是在需要存储财务数据时，仍然可以使用BIGINT
  • 大表ALTER TABLE非常耗时
  • MySQL执行大部分修改表结果操作的方法是用新的结构创建一个张空表，从旧表中查出所有的数据插入新表，然后再删除旧表
  • 索引是提高MySQL查询性能的一个重要途径，但过多的索引可能会导致过高的磁盘使用率以及过高的内存占用，从而影响应用程序的整体性能。
  • 索引是指B-Tree索引，它是目前关系型数据库中查找数据最为常用和有效的索引，大多数存储引擎都支持这种索引
  • B+Tree中的B是指balance，意为平衡。
  • 平衡二叉树首先需要符合二叉查找树的定义，其次必须满足任何节点的两个子树的高度差不能大于1。
  • 索引往往以索引文件的形式存储的磁盘上
  • 如何减少查找过程中的I/O存取次数？
  • 减少树的深度，将二叉树变为m叉树（多路搜索树），而B+Tree就是一种多路搜索树。
  • 页是计算机管理存储器的逻辑块，硬件及OS往往将主存和磁盘存储区分割为连续的大小相等的块
  • B+Tree为了保持平衡，对于新插入的值需要做大量的拆分页操作，而页的拆分需要I/O操作，为了尽可能的减少页的拆分操作，B+Tree也提供了类似于平衡二叉树的旋转功能。
  • 在多数情况下，在多个列上建立独立的索引并不能提高查询性能。理由非常简单，MySQL不知道选择哪个索引的查询效率更好
  • 当出现多个索引做联合操作时（多个OR条件），对结果集的合并、排序等操作需要耗费大量的CPU和内存资源，特别是当其中的某些索引的选择性不高，需要返回合并大量数据时，查询成本更高。
  • explain时如果发现有索引合并（Extra字段出现Using union），应该好好检查一下查询和表结构是不是已经是最优的
  • 索引选择性是指不重复的索引值和数据表的总记录数的比值
  • 唯一索引的选择性是1，这时最好的索引选择性，性能也是最好的。
  • 如果一个索引包含或者说覆盖所有需要查询的字段的值，那么就没有必要再回表查询，这就称为覆盖索引。
  • 对结果集进行排序的操作
  • 按照索引顺序扫描得出的结果自然是有序的
  • 如果explain的结果中type列的值为index表示使用了索引扫描来做排序。
  • 在设计索引时，如果一个索引既能够满足排序，有满足查询，是最好的。
  • 比如有一个索引(A,B)，再创建索引(A)就是冗余索引。
  • 对于非常小的表，简单的全表扫描更高效。对于中到大型的表，索引就非常有效。对于超大型的表，建立和维护索引的代价随之增长，这时候其他技术也许更有效，比如分区表。
  • explain后再提测是一种美德。
  • 如果要统计行数，直接使用COUNT(*)，意义清晰，且性能更好。
  • 执行EXPLAIN并不需要真正地去执行查询，所以成本非常低。
  • 确保ON和USING字句中的列上有索引。在创建索引的时候就要考虑到关联的顺序
  • 确保任何的GROUP BY和ORDER BY中的表达式只涉及到一个表中的列，这样MySQL才有可能使用索引来优化
  • MySQL关联执行的策略非常简单，它对任何的关联都执行嵌套循环关联操作，即先在一个表中循环取出单条数据，然后在嵌套循环到下一个表中寻找匹配的行，依次下去，直到找到所有表中匹配的行为为止。然后根据各个表匹配的行，返回查询中需要的各个列。
  • 最外层的查询是根据A.xx列来查询的，A.c上如果有索引的话，整个关联查询也不会使用。再看内层的查询，很明显B.c上如果有索引的话，能够加速查询，因此只需要在关联顺序中的第二张表的相应列上创建索引即可。
  • MySQL处理UNION的策略是先创建临时表，然后再把各个查询结果插入到临时表中，最后再来做查询。
  • 要使用UNION ALL，如果没有ALL关键字，MySQL会给临时表加上DISTINCT选项，这会导致整个临时表的数据做唯一性检查，这样做的代价非常高。
  • 尽可能不要使用存储过程
張 旭

RolifyCommunity/rolify: Role management library with resource scoping - 0 views

github.com/...rolify

rails model role system permission

shared by 張 旭 on 10 Jun 17 - No Cached
  • 張 旭 on 09 Aug 17
     
    "resource"
張 旭

MySQL 到底能不能放到 Docker 里跑？ - 0 views

mp.weixin.qq.com/s

mysql server docker

shared by 張 旭 on 07 Aug 17 - No Cached
  • 忙碌又容易出错的工作其实是无意义的
  • 单机多实例运行 MySQL
  • MySQL 运行的就是个进程而且对 IO 要求比较高
  • ...12 more annotations...
  • Docker 的资源限制用的就是 cgroups
  • Percona：我们的备份、慢日志分析、过载保护等功能都是基于 pt-tools 工具包来实现的。
  • Consul：分布式的服务发现和配置共享软件
  • 容器调度的开源产品主要有 Kubernetes 和 mesos
  • 适合自己现状的需求才是最好的
  • 有机会做到计算调度和存储调度分离的情况下我们可能会转向 Kubernetes 的方案
  • 根据这个需求按照我们的资源筛选规则 (比如主从不能在同一台机器、内存配置不允许超卖等等)，从现有的资源池中匹配出可用资源，然后依次创建主从关系、创建高可用管理、检查集群复制状态、推送集群信息到中间件 (选用了中间件的情况下) 控制中心、最后将以上相关信息都同步到 CMDB。
    • 張 旭
      張 旭 on 07 Aug 17
       
      感覺用 K8S 就不用那麼麻煩了。
  • 每一个工作都是通过服务端发送消息到 agent，然后由 agent 执行对应的脚本，脚本会返回指定格式的执行结果
  • 备份工具我们是用 percona-xtrabackup
  • zabbix 来实现监控告警
  • grafana 是监控画图界的扛把子，功能齐全的度量仪表盘和图形编辑器，经过简单配置就能完成各种监控图形的展示。
  • (MariaDB 不支持写 table，只能写 file)，极大减少了从库复制带来的 IOPS。
張 旭

How to Test Rails Models with RSpec - Semaphore - 0 views

semaphoreci.com/...o-test-rails-models-with-rspec

rails model test rspec

shared by 張 旭 on 31 Jul 17 - No Cached
  • Behaviour-driven Development (BDD) as a software development process is composed of multiple subtechniques.
  • Models can sometimes be full-blown objects with rich behaviour.
  • An alternative is to use the shoulda gem.
  • ...3 more annotations...
  • reflect_on_association
  • add the business logic
  • Covering Edge Cases
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