发生在IPFS上有趣的项目
ipfs is awesome
最近的研究重点在IPFS上，作为一个基于BitSwap和Merkle DAG的系统，IPFS在不断完善自身的技术栈。ipfs_research 中有许多很有想象力的新的协议。在这些新的协议的启发下，我们能在IPFS上开发出更多有意思的产品。
1. 为什么需要 pubsub?
参考文献https://ipfs.io/blog/25-pubsub/
消息的发布与订阅Publish-Subscribe, 简称为‘pubsub’, 是一种在大型网络中被用于处理事件的模式。发布者（‘Publishers’ ）按照主题发送信息或内容；接收者（ ‘subscribers’）接受他们感兴趣的主题。 信息的传输不需要发布者和接受者间存在直连。这样一来可以得到更大的网络扩展性和灵活性。
有些文档共享编辑的应用、动态内容的网站、聊天应用、游戏、持续演化的数据集和用户发布信息的webservice都需要用到消息的发布订阅。它使得在数据中心、局域网、大型P2P应用上使用IPFS变得更快速。在不远的将来，IPNS记录可以通过pubsub发布，使得IPNS记录的更新变得更快。节点间可以通过pubsub 追踪一个 merkle-linked global log的头信息。
Demo
- 以使用pubsub模式启动ipfs
<pre name="b88d" id="b88d" class="graf graf--pre graf-after--li" style="overflow: auto; font-family: Menlo, Monaco, "Courier New", Courier, monospace; font-size: 16px; margin: 43px 0px 0px; background: rgba(0, 0, 0, 0.05); padding: 20px; white-space: pre-wrap; color: rgba(0, 0, 0, 0.84); font-style: normal; font-variant-ligatures: normal; font-variant-caps: normal; font-weight: 400; letter-spacing: normal; orphans: 2; text-align: start; text-indent: 0px; text-transform: none; widows: 2; word-spacing: 0px; -webkit-text-stroke-width: 0px; text-decoration-style: initial; text-decoration-color: initial;">ipfs daemon — enable-pubsub-experiment</pre>
- 订阅“foo”主题
<pre name="5526" id="5526" class="graf graf--pre graf-after--li" style="overflow: auto; font-family: Menlo, Monaco, "Courier New", Courier, monospace; font-size: 16px; margin: 43px 0px 0px; background: rgba(0, 0, 0, 0.05); padding: 20px; white-space: pre-wrap; color: rgba(0, 0, 0, 0.84); font-style: normal; font-variant-ligatures: normal; font-variant-caps: normal; font-weight: 400; letter-spacing: normal; orphans: 2; text-align: start; text-indent: 0px; text-transform: none; widows: 2; word-spacing: 0px; -webkit-text-stroke-width: 0px; text-decoration-style: initial; text-decoration-color: initial;">ipfs pubsub sub foo</pre>
- 在另一个窗口发布一条消息，在另一个窗口可以显示“hello world”
<pre name="a638" id="a638" class="graf graf--pre graf-after--li" style="overflow: auto; font-family: Menlo, Monaco, "Courier New", Courier, monospace; font-size: 16px; margin: 43px 0px 0px; background: rgba(0, 0, 0, 0.05); padding: 20px; white-space: pre-wrap; color: rgba(0, 0, 0, 0.84); font-style: normal; font-variant-ligatures: normal; font-variant-caps: normal; font-weight: 400; letter-spacing: normal; orphans: 2; text-align: start; text-indent: 0px; text-transform: none; widows: 2; word-spacing: 0px; -webkit-text-stroke-width: 0px; text-decoration-style: initial; text-decoration-color: initial;">ipfs pubsub pub foo “hello world”</pre>
- 查看所有的订阅者
<pre name="8ce4" id="8ce4" class="graf graf--pre graf-after--li" style="overflow: auto; font-family: Menlo, Monaco, "Courier New", Courier, monospace; font-size: 16px; margin: 43px 0px 0px; background: rgba(0, 0, 0, 0.05); padding: 20px; white-space: pre-wrap; color: rgba(0, 0, 0, 0.84); font-style: normal; font-variant-ligatures: normal; font-variant-caps: normal; font-weight: 400; letter-spacing: normal; orphans: 2; text-align: start; text-indent: 0px; text-transform: none; widows: 2; word-spacing: 0px; -webkit-text-stroke-width: 0px; text-decoration-style: initial; text-decoration-color: initial;">ipfs pubsub peers</pre>
- 查看所有的主题
<pre name="1d87" id="1d87" class="graf graf--pre graf-after--li" style="overflow: auto; font-family: Menlo, Monaco, "Courier New", Courier, monospace; font-size: 16px; margin: 43px 0px 0px; background: rgba(0, 0, 0, 0.05); padding: 20px; white-space: pre-wrap; color: rgba(0, 0, 0, 0.84); font-style: normal; font-variant-ligatures: normal; font-variant-caps: normal; font-weight: 400; letter-spacing: normal; orphans: 2; text-align: start; text-indent: 0px; text-transform: none; widows: 2; word-spacing: 0px; -webkit-text-stroke-width: 0px; text-decoration-style: initial; text-decoration-color: initial;">ipfs pubsub ls</pre>
2. OrbitDB
orbit-db是一个去服务器的，分布式的P2P数据库。 orbit-db将数据存储在IPFS上，使用IPFS Pubsub自动同步各个节点的数据。 这是一个能够保证最终一致的数据库，它使用CRDT进行无冲突数据库合并，使orbit-db成为offline-first应用程序的绝佳选择。
案例-orbit
Orbit是一个P2P的聊天软件。
Devcon2上的介绍视频： Orbit Distributed, Real Time Web3 Apps with IPFS and Ethereum
<figure name="636e" id="636e" class="graf graf--figure graf-after--p" style="display: block; margin: 43px 0px 0px; position: relative; clear: both; outline: 0px; box-sizing: border-box; user-select: auto; z-index: 100; color: rgba(0, 0, 0, 0.84); font-family: medium-content-sans-serif-font, -apple-system, BlinkMacSystemFont, "Segoe UI", Roboto, Oxygen, Ubuntu, Cantarell, "Open Sans", "Helvetica Neue", sans-serif; font-size: 20px; font-style: normal; font-variant-ligatures: normal; font-variant-caps: normal; font-weight: 400; letter-spacing: normal; orphans: 2; text-align: start; text-indent: 0px; text-transform: none; white-space: normal; widows: 2; word-spacing: 0px; -webkit-text-stroke-width: 0px; background-color: rgb(255, 255, 255); text-decoration-style: initial; text-decoration-color: initial;">
<canvas class="progressiveMedia-canvas js-progressiveMedia-canvas" width="75" height="40" style="display: block; vertical-align: baseline; position: absolute; top: 0px; left: 0px; width: 700px; height: 394.797px; margin: auto; box-sizing: border-box; visibility: hidden; opacity: 0; backface-visibility: hidden; transition: visibility 0s linear 0.5s, opacity 0.1s 0.4s;"></canvas>
[图片上传失败...(image-a34ad7-1522941041721)]
</figure>
线上测试环境：https://orbit.chat/#/loading
Orbit在IPFS上开发出了P2P数据库OrbitDB。
Orbit的Git项目地址：https://github.com/orbitdb
安装
当Nodejs版本在8.0之上，
npm install -g orbit-db-cli
测试是否安装成功
orbitdb help
应出现以下内容：
_ _ _ _ _ | | (_) | | | | ___ _ __| |__ _| |_ __| | |__ / _ \| '__| '_ \| | __| / _` | '_ \ | (_) | | | |_) | | |_ | (_| | |_) | \___/|_| |_.__/|_|\__| \__,_|_.__/ Peer-to-Peer Database https://github.com/orbitdb/orbit-dbUsage: orbitdb <command> <database>Commands: add <database> [<data>] Add an entry to an eventlog or feed database. Can be only used on: eventlog|feed create <database> <type> Create a new database. Type can be one of: eventlog|feed|docstore|keyvalue|counter [aliases: new] del <database> <key> Delete an entry from a database. Only valid for data types of: docstore|keyvalue|feed [aliases: delete, remove] demo <name> Runs a sequence of commands as an example [aliases: tour] drop <database> yes Remove a database locally. This doesn't remove data on other nodes that have the removed database replicated. [aliases: destroy] get <database> [<search>] Query the database. [aliases: query, search] id Show information about current orbit-db id import <file> <database> <schema> Import a CSV file to a document database [aliases: csv] inc <database> [<increment>] Increase the value of a counter database. Default increment is 1\. [aliases: increase] info <database> Show information about a database [aliases: status] put <database> <document> Add a document to a document database replicate <database> Replicate a database with peers. set <database> <key> <value> Set a value of a key in KeyValue database version Show information about current orbit-dbOptions: -h, --help Show help [boolean]
测试数据库存储日志的特性：
- 创建一个feed用于存储log信息
orbitdb create hello feed/orbitdb/QmfSUsdr34iGio68eMezDzZLCKZTnbsxNJgiNipimZtpi1/hello
- 插入一条日志
orbitdb add /orbitdb/QmfSUsdr34iGio68eMezDzZLCKZTnbsxNJgiNipimZtpi1/hello "world"Added QmSwYZheHVa3eWf83XwnWNJtjGG7EWjiWTaTKLeFozVRnz
- 读取feed内容
$ orbitdb get /orbitdb/QmfSUsdr34iGio68eMezDzZLCKZTnbsxNJgiNipimZtpi1/hello"world"
- 删除某一条日志
$ orbitdb del /orbitdb/QmfSUsdr34iGio68eMezDzZLCKZTnbsxNJgiNipimZtpi1/hello QmSwYZheHVa3eWf83XwnWNJtjGG7EWjiWTaTKLeFozVRnzDeleted QmSwYZheHVa3eWf83XwnWNJtjGG7EWjiWTaTKLeFozVRnz
- 得到feed所有内容
orbitdb get /orbitdb/QmfSUsdr34iGio68eMezDzZLCKZTnbsxNJgiNipimZtpi1/helloDatabase '/orbitdb/QmfSUsdr34iGio68eMezDzZLCKZTnbsxNJgiNipimZtpi1/hello' is empty!
- 获取feed所有信息
orbitdb info hello/orbitdb/QmfSUsdr34iGio68eMezDzZLCKZTnbsxNJgiNipimZtpi1/hello> Type: feed> Owner: QmfSUsdr34iGio68eMezDzZLCKZTnbsxNJgiNipimZtpi1> Data file: ./orbitdb/QmfSUsdr34iGio68eMezDzZLCKZTnbsxNJgiNipimZtpi1/hello.orbitdb> Entries: 0> Oplog length: 2
参考文献：
https://en.wikipedia.org/wiki/Conflict-free_replicated_data_type
