108 lines
2.7 KiB
Markdown
108 lines
2.7 KiB
Markdown
# Mempool Link Unfurler Service
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This is a standalone nodejs service which implements the [Open Graph protocol](https://ogp.me/) for Mempool instances. It performs two main tasks:
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1. Serving Open Graph html meta tags to social media link crawler bots.
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2. Rendering link preview images for social media sharing.
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Some additional server configuration is required to properly route requests (see section 4 below).
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## Setup
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### 0. Install deps
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For Linux, in addition to NodeJS/npm you'll need at least:
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* nginx
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* cups
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* chromium-bsu
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* libatk1.0
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* libatk-bridge2.0
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* libxkbcommon-dev
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* libxcomposite-dev
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* libxdamage-dev
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* libxrandr-dev
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* libgbm-dev
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* libpango1.0-dev
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* libasound-dev
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### 1. Clone Mempool Repository
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Get the latest Mempool code:
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```
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git clone https://github.com/mempool/mempool
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cd mempool
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```
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Check out the latest release:
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```
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latestrelease=$(curl -s https://api.github.com/repos/mempool/mempool/releases/latest|grep tag_name|head -1|cut -d '"' -f4)
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git checkout $latestrelease
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```
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### 2. Prepare the Mempool Unfurler
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#### Install
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Install dependencies with `npm` and build the backend:
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```
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cd unfurler
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npm install
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```
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The npm install may fail if your system does not support automatic installation of Chromium for Puppeteer. In that case, manually install Puppeteer without Chromium first:
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```
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PUPPETEER_SKIP_CHROMIUM_DOWNLOAD=true npm install puppeteer
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npm install
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```
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#### Configure
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In the `unfurler` folder, make a copy of the sample config file:
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```
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cp config.sample.json config.json
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```
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Edit `config.json` as needed:
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| variable | usage |
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|---|---|
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| SERVER.HOST | the host where **this** service will be served |
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| SERVER.HTTP_PORT | the port on which **this** service should run |
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| MEMPOOL.HTTP_HOST | the host where **the Mempool frontend** is being served |
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| MEMPOOL.HTTP_PORT | the port on which **the Mempool frontend** is running (or `null`) |
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| PUPPETEER.CLUSTER_SIZE | the maximum number of Chromium browser instances to run in parallel, for rendering link previews |
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| PUPPETEER.EXEC_PATH | (optional) an absolute path to the Chromium browser executable, e.g. `/usr/local/bin/chrome`. Only required when using a manual installation of Chromium |
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#### Build
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```
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npm run build
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```
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### 3. Run the Mempool Unfurler
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```
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npm run start
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```
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### 4. Server configuration
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To enable social media link previews, the system serving the Mempool frontend should detect requests from social media crawler bots and proxy those requests to this service instead.
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Precise implementation is left as an exercise to the reader, but the following snippet may be of some help for Nginx users:
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```Nginx
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map $http_user_agent $crawler {
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default 0;
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~*facebookexternalhit 1;
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~*twitterbot 1;
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~*slackbot 1;
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~*redditbot 1;
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~*linkedinbot 1;
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~*pinterestbot 1;
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}
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```
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