[{"id":"cG9zdDo5Ng==","slug":"write-your-own-drone-plugin-from-scratch","title":"Write your own drone plugin from scratch","content":"\n

Recently Drone released it 1.0 version update. It came with a cleaner and more useful UI and a new structure for declaring the YAML drone pipelines files. Perfect time for writing our own drone plugin. 🎉

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TL;DR Get the code: https://github.com/CupCakeArmy/drone-deploy

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This should be a starting point to guide you in the right direction towards writing your first drone plugin. It’s easier than it might seems. Let’s go 🚀

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What do we want to achieve?

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Login with an ssh key from drone secrets
copy files to a remote location
execute remote commands

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How are Drone Plugins written?

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Very simple actually: drone plugins are nothing more than a docker image. The process is as follows:

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The code gets mounted inside your image at `/drone/src`
You make slack api calls, deploy, whatever you want.

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Since the source is mounted inside a container you can use whatever language you prefer! Cool. For this small project I decided to go with Python, but you could use node, go, whatever runs inside Docker.

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First lets look how a plugin is defined inside the .drone.yml file.

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kind: pipeline\nname: default\n\nsteps:\n\n  # build...\n\n  - name: deploy\n    image: you/your-drone-plugin # public docker image\n    settings:\n      host: example.org\n      user: root\n      password: h4x0rz

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How do we get those variables? Drone mounts them as environment variables inside the plugin container prefixed by PLUGIN_.
So host: example.org becomes $PLUGIN_HOST=example.org and so forth.

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In Python

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def main():\n    host = os.environ.get('PLUGIN_HOST')\n    port = os.environ.get('PLUGIN_PORT', 22)\n    user = os.environ.get('PLUGIN_USER')\n    password = os.environ.get('PLUGIN_PASSWORD')\n    key = os.environ.get('PLUGIN_KEY')\n\nmain()\n# example.org\n# 22\n# root\n# h4x0rz\n# None

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How do I get secrets? We need to use the from_secret syntax. Supposing you have saved your private key as a repository secret under ssh_key the example would look as follows:

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- name: deploy\n  settings:\n    key:\n      from_secret: ssh_key

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Easy 👌What about arrays? We want to copy a list of sources to the server.

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- name: deploy\n  settings:\n    sources:\n      - ./public\n      - docker-compose.yml

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This will result into PLUGIN_SOURCES=./public,docker-compose.yml. Basically we get a comma-separated-string.

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# Takes a string, splits it at the comma and removes empty elements\ndef clean_array(s: str) -> List[str]:\n    return list(filter(None, s.split(',')))\n\nsources = clean_array(os.environ.get('PLUGIN_SOURCES', ''))

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Putting it all together

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import paramiko\n\ndef execute(c: SSHClient, cmd: str, path: str = None, env:dict = None) -> str:\n    if path is not None:\n        cmd = 'cd {}; {}'.format(path, cmd)\n    stdin, stdout, stderr = c.exec_command(cmd, environment=env)\n    return stdout.read().decode('utf-8').strip()\n\n\ndef main():\n\n\t# Takes a string, splits it at the comma and removes empty elements\n    def clean_array(s: str) -> List[str]:\n        return list(filter(None, s.split(',')))\n\t\n    host = os.environ.get('PLUGIN_HOST')\n    port = os.environ.get('PLUGIN_PORT', 22)\n    user = os.environ.get('PLUGIN_USER')\n    password = os.environ.get('PLUGIN_PASSWORD')\n    key = os.environ.get('PLUGIN_KEY')\n    target = os.environ.get('PLUGIN_TARGET')\n    commands = clean_array(os.environ.get('PLUGIN_COMMANDS', ''))\n    sources = clean_array(os.environ.get('PLUGIN_SOURCES', ''))\n\n    ssh = paramiko.SSHClient()\n    try:\n        k = paramiko.RSAKey.from_private_key(io.StringIO(key))\n        ssh.set_missing_host_key_policy(paramiko.AutoAddPolicy())\n        ssh.connect(hostname=host, username=user, pkey=k, port=port, password=password)\n\n        sftp = ssh.open_sftp()\n        try:\n\t\t\t# Upload the files\n\t\t\t# for file in file....\n\t\t\tsftp.put(archive_local, archive_remote)\n        finally:\n            sftp.close()\n\n        for command in commands:\n            output = execute(ssh, command, target, envs)\n            print(command)\n            print(output)\n\n    finally:\n        ssh.close()

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This of course simplifies the code a lot, but should give a general idea how it’s done.

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For a full fledged example check out the repo: https://github.com/CupCakeArmy/drone-deploy

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Enjoy! 👋

\n","status":"publish","date":"2019-05-25T17:07:02","modified":"2020-09-22T20:46:45","tags":{"nodes":[{"id":"dGVybTo4","slug":"cd","name":"cd","count":2},{"id":"dGVybToxOQ==","slug":"drone","name":"drone","count":2},{"id":"dGVybToyNQ==","slug":"guide","name":"guide","count":1},{"id":"dGVybTo0Mw==","slug":"plugin","name":"plugin","count":1},{"id":"dGVybTo0Ng==","slug":"python","name":"python","count":3}]},"post":{"featured":{"srcSet":"https://api.nicco.io/wp-content/uploads/2019/05/asoggetti-418839-unsplash-300x200.jpg 300w, https://api.nicco.io/wp-content/uploads/2019/05/asoggetti-418839-unsplash-1024x684.jpg 1024w, https://api.nicco.io/wp-content/uploads/2019/05/asoggetti-418839-unsplash-150x100.jpg 150w, https://api.nicco.io/wp-content/uploads/2019/05/asoggetti-418839-unsplash-768x513.jpg 768w, https://api.nicco.io/wp-content/uploads/2019/05/asoggetti-418839-unsplash-1536x1025.jpg 1536w, https://api.nicco.io/wp-content/uploads/2019/05/asoggetti-418839-unsplash-2048x1367.jpg 2048w, https://api.nicco.io/wp-content/uploads/2019/05/asoggetti-418839-unsplash-500x334.jpg 500w, https://api.nicco.io/wp-content/uploads/2019/05/asoggetti-418839-unsplash-800x534.jpg 800w, https://api.nicco.io/wp-content/uploads/2019/05/asoggetti-418839-unsplash-1200x801.jpg 1200w, https://api.nicco.io/wp-content/uploads/2019/05/asoggetti-418839-unsplash-1500x1001.jpg 1500w, https://api.nicco.io/wp-content/uploads/2019/05/asoggetti-418839-unsplash-2000x1335.jpg 2000w","altText":"","sourceUrl":"https://api.nicco.io/wp-content/uploads/2019/05/asoggetti-418839-unsplash-scaled.jpg"}}}]