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@tradle/lambda-plugins

Loader for additional npm packages based on configuration in lamdba function.

How it works

Given a list of npm packages to load, this script will use npm install to install the packages in the temporary directory and provide an accessor to the plugins to load.

Usage with serverless

In this example we load the plugins from the envionment variable PLUGINS defined in the lambda settings. In your project you can load definitions from DynamoDB/S3/etc.

import { loadPlugins } from '@tradle/lambda-plugins'

export async function example (event) {
  const plugins = await loadPlugins(
    JSON.parse(process.env.PLUGINS ?? '{}')
  )

  for (const pluginName in plugins) {
    const plugin = plugins[pluginName]
    plugin.name === pluginName
    plugin.path // File path where the package is loaded from
    await plugin.package() // Loads the package.json for the package
    await plugin.data() // Loads the data
  }

  // ... the rest of your lambda code.
}

In this example the npm packages are separated by a , examples could be:

  • PLUGINS={} ... to load nothing
  • PLUGINS={"moment":"2.29.1"} ... to load the [moment][] package.
  • PLUGINS={"moment":"2.29.1", "lodash":"4.17.17"} ... to load both the moment and the [lodash][] package.
  • PLUGINS={"moment":"https://github.com/lodash/lodash/archive/refs/tags/4.0.0.tar.gz"} ... to load the (old) lodash package via https.
  • PLUGINS={"quick-lru":"github:sindresorhus/quick-lru#771392878fc0e2325b1172d04260e87afe94c8f7"} ... to load the quick-lru package directly from github.
  • PLUGINS={"moment":"s3://private-bucket/lodash-4.0.0.tar.gz"} ... to load the lodash package from a secret, ficitional s3 bucket.

etc.

S3 Bucket loading

You can publish private packages to s3. These s3 packages get downloaded directly, bypassing npm. In order for this to work you need to make sure that the lambda has permission to access this bucket:

- Effect: 'Allow'
  Action:
    - "s3:GetObject"
  Resource:
    'arn:aws:s3:::private-bucket/*'

Options

By default it will install the packages in the /tmp folder. You can override this by using the { tmpDir } option:

await loadPlugins(plugins, { tmpDir: '/other/tmp/dir' })

The /tmp folder persists between requests and every time loadPlugins is called, it checks the timestamp of the previous run and only checks if new plugins need to be installed if the last run was more than 2 minutes ago. You can override this by using the { maxAge: 1000 } option:

await loadPlugins(plugins, { maxAge: 1000 })

By default the loading of plugins does not allow loose semver-version definitions. Versions installed using semvers like ~1.0.0 or 1 or >=1 are not allowed. If you still want to use these, you need to pass the strict = false option.

await loadPlugins(plugins, { strict: false })

By default there will be also no error if the installation of the plugins happens to fail. In order to enable errors you need to pass failQuietly=false.

await loadPlugins(plugins, { failQuietyl: false })

To install private packages you will need to specify an authentication token.

await loadPlugins(plugins, { registryTokens: { 'host': 'token' } })

In practice it may look like:

await loadPlugins(plugins, { registryTokens: { "registry.npmjs.org/": "npm_Fo2387C3auJep6agQr41NCDHXW2BDz1S07mf" } } )

Depending on the registry, there are different ways to get a token. Here is the documentation for

Flow

Here is a flow explanation:

[request]
→ does /tmp/plugins exist?
 Yes → was updated within the last 2 minutes?
 |  Yes → start
 |  No  → is /tmp/plugins is up-to-date?
 |     Yes → start
 |     No -\  
 |         |→ load plugins
 |         \→ start
 No -\
     |→ load plugins
     \→ start

Furthermore, this package uses debug and by adding the DEBUG=* environment variable you can get insight on what happens.

Development

The code here uses a pretty straightforward development model. The only thing that may not be obvious is the example code in sls-aws-example. In order for that to work, we need do releases manually. When you do a release:

  1. Change the version number in the package.json
  2. In the sls-aws-example change the dependency to the same version as in the package.json.
  3. Run npm i in the sls-aws-example.
  4. Now add all files necessary should be prepared for the git commit.

Naturally when doing changes on this repo you should provide tests and expand on the example. To test the changes you have made with the example, run the npm run update-parent command in the sls-aws-example before deploying it to AWS.

License

MIT