JavaScript DSL overview

Instead of writing raw Elasticsearch Watcher JSON, you can define alerts in JavaScript using the Orwell DSL. JS watchers are more concise, composable, and easier to review.

When to use .js vs .json

Format	Use when
.json	Simple static watchers, no dynamic logic
.js	Script references, query composition, Slack markdown, environment-based logic

Both formats are supported and can coexist in the same alert folder.

How DSL files work

A file named watcher.*.js is evaluated in an isolated VM context. A set of global functions — schedule, input, condition, transform, webhookAction, metadata, query, rawQuery, script, markdown — are injected into that context.

You call these functions at the top level. Order does not matter. Orwell assembles the final Elasticsearch Watcher JSON from whatever you called.

watcher.server-a.non-prod.js

schedule({ interval: '2h' })

input({
  env: 'NON-PROD',
  logs: query({
    indexes: ['eks-*'],
    timeRange: '-2h to now',
    query: 'payment failed',
  })
})

condition({ 'logs.hits.total': gt(0) })

transform(script('./transform.groovy'))

webhookAction({
  name: 'notify_slack',
  transform: script('./transform.groovy'),
  message: markdown('./message.md', {
    actions: [{ text: 'View Logs', url: '{{ctx.payload.logsUrl}}' }],
  }),
  configs: {
    scheme: 'https',
    host: 'hooks.slack.com',
    port: 443,
    method: 'post',
    path: '{{ctx.payload.slackHookPath}}',
    body: '{{#toJson}}ctx.payload.message{{/toJson}}',
  }
})

Available globals

Function	Purpose
schedule(spec)	Set the trigger schedule
input(spec)	Define chain inputs (static values and/or queries)
query(spec)	Build an Elasticsearch search input
rawQuery(body)	Pass a raw search input object
condition(spec)	Set the condition for firing
transform(spec)	Add a transformation step
webhookAction(spec)	Add a webhook (Slack) action
metadata(spec)	Attach metadata to the watcher
script(path)	Reference a Groovy script file
markdown(path, opts?)	Compile a Markdown file to Slack Block Kit
gt, gte, lt, lte, eq, notEq, isOneOf	Comparison operators

Escaping to raw module.exports

If the DSL globals don’t cover your use case, you can export a plain object instead:

watcher.server-a.non-prod.js

module.exports = {
  trigger: { schedule: { interval: '1h' } },
  input: { simple: { env: 'NON-PROD' } },
  condition: { always: {} },
  actions: {},
};

Orwell detects that no DSL functions were called and uses module.exports directly.