expose apm instance from framework integrations

[vigneshshanmugam]

• Avoid having to import @elastic/apm-rum for the sole purpose of initialisation and avoid users from download duplicated apm-rum package if multiple packages are imported in different entry points.

Solutions

This is a common problem and we have to deal with it There are couple of options.

1. Exposing apmBase, apm from @elastic/apm-rum-*(react/angular/vue) packages

This would let users to use to initialise the agent from the imports of a single package and would remove the need to import @elastic/apm-rum for initialisation purpose alone. This is already done in VuePlugin and AngularService but react package doesn't expose it.

2. Relying on window.elasticApm in framework integrations

This has huge disadvantages.

• We expect the users to load apmbase before the framework package which would result in window.elasticApm not being found if any of the modules was downloaded async and we cannot dynamically import if the package isn't found.

Looking at both options, I would say No.1 is an easy solution and best approach.

[hmdhk]

@vigneshshanmugam , the first solution would not address the need to split the bundle (e.g. vendor vs app), we should investigate a bit more to find an optimal solution.

[vigneshshanmugam]

first solution would not address the need to split the bundle (e.g. vendor vs app),

Can you provide an example? With the 1st change, The user shouldn't even need to care about whether vendor or app. Because the bundler takes care of the duplication as its already imported ass part of the first page and not required to be downloaded for subsequent pages.

app.js

import { apm } from '@elastic/apm-rum-react'

apm.init({})

/page/apm.js

import { ApmRoute } from '@elastic/apm-rum-react'

React.render(<App>
    <ApmRoute path="/a" component={}>
</App>)

It is now the bundlers job to use the exported bundles and bundle them in the appropriate bundles. We can do a small setup with this using webpack and test it. Do you have any other case that I missed here?

[hmdhk]

@vigneshshanmugam , I've summarised a 3rd solution here: #804 , that is probably longer term and might require a breaking change.