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Assets Module

Browser SDKs should auto-instrument javascript, stylesheet and image assets with the ops resource.script, resource.css and resource.img respectively. The Asset module is technology agnostic, it only cares about span data properties.

Span conventions

Span Description

The description of an asset span should be the full URL of the asset, e.g., https://cdn.com/main.hash123.js?q=11274713.

Span Data

The following data should be provided for each asset span

Data KeyTypeDescriptionNotes
http.response_content_lengthintencoded size of the asset in bytes (what is sent over the network)required on all asset operations
http.decoded_response_content_lengthintthe decoded size of the asset in bytesrecommended; if not provided, would show up as 0 on the resource summary size chart
http.response_transfer_sizeintthe size of the encoded asset plus the response headers in bytesrecommended; if not provided, would show up as 0 on the resource summary size chart
resource.render_blocking_statusstringwhether the resource blocks UI rendering, values are 'non-blocking' or 'blocking'recommended; if not provided, the asset can't be narrowed down by their render blocking status

Instrumentation Example

The SDK should create a span per asset fetched by the browser.

Consider a basic HTML file that fetches a single script:

Copied
<head>
  <script src="https://cdn.com/main.hash123.js"></script>
</head>

Should result in the following span, assuming the request was successful:

Copied
{
  "description": "https://cdn.com/main.hash123.js",
  "op": "resource.script",
  "data": {
    "http.decoded_response_content_length": 123,
    "http.response_content_length": 123,
    "http.response_transfer_size": 123,
    "resource.render_blocking_status": "blocking",
    "server.address": "cdn.com",
    ... other span properties
  }
}
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