@prun/http-got

A prunjs component for a got httm-client.

Concerns

The concerns of this component are:

1. Augment http request headers with any tracking headers to all requests to internal services.
2. Augment http request headers with a verbose User-Agent header, listing versions of the project, node runtime and the got http client
3. Set a default request timeout for every request that does not specify an explicit one.

Composing User-Agent header

The user agent should include name and version for the following components:

1. the project (taken from the package.json)
2. the node runtime (taken from process.version)
3. the got http client library (taken from the package.json of the got http-client)

Tracking heaers

Many APM systems use a combination of network packet analytics and instrumentation of low-level hooks to analyse what internal requests are the result of a user-request. However, because of this nature, they come with a significant performance penalty.

Tracking http headers is a no-voodoo, low-footprint way to analyse how requests trickle down in a service mesh. The http-requests they employ differ from organization to organization, tipically one of x-correlation-id, x-transaction-id, x-trx-id - a unique identifier of the user-request. Additional headers may be x-flow-name, x-flow-initiator, x-request-id.

This component imnplements the http-client part of the following two parts:

1. the interface layer should add the base values on local context (in IoC name context). Tyipically, it's done in the http interface, however, any interface should be able to provide them.
2. http client picks up these values, and mounts them as http headers.

Then, given a log-centralizaion that holds the logs from all the services in the mesh, you can filter by these headers to get a complete narrative.

Configurations

• defaultTimeout : number, default: 2000
  • The timeout in in milliseconds
• internalDomains : string[], default: ['.local']
  • a request will be augmented with tracking headers if it is made to any of the provided domains or their subdomains.
  • a single string will be understood as an array of a single element
• contextToCustomHeaders: Record<contextKeyString, httpHeaderNameString>, default: {}
  • Mapping of any custom context keys to http-headers in addition to the default correlation headers.
• baseContextValues: Record<contextKeyString, httpHeaderNameString>.
  • default:

    {
      correlationId: 'x-correlation-id',
      flowName: 'x-flow-name',
      flowInitiator: 'x-flow-initiator',      
    },

• contextToHeaders: Record<contextKeyString, httpHeaderNameString>.
  • this computed internally as { ...baseContextValues, ...contextToCustomHeaders }.
  • you may provide an empy object or an explicit null if you wish to override this behavior alltogether, letting the component set for you only the default timeout and user-agent header.