grpc-error-strategy

A gRPC implementation of the error strategy interface.

ErrorStrategy Interface

interface ErrorStrategy {
  badImplementation: (message: string, innerError?: Error): Error,
  badRequest: (message: string, innerError?: Error): Error,
  forbidden: (message: string, innerError?: Error): Error,
  notFound: (message: string, innerError?: Error): Error,
  notImplemented: (message: string, innerError?: Error): Error,
  preconditionFailed: (message: string, innerError?: Error): Error,
  unavailable: (message: string, innerError?: Error): Error,
 
  propagate: (message: string, innerError: Error, targetErrorStrategy: ErrorStrategy): Error
}

Basic Error Creation

Here are some examples of how you might use this library:

const { unavailable, badRequest } = require('grpc-error-strategy')
 
let thing
try {
  thing = createThing()
} catch (e) {
  throw badRequest('error creating thing', e)
}
 
try {
  save(thing)
} catch (e) {
  throw unavailable('error saving thing', e)
}

Propagating Technology-Specific Error Metadata

It can be the case that the technology used to trigger some processing is not the same as technology used to trigger downstream processing. The propagate method allows one to take a gRPC error and generate an error using another ErrorStrategy implementation.

Consider an HTTP request handler that invokes a gRPC API. Say we would like to return the gRPC status code as an HTTP status code. Here's how you might accomplish this:

const GrpcErrorStrategy = require('grpc-error-strategy')
const HttpErrorStrategy = require('http-error-strategy')
 
try {
  grpcRequestToSaveThing()
} catch (e) {
  // the following will return an equivalent HTTP error
  throw GrpcErrorStrategy.propagate('unable to save thing', e, HttpErrorStrategy)
}

Usage Patterns to Consider

It may be wise to decouple your code from the technology used to trigger it (see ports and adapters). You may even want to support triggering your code in different ways - HTTP, gRPC, CLI.

Therefore, consider accepting ErrorStrategy instances instead of importing them directly to keep code agnostic of the triggering technology:

// you might consider destructuring ErrorStrategy into the methods you need...
const anOperation = (ErrorStrategy) => (input) => {
  let thing
  try {
    thing = createThing()
  } catch (e) {
    throw ErrorStrategy.badRequest('error creating thing', e)
  }
}

If your code is triggering specific downstream technology, then importing the appropriate ErrorStrategy is reasonable:

const { propagate } = require('grpc-error-strategy') // legit, you know it's gRPC your calling
 
const anOperation = (ErrorStrategy) => (input) => {
  try {
    grpcRequestToSaveThing()
  } catch (e) {
    // returns an error formatted as per the passed in ErrorStrategy
    throw propagate('unable to save thing', e, ErrorStrategy)
  }
}

Release Management

GitHub Actions are used to run linting, tests and code coverage on git push. Tags are used to create releases. Once a release is created, an action will cause the npm package to published.