#92 feat: add custom error handling option

README.md

@@ -152,6 +152,9 @@ Called when an http response is received from the source.
 The default behavior is `pump(stream, res)`, which will be disabled if the
 option is specified.
 
+##### onError(err, req, res)
+Called when an error is thrown from the source. If this option is specified, the default error handling will not be applied.
+
 ##### rewriteRequestHeaders(req, headers)
 Called to rewrite the headers of the request, before them being sent to the downstream server. 
 It must return the new headers object.

index.js

@@ -38,6 +38,7 @@ function fastProxy (opts = {}) {
       const onResponse = opts.onResponse
       const rewriteHeaders = opts.rewriteHeaders || rewriteHeadersNoOp
       const rewriteRequestHeaders = opts.rewriteRequestHeaders || rewriteRequestHeadersNoOp
+      const onError = opts.onError
 
       const url = getReqUrl(source || req.url, cache, base, opts)
       const sourceHttp2 = req.httpVersionMajor === 2
@@ -88,6 +89,12 @@ function fastProxy (opts = {}) {
       }
       request(reqParams, (err, response) => {
         if (err) {
+          // allow for errors to be passed to a custom callback
+          if (onError) {
+            onError(err, req, res)
+            return
+          }
+
           // check if response has already been sent and all data has been flushed
           // before configuring error response headers
           if (res.sent === false || res.writableFinished === false) {

test/4.opts.test.js

@@ -17,6 +17,10 @@ nock('http://dev.com')
     url: 'http://dev.com'
   })
 
+nock('http://dev.error')
+  .get('/service/error')
+  .replyWithError('Error')
+
 describe('fast-proxy smoke', () => {
   it('init', async () => {
     const fastProxy = require('../index')({
@@ -40,6 +44,10 @@ describe('fast-proxy smoke', () => {
         queryString: { age: 33 },
         onResponse (req, res, stream) {
           pump(stream, res)
+        },
+        onError (err, req, res) {
+          res.statusCode = 418
+          res.send(err.code)
         }
       })
     })
@@ -99,6 +107,15 @@ describe('fast-proxy smoke', () => {
       .expect(302)
   })
 
+  it('should allow for errors to be handled', async () => {
+    await request(gHttpServer)
+      .get('/service/error')
+      .set('base', 'http://dev.com')
+      .then(response => {
+        expect(response.statusCode).to.equal(418)
+      })
+  })
+
   it('close all', async () => {
     close()
     await gateway.close()