ECONNRESET errors with using REST transport in GCF

[alexander-fenster]

As reported in googleapis/nodejs-firestore#1943, @google-cloud/firestore used in GCF in REST mode {preferRest: true}, which translates to {fallback: 'rest'}, often results in ECONNRESET error. We need to investigate what might be going on.

[danielbankhead]

It appears we have 2 networking libraries in the fallback: 'rest' path:

• google-auth-library
• node-fetch

google-auth-library currently has retries for the ECONNRESET concern, however the node-fetch path does not. Perhaps a way forward is to swap node-fetch with gaxios with a retry configuration, here:

gax-nodejs/gax/src/fallbackServiceStub.ts

Lines 73 to 75 in d140b9c

	const fetch = hasWindowFetch()
	? window.fetch
	: (nodeFetch as unknown as NodeFetchType);