Confirm default of enabling http2 preface on client

Just wanted to confirm using the http2 preface is a good default for an armeria client. I ran into not being able to connect to Elasticsearch V7 when this is enabled with

com.linecorp.armeria.client.SessionProtocolNegotiationException: expected: http, reason: connection established, but session creation timed out:

The error message doesn’t really help debug and after being stuck for a while, I had the random idea of disabling the preface, which I think most users wouldn’t ever find.

If there are servers where the preface doesn’t work, is it actually a good idea to default to enabling it?

For reference, had failures in this build https://travis-ci.org/openzipkin/zipkin/builds/556693286?utm_source=github_status&utm_medium=notification

[minwoox]

Oops~ 😅

[ikhoon]

… I’d like to keep the current behavior as it is, i.e. useHttp2Preface = true by default, unless there’s strong objection.

+1 Even though the spec recommends to use HTTP/2 upgrade requests for cleartext, I think it is more important to work well with Armeria echo system using our default configuration.