I found that istio 1.1 supports now http 1.0 requests. When you set the environment variable for pilot
PILOT_HTTP10 = 1 then each envoy proxy gets the configuration with
accept_http_10: true. So it is possible to perform HTTP 1.0 request from one pod to another. But this configuration is not propagated to the envoy instance in istio-ingressgateway component and in the result external request is blocked with such response:
< HTTP/1.1 426 Upgrade Required < date: Thu, 04 Apr 2019 12:17:47 GMT < server: istio-envoy < content-length: 0
Is there a way to set a flag:
accept_http_10: true for envoy in istio-ingressgateway?