Envoy report attributes timeout when using http1.0 protocol

Istio version is 1.4 and install in kubernetes which version is 1.15.
There are 1s delay for each request when we use http1.0 protocol.
We added "- name: ISTIO_META_HTTP10 value: ‘1’ " to enable http1.0 on Ingress level.
Please check log on Ingress

I think there are some happen during reporting attributes.
BTW,It’s work fine when we change the protocol to http1.1.

Looking forward to reply