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Client Status Code 426 "Upgrade Required" Is Returned

Last updated: 2023-12-26 15:28:29
    Istio uses Envoy as the data plane to forward HTTP requests, and Envoy requires HTTP/1.1 or HTTP/2 by default. 426 Upgrade Required is returned when a client uses HTTP/1.0.

    Common nginx Scenario

    If nginx is used for proxy_pass reverse proxy, it uses HTTP/1.0 by default. You can explicitly set proxy_http_version to 1.1.
    upstream http_backend {
    keepalive 16;
    server {
    location /http/ {
    proxy_pass http://http_backend;
    proxy_http_version 1.1;
    proxy_set_header Connection "";

    Stress Test Scenario

    During ab stress test, HTTP/1.0 requests will be sent, and Envoy will always return 426 Upgrade Required but not forward them. Therefore, the stress test result will not be accurate. You can use other stress test tools, such as wrk.

    Enable Istio to Support HTTP/1.0

    Some SDKs or frameworks may use the HTTP/1.0 protocol. For example, they use HTTP/1.0 to pull configuration information from the resource center/configuration center. If you want your service to run on Istio without modifying code, you can modify the istiod configuration by adding the PILOT_HTTP10: 1 environment variable to enable HTTP/1.0.
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