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Protocol Detection Errors

Linkerd is capable of proxying all TCP traffic, including TLS connections, WebSockets, and HTTP tunneling. In most cases where the client speaks first when a new connection is made, Linkerd can detect the protocol in use, allowing it to perform per-request routing and metrics.

If your proxy logs contain messages like protocol detection timed out after 10s, or you’re experiencing 10-second delays when establishing connections, you’re probably running a situation where Linkerd cannot detect the protocol. This is most common for protocols where the server speaks first, and the client is waiting for information from the server. It may also occur with non-HTTP protocols for which Linkerd doesn’t yet understand the wire format of a request.

You’ll need to understand exactly what the situation is to fix this:

  • A server-speaks-first protocol will probably need to be configured as a skip or opaque port, as described in the protocol detection documentation.

  • If you’re seeing transient protocol detection timeouts, this is more likely to indicate a misbehaving workload.

  • If you know the protocol is client-speaks-first but you’re getting consistent protocol detection timeouts, you’ll probably need to fall back on a skip or opaque port.

Note that marking ports as skip or opaque has ramifications beyond protocol detection timeouts; see the protocol detection documentation for more information.