Difference between "idle_timeout" and "stream_idle_timeout" in HttpConnectionManager?

[bmgoau]

Hey Team,

We're trying to set a timeout on idle keepalive HTTP sessions that are not in the process of sending a request nor waiting for a reply. So your stock standard idle keepalive session.

We're not using gRPC, just vanilla HTTP.

We're curious how "stream_idle_timeout" differs from "idle_timeout" and which one is more appropriate to set and why?

https://www.envoyproxy.io/docs/envoy/latest/api-v2/config/filter/network/http_connection_manager/v2/http_connection_manager.proto

Looking at the documentation for those two they seem quite similar.

Is "stream_idle_timeout" specific to gRPC identified sessions? A few of us here looked through the code and (we're not experts with the code base) couldn't tell how "idle_timeout" and "stream_idle_timeout" differ from one another, one of us even believes they are effectively identical as a code level and mean the same thing.

[mattklein123]

"idle_timeout" is the time that a connection will stay alive when there are no active streams.

"stream_idle_timeout" is the time that a stream will stay alive when there are is no activity in either direction (headers, data, trailers, etc.).

Doc updates appreciated!

[kopper]

Related issue #7420

[bmgoau]

Thanks @mattklein123 .

In this sense if we translated the timers to nginx land we would have:

HttpConnectionManager.idle_timeout =
http://nginx.org/en/docs/http/ngx_http_core_module.html#keepalive_timeout and http://nginx.org/en/docs/http/ngx_http_upstream_module.html#keepalive_timeout
Effectively how long we will keep around a TCP connection that isn't in the process of sending a request or waiting for a reply. It's idle in the sense that its being held open opportunistically for a possible new conversation, to avoid the overhead of negotiating TCP and TLS again.

HttpConnectionManager.stream_idle_timeout is somewhat similar to http://nginx.org/en/docs/http/ngx_http_proxy_module.html#proxy_send_timeout and
http://nginx.org/en/docs/http/ngx_http_proxy_module.html#proxy_read_timeout
In that the TCP connection is "expected" to have some data flowing in either direction, for example a HTTP response from a server, but is "idle" in the sense that no bits and bytes are flowing on the connection. For example the upstream/server is doing work to prepare the response, or is completely stuck on some long running response.

It's too late now, but I might not have used the term "idle" in the configuration key stream_idle_timeout - and possibly gone with:

idle_timeout - how long HTTP keepalive TCP sessions should live if not being used.
connect_timeout - how long to wait for a TCP handshake and SSL handshake to succeed.
request_timeout - how long we are allowed to take to write out our request to the upstream server.
response_timeout - how long we will wait on the server to respond to a completely written request
total_stream_timeout - how long a TCP session associated with a live stream/HTTP conversation context is allowed to have no data flowing in either direction (should be longer than request_timeout + read/response_timeout)

Just my 2c :)

Thanks again!

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