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atenet-router limits kernel send queues to slow clients - #3321
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Chuang Wang (chuangw6) wants to merge 1 commit into
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Bowei Du (bowei)
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A client that stops reading lets each of its sockets queue up to tcp_wmem's maximum, 4 MiB on GKE nodes, charged to the Envoy container but missing from Envoy's statistics. With TCP_NOTSENT_LOWAT at 16 KiB, the backlog stays in Envoy's buffers and upstream. In the Envoy benchmark this cut socket memory behind a stalled client from 981 to 57 KiB per connection, with throughput within run-to-run noise. Add --router-tcp-notsent-lowat, default 16384, set as an Envoy socket option on the TLS listeners and on the clusters that dial atunnel. 0 leaves the kernel default. --router-tcp-send-buffer and --router-tcp-receive-buffer set fixed buffer sizes, off by default: they cap a connection at the buffer size per round trip. Signed-off-by: Chuang Wang <chuangw@google.com>
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Merged into #3320. |
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Part of #3133; design and data in
docs/network-socket-memory.md(#3319).The Envoy ingress router sets
TCP_NOTSENT_LOWATto 16 KiB on its client sockets and its sockets to atunnel. New flags:--router-tcp-notsent-lowat(default 16384),--router-tcp-send-bufferand--router-tcp-receive-buffer(default 0).Separately, the actor clusters keep Envoy's default 256 MiB HTTP/2 stream window. In the benchmark each stalled stream held about 15 MiB of heap and kept growing. That's phase 2; see the doc's "Not covered".