q's Introduction

q

A smol 🤏 static rust binary which can be used to surface kernel queueing metrics with eBPF kprobes.

The easiest metrics to surface are anything found in the sock API.

The following 'accept queues' are currently instrumented.

TCP/IPv4
TCP/IPv6
UDP (Connectionless)
Unix domain

Building

# Compile the eBPF probe, embed the probe into the binary, compile and install the static binary
make ebpf install

Running

sudo q

Observing The Linux Accept Queue

Execute the dysfunctional-listen-not-accept-tcp-exec server and send curl requests to localhost:9064.

Notice that the requests will accumulate in the accept queue even once the client has been killed. The only way to "flush" the queue is to terminate the server. I am currently unsure if Linux provides another way to clean up these orphaned connections.

[2023-03-13T04:50:35Z INFO  q] Success! Loaded eBPF probe into kernel
[2023-03-13T04:50:35Z INFO  q]  --> Attached: kprobe__tcp_conn_request
[2023-03-13T04:50:35Z INFO  q]  --> Attached: kprobe__inet_csk_accept
[2023-03-13T04:50:35Z INFO  q] Waiting for Ctrl-C...
[2023-03-13T04:50:44Z INFO  qprobe] AF_INET 'accept queue' qlen: 8, qmax: 4096, src address: 0.0.0.0, dest address: 0.0.0.0
[2023-03-13T04:50:48Z INFO  qprobe] AF_INET 'accept queue' qlen: 9, qmax: 4096, src address: 0.0.0.0, dest address: 0.0.0.0
[2023-03-13T04:50:50Z INFO  qprobe] AF_INET 'accept queue' qlen: 10, qmax: 4096, src address: 0.0.0.0, dest address: 0.0.0.0
[2023-03-13T04:50:51Z INFO  qprobe] AF_INET 'accept queue' qlen: 11, qmax: 4096, src address: 0.0.0.0, dest address: 0.0.0.0

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