Schedule bpftrace programs on your kubernetes cluster using the kubectl
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fntlnz fix(kubectl-trace): bpftracebase using specified version
Signed-off-by: Lorenzo Fontana <lo@linux.com>
Latest commit 04e3299 Jan 11, 2019

README.md

kubectl trace

kubectl trace is a kubectl plugin that allows you to schedule the execution of bpftrace programs in your Kubernetes cluster.

Screenshot showing the read.bt program for kubectl-trace

Installation

go get -u github.com/iovisor/kubectl-trace/cmd/kubectl-trace

This will download and compile kubectl-trace so that you can use it as a kubectl plugin with kubectl trace

Usage

You don't need to setup anything on your cluster before using it, please don't use it already on a production system, just because this isn't yet 100% ready.

Run a program from string literal:

In this case we are running a program that probes a tracepoint on the node ip-180-12-0-152.ec2.internal.

kubectl trace run ip-180-12-0-152.ec2.internal -e "tracepoint:syscalls:sys_enter_* { @[probe] = count(); }"

Run a program from file:

Here we run a program named read.bt against the node ip-180-12-0-152.ec2.internal

kubectl trace run ip-180-12-0-152.ec2.internal -f read.bt

Run a program against a Pod

Screenshot showing the read.bt program for kubectl-trace

That pod has a Go program in it that is at /caturday, that program has a function called main.counterValue in it that returns an integer every time it is called.

The purpose of this program is to load an uretprobe on the /caturday binary so that every time the main.counterValue function is called we get the return value out.

Since kubectl trace for pods is just an helper to resolve the context of a container's Pod, you will always be in the root namespaces but in this case you will have a variable $container_pid containing the pid of the root process in that container on the root pid namespace.

What you do then is that you get the /caturday binary via /proc/$container_pid/exe, like this:

kubectl trace run -e 'uretprobe:/proc/$container_pid/exe:"main.counterValue" { printf("%d\n", retval) }' pod/caturday-566d99889-8glv9 -a -n caturday

Running against a Pod vs against a Node

In general, you run kprobes/kretprobes, tracepoints, software, hardware and profile events against nodes using the node/node-name syntax or just use the node name, node is the default.

When you want to actually probe an userspace program with an uprobe/uretprobe or use an user-level static tracepoint (usdt) your best bet is to run it against a pod using the pod/pod-name syntax.

It's always important to remember that running a program against a pod, as of now, is just a facilitator to find the process id for the binary you want to probe on the root process namespace.

You could do the same thing when running in a Node by knowing the pid of your process yourself after entering in the node via another medium, e.g: ssh.

So, running against a pod doesn't mean that your bpftrace program will be contained in that pod but just that it will pass to your program some knowledge of the context of a container, in this case only the root process id is supported via the $container_pid variable.

More bpftrace programs

Need more programs? Look here.

Status of the project

🏆 All the MVP goals are done!

To consider this project (ready) the goals are:

  • basic program run and attach
  • list command to list running traces - command: kubectl trace get
  • delete running traces
  • run without attach
  • attach command to attach only - command: kubectl trace attach <program>
  • allow sending signals (probably requires a TTY), so that bpftrace commands can be notified to stop by the user before deletion and give back results

More things after the MVP:

The stuff here had been implemented - YaY

The program is now limited to run programs only on your nodes but the idea is to have the ability to attach only to the user namespace of a pod, like:

kubectl trace run pod/<pod-name> -f read.bt

And even on a specific container

kubectl trace run pod/<pod-name> -c <container> f read.bt

So I would say, the next thing is to run bpftrace programs at a pod scope other than at node scope.

bpftrace work

I also plan to contribute some IO functions to bpftrace to send data to a backend database like InfluxDB instead of only stdout because that would enable having things like graphs showing

Contributing

Please just do it, this is MIT licensed so no reason not to!