containerd-shim-katadbg-v2

#!/bin/bash
#
# Copyright (c) 2024 Red Hat, Inc.
#
# SPDX-License-Identifier: Apache-2.0
#
# This script allows debugging the GO kata shim using Delve.
# It will start the delve debugger in a way where it runs the program and waits
# for connections from your client interface (dlv commandline, vscode, etc).
#
# You need to configure crio or containerd to use this script in place of the
# regular kata shim binary.
# For cri-o, that would be in the runtime configuration, under
# /etc/crio/crio.conf.d/
#

# Use this for quick-testing the shim binary without a debugger
#NO_DEBUG=1

# Edit this to point to the actual shim binary that needs to be debugged
# Make sure you build it with the following flags:
# -gcflags=all=-N -l
SHIM_BINARY=/go/src/github.com/kata-containers/kata-containers/src/runtime/__debug_bin

DLV_PORT=12345

# Edit the following to make sure dlv is in the PATH
export PATH=/usr/local/go/bin/:$PATH

# The shim can be called multiple times for the same container.
# If it is already running, subsequent calls just return the socket address that
# crio/containerd need to connect to.
# This is useful for recovery, if crio/contaienrd is restarted and loses context.
#
# We usually don't want to debug those additional calls while we're already
# debugging the actual server process.
# To avoid running additional debuggers and blocking on them, we use a lock file.
LOCK_FILE=/tmp/shim_debug.lock
if [ -e $LOCK_FILE ]; then
    NO_DEBUG=1
fi

# crio can try to call the shim with the "features" or "--version" parameters
# to get capabilities from the runtime (assuming it's an OCI compatible runtime).
# No need to debug that, so just run the regular shim.
case "$1" in
  "features" | "--version")
    NO_DEBUG=1
  ;;
esac


if [ "$NO_DEBUG" == "1" ]; then
    $SHIM_BINARY "$@"
    exit $?
fi


# dlv commandline
#
# --headless: dlv run as a server, waiting for a connection
#
# --listen: port to listen to
#
# --accept-multiclient: allow multiple dlv client connections
#   Allows having both a commandline and a GUI
#
# -r: have the output of the shim redirected to a separate file.
#   This script will retrieve the output and return it to the
#   caller, while letting dlv run in the background for debugging.
#
# -- $@ => give the shim all the parameters this script was given 
#

SHIMOUTPUT=$(mktemp /tmp/shim_output_XXXXXX)

cat > $LOCK_FILE << EOF
#!/bin/bash
dlv exec ${SHIM_BINARY} --headless --listen=:$DLV_PORT --accept-multiclient -r stdout:$SHIMOUTPUT -r stderr:$SHIMOUTPUT -- "\$@"
rm $LOCK_FILE
EOF
chmod +x $LOCK_FILE

# We're starting dlv as a background task, so that it continues to run while
# this script returns, letting the caller resume its execution.
#
# We're redirecting the outputs of dlv itself to a separate file so that the
# only output the caller will have is the one from this script, giving it the
# address of the socket to connect to.
#
${LOCK_FILE} "$@" > /tmp/dlv_output 2>&1 &


# wait for the output file of the shim process to be filled with the address.
while [ ! -s $SHIMOUTPUT ]; do
    sleep 1
done

# write the adress to stdout
cat $SHIMOUTPUT
exit 0