docker/swarmkit

#!/bin/bash

## Installs delve, then runs it as a headless server
## Keeps running until killed
## Also adds some goodies: delve servers ignore interrupts, which is annoying...
## and also once a debugging session is done, the server just hangs there, which
## is equally annoying.
## This script takes care of both these things

SUBSHELL_PID=
DLV_PID_FILE=
RUNNING=true

main() {
  [ "$1" ] || usage

  ensure_delve_installed || exit $?

  local PORT="$DOCKER_SWARMKIT_DELVE_PORT"
  [ "$PORT" ] || PORT=2345

  local DLV_CMD="dlv test --accept-multiclient --headless --listen=:$PORT --api-version=2 --log $@"
  echo $DLV_CMD

  trap handle_interrupt INT

  DLV_PID_FILE=$(mktemp /tmp/dlv.XXXXXX.pid)
  local DLV_OUTPUT_FILE=$(mktemp /tmp/dlv.XXXXXX.out)

  # the weird regex is because we keep the output colored
  local HALTING_REGEX='^\e\[37mDEBU\e\[0m\[[0-9]+\] halting\s+\e\[37mlayer\e\[0m=debugger'
  while $RUNNING; do
    # using `script` to keep colored output, and `exec` to get the PID from the
    # subshell
    script --flush --quiet "$DLV_OUTPUT_FILE" --command 'printf $$ > '"$DLV_PID_FILE && exec $DLV_CMD" &
    SUBSHELL_PID=$!

    # wait for either the subshell to die, or for the "halting" line to appear
    # in the output
    tail --follow --pid="$SUBSHELL_PID" --sleep-interval=0.1 "$DLV_OUTPUT_FILE" 2> /dev/null | grep --perl-regex --line-buffered "$HALTING_REGEX" | ( read && kill_delve )

    wait "$SUBSHELL_PID"
  done

  rm -f "$DLV_PID_FILE" "$DLV_OUTPUT_FILE"
}

handle_interrupt() {
  RUNNING=false
  kill_delve
}

kill_delve() {
  if [ -r "$DLV_PID_FILE" ]; then
    local DLV_PID=$(cat "$DLV_PID_FILE")
    [ "$DLV_PID" ] && kill "$DLV_PID" &> /dev/null
  fi

  [ "$SUBSHELL_PID" ] && kill $SUBSHELL_PID &> /dev/null
}

ensure_delve_installed() {
  which dlv &> /dev/null || go get -u github.com/derekparker/delve/cmd/dlv
}

usage() {
  echo "Usage: $0 name/of/go/package [additional dlv test options]"
  exit 1
}

main "$@"