fix: x11vnc race condition with Xvfb, issue #349

This fix adds a new function that will wait until X11 socket is ready, and
then start x11vnc. As this can impact start-up scripts that require X
environment, the wait_x_socket is used before `X_SCRIPTS` are started.

Author: gnzsnz

Dockerfile.template

@@ -99,7 +99,8 @@ RUN apt-get update -y && \
   groupadd --gid ${USER_GID} ibgateway && \
   useradd -ms /bin/bash --uid ${USER_ID} --gid ${USER_GID} ibgateway && \
   echo "ibgateway ALL=(ALL) NOPASSWD:ALL" | tee -a /etc/sudoers && \
-  chmod a+x ${SCRIPT_PATH}/*.sh
+  chmod a+x ${SCRIPT_PATH}/*.sh && \
+  mkdir -p /tmp/.X11-unix && chmod 1777 /tmp/.X11-unix
 
 USER ${USER_ID}:${USER_GID}
 WORKDIR ${HOME}

image-files/scripts/common.sh

@@ -263,3 +263,23 @@ start_socat() {
 	fi
 
 }
+
+wait_x_socket() {
+	DISPLAY_NUM=${DISPLAY#:}
+	# wait for X11 socket
+	if [ -S "/tmp/.X11-unix/X${DISPLAY_NUM}" ]; then
+		return 0
+	fi
+	echo ".> Waiting for Xvfb socket on $DISPLAY..."
+	timeout=50 # 50 * .2 = 10 seconds max wait
+	elapsed=0
+	while [ ! -S "/tmp/.X11-unix/X${DISPLAY_NUM}" ]; do
+		sleep 0.2
+		elapsed=$((elapsed + 1))
+		if [ $elapsed -ge $timeout ]; then
+			echo "Error: Timed out waiting for Xvfb socket!"
+			exit 1
+		fi
+	done
+	echo ".> Xvfb socket ready!"
+}

image-files/scripts/run.sh

@@ -11,6 +11,7 @@ echo "*************************************************************************"
 # shellcheck disable=SC1091
 source "${SCRIPT_PATH}/common.sh"
 
+# shellcheck disable=SC2329
 stop_ibc() {
 	echo ".> 😘 Received SIGINT or SIGTERM. Shutting down IB Gateway."
 
@@ -54,6 +55,8 @@ start_xvfb() {
 }
 
 start_vnc() {
+	# wait for X11 socket to be ready
+	wait_x_socket
 	# start VNC server
 	file_env 'VNC_SERVER_PASSWORD'
 	if [ -n "$VNC_SERVER_PASSWORD" ]; then
@@ -120,6 +123,7 @@ start_vnc
 
 # run scripts once X environment is up
 if [ -n "$X_SCRIPTS" ]; then
+	wait_x_socket
 	run_scripts "$HOME/$X_SCRIPTS"
 fi