Add warning function that includes timestamp

Knowing when a process has terminated is helpful when looking through
log files (especially very large ones). This also refactors the terminal
coloring function to be used with custom prefix and colors.

warning_log outputs red text in the current e2e inspired format:
W0628 16:58:26]: this is a test

hack/local-up-cluster.sh

@@ -399,12 +399,12 @@ cleanup()
 # a process dies unexpectedly.
 function healthcheck {
   if [[ -n "${APISERVER_PID-}" ]] && ! sudo kill -0 ${APISERVER_PID} 2>/dev/null; then
-    warning "API server terminated unexpectedly, see ${APISERVER_LOG}"
+    warning_log "API server terminated unexpectedly, see ${APISERVER_LOG}"
     APISERVER_PID=
   fi
 
   if [[ -n "${CTLRMGR_PID-}" ]] && ! sudo kill -0 ${CTLRMGR_PID} 2>/dev/null; then
-    warning "kube-controller-manager terminated unexpectedly, see ${CTLRMGR_LOG}"
+    warning_log "kube-controller-manager terminated unexpectedly, see ${CTLRMGR_LOG}"
     CTLRMGR_PID=
   fi
 
@@ -412,32 +412,37 @@ function healthcheck {
     # TODO (https://github.com/kubernetes/kubernetes/issues/62474): check health also in this case
     :
   elif [[ -n "${KUBELET_PID-}" ]] && ! sudo kill -0 ${KUBELET_PID} 2>/dev/null; then
-    warning "kubelet terminated unexpectedly, see ${KUBELET_LOG}"
+    warning_log "kubelet terminated unexpectedly, see ${KUBELET_LOG}"
     KUBELET_PID=
   fi
 
   if [[ -n "${PROXY_PID-}" ]] && ! sudo kill -0 ${PROXY_PID} 2>/dev/null; then
-    warning "kube-proxy terminated unexpectedly, see ${PROXY_LOG}"
+    warning_log "kube-proxy terminated unexpectedly, see ${PROXY_LOG}"
     PROXY_PID=
   fi
 
   if [[ -n "${SCHEDULER_PID-}" ]] && ! sudo kill -0 ${SCHEDULER_PID} 2>/dev/null; then
-    warning "scheduler terminated unexpectedly, see ${SCHEDULER_LOG}"
+    warning_log "scheduler terminated unexpectedly, see ${SCHEDULER_LOG}"
     SCHEDULER_PID=
   fi
 
   if [[ -n "${ETCD_PID-}" ]] && ! sudo kill -0 ${ETCD_PID} 2>/dev/null; then
-    warning "etcd terminated unexpectedly"
+    warning_log "etcd terminated unexpectedly"
     ETCD_PID=
   fi
 }
 
-function warning {
+function print_color {
   message=$1
+  prefix=${2:+$2: } # add colon only if defined
+  color=${3:-1}     # default is red
+  echo -n $(tput bold)$(tput setaf ${color})
+  echo "${prefix}${message}"
+  echo -n $(tput sgr0)
+}
 
-  echo $(tput bold)$(tput setaf 1)
-  echo "WARNING: ${message}"
-  echo $(tput sgr0)
+function warning_log {
+  print_color "$1" "W$(date "+%m%d %H:%M:%S")]" 1
 }
 
 function start_etcd {
@@ -1071,14 +1076,14 @@ if [[ "${START_MODE}" != "nokubelet" ]]; then
   # Detect the OS name/arch and display appropriate error.
     case "$(uname -s)" in
       Darwin)
-        warning "kubelet is not currently supported in darwin, kubelet aborted."
+        print_color "kubelet is not currently supported in darwin, kubelet aborted."
         KUBELET_LOG=""
         ;;
       Linux)
         start_kubelet
         ;;
       *)
-        warning "Unsupported host OS.  Must be Linux or Mac OS X, kubelet aborted."
+        print_color "Unsupported host OS.  Must be Linux or Mac OS X, kubelet aborted."
         ;;
     esac
 fi