travis.yml: add race detector job for Swarm (#19148)

build/travis_keepalive.sh

@@ -0,0 +1,46 @@
+#!/usr/bin/env bash
+
+# travis_keepalive runs the given command and preserves its return value,
+# while it forks a child process what periodically produces a log line,
+# so that Travis won't abort the build after 10 minutes.
+
+# Why?
+# `t.Log()` in Go holds the buffer until the test does not pass or fail,
+# and `-race` can increase the execution time by 2-20x.
+
+set -euo pipefail
+
+readonly KEEPALIVE_INTERVAL=300 # seconds => 5m
+
+main() {
+  keepalive
+  $@
+}
+
+# Keepalive produces a log line in each KEEPALIVE_INTERVAL.
+keepalive() {
+  local child_pid
+  # Note: We fork here!
+  repeat "keepalive" &
+  child_pid=$!
+  ensureChildOnEXIT "${child_pid}"
+}
+
+repeat() {
+  local this="$1"
+  while true; do
+    echo "${this}"
+    sleep "${KEEPALIVE_INTERVAL}"
+  done
+}
+
+# Ensures that the child gets killed on normal program exit.
+ensureChildOnEXIT() {
+  # Note: SIGINT and SIGTERM are forwarded to the child process by Bash
+  # automatically, so we don't have to deal with signals.
+
+  local child_pid="$1"
+  trap "kill ${child_pid}" EXIT
+}
+
+main "$@"