Built on top of envoy-preflight.

cloudsql-proxy-is-up is a simple wrapper application which makes it easier to run applications which depend on Cloud SQL Proxy as a sidecar container for Cloud SQL access. It ensures that your application doesn't start until Cloud SQL Proxy is ready, and that Cloud SQL Proxy shuts down when the application exits. It is best used as a prefix to your existing Docker entrypoint. It executes any argument passed to it, doing a simple path lookup:

cloudsql-proxy-is-up echo "hi"
cloudsql-proxy-is-up /bin/ls -a
CMD [ \
  "/cloudsql-proxy-is-up", \
  "/usr/bin/java", \
  "-server", \
  "-Xms256m", \
  "-Xmx256m", \
  "-jar", \
  "/srv/some/artifact/application.jar" \
]

The cloudsql-proxy-is-up wrapper won't do anything unless you provide the CLOUDSQL_PROXY_API environment variable. This makes local development of your app easy.

If you do provide the CLOUDSQL_PROXY_API environment variable, cloudsql-proxy-is-up will poll the proxy indefinitely with backoff, waiting for Cloud SQL Proxy to report itself as live. Only then will it execute the command provided as an argument, so that your app can immediately start accessing the Cloud SQL.

All signals are passed to the underlying application. Be warned that SIGKILL cannot be passed, so this can leave behind a orphaned process.

When the application exits, as long as it does so with exit code 0, cloudsql-proxy-is-up will instruct Cloud SQL Proxy to shut down immediately.