google spanner singleton reconnect on fault

I am creating a SpannerSingleton to stay connected for the duration of the app's life. I'm interested in connection durability... if there is a session/connection issue how can I recreate a session?

One idea was to spawn a new connection increasing the setMaxSessions to a higher number if more than 90% of the pool is exhausted. Like the opposite of exponential backoff? But where / how can I do that? I could not find anything in the client library that would let me monitor the pool status or client count.

I went with bill-pugh-singleton cuz it seemed like a good choice...

Here is what I have:

public class SpannerSingleton {

    private static Spanner spanner;
    private static SpannerOptions options;

    private static SessionPoolOptions sessionPoolOps = SessionPoolOptions
            .setMaxSessions(1000)  // 1000 concurrent queries
            .setMinSessions(100)  // keep 100 alive
            .setMaxIdleSessions(100)  // how many to keep from being idle and closed

    private SpannerSingleton() {
        try {
            options = SpannerOptions

            spanner = options.getService();

        } catch (Exception e) {

    private static class SingletonHelper{
        private static final Spanner CONNECTION = new SpannerSingleton().spanner;

    public static synchronized Spanner getSpanner() {
        return SingletonHelper.CONNECTION;


I use a Factory pattern to make the dbClient

public SpannerFactory {

    private static Spanner spanner = SpannerSingleton.getSpanner();
    private static DatabaseId dbId;

    public static DatabaseClient getConnection(String instance) {
        if (Util.isEmpty(instance)) return null;

        if ("mickey".equalsIgnoreCase(instance)) {
            dbId = DatabaseId.of(spanner.getOptions().getProjectId(), "instance1", "mickey");

        if ("mouse".equalsIgnoreCase(instance)) {
            dbId = DatabaseId.of(spanner.getOptions().getProjectId(), "instance1", "mouse");

        return spanner.getDatabaseClient(dbId);


What I would like to add is something that would check for the connection pool to see how close to starved we are and then recreate itself... I might be over thinking it, but what might happen if the connection is disrupted?


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