How to Connect to Multiple Google spanner DB running on different host from Spring Boot App

Question

Hi I am trying to connect my spring boot application to multiple google cloud spanner DB. I am able to connect with Single database by making entry in application.yml file. My requirement is tonnect with two spanner database in same application. Please help me.

Answer 1

The approach is a lengthy one. The com.google.cloud:spring-cloud-gcp-starter-data-spanner lib autoconfigures using application.properties

To avoid this, a. you use spring-cloud-gcp-data-spanner b. You would have to define the spannerTemplate bean manually

Here is a quick code snippet

  @Bean
public com.google.auth.Credentials getCredentials() {

    try {
        return new DefaultCredentialsProvider(Credentials::new).getCredentials();
    } catch (IOException ex) {
        throw new RuntimeException(ex);
    }
}

@Bean
public SpannerOptions spannerOptions() {
    return SpannerOptions.newBuilder()
            .setProjectId("sab-dev-anciq-ml-gol-8565")
            .setSessionPoolOption(SessionPoolOptions.newBuilder().setMaxSessions(10).build())
            .setCredentials(getCredentials())
            .build();
}

@Bean
public Spanner spanner(SpannerOptions spannerOptions) {
    return spannerOptions.getService();
}

@Bean
public DatabaseId databaseId() {
    return DatabaseId.of("your_gcp_project_id",
            "instance_name",
            "db_name");
}

@Bean
public DatabaseClient spannerDatabaseClient(Spanner spanner, DatabaseId databaseId) {
    return spanner.getDatabaseClient(databaseId);
}


@Bean
public SpannerMappingContext spannerMappingContext(Gson gson) {
    return new SpannerMappingContext(gson);
}

@Bean
public SpannerEntityProcessor spannerConverter(SpannerMappingContext mappingContext) {
    return new ConverterAwareMappingSpannerEntityProcessor(mappingContext);
}

@Bean
public SpannerSchemaUtils spannerSchemaUtils(
        SpannerMappingContext spannerMappingContext, SpannerEntityProcessor spannerEntityProcessor) {
    return new SpannerSchemaUtils(spannerMappingContext, spannerEntityProcessor, true);
}

@Bean
public SpannerMutationFactory spannerMutationFactory(
        SpannerEntityProcessor spannerEntityProcessor,
        SpannerMappingContext spannerMappingContext,
        SpannerSchemaUtils spannerSchemaUtils) {
    return new SpannerMutationFactoryImpl(
            spannerEntityProcessor, spannerMappingContext, spannerSchemaUtils);
}

@Bean("hostSpannerTemplate")
public SpannerTemplate spannerTemplateForHostProject(
        DatabaseClient databaseClient,
        SpannerMappingContext mappingContext,
        SpannerEntityProcessor spannerEntityProcessor,
        SpannerMutationFactory spannerMutationFactory,
        SpannerSchemaUtils spannerSchemaUtils) {
    return new SpannerTemplate(
            () -> databaseClient,
            mappingContext,
            spannerEntityProcessor,
            spannerMutationFactory,
            spannerSchemaUtils);
}

You can now use spannerTemplateForHostProject as a bean to do your curd ops related to host project

Similiarly using Qualifiers you can now define another spannerTemplate that uses databaseClient2 using qualifier in argument