Since Cloud Spanner emulator’s beta launch in April, 2020, we have seen strong adoption of the local emulator from customers of Cloud Spanner. Several new and existing customers adopted the emulator in their development & continuous test pipelines. They noticed significant improvements in developer productivity, speed of test execution, and error-free applications deployed to production. We also added several features in this release based on the valuable feedback we received from beta users. The full list of features is documented in the GitHub readme.
Partition APIs
When reading or querying large amounts of data from Cloud Spanner, it can be useful to divide the query into smaller pieces, or partitions, and use multiple machines to fetch the partitions in parallel. The emulator now supports Partition Read, Partition Query, and Partition DML APIs.Cloud Spanner client libraries
With the GA launch, the latest versions of all the Cloud Spanner client libraries support the emulator. We have added support for C#, Node.js, PHP, Python, Ruby client libraries and the Cloud Spanner JDBC driver. This is in addition to C++, Go and Java client libraries that were already supported with the beta launch. Be sure to check out the minimum version for each of the client libraries that support the emulator.Use the Getting Started guides to try the emulator with the client library of your choice.
SQL features
Emulator now supports the full set of SQL features provided by Cloud Spanner. Some of the notable additions being support for SQL functions JSON_VALUE, JSON_QUERY, CEILING, POWER, CHARACTER_LENGTH, and FORMAT. We now also support untyped parameter bindings in SQL statements which are used by our client libraries written in languages with dynamic typing e.g., Python, PHP, Node.js and Ruby.Using Emulator in CI/CD pipelines
You may now point the majority of your existing CI/CD to the Cloud Spanner emulator instead of a real Cloud Spanner instance brought up on GCP. This will save you both cost and time, since an emulator instance comes up instantly and is free to use!What’s even better is that you can bring up multiple instances in a single execution of the emulator, and of course multiple databases. Thus, tests that interact with a Cloud Spanner database can now run in parallel since each of them can have their own database, making tests hermetic. This can reduce flakiness in unit tests and reduce the number of bugs that can make their way to continuous integration tests or to production.
In case your existing CI/CD architecture assumes the existence of a Cloud Spanner test instance and/or test database against which the tests run, you can achieve similar functionality with the emulator as well. Note that the emulator doesn’t come up with a default instance or a default database as we expect users to create instances and databases as required in their tests for hermeticity as explained above. Below are two examples of how you can bring up an emulator with a default instance or database: 1) By using a docker image or 2) Programmatically.
Starting Emulator from Docker
The emulator can be started using Docker on Linux, MacOS, and Windows. As a prerequisite, you would need to install Docker on your system. To bring up an emulator with a default database/instance, you can execute a shell script in your docker file to do so. Such a script would make RPC calls to CreateInstance and CreateDatabase after bringing up the emulator server. You can also look at this example on how to put this together when using docker.Run Emulator Programmatically
You can bring up the emulator binary in the same process as your test program. Then you can then create a default instance/database in your ‘Setup’ and clean up the same when the tests are over. Note that the exact procedure for bringing up an ‘in-process’ service may vary with the client library language and platform of your choice.Other alternatives to start the emulator, including pre-built linux binaries, are listed here.
Try it now
Learn more about Google Cloud Spanner emulator and try it out now.
By Asheesh Agrawal, Google Open Source
