HarbourBridge is a stand-alone open source tool for Cloud Spanner evaluation and migration, using data from an existing PostgreSQL, MySQL or DynamoDB database. The tool ingests schema and data from either a pg_dump/mysqldump file or directly from the source database, and supports both schema and data migration. For schema migration, HarbourBridge automatically builds a Spanner schema from the schema of the source database. This schema can be customized using the HarbourBridge schema assistant. For data migration, HarbourBridge creates a new Spanner database using the Spanner schema built during schema migration, and populates it with data from the source database.

For more details on schema customization and use of the schema assistant, see web/README. The rest of this README describes the command-line capabilities of HarbourBridge.

HarbourBridge is designed to simplify Spanner evaluation and migration, and in particular for migrating moderate-size PostgreSQL/MySQL/DynamoDB datasets to Spanner (up to about 100GB). Many features of PostgreSQL/MySQL, especially those that don't map directly to Spanner features, are ignored, e.g. stored functions and procedures, and sequences. Types such as integers, floats, char/text, bools, timestamps, and (some) array types, map fairly directly to Spanner, but many other types do not and instead are mapped to Spanner's STRING(MAX). In the case of DynamoDB, the schema is inferred based on a certain amount of sampled data.

View HarbourBridge as a way to get up and running fast, so you can focus on critical things like tuning performance and getting the most out of Spanner. Expect that you'll need to tweak and enhance what HarbourBridge produces.

To use the tool on a PostgreSQL database called mydb, run

# By default, the driver is "pg_dump".
pg_dump mydb | harbourbridge
# Or,
pg_dump mydb | harbourbridge -driver=pg_dump

To use the tool on a MySQL database called mydb, run

mysqldump mydb | harbourbridge -driver=mysqldump

To use the tool on a DynamoDB database, run

harbourbridge -driver=dynamodb

HarbourBridge accepts pg_dump/mysqldump's standard plain-text format, but not archive or custom formats. More details on usage can be found in Example usage section.

HarbourBridge automatically determines the cloud project and Spanner instance to use, and generates a new Spanner database name (prefixed with {driver}_ and today's date). Command-line flags can be used to explicitly set the Spanner instance or database name. See Options.

WARNING: Please check that permissions for the Spanner instance used by HarbourBridge are appropriate. Spanner manages access control at the database level, and the database created by HarbourBridge will inherit default permissions from the instance. All data written by HarbourBridge is visible to anyone who can access the created database.

As it processes the data, HarbourBridge reports on progress, provides stats on the schema and data conversion steps, and an overall assessment of the quality of the conversion. It also generates a schema file, report file and a session file (and a bad-data file if data was dropped). See Files Generated by HarbourBridge. Details of how source database's schema is mapped to Spanner can be found in the Schema Conversion section.

This tool is part of the Cloud Spanner Ecosystem, a community contributed and supported open source repository. Please report issues and send pull requests. See the HarbourBridge Whitepaper for a discussion of our plans for the tool.

Note that the HarbourBridge tool is not an officially supported Google product and is not officially supported as part of the Cloud Spanner product.

Complete the steps described in Set up, which covers creating and setting a default Google Cloud project, enabling billing, enabling the Cloud Spanner API, and setting up OAuth 2.0 to get authentication credentials to use the Cloud Spanner API.

In particular, ensure that you run

gcloud auth application-default login

to set up your local development environment with authentication credentials.

Set the GCLOUD_PROJECT environment variable to your Google Cloud project ID:

export GCLOUD_PROJECT=my-project-id

If you do not already have a Cloud Spanner instance, or you want to use a separate instance specifically for running HarbourBridge, then create a Cloud Spanner instance by following the "Create an instance" instructions on the Quickstart using the console guide. HarbourBridge will create a database for you, but it will not create a Spanner instance.

Install Go (download) on your development machine if it is not already installed, configure the GOPATH environment variable if it is not already configured using export GOPATH=$(go env GOPATH), and test your installation.

You can make a copy of the HarbourBridge codebase from the github repository and use "go run":

git clone https://github.com/cloudspannerecosystem/harbourbridge
cd harbourbridge
go run github.com/cloudspannerecosystem/harbourbridge -driver=pg_dump < my_pg_dump_file

alias harbourbridge="go run github.com/cloudspannerecosystem/harbourbridge"

This workflow also allows you to modify or customize the HarbourBridge codebase.

To use the tool on a PostgreSQL database called mydb, run

pg_dump mydb | harbourbridge -driver=pg_dump

To use the tool on a MySQL database called mydb, run

mysqldump mydb | harbourbridge -driver=mysqldump

To use the tool on a DynamoDB database, run

harbourbridge -driver=dynamodb

More details on running harbourbridge can be found in Example usage section.

This command will use the cloud project specified by the GCLOUD_PROJECT environment variable, automatically determine the Cloud Spanner instance associated with this project, convert the source schema to a Spanner schema (For MySQL/Postgres) or infer a schema from the DynamoDB instance, create a new Cloud Spanner database with this schema, and finally, populate this new database with the data from the source database. If the project has multiple instances, then list of available instances will be shown and you will have to pick one of the available instances and set the --instance flag. The new Cloud Spanner database will have a name of the form {DRIVER}_{DATE}_{RANDOM}, where{DRIVER} is the drivername specified,{DATE}is today's date, and{RANDOM} is a random suffix for uniqueness.

See the Troubleshooting Guide for help on debugging issues.

HarbourBridge also generates several files when it runs: a schema file, a report file (with detailed analysis of the conversion), a session file and a bad data file (if any data was dropped).

If you don't have ready access to a PostgreSQL or MySQL database, some example dump files can be found here. The files cart.pg_dump and cart.mysqldump contain pg_dump and mysqldump output for a very basic shopping cart application (just two tables, one for products and one for user carts). The files singers.pg_dump and singers.mysqldump contain pg_dump and mysqldump output for a version of the Cloud Spanner singers example. To use HarbourBridge on cart.pg_dump, download the file locally and run

harbourbridge -driver=pg_dump < cart.pg_dump

Once the tool has completed, you can verify the new database and its content using the Google Cloud Console. Go to the Cloud Spanner Instances page, select your Spanner instance, and then find the database created by HarbourBridge and select it. This will list the tables created by HarbourBridge. Select a table, and take a look at its schema and data. Next, go to the query page, and try some SQL statements. For example

SELECT COUNT(*) from mytable

to check the number of rows in table mytable.

The tables created by HarbourBridge provide a starting point for evaluation of Spanner. While they preserve much of the core structure of your PostgreSQL/MySQL schema and data, many key features have been dropped, including functions, sequences, procedures,triggers, and views. For DynamoDB, the conversion from schemaless to schema is focused on the use-case where customers use DynamoDB in a consistent, structured way with a fairly well defined set of columns and types.

As a result, the out-of-the-box performance you get from these tables could be slower than what you get from PostgreSQL/MySQL/DynamoDB.

To improve performance, also consider using Interleaved Tables to tune performance.

View HarbourBridge as a base set of functionality for Spanner evalution that can be readily expanded. Consider forking and modifying the codebase to add the functionality you need. Please file issues and send PRs for fixes and new functionality. See our backlog of open issues. Our plans and aspirations for developing HarbourBridge further are outlined in the HarbourBridge Whitepaper.

You can also change the way HarbourBridge behaves by directly editing the pg_dump/mysqldump output. For example, suppose you want to try out different primary keys for a table. First run pg_dump/mysqldump and save the output to a file. Then modify (or add) the relevant ALTER TABLE ... ADD CONSTRAINT ... PRIMARY KEY ... statement in the pg_dump/mysqldump output file so that the primary keys match what you need. Then run HarbourBridge on the modified pg_dump/mysqldump output.

HarbourBridge generates several files as it runs:

• Schema file (ending in schema.txt): contains the generated Spanner schema, interspersed with comments that cross-reference to the relevant PostgreSQL/MySQL schema definitions.

• Session file (ending in session.json): contains all schema and data conversion state endcoded as JSON. It is basically a snapshot of the session.

• Report file (ending in report.txt): contains a detailed analysis of the PostgreSQL/MySQL to Spanner migration, including table-by-table stats and an analysis of PostgreSQL/MySQL types that don't cleanly map onto Spanner types. Note that PostgreSQL/MySQL types that don't have a corresponding Spanner type are mapped to STRING(MAX).

• Bad data file (ending in dropped.txt): contains details of data that could not be converted and written to Spanner, including sample bad-data rows. If there is no bad-data, this file is not written (and we delete any existing file with the same name from a previous run).

By default, these files are prefixed by the name of the Spanner database (with a dot separator). The file prefix can be overridden using the -prefix option.

HarbourBridge accepts the following options:

-dbname Specifies the name of the Spanner database to create. This must be a new database. If dbname is not specified, HarbourBridge creates a new unique dbname.

-instance Specifies the Spanner instance to use. The new database will be created in this instance. If not specified, the tool automatically determines an appropriate instance using gcloud.

-driver Specifies the driver to use for schema and data conversion. Supported drivers are 'postgres', 'pg_dump', 'mysql' and 'mysqldump'. By default, the driver is 'pg_dump'.

-schema-sample-size Specifies the number of rows to use for inferring schema (only for DynamoDB). By default, the schema sample size is 100,000.

-prefix Specifies a file prefix for the report, schema, and bad-data files written by the tool. If no file prefix is specified, the name of the Spanner database (plus a '.') is used.

-v or -verbose Specifies verbose mode. This will cause HarbourBridge to output detailed messages about the conversion.

-schema-only Specifies that only schema processing will be performed. Any data in the source database will be ignored.

-data-only Specifies that only data migration will be performed. A spanner database will be created based on the schema state provided by a session file (-session) and data will be migrated.

-skip-foreign-keys Controls whether we add foreign key constraints after data migration is complete. This flag cannot be used with schema-only mode, and does not affect the generation of foreign key statements during schema processing i.e. foreign key constraints will still appear in the generated Spanner DDL files.

-session Specifies a session file that contains all schema and data conversion state endcoded as JSON.

-dump-file Specifies the path where the dump file is stored. If the location is Google Cloud Storage (GCS), you can use the following format: -dump-file=gs://{bucket_name}/{path/to/dump_file}. Please ensure you have read pemissions to the GCS bucket you would like to use.

Details on HarbourBridge example usage can be found here:

• PostgreSQL example usage
• MySQL example usage
• DynamoDB example usage

Details on HarbourBridge schema conversion can be found here:

• PostgreSQL schema conversion
• MySQL schema conversion
• DynamoDB schema conversion

HarbourBridge converts PostgreSQL/MySQL/DynamoDB data to Spanner data based on the Spanner schema it constructs. Conversion for most data types is fairly straightforward, but several types deserve discussion. Note that HarbourBridge is not intended for databases larger than about 100GB. Details on HarbourBridge data conversion can be found here:

• PostgreSQL data conversion
• MySQL data conversion
• DynamoDB data conversion

The following steps can help diagnose common issues encountered while running HarbourBridge.

First, check that the driver is correctly configured to connect to your database. Driver configuration varies depending on the driver used.

If you are using pg_dump (-driver=pg_dump), check that pg_dump is correctly configured to connect to your PostgreSQL database. Note that pg_dump uses the same options as psql to connect to your database. See the psql and pg_dump documentation.

Access to a PostgreSQL database is typically configured using the PGHOST, PGPORT, PGUSER, PGDATABASE environment variables, which are standard across PostgreSQL utilities.

It is also possible to configure access via pg_dump's command-line options --host, --port, and --username.

In this case, HarbourBridge connects directly to the PostgreSQL database to retrieve table schema and data. Set the -driver=postgres and provide the environment variables PGHOST, PGPORT, PGUSER, PGDATABASE. Password can be specified either in the PGPASSWORD environment variable or provided at the password prompt.

If you are using mysqldump (-driver=mysqldump), check that mysqldump is correctly configured to connect to your MySQL database via the command-line options --host, --port, and --user. Note that mysqldump uses the same options as mysql to connect to your database. See the mysql and mysqldump documentation.

In this case, HarbourBridge connects directly to the MySQL database to retrieve table schema and data. Set the -driver=mysql and provide the environment variables MYSQLHOST, MYSQLPORT, MYSQLUSER, MYSQLDATABASE. Password can be specified either in the MYSQLPWD environment variable or provided at the password prompt.

In this case, HarbourBridge connects directly to the DynamoDB database to retrieve table schema and data. Set the -driver=dynamodb and provide the environment variables AWS_ACCESS_KEY_ID, AWS_SECRET_ACCESS_KEY, AWS_REGION. If you use a custom endpoint for dynamodb, you can specify that using the environment variable DYNAMODB_ENDPOINT_OVERRIDE.

Next, verify that pg_dump/mysqldump is generating plain-text output. If your database is small, try running

{ pg_dump/mysqldump } > file

and look at the output file. It should be a plain-text file containing SQL commands. If your database is large, consider just dumping the schema via the --schema-only for pg_dump and --no-data for mysqldump command-line option.

pg_dump/mysqldump can export data in a variety of formats, but HarbourBridge only accepts plain format (aka plain-text). See the pg_dump documentation and mysqldump documentation for details about formats.

The HarbourBridge tool can fail for a number of reasons.

HarbourBridge needs to read the pg_dump/mysqldump output twice, once to build a schema and once for data ingestion. When pg_dump/mysqldump output is directly piped to HarbourBridge, stdin is not seekable, and so we write the output to a temporary file. That temporary file is created via Go's ioutil.TempFile. On many systems, this creates a file in /tmp, which is sometimes configured with minimal space. A simple workaround is to separately run pg_dump/mysqldump and write its output to a file in a directory with sufficient space. For example, if the current working directory has space, then:

{ pg_dump/mysqldump } > tmpfile
harbourbridge < tmpfile

Make sure you cleanup the tmpfile after HarbourBridge has been run. Another option is to set the location of Go's TempFile e.g. by setting the TMPDIR environment variable.

HarbourBridge uses the pg_query_go library for parsing pg_dump and pingcap parser for parsing mysqldump. It is possible that the pg_dump/mysqldump output is corrupted or uses features that aren't parseable. Parsing errors should generate an error message of the form Error parsing last 54321 line(s) of input.

HarbourBridge uses standard Google Cloud credential mechanisms for accessing Cloud Spanner. If this is mis-configured, you may see errors containing "unauthenticated", or "cannot fetch token", or "could not find default credentials". You might need to run gcloud auth application-default login. See the Before you begin section for details.

In this case, the error message printed by the tool should help identify the cause. It could be an API permissions issue. For example, the Cloud Spanner API may not be appropriately configured. See Before you begin section for details. Alternatively, you have have hit the limit on the number of databases per instances (currently 100). This can occur if you re-run the HarbourBridge tool many times, since each run creates a new database. In this case you'll need to delete some databases.

The schema, report, and bad-data files generated by HarbourBridge contain detailed information about the schema and data conversion process, including issues and problems encountered.

If you are having problems with HarbourBridge, please submit an issue.