This document explains the configurations of Scalar DB SQL.

Scalar DB SQL offers two connection modes: Direct and Server modes. With Direct mode, Scalar DB SQL client-side library directly uses Scalar DB API. On the other hand, with Server mode, Scalar DB SQL client-side library uses Scalar DB API indirectly through Scalar DB SQL Server.

There are Direct mode specific configurations and Server mode specific configurations. So we first explain the common configurations, then the Direct mode specific configurations, and the Server mode specific configurations. And lastly, we explain the Scalar DB SQL Server configurations.

Common configurations

The common configurations are as follows:

name description default
scalar.db.sql.default_transaction_mode Default transaction mode. TRANSACTION or TWO_PHASE_COMMIT_TRANSACTION can be set. TRANSACTION
scalar.db.sql.connection_mode Connection mode. DIRECT or SERVER can be set. DIRECT

Configurations for Direct mode

The configurations for Direct mode are as follows:

name description default
scalar.db.sql.statement_cache.enabled Enable the statement cache. false
scalar.db.sql.statement_cache.size The maximum number of cached statement. 100

Note that in the Direct mode, you need to configure underlining storage/database, as well. Please see Getting Started with Scalar DB for the details of the underlining storage/database configurations.

Please see also Scalar DB SQL Server for the details of Scalar DB SQL Server.

Configurations for Server mode

The configurations for Server mode are as follows:

name description default
scalar.db.sql.server_mode.host Host name for Scalar DB SQL Server to connect. false
scalar.db.sql.server_mode.port Port number for Scalar DB SQL Server. 60052
scalar.db.sql.server_mode.deadline_duration_millis a deadline duration (milliseconds) for gRPC connection. 60000

Configurations for Scalar DB SQL Server

The configurations for Scalar DB SQL Server are as follows:

name description default
scalar.db.sql.server.port Port number for grpc server. 60052
scalar.db.sql.server.prometheus_exporter_port Port number for Prometheus exporter. 8080

Please see also Scalar DB SQL Server for the details of Scalar DB SQL Server.

Configuration examples

Example 1

[App (Scalar DB SQL Library)] ---> [underlying storage/database]

In this setting, App (Scalar DB SQL Library) connects to the underlying storage/database (in this case Cassandra) directly. Note that this setting exists only for development purposes and is not recommended for production use. This is because the App needs to implement scalar-admin interface to take transactionally-consistent backups for Scalar DB, which requires an extra burden for users.

In this case, an example of configurations in App are as follows:

#
# For underlying storage/database configurations
#

# Comma separated contact points
scalar.db.contact_points=<cassandra host>

# Credential information to access the database
scalar.db.username=<username>
scalar.db.password=<password>

# Storage implementation
scalar.db.storage=cassandra

#
# For Scalar DB SQL
#

# Enable the statement cache
scalar.db.sql.statement_cache.enabled=true

# The maximum number of cached statement
scalar.db.sql.statement_cache.size=300

Example 2

[App (Scalar DB SQL Library)] ---> [Scalar DB SQL Server] ---> [Scalar DB Server] ---> [underlying storage/database]

In this setting, App (Scalar DB SQL Library) connects to an underlying storage/database through Scalar DB SQL Server and Scalar DB Server. This setting is recommended for production use. This is because Scalar DB Server implements scalar-admin interface, which enables you to take transactionally-consistent backups for Scalar DB by pausing the Scalar DB Server.

Let’s assume Scalar DB Server is already set up. Please see Scalar DB server for the details of configurations of Scalar DB Server.

In this case, an example of configurations for App is as follows:

#
# For Scalar DB SQL
#

# Connection mode
scalar.db.sql.connection_mode=SERVER

# Host name for Scalar DB SQL Server
scalar.db.sql.server_mode.host=<Scalar DB SQL Server host>

# Port number for Scalar DB SQL Server
scalar.db.sql.server_mode.port=<Scalar DB SQL Server port>

And an example of configurations for Scalar DB SQL Server is as follows:

#
# For underlying storage/database configurations
#

# Host name for Scalar DB Server
scalar.db.contact_points=<Scalar DB Server host>

# Port number for Scalar DB Server
scalar.db.contact_port=<Scalar DB Server port>

# Storage implementation
scalar.db.storage=grpc

#
# For Scalar DB SQL
#

# Enable the statement cache
scalar.db.sql.statement_cache.enabled=true

# The maximum number of cached statement
scalar.db.sql.statement_cache.size=300