Name

sqitch-configuration - Hierarchical engine and target configuration

Description

The specification of database targets is core to Sqitch database change management. A target consists of a database connection URI, a plan file, change script directories, a registry schema or database name, and the path to a database engine command-line client. Sqitch determines the values for these attributes via a hierarchical evaluation of the runtime configuration, examining and selecting from these values:

  1. Command-line options

  2. Target-specific configuration

  3. Engine-specific configuration

  4. Core configuration

  5. A reasonable default

This document explains how this evaluation works, and how to use the init, config, engine, and target commands to configure these values for various deployment scenarios.

Project Initialization

Typically, the first thing you do with Sqitch is use the init command to start a new project. Now, the most important thing Sqitch needs to know is what database engine you'll be managing, so it's best to use the --engine option right up front to start off on the right food. Here, we start a project called "widgets" to manage PostgreSQL databases:

  > sqitch --engine pg init widgets
  Created sqitch.conf
  Created sqitch.plan
  Created deploy/
  Created revert/
  Created verify/

This creates a very simple configuration file with most of the settings commented out, like so:

  > cat sqitch.conf
  [core]
    engine = pg
    # plan_file = sqitch.plan
    # top_dir = .
    # deploy_dir = deploy
    # revert_dir = revert
    # verify_dir = verify
    # extension = sql
  # [engine "pg"]
    # target = db:pg:
    # registry = sqitch
    # client = psql

The [core] section contains default configurations, the most important of which is the default engine, pg. Of course, it's the only engine this project supports, and the values of the other configuration variables are reasonable for a single-engine project. If your Sqitch project never needs to manage more than one database engine, this might be all you need: the current directory is the top directory of the project, and it's here you'll find the plan file as well as the deploy, revert, and verify script directories. Once you start using the add command to add changes, and the deploy command to deploy changes to a database, these variables will be used extensively.

The [engine "pg"] section houses the variables more specific to the engine. The target defines the default database URI for connecting to a PostgreSQL database. As you can see there isn't much here, but if you were to distribute this project, it's likely that your users would specify a target URI when deploying to their own databases. The registry determines where Sqitch will store its own metadata when managing a database; generally the default, "sqitch", is fine.

More interesting, perhaps, is the client setting, which defaults to the appropriate engine-specific client name appropriate for your OS. Sqitch will assume it can find psql in your path.

Global Configuration

But sometimes that's not the case. Let's say that the psql client on your system is not in the path, but instead in /usr/local/pgsql/bin/psql. You could set its location right here in the project configuration file, but that won't do if you end up distributing the project to other users who might have their client somewhere else. For that use case, the default path-specific value is probably best.

A better idea is to tell Sqitch where to find psql for all of your projects. Use the config command's --user option to set that configuration for yourself:

  > sqitch config --user engine.pg.client /usr/local/pgsql/bin/psql

This won't change the project configuration file at all, but add the value to ~/.sqitch/sqitch.conf, which is your personal cross-project Sqitch configuration. In other words, it sets the PostgreSQL client for all Sqitch projects you manage on this host. In fact, it can be a good idea to configure yourself and clients not in the path first thing whenever you start working on a new host:

  > sqitch config --user user.name 'Marge N. O’Vera'
  > sqitch config --user user.email 'marge@example.com'
  > sqitch config --user engine.pg.client /usr/local/pgsql/bin/psql
  > sqitch config --user engine.mysql.client /usr/local/mysql/bin/mysql
  > sqitch config --user engine.sqlite.client /sbin/sqlite3

If you'd like to make the configuration global to all accounts on your host, use the `--system` option, instead:

  > sudo sqitch config --system engine.pg.client /usr/local/pgsql/bin/psql
  > sudo sqitch config --system engine.mysql.client /usr/local/mysql/bin/mysql
  > sudo sqitch config --system engine.sqlite.client /sbin/sqlite3

That will put the values into the global Sqitch configuration file, which is in `sqitch --etc-path`/sqitch.conf.

Engine Configuration

So you've got the widgets project well developed, and now you've been asked to port it to SQLite. Fundamentally, that means porting all of your deploy, revert, and verify scripts. The simplest way to organize files for this configuration is with top-level directories for each engine. First, let's move the existing PostgreSQL stuff to a subdirectory.

  > mkdir pg
  > mv deploy revert verify sqitch.plan pg
  > ls  pg  
  deploy/ revert/ verify/

Now we need to tell Sqitch where things are. To create an engine-specific configuration, use the engine command's add action:

  sqitch engine add pg --set top_dir=pg

The add action adds the pg engine to the configuration, setting the top directory to our newly-created pg directory. The configuration looks like this (with comments removed for clarity):

  [core]
    engine = pg
  [engine "pg"]
    target = db:pg:
    top_dir = pg

Curious about all the other settings for the engine? Let sqitch engine show show you:

  > sqitch engine show pg
  * pg
    Target:           db:pg:
    Registry:         sqitch
    Client:           /usr/local/pgsql/bin/psql
    Top Directory:    pg
    Plan File:        pg/sqitch.plan
    Deploy Directory: pg/deploy
    Revert Directory: pg/revert
    Verify Directory: pg/verify
    Extension:        sql

The show action nicely presents the result of the fully-evaluated configuration, even though only the top directory and client have been set. Nice, right?

Now, to add the SQLite support. There are two basic ways to go about it. We'll start with the more obvious one.

Separate Plans

The first approach is to create an entirely independent SQLite project with its own plan and scripts. This is almost like starting from scratch: just create a new directory and add initialize it as a new Sqitch project:

  > sqitch --top-dir sqlite --engine sqlite init widgets
  Created sqlite/sqitch.plan
  Created sqlite/deploy/
  Created sqlite/revert/
  Created sqlite/verify/

Note that no sqitch.plan file is created. We can use the same configuration file to manage both the PostgreSQL and the SQLite engines. Just add the SQLite engine:

  > sqitch engine add sqlite -s top_dir=sqlite
  > sqitch engine show sqlite
  * sqlite
    Target:           db:sqlite:
    Registry:         sqitch
    Client:           sqlite3
    Top Directory:    sqlite
    Plan File:        sqlite/sqitch.plan
    Deploy Directory: sqlite/deploy
    Revert Directory: sqlite/revert
    Verify Directory: sqlite/verify
    Extension:        sql

Good, everything's in the right place. Start adding changes to the SQLite plan by passing the --engine option, to force it to use the SQLite configuration:

  > sqitch --engine sqlite add users
  Created sqlite/deploy/users.sql
  Created sqlite/revert/users.sql
  Created sqlite/verify/users.sql
  Added "users" to sqlite/sqitch.plan

Use --engine pg when adding PostgreSQL changes, or omit it, in which case Sqitch will fall back on the default engine, defined by the core.engine variable set when we created the PostgreSQL project.

Shared Plan

The other approach is to have both the PostgreSQL and the SQLite projects share the same plan. In that case, we should move the plan file out of the PostgreSQL directory:

  > mv pg/sqitch.plan .
  > sqitch engine set-plan-file pg sqitch.plan
  > sqitch engine show pg
  * pg
    Target:           db:pg:
    Registry:         sqitch
    Client:           /usr/local/pgsql/bin/psql
    Top Directory:    pg
    Plan File:        sqitch.plan
    Deploy Directory: pg/deploy
    Revert Directory: pg/revert
    Verify Directory: pg/verify
    Extension:        sql

Good, it's now using ./sqitch.plan. Now let's start the SQLite project. Since we're going to use the same plan, we'll need to port all the scripts from PostgreSQL. Let's just copy them, and then configure the SQLite engine to use the shared plan file:

  > cp -rf pg sqlite
  > sqitch engine add sqlite --set plan_file=sqitch.plan --set top_dir=sqlite
  > sqitch engine show sqlite
  * sqlite
    Target:           db:sqlite:
    Registry:         sqitch
    Client:           sqlite3
    Top Directory:    sqlite
    Plan File:        sqitch.plan
    Deploy Directory: sqlite/deploy
    Revert Directory: sqlite/revert
    Verify Directory: sqlite/verify
    Extension:        sql

Looks good! Now port all the scripts in the sqlite directory from PostgreSQL to SQLite and you're ready to go.

Later, when you want to add a new change to both projects, just do it:

  > sqitch add users -n 'Creates users table.'
  Created pg/deploy/users.sql
  Created pg/revert/users.sql
  Created pg/verify/users.sql
  Added "users" to sqitch.plan

Then copy the scripts to the sqlite directory:

  > cp pg/deploy/users.sql sqlite/deploy
  > cp pg/revert/users.sql sqlite/revert
  > cp pg/verify/users.sql sqlite/verify

Yeah, this last bit is slightly annoying; it will be fixed soon.

Database Interactions

With either of these two approaches, you can now manage database interactions by passing a database URI to the database commands. For example, to deploy to a PostgreSQL database named "widgets" on host db.example.com:

  sqitch deploy db:pg://db.example.com/widgets

Sqitch is smart enough to pick out the proper engine from the URI. If you pass a db:pg: URI, rest assured that Sqitch won't try to deploy the SQLite changes. Use a db:sqlite: URI to interact with an SQLite database:

  sqitch log db:sqlite:/var/db/widgets.db

The commands that take URI arguments include:

All other commands rely on the --engine option or the core.engine configuration variable to determine path locations.

Target Configuration

Great, now we can easily manage changes for multiple database engines. But what about multiple databases for the same engine? For example, you might want to deploy your database to two hosts in a primary/standby configuration. To make things as simple as possible for your IT organization, set up named targets for those servers:

  > sqitch target add prod-primary db:pg://sqitch@db1.example.com/widgets
  > sqitch target add prod-standby db:pg://sqitch@db2.example.com/widgets

Targets inherit configuration from engines, based on the engine specified in the URI. Thus the configuration all comes together:

  > sqitch target show prod-primary prod-standby
  * prod-primary
    URI:              db:pg://sqitch@db1.example.com/widgets
    Registry:         sqitch
    Client:           /usr/local/pgsql/bin/psql
    Top Directory:    pg
    Plan File:        sqitch.plan
    Deploy Directory: pg/deploy
    Revert Directory: pg/revert
    Verify Directory: pg/verify
    Extension:        sql
  * prod-standby
    URI:              db:pg://sqitch@db2.example.com/widgets
    Registry:         sqitch
    Client:           /usr/local/pgsql/bin/psql
    Top Directory:    pg
    Plan File:        sqitch.plan
    Deploy Directory: pg/deploy
    Revert Directory: pg/revert
    Verify Directory: pg/verify
    Extension:        sql

Note the use of the shared plan and the pg directory for scripts. We can add a target for our SQLite database, too. Maybe it's used for development?

  > sqitch target add dev-sqlite db:sqlite:/var/db/widgets_dev.db
  > sqitch target show dev-sqlite
  * dev-sqlite
    URI:              db:sqlite:/var/db/widgets_dev.db
    Registry:         sqitch
    Client:           sqlite3
    Top Directory:    sqlite
    Plan File:        sqitch.plan
    Deploy Directory: sqlite/deploy
    Revert Directory: sqlite/revert
    Verify Directory: sqlite/verify
    Extension:        sql

Now deploying any of these databases is as simple as specifying the target name when executing the deploy command (assuming the sqitch user is configured to authenticate to PostgreSQL without prompting for a password):

  > sqitch deploy prod-primary
  > sqitch deploy prod-standby

Different Target, Different Plan

What about a project that manages different -- but related -- schemas on the same engine? For example, say you have two plans for PostgreSQL, one for a canonical data store, and one for a read-only copy that will have a subset of data replicated to it. Maybe your billing database just needs an up-to-date copy of the customers and users tables.

Targets can help us here, too. Just create the new plan file. It might use some of the same change scripts as the canonical plan, or its own scripts, or some of each. Just be sure all of its scripts are in the same top directory. Then add targets for the specific servers and plans:

  > sqitch target add prod-primary db:pg://db1.example.com/widgets
  > sqitch target add prod-billing db:pg://cpa.example.com/billing -s plan_file=target.plan
  > sqitch target show prod-billing
  * prod-primary
    URI:              db:pg://db1.example.com/widgets
    Registry:         sqitch
    Client:           /usr/local/pgsql/bin/psql
    Top Directory:    pg
    Plan File:        sqitch.plan
    Deploy Directory: pg/deploy
    Revert Directory: pg/revert
    Verify Directory: pg/verify
    Extension:        sql
  * prod-billing
    URI:              db:pg://cpa.example.com/billing
    Registry:         sqitch
    Client:           /usr/local/pgsql/bin/psql
    Top Directory:    pg
    Plan File:        target.plan
    Deploy Directory: pg/deploy
    Revert Directory: pg/revert
    Verify Directory: pg/verify
    Extension:        sql

Now, any management of the prod-billing target will use the target.plan plan file.

Other Options

You can see by the output of the engine and target commands that there are quite a few other properties that can be set on a per-engine or per-target database. To determine the value of each Sqitch looks at a combination of command-line options and configuration variables. Here's a complete list, including specification of their values and how to set them.

target

The target database. May be a database URI or a named target managed by the target commands. On each run, its value will be determined by examining each of the following in turn:

Command target argument or option
  sqitch deploy $target
  sqitch revert --target $target
core.target
  sqitch config core.target $target
engine.$engine.target
  sqitch engine add $engine --set target=$target
  sqitch engine set-target $engine $target
uri

The database URI to which to connect. May only be specified as a target argument or via a named target:

Command target argument or option
  sqitch deploy $uri
  sqitch revert --target uri
target.$target.uri
  sqitch target add $target --set uri=$uri
  sqitch target set-target $target $target
client

The path to the engine client. The default is engine- and OS-specific, which will generally work for clients in the path. If you need a custom client, you can specify it via the following:

--client
  sqitch --client $client deploy
core.client
  sqitch config --user core.client $client
  sqitch config core.client $client
engine.$engine.client
  sqitch engine add $engine --set client=$client
  sqitch engine set-client $engine $client
  sqitch config --user engine.$engine.client $client
target.$target.client
  sqitch target add $target --set client=$client
  sqitch target set-client $target $client
  sqitch config --user target.$target.client $client
registry

The name of the Sqitch registry schema or database. The default is sqitch, which should work for most uses. If you need a custom registry, specify it via the following:

--registry
  sqitch --registry $registry
core.registry
  sqitch config core.registry $registry
engine.$engine.registry
  sqitch engine add $engine --set registry=$registry
  sqitch engine set-registry $engine $registry
target.$target.registry
  sqitch target add $target --set registry=$registry
  sqitch target set-registry $target $registry
top_dir

The directory in which project files an subdirectories can be found, including the plan file and script directories. The default is the current directory. If you need a custom directory, specify it via the following:

--top-dir
  sqitch --top-dir $top_dir
core.top_dir
  sqitch config core.top_dir $top_dir
engine.$engine.top_dir
  sqitch engine add $engine --set top_dir=$top_dir
  sqitch engine set-top-dir $engine $top_dir
target.$target.top_dir
  sqitch target add $target --set top_dir=$top_dir
  sqitch target set-top-dir $target $top_dir
plan_file

The project deployment plan file, which defaults to $top_dir/sqitch.plan. If you need a different file, specify it via the following:

--plan-file
  sqitch --plan-file $plan_file
core.plan_file
  sqitch config core.plan_file $plan_file
engine.$engine.plan_file
  sqitch engine add $engine --set plan_file=$plan_file
  sqitch engine set-plan-file $engine $plan_file
target.$target.plan_file
  sqitch target add $target --set plan_file=$plan_file
  sqitch target set-plan-file $target $plan_file
deploy_dir

The directory in which project deploy scripts can be found. Defaults to $top_dir/deploy. If you need a different directory, specify it via the following:

--deploy-dir
  sqitch --deploy-dir $deploy_dir
core.deploy_dir
  sqitch config core.deploy_dir $deploy_dir
engine.$engine.deploy_dir
  sqitch engine add $engine --set deploy_dir=$deploy_dir
  sqitch engine set-deploy-dir $engine $deploy_dir
target.$target.deploy_dir
  sqitch target add $target --set deploy_dir=$deploy_dir
  sqitch target set-deploy-dir $target $deploy_dir
revert_dir
$top_dir/deploy

The directory in which project revert scripts can be found. Defaults to $top_dir/revert. If you need a different directory, specify it via the following:

--revert-dir
  sqitch --revert-dir $revert_dir
core.revert_dir
  sqitch config core.revert_dir $revert_dir
engine.$engine.revert_dir
  sqitch engine add $engine --set revert_dir=$revert_dir
  sqitch engine set-revert-dir $engine $revert_dir
target.$target.revert_dir
  sqitch target add $target --set revert_dir=$revert_dir
  sqitch target set-revert-dir $target $revert_dir
verify_dir

The directory in which project verify scripts can be found. Defaults to $top_dir/verify. If you need a different directory, specify it via the following:

--verify-dir
  sqitch --verify-dir $verify_dir
core.verify_dir
  sqitch config core.verify_dir $verify_dir
engine.$engine.verify_dir
  sqitch engine add $engine --set verify_dir=$verify_dir
  sqitch engine set-verify-dir $engine $verify_dir
target.$target.verify_dir
  sqitch target add $target --set verify_dir=$verify_dir
  sqitch target set-verify-dir $target $verify_dir
extension

The file name extension to append to change names for change script file names. Defaults to sql. If you need a custom extension, specify it via the following:

--extension
core.extension
  sqitch config core.extension $extension
engine.$engine.extension
  sqitch engine add $engine --set extension=$extension
  sqitch engine set-extension $engine $extension
target.$target.extension
  sqitch target add $target --set extension=$extension
  sqitch target set-extension $target $extension

See Also

Sqitch

Part of the sqitch suite.