Class: Potluck::Postgres

Inherits:
Service
  • Object
show all
Defined in:
lib/potluck/postgres.rb

Overview

A Ruby interface for controlling and connecting to Postgres. Uses [Sequel](github.com/jeremyevans/sequel) to connect and perform automatic role and database creation, as well as for utility methods such as database schema migration.

Constant Summary collapse

ROLE_NOT_FOUND_REGEX = 
/role .* does not exist/.freeze
DATABASE_NOT_FOUND_REGEX = 
/database .* does not exist/.freeze
STARTING_UP_STRING = 
'the database system is starting up'
STARTING_UP_TIMEOUT = 
30
CONNECTION_REFUSED_STRING = 
'connection refused'
CONNECTION_REFUSED_TIMEOUT = 
3

Instance Attribute Summary collapse

Class Method Summary collapse

Instance Method Summary collapse

Constructor Details

#initialize(config, **args) ⇒ Postgres

Creates a new instance.

  • config - Configuration hash to pass to Sequel.connect.

  • args - Arguments to pass to Potluck::Service.new (optional).



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# File 'lib/potluck/postgres.rb', line 49

def initialize(config, **args)
  super(**args)

  @config = config
end

Instance Attribute Details

#database ⇒ Object (readonly)

Returns the value of attribute database.



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# File 'lib/potluck/postgres.rb', line 41

def database
  @database
end

Class Method Details

.plist ⇒ Object

Content of the launchctl plist file.



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# File 'lib/potluck/postgres.rb', line 191

def self.plist
  super(
    <<~EOS
      <key>ProgramArguments</key>
      <array>
        <string>/usr/local/opt/postgresql/bin/postgres</string>
        <string>-D</string>
        <string>/usr/local/var/postgres</string>
      </array>
      <key>WorkingDirectory</key>
      <string>/usr/local</string>
      <key>StandardOutPath</key>
      <string>/usr/local/var/log/postgres.log</string>
      <key>StandardErrorPath</key>
      <string>/usr/local/var/log/postgres.log</string>
    EOS
  )
end

Instance Method Details

#connect ⇒ Object

Connects to the configured Postgres database.



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# File 'lib/potluck/postgres.rb', line 66

def connect
  (tries ||= 0) && (tries += 1)
  @database = Sequel.connect(@config, logger: @logger)
rescue Sequel::DatabaseConnectionError => e
  if (dud = Sequel::DATABASES.last)
    dud.disconnect
    Sequel.synchronize { Sequel::DATABASES.delete(dud) }
  end

  message = e.message.downcase

  if message =~ ROLE_NOT_FOUND_REGEX && tries == 1
    create_database_role
    create_database
    retry
  elsif message =~ DATABASE_NOT_FOUND_REGEX && tries == 1
    create_database
    retry
  elsif message.include?(STARTING_UP_STRING) && tries < STARTING_UP_TIMEOUT
    sleep(1)
    retry
  elsif message.include?(CONNECTION_REFUSED_STRING) && tries < CONNECTION_REFUSED_TIMEOUT && manage?
    sleep(1)
    retry
  elsif message.include?(CONNECTION_REFUSED_STRING)
    raise(PostgresError.new(e.message.strip, e))
  else
    raise
  end
end

#disconnect ⇒ Object

Disconnects from the database if a connection was made.



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# File 'lib/potluck/postgres.rb', line 100

def disconnect
  @database&.disconnect
end

#migrate(dir, steps = nil) ⇒ Object

Runs database migrations by way of Sequel’s migration extension. Migration files must use the timestamp naming strategy as opposed to integers.

  • dir - Directory where migration files are located.

  • steps - Number of steps forward or backward to migrate from the current migration, otherwise will migrate to latest (optional).



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# File 'lib/potluck/postgres.rb', line 112

def migrate(dir, steps = nil)
  return unless File.directory?(dir)

  Sequel.extension(:migration)

  # Suppress Sequel schema migration table queries.
  original_level = @logger.level
  @logger.level = Logger::WARN if @logger.level == Logger::INFO

  args = [Sequel::Model.db, dir, {allow_missing_migration_files: true}]
  migrator = Sequel::TimestampMigrator.new(*args)

  return if migrator.files.empty?

  if steps
    all = migrator.files.map { |f| File.basename(f) }
    applied = migrator.applied_migrations
    current = applied.last

    return if applied.empty? && steps <= 0

    index = [[0, (all.index(current) || -1) + steps].max, all.size].min
    file = all[index]

    args.last[:target] = migrator.send(:migration_version_from_file, file)
  end

  migrator = Sequel::TimestampMigrator.new(*args)
  @logger.level = original_level
  migrator.run
ensure
  @logger.level = original_level if original_level
end

#stop ⇒ Object

Disconnects and stops the Postgres process.



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# File 'lib/potluck/postgres.rb', line 58

def stop
  disconnect
  super
end