Module: Pgbus::DedicatedConnection

Defined in:
lib/pgbus/dedicated_connection.rb

Overview

Single choke point for opening a DEDICATED PG connection outside the pgmq pools — the streamer's LISTEN connection and the worker NotifyListener. Every such path MUST route through here (enforced by spec/pgbus/pg_connect_guard_spec.rb): in :session GUC mode, Configuration#forward_connection_variables leaves the database.yml variables: hash on the connection options for the caller to apply post-connect, and :variables is not a libpq keyword — a raw PG.connect(**opts) fails with invalid connection option "variables" (issue #352). This mirrors Client#wrap_session_gucs, which does the same for pool connections: the GUCs are applied via post-connect SET because a transaction-mode pooler rejects the libpq options startup param (the reason :session mode exists).

Constant Summary collapse

APP_NAME =

Stable census tag for every dedicated LISTEN connection, so operators can count them: SELECT count(*) FROM pg_stat_activity WHERE application_name

'pgbus-listen' (issue #381 connection budget). Applied as

fallback_application_name so an explicit application_name in the URL / hash — or PGAPPNAME in the environment — always wins.

"pgbus-listen"

Class Method Summary collapse

Class Method Details

.close_quietly(conn) ⇒ Object 



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# File 'lib/pgbus/dedicated_connection.rb', line 74

def close_quietly(conn)
  conn.close
rescue StandardError
  nil
end

.connect(opts) ⇒ Object 



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# File 'lib/pgbus/dedicated_connection.rb', line 26

def connect(opts)
  require "pg" unless defined?(::PG::Connection)
  case opts
  when String then ::PG.connect(with_app_name(opts))
  when Hash then connect_from_hash(opts)
  else
    raise Pgbus::ConfigurationError,
          "Cannot build a dedicated PG connection from #{opts.class}. " \
          "Set database_url or connection_params so pgbus can open its own connection."
  end
end

.connect_from_hash(opts) ⇒ Object 



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# File 'lib/pgbus/dedicated_connection.rb', line 52

def connect_from_hash(opts)
  variables = opts[:variables]
  conn = ::PG.connect(**with_app_name_hash(opts.except(:variables)))
  begin
    variables&.each { |name, value| conn.exec("SET #{name} = '#{value}'") }
  rescue StandardError
    # A failing SET (e.g. a bogus GUC name in database.yml variables:)
    # must not orphan the freshly opened socket — the reconnect loops
    # retry on a tight backoff and would leak one server connection per
    # attempt until PostgreSQL exhausts max_connections.
    close_quietly(conn)
    raise
  end
  conn
end

.with_app_name(conninfo) ⇒ Object

Append the census tag to a conninfo String — URL query-param style for postgres:// URLs, space-separated keyword style otherwise. A string that already mentions application_name (either keyword) is left untouched.



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# File 'lib/pgbus/dedicated_connection.rb', line 41

def with_app_name(conninfo)
  return conninfo if conninfo.include?("application_name")

  if conninfo.include?("://")
    separator = conninfo.include?("?") ? "&" : "?"
    "#{conninfo}#{separator}fallback_application_name=#{APP_NAME}"
  else
    "#{conninfo} fallback_application_name=#{APP_NAME}".strip
  end
end

.with_app_name_hash(opts) ⇒ Object 



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# File 'lib/pgbus/dedicated_connection.rb', line 68

def with_app_name_hash(opts)
  return opts if opts.key?(:application_name) || opts.key?(:fallback_application_name)

  opts.merge(fallback_application_name: APP_NAME)
end