Class: PgEasyReplicate::Orchestrate

Inherits:
Object
  • Object
show all
Extended by:
Helper
Defined in:
lib/pg_easy_replicate/orchestrate.rb

Constant Summary collapse

DEFAULT_LAG =

200kb

200_000
DEFAULT_WAIT =

seconds

5

Class Method Summary collapse

Methods included from Helper

abort_with, connection_info, db_name, db_user, internal_schema_name, internal_user_name, logger, publication_name, secondary_source_db_url, source_db_url, subscription_name, target_db_url, test_env?, underscore

Class Method Details

.add_tables_to_publication(schema:, group_name:, conn_string:, tables: "") ⇒ Object 



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# File 'lib/pg_easy_replicate/orchestrate.rb', line 73

def add_tables_to_publication(
  schema:,
  group_name:,
  conn_string:,
  tables: ""
)
  logger.info(
    "Adding tables up publication",
    { publication_name: publication_name(group_name) },
  )
  tables = tables&.split(",") || []
  unless tables.size > 0
    tables = list_all_tables(schema: schema, conn_string: conn_string)
  end

  tables.map do |table_name|
    Query.run(
      query:
        "ALTER PUBLICATION #{publication_name(group_name)} ADD TABLE \"#{table_name}\"",
      connection_url: conn_string,
      schema: schema,
    )
  end
rescue => e
  raise "Unable to add tables to publication: #{e.message}"
end

.create_publication(group_name:, conn_string:) ⇒ Object 



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# File 'lib/pg_easy_replicate/orchestrate.rb', line 58

def create_publication(group_name:, conn_string:)
  logger.info(
    "Setting up publication",
    { publication_name: publication_name(group_name) },
  )

  Query.run(
    query: "create publication #{publication_name(group_name)}",
    connection_url: conn_string,
    user: db_user(conn_string),
  )
rescue => e
  raise "Unable to create publication: #{e.message}"
end

.create_subscription(group_name:, source_conn_string:, target_conn_string:) ⇒ Object 



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# File 'lib/pg_easy_replicate/orchestrate.rb', line 125

def create_subscription(
  group_name:,
  source_conn_string:,
  target_conn_string:
)
  logger.info(
    "Setting up subscription",
    {
      publication_name: publication_name(group_name),
      subscription_name: subscription_name(group_name),
    },
  )

  Query.run(
    query:
      "CREATE SUBSCRIPTION #{subscription_name(group_name)} CONNECTION '#{source_conn_string}' PUBLICATION #{publication_name(group_name)}",
    connection_url: target_conn_string,
    user: db_user(target_conn_string),
    transaction: false,
  )
rescue Sequel::DatabaseError => e
  if e.message.include?("canceling statement due to statement timeout")
    abort_with(
      "Subscription creation failed, please ensure both databases are in the same network region: #{e.message}",
    )
  end

  raise "Unable to create subscription: #{e.message}"
end

.drop_publication(group_name:, conn_string:) ⇒ Object 



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# File 'lib/pg_easy_replicate/orchestrate.rb', line 111

def drop_publication(group_name:, conn_string:)
  logger.info(
    "Dropping publication",
    { publication_name: publication_name(group_name) },
  )
  Query.run(
    query: "DROP PUBLICATION IF EXISTS #{publication_name(group_name)}",
    connection_url: conn_string,
    user: db_user(conn_string),
  )
rescue => e
  raise "Unable to drop publication: #{e.message}"
end

.drop_subscription(group_name:, target_conn_string:) ⇒ Object 



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# File 'lib/pg_easy_replicate/orchestrate.rb', line 155

def drop_subscription(group_name:, target_conn_string:)
  logger.info(
    "Dropping subscription",
    {
      publication_name: publication_name(group_name),
      subscription_name: subscription_name(group_name),
    },
  )
  Query.run(
    query: "DROP SUBSCRIPTION IF EXISTS #{subscription_name(group_name)}",
    connection_url: target_conn_string,
    transaction: false,
  )
rescue => e
  raise "Unable to drop subscription: #{e.message}"
end

.list_all_tables(schema:, conn_string:) ⇒ Object 



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# File 'lib/pg_easy_replicate/orchestrate.rb', line 100

def list_all_tables(schema:, conn_string:)
  Query
    .run(
      query:
        "SELECT table_name FROM information_schema.tables WHERE table_schema = '#{schema}'",
      connection_url: conn_string,
    )
    .map(&:values)
    .flatten
end

.mark_switchover_complete(group_name) ⇒ Object 



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# File 'lib/pg_easy_replicate/orchestrate.rb', line 320

def mark_switchover_complete(group_name)
  Group.update(group_name: group_name, switchover_completed_at: Time.now)
end

.refresh_sequences(conn_string:, schema: nil) ⇒ Object 



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# File 'lib/pg_easy_replicate/orchestrate.rb', line 286

def refresh_sequences(conn_string:, schema: nil)
  logger.info("Refreshing sequences")
  sql = <<~SQL
    DO $$
    DECLARE
    i TEXT;
    BEGIN
      FOR i IN (
        SELECT 'SELECT SETVAL('
            || quote_literal(quote_ident(PGT.schemaname) || '.' || quote_ident(S.relname))
            || ', COALESCE(MAX(' ||quote_ident(C.attname)|| '), 1) ) FROM '
            || quote_ident(PGT.schemaname)|| '.'||quote_ident(T.relname)|| ';'
          FROM pg_class AS S,
              pg_depend AS D,
              pg_class AS T,
              pg_attribute AS C,
              pg_tables AS PGT
        WHERE S.relkind = 'S'
          AND S.oid = D.objid
          AND D.refobjid = T.oid
          AND D.refobjid = C.attrelid
          AND D.refobjsubid = C.attnum
          AND T.relname = PGT.tablename
      ) LOOP
          EXECUTE i;
      END LOOP;
    END $$;
  SQL

  Query.run(query: sql, connection_url: conn_string, schema: schema)
rescue => e
  raise "Unable to refresh sequences: #{e.message}"
end

.restore_connections_on_source_db(group_name) ⇒ Object 



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# File 'lib/pg_easy_replicate/orchestrate.rb', line 278

def restore_connections_on_source_db(group_name)
  logger.info("Restoring connections")

  alter_sql =
    "ALTER USER #{db_user(source_db_url)} set default_transaction_read_only = false"
  Query.run(query: alter_sql, connection_url: source_db_url)
end

.revoke_connections_on_source_db(group_name) ⇒ Object 



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# File 'lib/pg_easy_replicate/orchestrate.rb', line 261

def revoke_connections_on_source_db(group_name)
  logger.info(
    "Lag is now below #{DEFAULT_LAG}, marking source DB to read only",
  )

  alter_sql =
    "ALTER USER #{db_user(source_db_url)} set default_transaction_read_only = true"
  Query.run(query: alter_sql, connection_url: source_db_url)

  kill_sql =
    "SELECT pg_terminate_backend(pg_stat_activity.pid) FROM pg_stat_activity WHERE usename = '#{db_user(source_db_url)}';"

  Query.run(query: kill_sql, connection_url: source_db_url)
rescue => e
  raise "Unable to revoke connections on source db: #{e.message}"
end

.start_sync(options) ⇒ Object 



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# File 'lib/pg_easy_replicate/orchestrate.rb', line 11

def start_sync(options)
  create_publication(
    group_name: options[:group_name],
    conn_string: source_db_url,
  )

  add_tables_to_publication(
    group_name: options[:group_name],
    tables: options[:tables],
    conn_string: source_db_url,
    schema: options[:schema],
  )

  create_subscription(
    group_name: options[:group_name],
    source_conn_string: secondary_source_db_url || source_db_url,
    target_conn_string: target_db_url,
  )

  Group.create(
    name: options[:group_name],
    table_names: options[:tables],
    schema_name: options[:schema],
    started_at: Time.now.utc,
  )
rescue => e
  stop_sync(
    group_name: options[:group_name],
    source_conn_string: source_db_url,
    target_conn_string: target_db_url,
  )

  if Group.find(options[:group_name])
    Group.update(group_name: options[:group_name], failed_at: Time.now)
  else
    Group.create(
      name: options[:group_name],
      table_names: options[:tables],
      schema_name: options[:schema],
      started_at: Time.now.utc,
      failed_at: Time.now.utc,
    )
  end

  abort_with("Starting sync failed: #{e.message}")
end

.stop_sync(group_name:, source_conn_string: source_db_url, target_conn_string: target_db_url) ⇒ Object 



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# File 'lib/pg_easy_replicate/orchestrate.rb', line 172

def stop_sync(
  group_name:,
  source_conn_string: source_db_url,
  target_conn_string: target_db_url
)
  logger.info(
    "Stopping sync",
    {
      publication_name: publication_name(group_name),
      subscription_name: subscription_name(group_name),
    },
  )
  drop_publication(
    group_name: group_name,
    conn_string: source_conn_string,
  )
  drop_subscription(
    group_name: group_name,
    target_conn_string: target_conn_string,
  )
rescue => e
  raise "Unable to stop sync user: #{e.message}"
end

.switchover(group_name:, source_conn_string: source_db_url, target_conn_string: target_db_url, lag_delta_size: DEFAULT_LAG) ⇒ Object 



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# File 'lib/pg_easy_replicate/orchestrate.rb', line 196

def switchover(
  group_name:,
  source_conn_string: source_db_url,
  target_conn_string: target_db_url,
  lag_delta_size: DEFAULT_LAG
)
  group = Group.find(group_name)

  watch_lag(group_name: group_name, lag: lag_delta_size)
  revoke_connections_on_source_db(group_name)
  wait_for_remaining_catchup(group_name)
  refresh_sequences(
    conn_string: target_conn_string,
    schema: group[:schema_name],
  )
  mark_switchover_complete(group_name)
  drop_subscription(
    group_name: group_name,
    target_conn_string: target_conn_string,
  )
rescue => e
  restore_connections_on_source_db(group_name)

  abort_with("Switchover sync failed: #{e.message}")
end

.wait_for_remaining_catchup(group_name) ⇒ Object 



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# File 'lib/pg_easy_replicate/orchestrate.rb', line 253

def wait_for_remaining_catchup(group_name)
  logger.info("Waiting for remaining WAL to get flushed")

  watch_lag(group_name: group_name, lag: 0, wait_time: 0.2)

  logger.info("Caught up on remaining WAL lag")
end

.watch_lag(group_name:, wait_time: DEFAULT_WAIT, lag: DEFAULT_LAG) ⇒ Object 



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# File 'lib/pg_easy_replicate/orchestrate.rb', line 222

def watch_lag(group_name:, wait_time: DEFAULT_WAIT, lag: DEFAULT_LAG)
  logger.info("Watching lag stats")

  loop do
    sleep(wait_time)

    unless Stats.all_tables_replicating?(group_name)
      logger.debug(
        "All tables haven't reached replicating state, skipping check",
      )
      next
    end

    lag_stat = Stats.lag_stats(group_name).first
    if lag_stat[:write_lag].nil? || lag_stat[:flush_lag].nil? ||
         lag_stat[:replay_lag].nil?
      next
    end

    logger.debug("Current lag stats: #{lag_stat}")

    below_write_lag = lag_stat[:write_lag] <= lag
    below_flush_lag = lag_stat[:flush_lag] <= lag
    below_replay_lag = lag_stat[:replay_lag] <= lag

    break if below_write_lag && below_flush_lag && below_replay_lag
  end

  logger.info("Lag below #{DEFAULT_LAG} bytes. Continuing...")
end