module Mongo::Retryable
Defines basic behavior around retrying operations.
@since 2.1.0
Public Instance Methods
Execute a read operation with a single retry on network errors.
This method is used by the driver for some of the internal housekeeping operations. Application-requested reads should use read_with_retry
rather than this method.
@api private
@example Execute the read.
read_with_one_retry do ... end
@note This only retries read operations on socket errors.
@param [ Hash ] options Options
. @param [ Proc ] block The block to execute.
@option options [ String ] :retry_message Message to log when retrying.
@return [ Result ] The result of the operation.
@since 2.2.6
# File lib/mongo/retryable.rb, line 149 def read_with_one_retry(options = nil) yield rescue Error::SocketError, Error::SocketTimeoutError => e retry_message = options && options[:retry_message] log_retry(e, message: retry_message) yield end
Execute a read operation with retrying.
This method performs server selection for the specified server selector and yields to the provided block, which should execute the initial query operation and return its result. The block will be passed the server selected for the operation. If the block raises an exception, and this exception corresponds to a read retryable error, and read retries are enabled for the client, this method will perform server selection again and yield to the block again (with potentially a different server). If the block returns successfully, the result of the block is returned.
If modern retry reads are on (which is the default), the initial read operation will be retried once. If legacy retry reads are on, the initial read operation will be retried zero or more times depending on the :max_read_retries client setting, the default for which is 1. To disable read retries, turn off modern read retries by setting retry_reads: false and set :max_read_retries to 0 on the client.
@api private
@example Execute the read.
read_with_retry(session, server_selector) do |server| ... end
@param [ Mongo::Session
] session The session that the operation is being
run on.
@param [ Mongo::ServerSelector::Selectable
] server_selector Server
selector for the operation.
@param [ Proc ] block The block to execute.
@return [ Result ] The result of the operation.
# File lib/mongo/retryable.rb, line 99 def read_with_retry(session = nil, server_selector = nil, &block) if session.nil? && server_selector.nil? # Older versions of Mongoid call read_with_retry without arguments. # This is already not correct in a MongoDB 3.6+ environment with # sessions. For compatibility we emulate the legacy driver behavior # here but upgrading Mongoid is strongly recommended. unless $_mongo_read_with_retry_warned $_mongo_read_with_retry_warned = true Logger.logger.warn("Legacy read_with_retry invocation - please update the application and/or its dependencies") end # Since we don't have a session, we cannot use the modern read retries. # And we need to select a server but we don't have a server selector. # Use PrimaryPreferred which will work as long as there is a data # bearing node in the cluster; the block may select a different server # which is fine. server_selector = ServerSelector.get(mode: :primary_preferred) legacy_read_with_retry(nil, server_selector, &block) elsif session && session.retry_reads? modern_read_with_retry(session, server_selector, &block) elsif client.max_read_retries > 0 legacy_read_with_retry(session, server_selector, &block) else server = select_server(cluster, server_selector) yield server end end
Execute a read operation returning a cursor with retrying.
This method performs server selection for the specified server selector and yields to the provided block, which should execute the initial query operation and return its result. The block will be passed the server selected for the operation. If the block raises an exception, and this exception corresponds to a read retryable error, and read retries are enabled for the client, this method will perform server selection again and yield to the block again (with potentially a different server). If the block returns successfully, the result of the block (which should be a Mongo::Operation::Result
) is used to construct a Mongo::Cursor
object for the result set. The cursor is then returned.
If modern retry reads are on (which is the default), the initial read operation will be retried once. If legacy retry reads are on, the initial read operation will be retried zero or more times depending on the :max_read_retries client setting, the default for which is 1. To disable read retries, turn off modern read retries by setting retry_reads: false and set :max_read_retries to 0 on the client.
@api private
@example Execute a read returning a cursor.
cursor = read_with_retry_cursor(session, server_selector, view) do |server| # return a Mongo::Operation::Result ... end
@param [ Mongo::Session
] session The session that the operation is being
run on.
@param [ Mongo::ServerSelector::Selectable
] server_selector Server
selector for the operation.
@param [ CollectionView ] view The CollectionView
defining the query. @param [ Proc ] block The block to execute.
@return [ Cursor
] The cursor for the result set.
# File lib/mongo/retryable.rb, line 59 def read_with_retry_cursor(session, server_selector, view, &block) read_with_retry(session, server_selector) do |server| result = yield server Cursor.new(view, result, server, session: session) end end
Implements write retrying functionality by yielding to the passed block one or more times.
If the session is provided (hence, the deployment supports sessions), and modern retry writes are enabled on the client, the modern retry logic is invoked. Otherwise the legacy retry logic is invoked.
If ending_transaction parameter is true, indicating that a transaction is being committed or aborted, the operation is executed exactly once. Note that, since transactions require sessions, this method will raise ArgumentError if ending_transaction is true and session is nil.
@api private
@example Execute the write.
write_with_retry do ... end
@note This only retries operations on not master failures, since it is
the only case we can be sure a partial write did not already occur.
@param [ nil | Session
] session Optional session to use with the operation. @param [ nil | Hash | WriteConcern::Base
] write_concern The write concern. @param [ true | false ] ending_transaction True if the write operation is abortTransaction or
commitTransaction, false otherwise.
@param [ Proc ] block The block to execute.
@yieldparam [ Server
] server The server to which the write should be sent. @yieldparam [ Integer ] txn_num Transaction number (NOT the ACID kind).
@return [ Result ] The result of the operation.
@since 2.1.0
# File lib/mongo/retryable.rb, line 191 def write_with_retry(session, write_concern, ending_transaction = false, &block) if ending_transaction && !session raise ArgumentError, 'Cannot end a transaction without a session' end unless ending_transaction || retry_write_allowed?(session, write_concern) return legacy_write_with_retry(nil, session, &block) end # If we are here, session is not nil. A session being nil would have # failed retry_write_allowed? check. server = cluster.next_primary unless ending_transaction || server.retry_writes? return legacy_write_with_retry(server, session, &block) end begin txn_num = session.in_transaction? ? session.txn_num : session.next_txn_num yield(server, txn_num, false) rescue Error::SocketError, Error::SocketTimeoutError => e if session.in_transaction? && !ending_transaction raise end retry_write(e, txn_num, &block) rescue Error::OperationFailure => e if (session.in_transaction? && !ending_transaction) || !e.write_retryable? raise end retry_write(e, txn_num, &block) end end
Private Instance Methods
# File lib/mongo/retryable.rb, line 245 def legacy_read_with_retry(session, server_selector) attempt = 0 server = select_server(cluster, server_selector) begin attempt += 1 yield server rescue Error::SocketError, Error::SocketTimeoutError => e if attempt > client.max_read_retries || (session && session.in_transaction?) raise end log_retry(e, message: 'Legacy read retry') server = select_server(cluster, server_selector) retry rescue Error::OperationFailure => e if cluster.sharded? && e.retryable? && !(session && session.in_transaction?) if attempt > client.max_read_retries raise end log_retry(e, message: 'Legacy read retry') sleep(client.read_retry_interval) server = select_server(cluster, server_selector) retry else raise end end end
# File lib/mongo/retryable.rb, line 328 def legacy_write_with_retry(server = nil, session = nil) # This is the pre-session retry logic, and is not subject to # current retryable write specifications. # In particular it does not retry on SocketError and SocketTimeoutError. attempt = 0 begin attempt += 1 yield(server || cluster.next_primary) rescue Error::OperationFailure => e server = nil if attempt > client.max_write_retries raise end if e.write_retryable? && !(session && session.in_transaction?) log_retry(e, message: 'Legacy write retry') cluster.scan!(false) retry else raise end end end
Log a warning so that any application slow down is immediately obvious.
# File lib/mongo/retryable.rb, line 358 def log_retry(e, options = nil) message = if options && options[:message] options[:message] else "Retry" end Logger.logger.warn "#{message} due to: #{e.class.name} #{e.message}" end
# File lib/mongo/retryable.rb, line 227 def modern_read_with_retry(session, server_selector, &block) attempt = 0 server = select_server(cluster, server_selector) begin yield server rescue Error::SocketError, Error::SocketTimeoutError => e if session.in_transaction? raise end retry_read(e, server_selector, &block) rescue Error::OperationFailure => e if session.in_transaction? || !e.write_retryable? raise end retry_read(e, server_selector, &block) end end
# File lib/mongo/retryable.rb, line 288 def retry_read(original_error, server_selector, &block) begin server = select_server(cluster, server_selector) rescue raise original_error end log_retry(original_error, message: 'Read retry') begin yield server, true rescue Error::SocketError, Error::SocketTimeoutError => e raise e rescue Error::OperationFailure => e raise original_error unless e.write_retryable? raise e rescue raise original_error end end
# File lib/mongo/retryable.rb, line 309 def retry_write(original_error, txn_num, &block) # We do not request a scan of the cluster here, because error handling # for the error which triggered the retry should have updated the # server description and/or topology as necessary (specifically, # a socket error or a not master error should have marked the respective # server unknown). Here we just need to wait for server selection. server = cluster.next_primary raise original_error unless (server.retry_writes? && txn_num) log_retry(original_error, message: 'Write retry') yield(server, txn_num, true) rescue Error::SocketError, Error::SocketTimeoutError => e raise e rescue Error::OperationFailure => e raise original_error unless e.write_retryable? raise e rescue raise original_error end
# File lib/mongo/retryable.rb, line 273 def retry_write_allowed?(session, write_concern) unless session && session.retry_writes? return false end if write_concern.nil? true else unless write_concern.is_a?(WriteConcern::Base) write_concern = WriteConcern.get(write_concern) end write_concern.acknowledged? end end
This is a separate method to make it possible for the test suite to assert that server selection is performed during retry attempts.
# File lib/mongo/retryable.rb, line 353 def select_server(cluster, server_selector) server_selector.select_server(cluster) end