Automatic transaction retry after session failure

A method, comprising:

• receiving a replicated session state from a first database server at a second database server, the replicated session state being a copy of a session state generated at the first database server to handle a database query for a client, the replicated session state including a session identifier and a transaction log associated with a transaction, the transaction log storing one or more command identifiers associated with one or more commands received at the first database server from the client within the transaction, and indicating whether each received command has been successfully executed;
• receiving a request at the second database server from a client to establish a session with the client due to a failure in a first session established between the client and the first database server;
• determining that a session identifier included in the request matches the session identifier included in the replicated session state;
• reestablishing a second session with the client at the second database server;
• receiving a further command associated with the transaction from the client at the second database server;
• determining whether a command identifier for the further command has already been stored in the transaction log;
• and
• if the command identifier associated with the further command is determined to not already have been stored in the transaction log,
• attempting to execute the further command, and
• annotating the transaction log with the command identifier associated with the further command and an indication of whether the further command has been successfully executed.

A system, comprising:

• a first database server that includes
• a session manager that establishes a first session with a client to handle a database query for the client, opens a transaction of the first session to execute a plurality of commands associated with the transaction for the client, and receives at least one command associated with the transaction from the client, each received command being received with an associated command identifier, and
• a transaction log manager that generates a transaction log that stores the command identifier associated with each received command and indicates whether each received command has been successfully executed;
• the session manager receives a request to reestablish the first session, a further command associated with the transaction, and a command identifier for the further command from the client after a failure in the first session;
• the session manager reestablishes the first session with the client, and determines whether a command identifier for the further command has already been stored in the transaction log;
• and
• if the session manager determines that the command identifier associated with the further command was not already stored in the transaction log, the further command is attempted to be executed, and the transaction log manager annotates the transaction log with the command identifier associated with the further command and an indication of whether the further command has been successfully executed.