Systems and methods recovering from the failure of a server load balancer

A system for recovering from the failure of a primary server load balancer (SLB) that is operable to balance traffic across a plurality of target processing units using connection data that comprises information mapping sessions with target processing units, the system comprising:

• an SLB monitor;
• and
• a stand-by SLB, wherein
• the SLB monitor is configured to detect when the primary SLB has experienced a failure;
• the SLB is further configured such that, in response to detecting that the primary SLB has experienced a failure, the SLB monitor causes a target processing unit to transmit to the stand-by SLB a message comprising a session identifier and a target processing unit identifier identifying the target processing unit;
• the stand-by SLB is configured such that, in response to receiving the message, the stand-by SLB stores information linking the session identifier with the target processing unit identifier;
• and
• the stand-by SLB is further configured such that, in response to the stand-by SLB receiving a packet, the stand-by SLB:
• obtains data included in the received packet;
• uses the obtained data to generate a second session identifier;
• determines whether the packet corresponds to a new session;
• in response to determining that the packet does not correspond to a new session, the stand-by SLB obtains a target processing unit identifier with which the second session identifier is linked;
• and
• after obtaining the target processing unit identifier with which the second session identifier is linked, forwards the packet to a target processing unit identified by the target processing unit identifier with which the second session identifier is linked.

A primary server load balance (SLB) for balancing traffic across a plurality of target processing units, wherein the primary SLB is operable to:

• receive a packet corresponding to a session;
• obtain data included in the received first packet;
• use the obtained data to generate a session identifier identifying the session;
• determine whether the session to which the packet corresponds is a new session;
• and
• in response to determining that the session to which the packet corresponds is a new session:
• (a) use a load balancing procedure to select a particular target processing unit from the plurality of target processing units,
• (b) update the stored connection data so that the connection data will comprise information mapping the session with the selected target processing unit, and
• (c) transmit to a replication agent running on the selected target processing unit a connection data update message comprising the generated session identifier identifying the session.

A method performed by a primary server load balance (SLB) for balancing traffic across a plurality of target processing units, the method comprising:

• receiving a packet corresponding to a session;
• obtaining data included in the received first packet;
• using the obtained data, generating a session identifier identifying the session;
• determining whether the session to which the packet corresponds is a new session;
• and
• in response to determining that the session to which the packet corresponds is a new session:
• (a) using a load balancing procedure to select a particular target processing unit from the plurality of target processing units,
• (b) updating the stored connection data so that the connection data will comprise information mapping the session with the selected target processing unit, and
• (c) transmitting to a replication agent running on the selected target processing unit a connection data update message comprising the generated session identifier identifying the session.

A target processing unit, the target processing unit being operable to:

• receive from a primary server load balancer (SLB) a packet comprising application data;
• in response to receiving the packet, provide the application data to an application running on the target processing unit;
• receive from the primary SLB a connection data update message comprising a session identifier generated by the primary SLB;
• store the session identifier in response to receiving the connection data update message;
• receive a synchronization message indicating that the primary SLB has experienced a failure;
• and
• in response to receiving the synchronization message, retrieve the stored session identifier and transmit to a stand-by SLB a connection data replication message comprising the session identifier generated by the primary SLB and a target processing unit identifier identifying the target processing unit.

A method performed by a target processing unit, the method comprising:

• receiving from a primary server load balancer (SLB) a packet comprising application data;
• in response to receiving the packet, providing the application data to an application running on the target processing unit;
• receiving from the primary SLB a connection data update message comprising a session identifier generated by the primary SLB;
• storing the session identifier in response to receiving the connection data update message;
• receiving a synchronization message indicating that the primary SLB has experienced a failure;
• and
• in response to receiving the synchronization message indicating that the primary SLB has experienced a failure:
• 1) retrieving the stored session identifier;
• and
• 2) transmitting to a first stand-by SLB a connection data replication message comprising the session identifier generated by the primary SLB and a target processing unit identifier identifying the target processing unit.