Processing incoming transactions based on resource utilization status of backend systems in an appliance cluster

A method comprising:

• receiving, by a first application level firewall (ALF) of a plurality of ALFs, an incoming transaction, wherein the plurality of ALFs are part of a distributed computer system that includes a plurality of reverse proxy appliances that share a common backend sub-system, with each given reverse proxy appliance of the plurality of reverse proxy appliances being:
• (i) configured to perform service level monitoring (SLM) to prevent the common backend sub-system from being overwhelmed by unanticipated burst messages, (ii) characterized by a current threshold level which is a sum of a quantity of transactions that can be directly processed by the given reverse proxy appliance and a quantity of transactions that can be processed by other reverse proxy appliance(s) on behalf of the given reverse proxy appliance, and (iii) further characterized by a current transaction count;
• determining, by machine logic, that the incoming transaction cannot be directly processed by the first ALF based, at least in part, upon a current threshold level of the first ALF being less than a sum of a current transaction count of the first ALF and a size of the incoming transaction:
• responsive to the determination that the incoming transaction cannot be directly processed by the first ALF, negotiating, by a second ALF of the plurality of ALFs as a negotiation device and a third ALF of the plurality of ALFs, to determine that the third Al will process the incoming transaction;
• and
• responsive to the negotiation, sending the incoming transaction to the third ALF for processing of the incoming transaction on behalf of the first reverse proxy appliance by the third reverse proxy appliance lending at least one transaction unit to the first reverse proxy appliance.

A method comprising:

• receiving global current threshold level data including information indicative of current threshold levels for a quantity of transactions that can be handled by each reverse proxy appliance (RPA) of a plurality of RPAs, wherein the plurality of RPAs are part of a distributed computer system, with each given RPA of the plurality of RPAs being:
• (i) configured to perform service level monitoring (SLM) to prevent a common backend sub-system from being overwhelmed by unanticipated burst messages, (ii) characterized by a current threshold level which is a sum of a quantity of transactions that can be directly processed by the given reverse proxy appliance and a quantity of transactions that can be processed by other reverse proxy appliance(s) on behalf of the given reverse proxy appliance, and (iii) further characterized by a current transaction count;
• receiving backend load data including information indicative of backend load(s) on a set of backend sub-system(s) served by the plurality of RPAs;
• and
• adjusting a current threshold level of a first RPA of the plurality of RPAs based, at least in part, upon both of the following:
• (i) the global current threshold level data of the first RPS being less than a sum of a current RPA transaction count for the first RPA and a size of an incoming transaction, and (ii) the backend load data wherein the current threshold level of the first RPA is adjusted by a second RPA processing the incoming transaction on behalf of the first RPA by lending the first RPA at least one transaction unit.