Chameleon: adaptive fault tolerance using reliable, mobile agents

In networked computing systems, a broad range of commercial and scientific applications that need varying degrees of availability must coexist. It is not cost-effective to develop a reliable platform in each case. It is more efficient to build an infrastructure that provides the required level of dependability for each application's needs. It is also essential that the proposed alternatives should leverage off-the-shelf components. There have been exhaustive studies on fault tolerance strategies capable of providing efficient mechanisms to deal with system operational failures. Most of this work has focused on specific application needs and thus provided only piecemeal solutions. Little work has been done in addressing how to build a reliable networked computing system out of unreliable computation nodes. As a result, there is no comprehensive solution for providing a wide range of fault-tolerant services in a single networked environment. The most feasible way of understanding how such a software environment would fit on top of existing layers (the operating system, the network interfaces, etc.) is to implement an infrastructure for providing a range of reliable services. Fundamental components of the envisioned infrastructure (Chameleon) have been designed so that none of them is a single point of failure. Each of the components is active for a certain period, e.g. during the setting up the system configuration. If a component fails during its active phase, there is a provision for recovery, either by switching to a backup or by regenerating the component.