DEAS2005Michael Shin Copyright1 Connector-Based Self-Healing Mechanism for Components of a Reliable System Michael E. Shin Department of Computer Science Texas Tech University Daniel Cooke Department of Computer Science Texas Tech University

DEAS2005Michael Shin Copyright2 Outline Introduction Self-healing component Architecture Connector-based self-healing mechanism Connectors supporting self-healing mechanism Conclusions

DEAS2005Michael Shin Copyright3 Introduction Each component in a system structured with Tasks – active or concurrent objects Passive objects accessed by tasks – e.g., entity object Connectors between tasks – synchronization mechanism For each component of reliable system Needs to self-heal anomalies such as design faults Encapsulates self-healing mechanism In previous paper [Shin05] Self-healing mechanism in a component This paper Specifications of connectors for self-healing mechanism

DEAS2005Michael Shin Copyright4 Self-Healing Component Architecture Self-healing component enables Autonomously detect, isolate and repair anomalies Layered software architecture Service layer Normal phase Provide full functionality requested Notify the status of objects to healing layer Healing phase Provide no service or degraded services Healing layer Normal phase Monitoring of objects in service layer Healing phase Reconfigure objects in service layer Repair sick objects in service layer

DEAS2005Michael Shin Copyright5 Service layer Tasks, Passive objects, and Connectors Healing layer Component Monitor Statecharts for each task thread in the service layer Supervise behavior of objects using statecharts Component Reconfiguration Plan Generator and Executor Generates reconfiguration plans and reconfigures objects in service layer Component Repair Plan Generator and Executor Generates repair plans and carries out the plans Component Self-Healing Controller Controls healing process Self-Healing Component Architecture

DEAS2005Michael Shin Copyright6 Self-Healing Component Architecture

DEAS2005Michael Shin Copyright7 Connector-based Self-healing Mechanism Connector Encapsulates synchronization mechanism Extended to self-healing mechanism Detection, reconfiguration, and repair Anomaly detection Connector notifies Component Monitor Message arrivals from a task Placing a message in a queue or buffer Passive object accessed by tasks notifies Invoked by a task finishing an operation Component Monitor Encapsulates statecharts for task threads Detect anomalies of objects in service layer If expected message does not arrive within a time interval

DEAS2005Michael Shin Copyright8 Reconfiguration Isolation of sick objects from healthy objects Minimize impact from sick objects Connectors involved in reconfiguration Incoming connectors block adding a new message Outgoing connectors block other tasks’ reading messages Freeze communication between a sick task and healthy tasks Reconfiguration again when a sick object is repaired Repair Reinitialized, reinstalled, or replaced with a variant Testing after repair Test data are delivered to repaired objects via connectors Connector-based Self-healing Mechanism

DEAS2005Michael Shin Copyright9 Connector between tasks classified to Message queue connector Message buffer connector Message buffer and response connector To support self-healing mechanism Defines self-healing connectors Specialization of connectors to self-healing connectors Connectors supporting self-healing mechanism

DEAS2005Michael Shin Copyright10 Message Queue Self-Healing Connector

DEAS2005Michael Shin Copyright11 Message Buffer Self-Healing Connector, and Message Buffer and Response connector

DEAS2005Michael Shin Copyright12 Conclusions Described connector-based self-healing mechanism for self-healing components Connectors play key roles in self-healing mechanism This approach Connectors support Self-healing mechanism Low performance due to communication Future Research Extension to inter-components interaction at software architecture