ASSIGNMENT 1 - ABDUL HANIF BIN ABDUL AZIZ U2101905

[Nipz652]

1. Addressed Issue

There is some issue that I have found during my exploration through the OpenHab bundles such as:

• CPU and Disk I/O exhaustion caused by processing redundant events. (Resource Management Issues)

• Unsafe access to shared memory resources (HashSet) which caused runtime crashes. (Resource Management Issues)

• UI thread blocking caused by coarse-grained synchronization locks. (Synchronous, Blocking I/O)

• Thread starvation caused by synchronous processing of high-frequency network packets. (Synchronous, Blocking I/O)

• Sequential processing bottlenecks during "bursty" network traffic. (Synchronous, Blocking I/O)

• Redundant thread locking (synchronized keyword) during slow hardware scanning. (Synchronous, Blocking I/O)

2. What I Have Reengineered

• Implemented a Throttling Mechanism using a timestamp cache to drop duplicate events within a 2-second window.

• Replaced blocking ArrayList with CopyOnWriteArrayList and removed synchronized blocks to allow non-blocking reads.

• Implemented Asynchronous Batch Processing by decoupling event reception into a BlockingQueue.

• Replaced non-thread-safe collections with ConcurrentHashMap.newKeySet() to ensure safe concurrent access.

• Converted the remoteDeviceAdded callback to an Asynchronous Queue-based handler, moving logic to a background thread.

• Removed the synchronized modifier from listener methods, relying on existing thread-safe collections.

3. Reengineering Strategy or Approach Used

For the approaches that I use, I have use rework strategy to overcome addressed issue and improvise the system performance. Strategy that I have use are:

• Alteration. Altered the internal control flow to include conditional logic (throttling).

• Concurrency Refactoring. Shifted the concurrency model from "Blocking" to "Non-Blocking".

• Buffering. Introduced an intermediate buffer to manage data flow efficiency.

• Thread Safety. Altered data structure implementation to support atomic operations.

• Asynchronous Processing. Changed execution flow from synchronous to deferred/background execution.

• Non-Blocking Concurrency. Removed redundant locking mechanisms to improve execution flow.

4. Impact of Changes

• Reduced Resource Exhaustion. Prevented "Event Storms" from triggering excessive CPU processing and disk writes.

• Improved UI Responsiveness. Allowed the Add-on Store to load instantly even while finders are updating in the background.

• Prevented Thread Starvation. Ensured network bursts (device startups) are processed efficiently in chunks.

• System Stability. Eliminated ConcurrentModificationException crashes during simultaneous read/write operations.

• Decoupled Latency. Prevented network delays from freezing the main application logic.

• Prevented Deadlocks. Ensured the OSGi service registry does not lock up during slow USB hardware scans.