Enhance Resource Efficiency: Optionally Disable Worker Thread Pool for Low-Memory Profiles

[quiet-node]

Problem Description

The Relay currently utilizes a worker thread pool (via piscina) to parallelize CPU-intensive tasks such as block processing and Ethereum log fetching. While beneficial for high-throughput environments, this architecture imposes a high memory floor. Each worker thread initializes a separate V8 Isolate, contributing significantly to the process's Resident Set Size (RSS).

Current Behavior & Impact

In resource-constrained deployments (e.g., containers with a 128MB RAM limit), the relay is prone to frequent OOMKilled events.

Observations:

• Isolate Overhead: Each worker thread adds roughly 20-30MB of RSS baseline overhead.
• Peak Spikes: Inter-thread communication using postMessage involves the Structured Clone algorithm, which creates temporary data copies, leading to memory surges during heavy request processing.
• OOM Vulnerability: With 2-4 workers enabled (the default), the idle RSS baseline often hovers around 140MB+, making it impossible to operate stably within a strict memory limited environment.

Proposed Solution

Introduce a configuration flag, WORKERS_POOL_ENABLED, to allow operators to explicitly disable the worker pool.

• Logic: When WORKERS_POOL_ENABLED=false, the WorkersPool service should bypass Piscina and execute task handlers directly on the main event loop.
• Dynamic Loading: Use dynamic imports to load worker logic only when needed, maintaining a clean separation of concerns.
• Optimization: This "Single-Threaded" or "Local Bypass" mode reduces the idle RSS, providing sufficient headroom for heap growth and network buffers within a memory limited container.

Rationale

While multi-threading improves performance on multi-core systems, process stability is the primary requirement for low-tier deployments. Providing a mechanism to opt-out of worker overhead allows the Hedera JSON-RPC Relay to support a wider range of hardware specifications and reduces the total cost of ownership (TCO) for lite relay operators.

Acceptance Criteria

• New WORKERS_POOL_ENABLED configuration variable (default true).
• WorkersPool.ts updated to support local, main thread execution.
• Error handling utility (WorkersErrorUtils) extracted to prevent circular dependencies in local mode.
• Validation that the relay survives acceptance tests on a memory limited environment with workers disabled.

[quiet-node]

A POC can be found here: 1019faf