feat: add flag to specify number of verifier workers to use

[chatton]

Overview

Enables support for specifying the --verifier.workers to limit the number of go routines being created.

[gemini-code-assist]

Summary of Changes

Hello @chatton, I'm Gemini Code Assist¹! I'm currently reviewing this pull request and will post my feedback shortly. In the meantime, here's a summary to help you and other reviewers quickly get up to speed!

This pull request enhances the block verification process by introducing a configurable worker pool. This change allows for better control over resource utilization during block verification by limiting the number of concurrent operations, which can prevent performance degradation under high load and improve overall stability.

Highlights

• New Configuration Flag: Introduced a new command-line flag, --verifier.workers, allowing users to specify the number of concurrent goroutines used for block verification. The default value for this flag is set to 50.
• Worker Pool Implementation: Refactored the block verification logic to utilize a worker pool pattern. Instead of spawning a new goroutine for each incoming block, blocks are now queued and processed by a fixed number of worker goroutines, improving resource management.
• Documentation Update: The README.md file has been updated to include documentation for the newly added --verifier.workers flag, ensuring users are aware of this new configuration option.

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[gemini-code-assist]

Code Review

This pull request introduces a --verifier.workers flag to configure the number of concurrent workers for block verification, which is a valuable addition for managing resource usage. The implementation correctly uses a worker pool pattern. My review includes two main points: a critical fix to validate the number of workers to prevent panics or deadlocks from invalid user input, and a medium-severity refactoring suggestion to simplify the graceful shutdown logic, improving code clarity and maintainability.

[gemini-code-assist]

The number of workers is not validated. If a user provides a non-positive value for --verifier.workers (e.g., 0 or -1), it will cause issues. A negative value will cause a panic when creating the blockQueue channel, and a value of 0 will lead to a deadlock as blocks will be added to the queue but never processed. It's crucial to validate this input and fail fast if it's invalid. I suggest panicking to ensure the application doesn't start in an invalid state.

Suggested change

	return &exporter{
	if workers <= 0 {
	panic("number of verifier workers must be a positive integer")
	}
	return &exporter{

[chatton]

it has a default value at the flag level so this will never be hit.