Applied consistent hashing as a default function

[nishidy]

This is to enable consistent hashing to get a server for a key statically. There is already an issue about this raised at #33. Tests are included but I will add more if necessary. I will add features on this to fully utilize this function like decreasing and increasing the number of nodes.

Summary by CodeRabbit

• New Features

  • Introduced a new continuum structure for improved key-based connection management.
  • Enhanced client capabilities with methods for adding virtual nodes and selecting connections using key hashes.

• Refactor

  • Updated the client's internal handling of connections to leverage the new continuum system.

• Bug Fixes

  • Implemented a placeholder hash function to ensure consistent client behavior during development.

[aisk]

Will this make the first node (index zero) more weight than others?

[aisk]

@coderabbitai review

[coderabbitai]

Walkthrough

The update restructures the Client to integrate a Continuum for managing a distributed system's nodes. It introduces a consistent hashing mechanism, where a Continuum holds VNodes, and the Client uses this to route requests. The Client now has a new hash function and leverages the Continuum to determine the target node for a given key based on its hash.

Changes

File(s)	Change Summary
src/client.rs	Introduced Continuum struct with VNode management and search methods; updated Client with new continuum field and methods for node selection based on key hashes; added empty_hash_function.

🐇✨
To the code, we hop and leap,
A Continuum now the Client keeps.
With hashes and nodes, so deftly we weave,
A distributed dance, in Rust, we achieve. 🌐🔑

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Review Status

Actionable comments generated: 0

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Commits

Files that changed from the base of the PR and between b51a81f and 6f411ca.

Files selected for processing (1)

• src/client.rs (5 hunks)

Additional comments: 7

src/client.rs (7)

• 50-65: The Client struct has been correctly updated to include the continuum field and the hash_function field. The Continuum struct and VNode struct are also correctly defined to support consistent hashing.

• 72-77: The empty_hash_function is a placeholder and should be replaced with a proper hash function to ensure a good distribution of keys across the continuum.

• 86-133: The Continuum struct's methods for managing virtual nodes and searching the continuum are correctly implemented.

• 142-147: The get_connections_index method correctly uses the continuum to find the connection index, ensuring that keys are distributed based on the hash.

• 181-189: The get_connection method uses a comparison to check if the hash_function is the empty_hash_function. This is a temporary measure and should be replaced with a proper hash function to ensure consistent hashing.

• 308-324: The gets method is correctly implemented to handle multiple keys by grouping them by connection index, which reduces network workloads.

• 563-675: The tests cover the bsearch_continuum_index method and key distribution, which is good. Consider adding a test for the empty_hash_function to ensure it behaves as expected until it is replaced with a proper hash function.