feat: support batch lookup

[linguoxuan]

Purpose

Linked issue: close #195

Brief change log

Tests

API and Format

Documentation

[linguoxuan]

Hi, @luoyuxia @leekeiabstraction Please take a look if you have time.

[Copilot]

Pull request overview

This pull request adds batch lookup support to the Rust client, achieving parity with the Java client by implementing a queuing and batching mechanism that reduces network round trips for improved throughput.

Changes:

• Adds a LookupClient with background sender task that batches multiple lookup operations
• Implements retry logic with configurable limits and error classification
• Adds five new configuration parameters for lookup batching, queuing, and retry behavior

Reviewed changes

Copilot reviewed 12 out of 12 changed files in this pull request and generated 10 comments.

Show a summary per file

File	Description
crates/fluss/src/config.rs	Adds configuration parameters for lookup queue size, batch size, timeout, inflight requests, and max retries
crates/fluss/src/rpc/message/lookup.rs	Adds new_batched method to create lookup requests with multiple buckets
crates/fluss/src/rpc/fluss_api_error.rs	Adds is_retriable() method to classify errors for retry logic
crates/fluss/src/client/connection.rs	Adds get_or_create_lookup_client() to manage shared lookup client instance
crates/fluss/src/client/mod.rs	Exports new lookup module and LookupClient
crates/fluss/src/client/lookup/mod.rs	Defines lookup module structure with client, query, queue, and sender
crates/fluss/src/client/lookup/lookup_query.rs	Represents individual lookup operation with retry tracking and oneshot channel for result
crates/fluss/src/client/lookup/lookup_queue.rs	Implements queue with batch draining and retry prioritization
crates/fluss/src/client/lookup/lookup_sender.rs	Background task that groups lookups by destination, batches requests, and handles responses/retries
crates/fluss/src/client/lookup/lookup_client.rs	Public API for batched lookups with background sender task management
crates/fluss/src/client/table/lookup.rs	Updates Lookuper to use shared LookupClient instead of direct RPC calls
crates/fluss/tests/integration/kv_table.rs	Adds integration tests for batched lookups with various scenarios

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[leekeiabstraction]

Thank you for the PR, left initial comments

[leekeiabstraction]

Also, consider squashing the integration test cases into 1 test case. Concurrent lookups, looking up same key, looking up non-existing key should be able to be rolled into one.

I'm starting to think that we may also want to add number of tablet servers for integration test so that we can check the behaviour of bucketing as well. What do you think @luoyuxia . We can potentially raise that as a separate issue.

[leekeiabstraction]

Thank you for the update! One comment left from me.

[leekeiabstraction]

Approved and thank you for the PR! Left a small comment.

[Copilot]

Pull request overview

Copilot reviewed 12 out of 12 changed files in this pull request and generated 4 comments.

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[luoyuxia]

@linguoxuan Hi, thanks for your contribution. But since we're getting to code freeze for 0.1. I'd like to get it merged int next version. Does it work for you?

[linguoxuan]

@linguoxuan Hi, thanks for your contribution. But since we're getting to code freeze for 0.1. I'd like to get it merged int next version. Does it work for you?

ok.