chrislu
8762a1a4af
Multi-batch Fetch support completed: ## Core Features - **MaxBytes compliance**: Respects fetch request MaxBytes limits to prevent oversized responses - **Multi-batch concatenation**: Properly concatenates multiple record batches in single response - **Size estimation**: Pre-estimates batch sizes to optimize MaxBytes usage before construction - **Kafka-compliant behavior**: Always returns at least one batch even if it exceeds MaxBytes (first batch rule) ## Implementation Details - **MultiBatchFetcher**: New dedicated class for multi-batch operations - **Intelligent batching**: Adapts record count per batch based on available space (10-50 records) - **Proper concatenation format**: Each batch maintains independent headers and structure - **Fallback support**: Graceful fallback to single batch if multi-batch fails ## Advanced Features - **Compression ready**: Basic support for compressed record batches (GZIP placeholder) - **Size tracking**: Tracks total response size and batch count across operations - **Edge case handling**: Handles large single batches, empty responses, partial batches ## Integration & Testing - **Fetch API integration**: Seamlessly integrated with existing handleFetch pipeline - **17 comprehensive tests**: Multi-batch scenarios, size limits, concatenation format validation - **E2E compatibility**: Sarama tests pass with no regressions - **Performance validation**: Benchmarks for batch construction and multi-fetch operations ## Performance Improvements - **Better bandwidth utilization**: Fills available MaxBytes space efficiently - **Reduced round trips**: Multiple batches in single response - **Adaptive sizing**: Smaller batches when space limited, larger when space available Ready for Phase 6: Basic flexible versions support
SeaweedMQ Message Queue on SeaweedFS (WIP, not ready)
What are the use cases it is designed for?
Message queues are like water pipes. Messages flow in the pipes to their destinations.
However, what if a flood comes? Of course, you can increase the number of partitions, add more brokers, restart, and watch the traffic level closely.
Sometimes the flood is expected. For example, backfill some old data in batch, and switch to online messages. You may want to ensure enough brokers to handle the data and reduce them later to cut cost.
SeaweedMQ is designed for use cases that need to:
- Receive and save large number of messages.
- Handle spike traffic automatically.
What is special about SeaweedMQ?
- Separate computation and storage nodes to scale independently.
- Unlimited storage space by adding volume servers.
- Unlimited message brokers to handle incoming messages.
- Offline messages can be operated as normal files.
- Scale up and down with auto split and merge message topics.
- Topics can automatically split into segments when traffic increases, and vice verse.
- Pass messages by reference instead of copying.
- Clients can optionally upload the messages first and just submit the references.
- Drastically reduce the broker load.
- Stateless brokers
- All brokers are equal. One broker is dynamically picked as the leader.
- Add brokers at any time.
- Allow rolling restart brokers or remove brokers at a pace.
Design
How it works?
Brokers are just computation nodes without storage. When a broker starts, it reports itself to masters. Among all the brokers, one of them will be selected as the leader by the masters.
A topic needs to define its partition key on its messages.
Messages for a topic are divided into segments. One segment can cover a range of partitions. A segment can be split into 2 segments, or 2 neighboring segments can be merged back to one segment.
During write time, the client will ask the broker leader for a few brokers to process the segment.
The broker leader will check whether the segment already has assigned the brokers. If not, select a few brokers based on their loads, save the selection into filer, and tell the client.
The client will write the messages for this segment to the selected brokers.
Failover
The broker leader does not contain any state. If it fails, the masters will select a different broker.
For a segment, if any one of the selected brokers is down, the remaining brokers should try to write received messages to the filer, and close the segment to the clients.
Then the clients should start a new segment. The masters should assign other healthy brokers to handle the new segment.
So any brokers can go down without losing data.
Auto Split or Merge
(The idea is learned from Pravega.)
The brokers should report its traffic load to the broker leader periodically.
If any segment has too much load, the broker leader will ask the brokers to tell the client to close current one and create two new segments.
If 2 neighboring segments have the combined load below average load per segment, the broker leader will ask the brokers to tell the client to close this 2 segments and create a new segment.