Chris LuandGitHub
979c54f693
* fix(wdclient,volume): compare master leader with ServerAddress.Equals Raft leader is advertised as host:httpPort.grpcPort, but clients dial host:httpPort. Raw string comparison against VolumeLocation.Leader / HeartbeatResponse.Leader therefore never matches, causing the masterclient and the volume server heartbeat loop to continuously "redirect" to the already-connected master, tearing down the stream and reconnecting. Use ServerAddress.Equals, which normalizes the grpc-port suffix. * fix(filer,mq): compare ServerAddress via Equals in two more sites filer bootstrap skip (MaybeBootstrapFromOnePeer) and the broker's local partition assignment check both compared a wire-supplied address string against the local self ServerAddress with raw string equality. Both are vulnerable to the same plain-vs-host:port.grpcPort mismatch as the masterclient/volume heartbeat sites: filer would bootstrap from itself, and the broker would fail to claim a partition it was actually assigned. Route both through ServerAddress.Equals. * fix(master,shell): more ServerAddress comparisons via Equals - raft_server_handlers.go HealthzHandler: s.serverAddr == leader would skip the child-lock check on the real leader when the two carry different plain/grpc-suffix forms, returning 200 OK instead of 423. - master_server.go SetRaftServer leader-change callback: the Leader() == Name() guard for ensureTopologyId could disagree with topology.IsLeader() (which already uses Equals), so leader-only initialization could be skipped after an election. - command_volume_merge.go isReplicaServer: the -target guard compared user-supplied host:port against NewServerAddressFromDataNode(...) with ==, letting an existing replica slip through when topology carries the embedded gRPC port. All routed through pb.ServerAddress.Equals. * fix(mq,cluster): more ServerAddress comparisons via Equals - broker_grpc_lookup.go GetTopicPublishers/GetTopicSubscribers: the partition ownership check gated listing on raw LeaderBroker == BrokerAddress().String(), so listings silently omitted partitions hosted locally when the assignment carried the other host:port / host:port.grpcPort form. - lock_client.go: LockHostMovedTo comparison and the seedFiler fallback guard both used raw string equality against configured filer addresses (which may be plain host:port while LockHostMovedTo comes back suffixed), causing spurious host-change churn and blocking the seed-filer fallback. * fix(mq): more ServerAddress comparisons via Equals - pub_balancer/allocate.go EnsureAssignmentsToActiveBrokers: direct activeBrokers.Get() lookup missed brokers when a persisted assignment carried a different address encoding than the registered broker key, triggering a bogus reassignment on every read/write cycle. Added a findActiveBroker helper that falls back to an Equals-based scan and canonicalizes the assignment in place so later writes are stable. - broker_grpc_lookup.go isLockOwner: used raw string equality between LockOwner() and BrokerAddress().String(), so a lock owner could fail to recognize itself and proxy local lookup/config/admin RPCs away. - pub_client/scheduler.go onEachAssignments: reused publisher jobs only on exact LeaderBroker match, so an encoding flip in lookup results tore down and recreated a stream to the same broker.
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.