Instead of isTerminated we now use death watch on subscribers.
! Breaking change - ActorClassification based event buses now require
and actor system. Previously no actors were involved, but now someone
has to `watch` the subscribers. The unsubscriber is an system actor,
and won't be stopped automagically if a bus stops to be used (hard to
determine what "stops being used" is)
* Replaced isTerminated checks with watching actors
* backing structure for ActorClassification swaped from
ConcurrentHashMap to immutable.Map with CAS operations on it. This is
required to avoid races and guarantee register/unregister ordering
(messages sent with proper sequence numbers) to the unsubscriber.
Performance tested it and still above 1.3million subscribe+unsubscribe
ops per second (mac i7, retina), where as the CHM version was
4 million - but that one could only work in the presence of
itTerminated - so we pay the price here for removing it.
* `ActorClassification` starts the unsubscriber instance by itself,
the unsubscriber is an system actor, and can be stopped via
`ActorClassification#shutdown`
* Will unregister from unsubscriber, when no more subscriptions for
given subscriber are left in this bus.
* Added missing "Java API: " for some types
* Updated docs to point out the automatic subscriber purging (on terminated)
- Built-in redelivery mechanism for Channel and PersistentChannel
- redelivery counter on ConfirmablePersistent
- redeliveries out of initial message delivery order
- relative order of redelivered messages is preserved
- configurable redelivery policy (ChannelSettings)
- Major refactorings of channels (and channel tests)
- Throughput load test for PersistentChannel
Todo:
- Paged/throtlled replay (another pull request)
- Resequencer (another pull request)
- internal batching of individually received Persistent messages
- testing fault tolerance of Processor in presence of random
* journaling failures
* processing failures
- single and bulk deletion of messages
- single and bulk deletion of snapshots
- run journal and snapshot store as system actors
- rename physical parameter in delete methods to permanent
- StashSupport.prepend docs and implementation enhancements
- Persistent channel
- ConfirmablePersistent message type delivered by channel
- Sender resolution performance improvements
* unstash() instead of unstashAll()
These enhancements required the following changes
- Unified implementation of processor stash and user stash
- Persistence message plugin API separated from implementation
- Physical deletion of messages
- batch-write of persistent messages (user API)
- batch-write of events (in EventsourcedProcessor)
- command processing in EventsourcedProcessor by unstashing messages one-by-one from the internal stash
* fixes performance issues that come up with unstashAll
- commands are not looped through journal actor but processed directly
- initial performance tests
* command sourcing
* event sourcing
* event sourcing with user stash operations
- suppress stack traces in tests
- Journal plugin API for storage backends with asynchronous client API (default impl: in-memory journal)
- Journal plugin API for storage backends with synchronous client API (default impl: LevelDB journal)
- Snapshot store plugin API (default impl: local filesystem snapshot store)
- capture and save snapshots of processor state
- start processor recovery from saved snapshots
- snapshot storage on local filesystem
- snapshot store completely isolated from journal
- LevelDB journal modularized (and completely re-rwritten)
- In-memory journal removed
- introduce around life cycle hooks for symmetry with aroundReceive
- no custom processor-specific life cycle hooks needed any more
- preStart and preRestart can be overridden with empty implementation
(interceptors ensure that super.preXxx calls are still executed)
- all around life cycle hooks can be final
- standard life cycle hooks are non-final to preserve composability with existing traits (FSM, ...)
The most prominent changes compared to eventsourced are:
- No central processor and channel registry any more
- Auto-recovery of processors on start and restart (can be disabled)
- Recovery of processor networks doesn't require coordination
- Explicit channel activation not needed any more
- Message sequence numbers generated per processor (no gaps)
- Sender references are journaled along with messages
- Processors can determine their recovery status
- No custom API on extension object, only messages
- Journal created by extension from config, not by application
- Applications only interact with processors and channels via messages
- Internal design prepared for having processor-specific journal actors (for later optimization possibilities)
Further additions and changes during review:
- Allow processor implementation classes to use inherited stash
- Channel support to resolve (potentially invalid) sender references
- Logical intead of physical deletion of messages
- Pinned dispatcher for LevelDB journal
- Processor can handle failures during recovery
- Message renamed to Persistent
This prototype has the following limitations:
- Serialization of persistent messages and their payload via JavaSerializer only (will be configurable later)
- The LevelDB journal implementation based on a LevelDB Java port, not the native LevelDB (will be configurable later)
The following features will be added later using separate tickets:
- Snapshot-based recovery
- Reliable channels
- Journal plugin API
- Optimizations
- ...
