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new e43fbc5d4b IGNITE-18454 Explain treading model in corresponding
README.md file for TableManager (#1937)
e43fbc5d4b is described below
commit e43fbc5d4b99d78a1c21b691ca883177edc516ff
Author: Denis Chudov <moongll...@gmail.com>
AuthorDate: Thu Apr 13 22:15:21 2023 +0300
IGNITE-18454 Explain treading model in corresponding README.md file for
TableManager (#1937)
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+# Table manager
+
+Table manager is responsible for creating distributed tables. It reacts to
changes in distributed configuration changes related to tables and assignments,
and fires TableEvent processed by consumers in other components.
+
+Table manager creates and destroys internal representation of tables, calls
ReplicaManager to start and stop replicas, creates and destroys table storages.
+
+## Threading model
+
+There are following thread pools that are maintained by TableManager:
+
+**rebalanceScheduler**
+
+It is passed to RebalanceRaftGroupEventsListener and is used to do rebalance
related operations.
+Size is calculated as
+```java
+private static final int REBALANCE_SCHEDULER_POOL_SIZE =
Math.min(Runtime.getRuntime().availableProcessors() * 3, 20);
+```
+Thread prefix: `rebalance-scheduler`
+
+**scanRequestExecutor**
+
+It is single thread executor that is passed to replica listeners and is used
to process scan requests, provides effective tail recursion execution without
deep recursive calls.
+
+Thread prefix: `scan-query-executor-`.
+
+**txStateStorageScheduledPool**
+
+It is single thread executor that is used for flushing purposes for
transaction state storages.
+Thread prefix: `tx-state-storage-scheduled-pool
+`
+**txStateStoragePool**
+
+It is thread executor that is used for flushing purposes for transaction state
storages. Size is calculated as available processors count.
+Thread prefix: `tx-state-storage-scheduled-pool
+
+**ioExecutor**
+
+It is used for asynchronous start Raft nodes and clients. Size is calculated
as `Math.min(cpus * 3, 25)`.
+Thread prefix: `tableManager-io`
+
+### Activities of TableManager are processed in following threads:
+
+**Distributed configuration thread pool**
+
+Most of operations related to configuration listeners happen here. Should not
be blocked, asynchronous operations are preferred.
+
+**ioExecutor**
+
+It is used for asynchronous start Raft nodes and clients.
+
+**Raft disruptor pool**
+**Raft group client pool**
+
+It depends on the role of the node in meta storage group. Some parts of
updater of tables' versioned value (VV) in the update assignments procedure
happen within this pool, as the previous updater future is completed from this
pool's thread:
+- tables's VV is updated from `createTableLocally`
+- this updater waits for completion of schemas' VV
+- schemas' VV is updated from `SchemaManager#onSchemaChange`, schema is
registered in meta storage
+- schemas' VV is ready to be completed after meta storage future is complete.
+So, meta storage invoke future completes schemas' updater, which completes
tables' updater, which allows the next updater to start, and this updater
executes the code of assignments update in TableManager.
+
+This thread should not be blocked.
