meatballspaghetti opened a new pull request, #5451:
URL: https://github.com/apache/accumulo/pull/5451
This PR is to improve efficiency and reduce slowdown of retrieving and
writing table names in ZooKeeper. These particular changes modify how table
names are managed, and follow #4996 which made the same modification for
namespace names. It replaces the use of the `/name` nodes under tables in
`/tables` with a table id-to-name mapping in a Json format stored under each
namespace in `/namespaces`, under a new node `/tables` (different from the main
`/tables` node that holds all tables). With this, when any function wants to
retrieve a table name, ZooKeeper will only need to read one or several mappings
instead of iterating through all `/name` nodes every time.
Previous Location of Table Names in ZooKeeper:
- `/tables/<tableAId>/name` (`/name` holds `namespaceA.tableAName`)
- `/tables/<tableBId>/name` (`/name` holds `namespaceA.tableBName`)
- `/tables/<tableCId>/name` (`/name` holds `namespaceB.tableCName`)
- `/tables/<tableDId>/name` (`/name` holds `namespaceB.tableDName`)
- etc.
Migration of Table Names into mappings under respective namespaces:
- `/namespaces/namespaceA/tables` (`/tables` holds `{tableAId:tableAName,
tableBId:tableBName}`)
- `/namespaces/namespaceB/tables` (`/tables` holds `{tableCId:tableCName,
tableDId:tableDName}`)
- etc.
**New files added:**
- `/accumulo/core/util/tables/TableMapping.java`:
Class that holds functionality for putting, renaming, removing, and
retrievingtable id-to-name map (and name-to-id map).
**Main Files changed for implementation:**
- `Constants.java`: Delete ZTABLE_NAME.
- `ClientContext.java`: Allow table mapping to be retrieved by referencing
the context. Mapping initialized as a Cache.
- `NamespaceMapping.java` + `NamespaceMappingTest.java`: Rename
serialization/deserialization methods to specify they are for Maps, as they are
also used in TableMapping.java.
- `AccumuloTable.java`: Add functionality to retrieve built-in table IDs and
names.
- `TableMap.java`: Deleted. Functionality moved into TableZooHelper.
- `TableZooHelper.java`: Add functionality from TableMap to create map of
all tables with qualified names. Change methods to use new TableMapping instead
of pulling directly from ZooCache.
- `ZooKeeperInitializer.java`: Initialize table mappings with built-in
tables upon starting ZooKeeper.
- `Utils.java`: Remove method for checking if table already exists, as it is
now checked within mutateExisting method calls in TableMapping.java.
- `CloneZookeeper.java` + `PopulateZookeeper.java` +
`ImportPopulateZookeeper.java` + `RenameTable.java`: Call new methods in
TableMapping to make respective updates.
**Developments yet to be made:**
- Finish implementing Cache into ClientContext to store
- Add table mapping to applicable upgrader and upgrader test
- Potentially rename TableZooHelper
- Run ITs
Original Issue: #4698
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