mirror of https://github.com/citusdata/citus.git
27ddb4fc8e
Do not obtain AccessShareLock before acquiring the distributed locks.
Acquiring an AccessShareLock ensures that the relations which we are trying to get a distributed lock on will not be dropped in the time between when the LOCK command is issued and the LOCK commands are send to the worker. However, this also leads to distributed deadlocks in such scenarios:
```sql
-- for dist lock acquiring order coor, w1, w2
-- on w2
LOCK t1 IN ACCESS EXLUSIVE MODE;
-- acquire AccessShareLock locally on t1 to ensure it is not dropped while we get ready to distribute the lock
-- concurrently on w1
LOCK t1 IN ACCESS EXLUSIVE MODE;
-- acquire AccessShareLock locally on t1 to ensure it is not dropped while we get ready to distribute the lock
-- acquire dist lock on coor, w1, gets blocked on local AccessShareLock on w2
-- on w2 continuation of the execution above
-- starts to acquire dist locks and gets blocked on the coor by the lock acquired by w1
-- distributed deadlock
```
We opt for avoiding such deadlocks with the cost of the possibility of running into errors when the relations on which we are trying to acquire locks on get dropped.
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|---|---|---|
| .. | ||
| README.md | ||
| columnar_index_concurrency.spec | ||
| columnar_temp_tables.spec | ||
| columnar_vacuum_vs_insert.spec | ||
| columnar_write_concurrency.spec | ||
| columnar_write_concurrency_index.spec | ||
| isolation_acquire_distributed_locks.spec | ||
| isolation_add_node_vs_reference_table_operations.spec | ||
| isolation_add_remove_node.spec | ||
| isolation_blocking_move_multi_shard_commands.spec | ||
| isolation_blocking_move_multi_shard_commands_on_mx.spec | ||
| isolation_blocking_move_single_shard_commands.spec | ||
| isolation_blocking_move_single_shard_commands_on_mx.spec | ||
| isolation_cancellation.spec | ||
| isolation_check_mx.spec | ||
| isolation_citus_dist_activity.spec | ||
| isolation_cluster_management.spec | ||
| isolation_concurrent_dml.spec | ||
| isolation_copy_placement_vs_copy_placement.spec | ||
| isolation_copy_placement_vs_modification.spec | ||
| isolation_copy_vs_all_on_mx.spec | ||
| isolation_create_citus_local_table.spec | ||
| isolation_create_distributed_table.spec | ||
| isolation_create_restore_point.spec | ||
| isolation_create_table_vs_add_remove_node.spec | ||
| isolation_data_migration.spec | ||
| isolation_ddl_vs_all.spec | ||
| isolation_delete_vs_all.spec | ||
| isolation_dis2ref_foreign_keys_on_mx.spec | ||
| isolation_distributed_deadlock_detection.spec | ||
| isolation_distributed_transaction_id.spec | ||
| isolation_dml_vs_repair.spec | ||
| isolation_drop_alter_index_select_for_update_on_mx.spec | ||
| isolation_drop_shards.spec | ||
| isolation_drop_vs_all.spec | ||
| isolation_dump_global_wait_edges.spec | ||
| isolation_dump_local_wait_edges.spec | ||
| isolation_ensure_dependency_activate_node.spec | ||
| isolation_extension_commands.spec | ||
| isolation_fix_partition_shard_index_names.spec | ||
| isolation_get_all_active_transactions.spec | ||
| isolation_get_distributed_wait_queries_mx.spec | ||
| isolation_global_pid.spec | ||
| isolation_hash_copy_vs_all.spec | ||
| isolation_insert_select_conflict.spec | ||
| isolation_insert_select_repartition.spec | ||
| isolation_insert_select_vs_all.spec | ||
| isolation_insert_select_vs_all_on_mx.spec | ||
| isolation_insert_vs_all.spec | ||
| isolation_insert_vs_all_on_mx.spec | ||
| isolation_insert_vs_vacuum.spec | ||
| isolation_master_update_node.spec | ||
| isolation_max_client_connections.spec | ||
| isolation_metadata_sync_deadlock.spec | ||
| isolation_metadata_sync_vs_all.spec | ||
| isolation_modify_with_subquery_vs_dml.spec | ||
| isolation_multi_shard_modify_vs_all.spec | ||
| isolation_multiuser_locking.spec | ||
| isolation_mx_common.include.spec | ||
| isolation_partitioned_copy_vs_all.spec | ||
| isolation_progress_monitoring.spec | ||
| isolation_range_copy_vs_all.spec | ||
| isolation_rebalancer_deferred_drop.spec | ||
| isolation_ref2ref_foreign_keys.spec | ||
| isolation_ref2ref_foreign_keys_on_mx.spec | ||
| isolation_ref_select_for_update_vs_all_on_mx.spec | ||
| isolation_ref_update_delete_upsert_vs_all_on_mx.spec | ||
| isolation_reference_copy_vs_all.spec | ||
| isolation_reference_on_mx.spec | ||
| isolation_replace_wait_function.spec | ||
| isolation_replicate_reference_tables_to_coordinator.spec | ||
| isolation_replicated_dist_on_mx.spec | ||
| isolation_select_for_update.spec | ||
| isolation_select_vs_all.spec | ||
| isolation_select_vs_all_on_mx.spec | ||
| isolation_shard_rebalancer.spec | ||
| isolation_shard_rebalancer_progress.spec | ||
| isolation_shouldhaveshards.spec | ||
| isolation_transaction_recovery.spec | ||
| isolation_truncate_vs_all.spec | ||
| isolation_truncate_vs_all_on_mx.spec | ||
| isolation_undistribute_table.spec | ||
| isolation_update_delete_upsert_vs_all_on_mx.spec | ||
| isolation_update_node.spec | ||
| isolation_update_node_lock_writes.spec | ||
| isolation_update_vs_all.spec | ||
| isolation_upsert_vs_all.spec | ||
| isolation_validate_vs_insert.spec | ||
| shared_connection_waits.spec | ||
README.md
In this folder, all tests which in the format of '*_add.spec' organized according to specific format.
You should use // in mx files not //. We preprocess mx files with cpp to
include isolation_mx_common.include.spec.
For isolation tests, we selected 'n' representative operations and we aimed to perform all possible pairs of 'n' operations together. So first test just runs first of these 'n' operation with remaining 'n - 1' operation. Similary, second test just runs second operation with remaining 'n - 2' operation. With this logic, we eventually run every selected operation with every other selected operation.