test(tablets): split and merge on writes and deletions

A test of high load, causing rapid tablet splits.
Then have a deletion burst and a major compaction to trigger rapid tablets merges.

jenkins-pipelines/oss/longevity/tablets-split-merge-long-test.jenkinsfile

@@ -0,0 +1,12 @@
+#!groovy
+
+// trick from https://github.com/jenkinsci/workflow-cps-global-lib-plugin/pull/43
+def lib = library identifier: 'sct@snapshot', retriever: legacySCM(scm)
+
+longevityPipeline(
+    backend: 'aws',
+    region: 'eu-west-1',
+    test_name: 'tablets_split_merge_test.TabletsSplitMergeTest.test_tablets_split_merge',
+    test_config: 'test-cases/features/tablets/tablets-split-merge-long-test.yaml'
+
+)

jenkins-pipelines/oss/longevity/tablets-split-merge-test.jenkinsfile

@@ -0,0 +1,12 @@
+#!groovy
+
+// trick from https://github.com/jenkinsci/workflow-cps-global-lib-plugin/pull/43
+def lib = library identifier: 'sct@snapshot', retriever: legacySCM(scm)
+
+longevityPipeline(
+    backend: 'aws',
+    region: 'eu-west-1',
+    test_name: 'tablets_split_merge_test.TabletsSplitMergeTest.test_tablets_split_merge',
+    test_config: 'test-cases/features/tablets/tablets-split-merge-test.yaml'
+
+)

sdcm/provision/scylla_yaml/scylla_yaml.py

@@ -353,6 +353,7 @@ def set_authorizer(cls, authorizer: str):
     compaction_collection_items_count_warning_threshold: int = None  # None
 
     enable_tablets: bool = None  # False, but default scylla.yaml for some versions (e.g. 6.0) override it to True
+    target_tablet_size_in_bytes: int = None
     force_gossip_topology_changes: bool = None  # False
 
     reader_concurrency_semaphore_cpu_concurrency: int = None

sdcm/utils/tablets/common.py

@@ -43,3 +43,20 @@ def wait_for_tablets_balanced(node):
                                 params={}, timeout=3600, retry=3)
         time.sleep(5)
     LOGGER.info("Tablets are balanced")
+
+
+def get_tablets_count(keyspace: str, session) -> int:
+    """
+    Returns the number of tablets in a keyspace.
+    :param session:
+    :param keyspace:
+    :return: tablets count int
+    """
+    cmd = f"select tablet_count from system.tablets where keyspace_name='{keyspace}' ALLOW FILTERING"
+    cql_result = session.execute(cmd)
+    if not cql_result or not cql_result.current_rows:
+        return 0
+    LOGGER.debug(f"Got CQL result of: {cql_result.current_rows}")
+    tablet_count = cql_result.current_rows[0].tablet_count
+    LOGGER.debug('Retrieved a tablets count of: %s for keyspace %s', tablet_count, keyspace)
+    return int(tablet_count)

tablets_split_merge_test.py

@@ -0,0 +1,232 @@
+import threading
+import time
+from functools import partial
+
+from cassandra import ConsistencyLevel
+from cassandra.query import SimpleStatement
+
+from longevity_test import LongevityTest
+from sdcm import wait
+from sdcm.sct_events import Severity
+from sdcm.sct_events.system import InfoEvent
+from sdcm.utils.common import ParallelObject
+from sdcm.utils.tablets.common import get_tablets_count
+from test_lib.scylla_bench_tools import create_scylla_bench_table_query
+
+KEYSPACE_NAME = 'scylla_bench'
+TABLE_NAME = 'test'
+KS_CF = f"{KEYSPACE_NAME}.{TABLE_NAME}"
+GB_IN_BYTES = 1_073_741_824
+
+
+class TabletsSplitMergeTest(LongevityTest):
+
+    def __init__(self, *args, **kwargs):
+        super().__init__(*args, **kwargs)
+        self.max_tablets_num = 0
+        self.query_tablets_num_stop_event = threading.Event()
+
+    def _background_query_tablets_num(self):
+        """Background thread to query the tablets number."""
+        while not self.query_tablets_num_stop_event.is_set():
+            try:
+                tablets_num = self._get_tablets_number()
+                self.max_tablets_num = max(self.max_tablets_num, tablets_num)
+                self.log.debug(f"Updated max tablets number: {self.max_tablets_num}")
+            except Exception as e:  # pylint: disable=broad-except  # noqa: BLE001
+                self.log.error(f"Error in background tablet query: {e}")
+            time.sleep(15)  # Wait 15 seconds before next query
+
+    def _get_tablets_number(self) -> int:
+        with self.db_cluster.cql_connection_patient(self.db_cluster.nodes[0]) as session:
+            tablets_number = get_tablets_count(keyspace=KEYSPACE_NAME, session=session)
+        self.log.debug(f"Tablets number for {KEYSPACE_NAME} is: {tablets_number}")
+        return tablets_number
+
+    def _update_target_tablet_size(self, target_tablet_size_in_bytes: int):
+        for node in self.db_cluster.nodes:
+            self.log.info(f"Updating {node} with new target_tablet_size_in_bytes = {target_tablet_size_in_bytes}")
+            append_scylla_yaml = {"target_tablet_size_in_bytes": target_tablet_size_in_bytes}
+            with node.remote_scylla_yaml() as scylla_yaml:
+                scylla_yaml.update(append_scylla_yaml)
+            self.log.debug(f"Restarting node {node} to apply new target_tablet_size_in_bytes")
+            node.restart_scylla_server()
+
+    def _pre_create_large_partitions_schema(self):
+        self.run_pre_create_keyspace()
+        with self.db_cluster.cql_connection_patient(self.db_cluster.nodes[0]) as session:
+            session.execute(create_scylla_bench_table_query())
+
+    def _start_stress_if_not_running(self, stress_queue, stress_params):
+        if self._is_stress_finished(stress_queue=stress_queue):
+            InfoEvent(message="The Stress is not running. Rerunning it.").publish()
+            self._run_all_stress_cmds(stress_queue, stress_params)
+
+    def test_tablets_split_merge(self):  # pylint: disable=too-many-locals  # noqa: PLR0914
+        """
+        (1) writing initial schema and get initial number of tablets.
+        (2) start write and read stress simultaneously.
+        (3) wait for tablets split.
+        (4) wait for stress completion.
+        (5) run deletions, nodetool flush and major compaction.
+        (6) wait for tablets merge, following a shrunk dataset size.
+        (7) redo more such cycles.
+        """
+
+        # (1) initiate schema.
+        InfoEvent(message=f"Create a keyspace with tablets initial value").publish()
+        self._pre_create_large_partitions_schema()
+        stress_cmd = self.params.get('stress_cmd')
+        stress_read_cmd = self.params.get('stress_read_cmd')
+        deletion_percentage = 80  # How many of dataset partitions should be deleted.
+
+        # Run prepare stress
+        self.run_prepare_write_cmd()
+
+        # Run Read background stress
+        stress_read_queue = []
+        read_params = {'keyspace_num': 1, 'stress_cmd': stress_read_cmd}
+        self._run_all_stress_cmds(stress_read_queue, read_params)
+        self.node1 = self.db_cluster.nodes[0]
+
+        # Run cycles of writes and deletions
+        cycles_num = 10
+        for cycle in range(cycles_num):
+            initial_tablets_num = self.max_tablets_num = self._get_tablets_number()
+            InfoEvent(
+                message=f"Cycle {cycle }, Initial tablets number before stress is: {initial_tablets_num}").publish()
+            InfoEvent(message=f"Starting write load: {stress_cmd}").publish()
+            stress_queue = []
+            self.assemble_and_run_all_stress_cmd(stress_queue=stress_queue, stress_cmd=stress_cmd, keyspace_num=1)
+
+            self._start_stress_if_not_running(stress_read_queue, read_params)
+
+            InfoEvent(message="Wait for write stress to finish (if running)").publish()
+            for stress in stress_queue:
+                self.verify_stress_thread(cs_thread_pool=stress)
+
+            self.log.debug("Starting background thread to query tablets number.")
+            background_thread = threading.Thread(target=self._background_query_tablets_num, daemon=True)
+            background_thread.start()
+
+            self._start_stress_if_not_running(stress_read_queue, read_params)
+            InfoEvent(message=f"Start deletions to trigger a tablets merge.").publish()
+            self.delete_partitions_in_batch(deletion_percentage)
+
+            InfoEvent(message=f"Run a flush for {KEYSPACE_NAME} on nodes").publish()
+            triggers = [partial(node.run_nodetool, sub_cmd=f"flush -- {KEYSPACE_NAME}", )
+                        for node in self.db_cluster.data_nodes]
+            ParallelObject(objects=triggers, timeout=2400).call_objects()
+
+            InfoEvent(message=f"Run a major compaction for {KEYSPACE_NAME} on nodes").publish()
+            triggers = [partial(node.run_nodetool, sub_cmd="compact", args=f"{KEYSPACE_NAME} {TABLE_NAME}", ) for
+                        node in self.db_cluster.data_nodes]
+            ParallelObject(objects=triggers, timeout=2400).call_objects()
+
+            self._wait_for_tablet_split(tablets_num=initial_tablets_num)
+            self.log.debug(f"Final max tablets number: {self.max_tablets_num}")
+
+            if self.max_tablets_num <= initial_tablets_num:
+                InfoEvent(
+                    message=f"The maximum number of tablets [{self.max_tablets_num}] is not bigger than the initial number [{initial_tablets_num}].", severity=Severity.ERROR).publish()
+            InfoEvent(message="Wait for tablets merge after deletion is done.").publish()
+            self._wait_for_tablets_merge()
+            self.log.debug("Stopping background thread.")
+            self.query_tablets_num_stop_event.set()
+            background_thread.join()
+
+        InfoEvent(message="Wait for read stress to finish.").publish()
+
+        for stress in stress_read_queue:
+            self.verify_stress_thread(cs_thread_pool=stress)
+
+    def _is_stress_finished(self, stress_queue) -> bool:
+        for index, stress in enumerate(stress_queue):
+            self.log.debug(f"Checking stress task {index + 1}/{len(stress_queue)}: {stress.stress_cmd}")
+            if not all(future.done() for future in stress.results_futures):
+                self.log.debug(f"Stress task {index + 1} is still running.")
+                return False
+            self.log.debug(f"Stress task {index + 1} has completed.")
+        self.log.debug("All stress tasks have finished.")
+        return True
+
+    def _wait_for_tablets_merge(self, timeout_min: int = 240):
+        """
+        Waits for a tablets number smaller than tablets_num
+        """
+        text = f"Waiting for a smaller tablets number"
+        res = wait.wait_for(func=lambda: self._get_tablets_number() < self.max_tablets_num, step=60,
+                            text=text, timeout=60 * timeout_min, throw_exc=False)
+        if not res:
+            InfoEvent(message=f"{text} FAILED.", severity=Severity.ERROR).publish()
+
+    def _wait_for_tablet_split(self, tablets_num: int, timeout_min: int = 15):
+        """
+        Waits for tablets number bigger than tablets_num
+        """
+        text = f"Waiting for a tablets number bigger than {tablets_num}"
+        res = wait.wait_for(func=lambda: self.max_tablets_num > tablets_num, step=60,
+                            text=text, timeout=60 * timeout_min, throw_exc=False)
+        if not res:
+            InfoEvent(message=f"{text} FAILED.", severity=Severity.ERROR).publish()
+
+    def delete_partitions(self, deletion_percentage: int):
+        """
+        Deletes a percentage of table's partitions.
+        Example:
+            partition_end_range = 10
+            max_partitions_to_delete = 100
+            deletion_percentage = 70
+            ==> 70 partitions from 11 up to 81 will be deleted.
+        """
+        start_partition = self.partitions_attrs.partition_end_range + 1
+        max_partitions_to_delete = self.partitions_attrs.max_partitions_in_test_table - self.partitions_attrs.partition_end_range
+        num_of_partitions_to_delete = int(max_partitions_to_delete * deletion_percentage / 100)
+        end_partition = start_partition + num_of_partitions_to_delete
+
+        self.log.debug(
+            f"Preparing to delete {num_of_partitions_to_delete} partitions from {start_partition} to {end_partition}.")
+        for pkey in range(start_partition, end_partition):
+            delete_query = f"delete from {KS_CF} where pk = {pkey}"
+            self.log.debug(f'delete query: {delete_query}')
+            try:
+                with self.db_cluster.cql_connection_patient(self.node1, connect_timeout=300) as session:
+                    session.execute(SimpleStatement(delete_query, consistency_level=ConsistencyLevel.QUORUM),
+                                    timeout=3600)
+            except Exception as e:  # pylint: disable=broad-except  # noqa: BLE001
+                message = f"Failed to execute delete: {e}"
+                InfoEvent(message=message, severity=Severity.ERROR).publish()
+
+    def delete_partitions_in_batch(self, deletion_percentage: int):
+        """
+        Deletes a percentage of table's partitions using batched queries.
+        """
+        start_partition = self.partitions_attrs.partition_end_range + 1
+        max_partitions_to_delete = self.partitions_attrs.max_partitions_in_test_table - self.partitions_attrs.partition_end_range
+        num_of_partitions_to_delete = int(max_partitions_to_delete * deletion_percentage / 100)
+        end_partition = start_partition + num_of_partitions_to_delete
+        batch_size: int = 1000
+        self.log.debug(
+            f"Preparing to delete {num_of_partitions_to_delete} partitions from {start_partition} to {end_partition} in batches of {batch_size}.")
+        batch = []
+        try:
+            with self.db_cluster.cql_connection_patient(self.node1, connect_timeout=300) as session:
+                for pkey in range(start_partition, end_partition):
+                    delete_query = f"DELETE FROM {KS_CF} WHERE pk = {pkey}"
+                    batch.append(delete_query)
+
+                    # Execute batch when it reaches the batch size
+                    if len(batch) >= batch_size:
+                        batch_query = "BEGIN BATCH\n" + "\n".join(batch) + "\nAPPLY BATCH;"
+                        session.execute(SimpleStatement(
+                            batch_query, consistency_level=ConsistencyLevel.QUORUM), timeout=3600)
+                        batch.clear()  # Clear batch after execution
+
+                # Execute any remaining queries in the batch
+                if batch:
+                    batch_query = "BEGIN BATCH\n" + "\n".join(batch) + "\nAPPLY BATCH;"
+                    session.execute(SimpleStatement(
+                        batch_query, consistency_level=ConsistencyLevel.QUORUM), timeout=3600)
+        except Exception as e:  # pylint: disable=broad-except  # noqa: BLE001
+            message = f"Failed to execute batch delete: {e}"
+            InfoEvent(message=message, severity=Severity.ERROR).publish()

test-cases/features/tablets/tablets-split-merge-long-test.yaml

@@ -0,0 +1,28 @@
+test_duration: 3000
+
+prepare_write_cmd: "scylla-bench -workload=sequential -mode=write -replication-factor=3 -partition-count=100 -clustering-row-count=5555                       -clustering-row-size=1884 -concurrency=80 -connection-count=80 -consistency-level=quorum -rows-per-request=50 -timeout=30s -validate-data"
+stress_cmd:        "scylla-bench -workload=sequential -mode=write -replication-factor=3 -partition-count=100000 -clustering-row-count=5555 -partition-offset=101 -clustering-row-size=1884 -concurrency=80 -connection-count=80 -consistency-level=quorum -rows-per-request=50 -timeout=30s"
+stress_read_cmd:   "scylla-bench -workload=sequential -mode=read -replication-factor=3 -partition-count=100 -clustering-row-count=5555                        -clustering-row-size=1884 -concurrency=40 -connection-count=40 -consistency-level=quorum -rows-per-request=1 -timeout=30s -retry-number=30 -retry-interval=80ms,1s -iterations 0 -duration=30m"
+
+pre_create_keyspace: "CREATE KEYSPACE IF NOT EXISTS scylla_bench WITH replication = {'class': 'NetworkTopologyStrategy', 'replication_factor': 3} and tablets={'initial':64};"
+
+data_validation: |
+  validate_partitions: true
+  table_name: "scylla_bench.test"
+  primary_key_column: "pk"
+  max_partitions_in_test_table: 100100
+  partition_range_with_data_validation: 0-100
+
+n_db_nodes: 3
+n_loaders: 1
+n_monitor_nodes: 1
+instance_type_db: 'i3.4xlarge'
+
+append_scylla_yaml:
+  target_tablet_size_in_bytes: 536870912  # 0.5GB
+  enable_tablets: true
+
+user_prefix: 'tablets-split-merge'
+use_mgmt: false
+
+post_prepare_cql_cmds: "ALTER TABLE scylla_bench.test with gc_grace_seconds = 0"

test-cases/features/tablets/tablets-split-merge-test.yaml

@@ -0,0 +1,28 @@
+test_duration: 240
+
+prepare_write_cmd: "scylla-bench -workload=sequential -mode=write -replication-factor=3 -partition-count=100 -clustering-row-count=5555                       -clustering-row-size=1884 -concurrency=80 -connection-count=80 -consistency-level=quorum -rows-per-request=50 -timeout=30s -validate-data"
+stress_cmd:        "scylla-bench -workload=sequential -mode=write -replication-factor=3 -partition-count=10000 -clustering-row-count=5555 -partition-offset=101 -clustering-row-size=1884 -concurrency=80 -connection-count=80 -consistency-level=quorum -rows-per-request=50 -timeout=30s"
+stress_read_cmd:   "scylla-bench -workload=sequential -mode=read -replication-factor=3 -partition-count=100 -clustering-row-count=5555                        -clustering-row-size=1884 -concurrency=40 -connection-count=40 -consistency-level=quorum -rows-per-request=1 -timeout=30s -retry-number=30 -retry-interval=80ms,1s -iterations 0 -duration=30m"
+
+pre_create_keyspace: "CREATE KEYSPACE IF NOT EXISTS scylla_bench WITH replication = {'class': 'NetworkTopologyStrategy', 'replication_factor': 3} and tablets={'initial':64};"
+
+data_validation: |
+  validate_partitions: true
+  table_name: "scylla_bench.test"
+  primary_key_column: "pk"
+  max_partitions_in_test_table: 10100
+  partition_range_with_data_validation: 0-100
+
+n_db_nodes: 3
+n_loaders: 1
+n_monitor_nodes: 1
+instance_type_db: 'i3.8xlarge'
+
+append_scylla_yaml:
+  target_tablet_size_in_bytes: 536870912  # 0.5GB
+  enable_tablets: true
+
+user_prefix: 'tablets-split-merge'
+use_mgmt: false
+
+post_prepare_cql_cmds: "ALTER TABLE scylla_bench.test with gc_grace_seconds = 0"

unit_tests/test_scylla_yaml.py

@@ -407,6 +407,7 @@ def test_scylla_yaml(self):
                 'workdir': None,
                 'write_request_timeout_in_ms': None,
                 'enable_tablets': None,
+                'target_tablet_size_in_bytes': None,
                 'force_gossip_topology_changes': None,
                 'reader_concurrency_semaphore_cpu_concurrency': None,
             }