connectionContext.py

Go to the documentation of this file.

# This file is part of dax_apdb.
#
# Developed for the LSST Data Management System.
# This product includes software developed by the LSST Project
# (http://www.lsst.org).
# See the COPYRIGHT file at the top-level directory of this distribution
# for details of code ownership.
#
# This program is free software: you can redistribute it and/or modify
# it under the terms of the GNU General Public License as published by
# the Free Software Foundation, either version 3 of the License, or
# (at your option) any later version.
#
# This program is distributed in the hope that it will be useful,
# but WITHOUT ANY WARRANTY; without even the implied warranty of
# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
# GNU General Public License for more details.
#
# You should have received a copy of the GNU General Public License
# along with this program.  If not, see <http://www.gnu.org/licenses/>.
 
from __future__ import annotations
 
__all__ = ["ConnectionContext", "DbVersions"]
 
import dataclasses
import logging
from collections.abc import Mapping
 
# If cassandra-driver is not there the module can still be imported
# but ApdbCassandra cannot be instantiated.
try:
    from cassandra.cluster import Session
except ImportError:
    pass
 
from ..apdbConfigFreezer import ApdbConfigFreezer
from ..apdbSchema import ApdbTables
from ..monitor import MonAgent
from ..schema_model import Table
from ..versionTuple import VersionTuple
from .apdbCassandraReplica import ApdbCassandraReplica
from .apdbCassandraSchema import ApdbCassandraSchema
from .apdbMetadataCassandra import ApdbMetadataCassandra
from .cassandra_utils import PreparedStatementCache
from .config import ApdbCassandraConfig, ApdbCassandraTimePartitionRange
from .partitioner import Partitioner
 
_LOG = logging.getLogger(__name__)
 
_MON = MonAgent(__name__)
 
 
@dataclasses.dataclass
class DbVersions:
    """Versions defined in APDB metadata table."""
 
    schema_version: VersionTuple
    """Version of the schema from which database was created."""
 
    code_version: VersionTuple
    """Version of ApdbCassandra with which database was created."""
 
    replica_version: VersionTuple | None
    """Version of ApdbCassandraReplica with which database was created, None
    if replication was not configured.
    """
 
 
class ConnectionContext:
    """Container for all kinds ob objects that are instantiated once the
    connection to Cassandra is established.
 
    Parameters
    ----------
    session : `cassandra.cluster.Sesion`
        Cassandra session.
    config : `ApdbCassandraConfig`
        Configuration object.
    table_schemas : `~collection.abc.Mapping` [`ApdbTables`, `Table`]
        Schema definitions for regular APDB tables.
    """
 
    metadataSchemaVersionKey = "version:schema"
    """Name of the metadata key to store schema version number."""
 
    metadataCodeVersionKey = "version:ApdbCassandra"
    """Name of the metadata key to store code version number."""
 
    metadataReplicaVersionKey = "version:ApdbCassandraReplica"
    """Name of the metadata key to store replica code version number."""
 
    metadataConfigKey = "config:apdb-cassandra.json"
    """Name of the metadata key to store frozen part of the configuration."""
 
    frozen_parameters = (
        "enable_replica",
        "ra_dec_columns",
        "replica_skips_diaobjects",
        "replica_sub_chunk_count",
        "partitioning.part_pixelization",
        "partitioning.part_pix_level",
        "partitioning.time_partition_tables",
        "partitioning.time_partition_days",
    )
    """Names of the config parameters to be frozen in metadata table."""
 
    def __init__(
        self, session: Session, config: ApdbCassandraConfig, table_schemas: Mapping[ApdbTables, Table]
    ):
        self.session = session
 
        meta_table_name = ApdbTables.metadata.table_name(config.prefix)
        self.metadata = ApdbMetadataCassandra(
            self.session, meta_table_name, config.keyspace, "read_tuples", "write"
        )
 
        # Read frozen config from metadata.
        config_json = self.metadata.get(self.metadataConfigKey)
        if config_json is not None:
            # Update config from metadata.
            freezer = ApdbConfigFreezer[ApdbCassandraConfig](self.frozen_parameters)
            self.config = freezer.update(config, config_json)
        else:
            self.config = config
        del config
 
        # Read versions stored in database.
        self.db_versions = self._readVersions(self.metadata)
        _LOG.debug("Database versions: %s", self.db_versions)
 
        # Since replica version 1.1.0 we use finer partitioning for replica
        # chunk tables.
        self.has_chunk_sub_partitions = False
        if self.config.enable_replica:
            assert self.db_versions.replica_version is not None, "Replica version must be defined"
            self.has_chunk_sub_partitions = ApdbCassandraReplica.hasChunkSubPartitions(
                self.db_versions.replica_version
            )
 
        # Since version 0.1.3 we have metadata for time partitions.
        self.has_time_partition_meta = self.db_versions.code_version >= VersionTuple(0, 1, 3)
 
        # Since version 0.1.2 we have an extra table for visit/detector.
        self.has_visit_detector_table = self.db_versions.code_version >= VersionTuple(0, 1, 2)
 
        # Support for DiaObjectLastToPartition was added at code version 0.1.1
        # in a backward-compatible way (we only use the table if it is there).
        self.has_dia_object_last_to_partition = self.db_versions.code_version >= VersionTuple(0, 1, 1)
 
        # Cache for prepared statements
        self.preparer = PreparedStatementCache(self.session)
 
        self.partitioner = Partitioner(self.config)
 
        self.schema = ApdbCassandraSchema(
            session=self.session,
            keyspace=self.config.keyspace,
            table_schemas=table_schemas,
            prefix=self.config.prefix,
            time_partition_tables=self.config.partitioning.time_partition_tables,
            enable_replica=self.config.enable_replica,
            has_chunk_sub_partitions=self.has_chunk_sub_partitions,
            has_visit_detector_table=self.has_visit_detector_table,
        )
 
    @property
    def time_partitions_range(self) -> ApdbCassandraTimePartitionRange | None:
        """Time partition range or None if instance does not use
        time-partitioned tables (`ApdbCassandraTimePartitionRange` or `None`).
        """
        if not self.config.partitioning.time_partition_tables:
            return None
 
        if self.has_time_partition_meta:
            return ApdbCassandraTimePartitionRange.from_meta(self.metadata)
        else:
            # Scan DiaSource tables and see which partitions are present.
            partitions = set()
            tables = self.schema.existing_tables(ApdbTables.DiaSource)
            for table_name in tables[ApdbTables.DiaSource]:
                _, _, part_str = table_name.rpartition("_")
                partitions.add(int(part_str))
            if not partitions:
                raise LookupError("Failed to find any partitioned DiaSource table.")
            return ApdbCassandraTimePartitionRange(start=min(partitions), end=max(partitions))
 
    def _readVersions(self, metadata: ApdbMetadataCassandra) -> DbVersions:
        """Read versions of all objects from metadata."""
 
        def _get_version(key: str) -> VersionTuple:
            """Retrieve version number from given metadata key."""
            version_str = metadata.get(key)
            if version_str is None:
                # Should not happen with existing metadata table.
                raise RuntimeError(f"Version key {key!r} does not exist in metadata table.")
            return VersionTuple.fromString(version_str)
 
        db_schema_version = _get_version(self.metadataSchemaVersionKey)
        db_code_version = _get_version(self.metadataCodeVersionKey)
 
        # Check replica code version only if replica is enabled.
        db_replica_version: VersionTuple | None = None
        if self.config.enable_replica:
            db_replica_version = _get_version(self.metadataReplicaVersionKey)
 
        return DbVersions(
            schema_version=db_schema_version, code_version=db_code_version, replica_version=db_replica_version
        )