Source code for cassandra.query

# Copyright DataStax, Inc.
# Licensed under the Apache License, Version 2.0 (the "License");
# you may not use this file except in compliance with the License.
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# Unless required by applicable law or agreed to in writing, software
# distributed under the License is distributed on an "AS IS" BASIS,
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# limitations under the License.

This module holds classes for working with prepared statements and
specifying consistency levels and retry policies for individual

from collections import namedtuple
from datetime import datetime, timedelta
import re
import struct
import time
import six
from six.moves import range, zip

from cassandra import ConsistencyLevel, OperationTimedOut
from cassandra.util import unix_time_from_uuid1
from cassandra.encoder import Encoder
import cassandra.encoder
from cassandra.protocol import _UNSET_VALUE
from cassandra.util import OrderedDict, _sanitize_identifiers

import logging
log = logging.getLogger(__name__)

Specifies an unset value when binding a prepared statement.

Unset values are ignored, allowing prepared statements to be used without specify

See for further details on semantics.

.. versionadded:: 2.6.0

Only valid when using native protocol v4+

NON_ALPHA_REGEX = re.compile('[^a-zA-Z0-9]')
START_BADCHAR_REGEX = re.compile('^[^a-zA-Z0-9]*')
END_BADCHAR_REGEX = re.compile('[^a-zA-Z0-9_]*$')

_clean_name_cache = {}

def _clean_column_name(name):
        return _clean_name_cache[name]
    except KeyError:
        clean = NON_ALPHA_REGEX.sub("_", START_BADCHAR_REGEX.sub("", END_BADCHAR_REGEX.sub("", name)))
        _clean_name_cache[name] = clean
        return clean

[docs]def tuple_factory(colnames, rows): """ Returns each row as a tuple Example:: >>> from cassandra.query import tuple_factory >>> session = cluster.connect('mykeyspace') >>> session.row_factory = tuple_factory >>> rows = session.execute("SELECT name, age FROM users LIMIT 1") >>> print rows[0] ('Bob', 42) .. versionchanged:: 2.0.0 moved from ``cassandra.decoder`` to ``cassandra.query`` """ return rows
[docs]def named_tuple_factory(colnames, rows): """ Returns each row as a `namedtuple <>`_. This is the default row factory. Example:: >>> from cassandra.query import named_tuple_factory >>> session = cluster.connect('mykeyspace') >>> session.row_factory = named_tuple_factory >>> rows = session.execute("SELECT name, age FROM users LIMIT 1") >>> user = rows[0] >>> # you can access field by their name: >>> print "name: %s, age: %d" % (, user.age) name: Bob, age: 42 >>> # or you can access fields by their position (like a tuple) >>> name, age = user >>> print "name: %s, age: %d" % (name, age) name: Bob, age: 42 >>> name = user[0] >>> age = user[1] >>> print "name: %s, age: %d" % (name, age) name: Bob, age: 42 .. versionchanged:: 2.0.0 moved from ``cassandra.decoder`` to ``cassandra.query`` """ clean_column_names = map(_clean_column_name, colnames) try: Row = namedtuple('Row', clean_column_names) except Exception: clean_column_names = list(map(_clean_column_name, colnames)) # create list because py3 map object will be consumed by first attempt log.warning("Failed creating named tuple for results with column names %s (cleaned: %s) " "(see Python 'namedtuple' documentation for details on name rules). " "Results will be returned with positional names. " "Avoid this by choosing different names, using SELECT \"<col name>\" AS aliases, " "or specifying a different row_factory on your Session" % (colnames, clean_column_names)) Row = namedtuple('Row', _sanitize_identifiers(clean_column_names)) return [Row(*row) for row in rows]
[docs]def dict_factory(colnames, rows): """ Returns each row as a dict. Example:: >>> from cassandra.query import dict_factory >>> session = cluster.connect('mykeyspace') >>> session.row_factory = dict_factory >>> rows = session.execute("SELECT name, age FROM users LIMIT 1") >>> print rows[0] {u'age': 42, u'name': u'Bob'} .. versionchanged:: 2.0.0 moved from ``cassandra.decoder`` to ``cassandra.query`` """ return [dict(zip(colnames, row)) for row in rows]
[docs]def ordered_dict_factory(colnames, rows): """ Like :meth:`~cassandra.query.dict_factory`, but returns each row as an OrderedDict, so the order of the columns is preserved. .. versionchanged:: 2.0.0 moved from ``cassandra.decoder`` to ``cassandra.query`` """ return [OrderedDict(zip(colnames, row)) for row in rows]
[docs]class Statement(object): """ An abstract class representing a single query. There are three subclasses: :class:`.SimpleStatement`, :class:`.BoundStatement`, and :class:`.BatchStatement`. These can be passed to :meth:`.Session.execute()`. """ retry_policy = None """ An instance of a :class:`cassandra.policies.RetryPolicy` or one of its subclasses. This controls when a query will be retried and how it will be retried. """ consistency_level = None """ The :class:`.ConsistencyLevel` to be used for this operation. Defaults to :const:`None`, which means that the default consistency level for the Session this is executed in will be used. """ fetch_size = FETCH_SIZE_UNSET """ How many rows will be fetched at a time. This overrides the default of :attr:`.Session.default_fetch_size` This only takes effect when protocol version 2 or higher is used. See :attr:`.Cluster.protocol_version` for details. .. versionadded:: 2.0.0 """ keyspace = None """ The string name of the keyspace this query acts on. This is used when :class:`~.TokenAwarePolicy` is configured for :attr:`.Cluster.load_balancing_policy` It is set implicitly on :class:`.BoundStatement`, and :class:`.BatchStatement`, but must be set explicitly on :class:`.SimpleStatement`. .. versionadded:: 2.1.3 """ custom_payload = None """ :ref:`custom_payload` to be passed to the server. These are only allowed when using protocol version 4 or higher. .. versionadded:: 2.6.0 """ is_idempotent = False """ Flag indicating whether this statement is safe to run multiple times in speculative execution. """ _serial_consistency_level = None _routing_key = None def __init__(self, retry_policy=None, consistency_level=None, routing_key=None, serial_consistency_level=None, fetch_size=FETCH_SIZE_UNSET, keyspace=None, custom_payload=None, is_idempotent=False): if retry_policy and not hasattr(retry_policy, 'on_read_timeout'): # just checking one method to detect positional parameter errors raise ValueError('retry_policy should implement cassandra.policies.RetryPolicy') if retry_policy is not None: self.retry_policy = retry_policy if consistency_level is not None: self.consistency_level = consistency_level self._routing_key = routing_key if serial_consistency_level is not None: self.serial_consistency_level = serial_consistency_level if fetch_size is not FETCH_SIZE_UNSET: self.fetch_size = fetch_size if keyspace is not None: self.keyspace = keyspace if custom_payload is not None: self.custom_payload = custom_payload self.is_idempotent = is_idempotent def _key_parts_packed(self, parts): for p in parts: l = len(p) yield struct.pack(">H%dsB" % l, l, p, 0) def _get_routing_key(self): return self._routing_key def _set_routing_key(self, key): if isinstance(key, (list, tuple)): if len(key) == 1: self._routing_key = key[0] else: self._routing_key = b"".join(self._key_parts_packed(key)) else: self._routing_key = key def _del_routing_key(self): self._routing_key = None routing_key = property( _get_routing_key, _set_routing_key, _del_routing_key, """ The :attr:`~.TableMetadata.partition_key` portion of the primary key, which can be used to determine which nodes are replicas for the query. If the partition key is a composite, a list or tuple must be passed in. Each key component should be in its packed (binary) format, so all components should be strings. """) def _get_serial_consistency_level(self): return self._serial_consistency_level def _set_serial_consistency_level(self, serial_consistency_level): acceptable = (None, ConsistencyLevel.SERIAL, ConsistencyLevel.LOCAL_SERIAL) if serial_consistency_level not in acceptable: raise ValueError( "serial_consistency_level must be either ConsistencyLevel.SERIAL " "or ConsistencyLevel.LOCAL_SERIAL") self._serial_consistency_level = serial_consistency_level def _del_serial_consistency_level(self): self._serial_consistency_level = None serial_consistency_level = property( _get_serial_consistency_level, _set_serial_consistency_level, _del_serial_consistency_level, """ The serial consistency level is only used by conditional updates (``INSERT``, ``UPDATE`` and ``DELETE`` with an ``IF`` condition). For those, the ``serial_consistency_level`` defines the consistency level of the serial phase (or "paxos" phase) while the normal :attr:`~.consistency_level` defines the consistency for the "learn" phase, i.e. what type of reads will be guaranteed to see the update right away. For example, if a conditional write has a :attr:`~.consistency_level` of :attr:`~.ConsistencyLevel.QUORUM` (and is successful), then a :attr:`~.ConsistencyLevel.QUORUM` read is guaranteed to see that write. But if the regular :attr:`~.consistency_level` of that write is :attr:`~.ConsistencyLevel.ANY`, then only a read with a :attr:`~.consistency_level` of :attr:`~.ConsistencyLevel.SERIAL` is guaranteed to see it (even a read with consistency :attr:`~.ConsistencyLevel.ALL` is not guaranteed to be enough). The serial consistency can only be one of :attr:`~.ConsistencyLevel.SERIAL` or :attr:`~.ConsistencyLevel.LOCAL_SERIAL`. While ``SERIAL`` guarantees full linearizability (with other ``SERIAL`` updates), ``LOCAL_SERIAL`` only guarantees it in the local data center. The serial consistency level is ignored for any query that is not a conditional update. Serial reads should use the regular :attr:`consistency_level`. Serial consistency levels may only be used against Cassandra 2.0+ and the :attr:`~.Cluster.protocol_version` must be set to 2 or higher. See :doc:`/lwt` for a discussion on how to work with results returned from conditional statements. .. versionadded:: 2.0.0 """)
[docs]class SimpleStatement(Statement): """ A simple, un-prepared query. """ def __init__(self, query_string, retry_policy=None, consistency_level=None, routing_key=None, serial_consistency_level=None, fetch_size=FETCH_SIZE_UNSET, keyspace=None, custom_payload=None, is_idempotent=False): """ `query_string` should be a literal CQL statement with the exception of parameter placeholders that will be filled through the `parameters` argument of :meth:`.Session.execute()`. See :class:`Statement` attributes for a description of the other parameters. """ Statement.__init__(self, retry_policy, consistency_level, routing_key, serial_consistency_level, fetch_size, keyspace, custom_payload, is_idempotent) self._query_string = query_string @property def query_string(self): return self._query_string def __str__(self): consistency = ConsistencyLevel.value_to_name.get(self.consistency_level, 'Not Set') return (u'<SimpleStatement query="%s", consistency=%s>' % (self.query_string, consistency)) __repr__ = __str__
[docs]class PreparedStatement(object): """ A statement that has been prepared against at least one Cassandra node. Instances of this class should not be created directly, but through :meth:`.Session.prepare()`. A :class:`.PreparedStatement` should be prepared only once. Re-preparing a statement may affect performance (as the operation requires a network roundtrip). |prepared_stmt_head|: Do not use ``*`` in prepared statements if you might change the schema of the table being queried. The driver and server each maintain a map between metadata for a schema and statements that were prepared against that schema. When a user changes a schema, e.g. by adding or removing a column, the server invalidates its mappings involving that schema. However, there is currently no way to propagate that invalidation to drivers. Thus, after a schema change, the driver will incorrectly interpret the results of ``SELECT *`` queries prepared before the schema change. This is currently being addressed in `CASSANDRA-10786 <>`_. .. |prepared_stmt_head| raw:: html <b>A note about <code>*</code> in prepared statements</b> """ column_metadata = None #TODO: make this bind_metadata in next major retry_policy = None consistency_level = None custom_payload = None fetch_size = FETCH_SIZE_UNSET keyspace = None # change to prepared_keyspace in major release protocol_version = None query_id = None query_string = None result_metadata = None result_metadata_id = None routing_key_indexes = None _routing_key_index_set = None serial_consistency_level = None def __init__(self, column_metadata, query_id, routing_key_indexes, query, keyspace, protocol_version, result_metadata, result_metadata_id): self.column_metadata = column_metadata self.query_id = query_id self.routing_key_indexes = routing_key_indexes self.query_string = query self.keyspace = keyspace self.protocol_version = protocol_version self.result_metadata = result_metadata self.result_metadata_id = result_metadata_id self.is_idempotent = False @classmethod def from_message(cls, query_id, column_metadata, pk_indexes, cluster_metadata, query, prepared_keyspace, protocol_version, result_metadata, result_metadata_id): if not column_metadata: return PreparedStatement(column_metadata, query_id, None, query, prepared_keyspace, protocol_version, result_metadata, result_metadata_id) if pk_indexes: routing_key_indexes = pk_indexes else: routing_key_indexes = None first_col = column_metadata[0] ks_meta = cluster_metadata.keyspaces.get(first_col.keyspace_name) if ks_meta: table_meta = ks_meta.tables.get(first_col.table_name) if table_meta: partition_key_columns = table_meta.partition_key # make a map of {column_name: index} for each column in the statement statement_indexes = dict((, i) for i, c in enumerate(column_metadata)) # a list of which indexes in the statement correspond to partition key items try: routing_key_indexes = [statement_indexes[] for c in partition_key_columns] except KeyError: # we're missing a partition key component in the prepared pass # statement; just leave routing_key_indexes as None return PreparedStatement(column_metadata, query_id, routing_key_indexes, query, prepared_keyspace, protocol_version, result_metadata, result_metadata_id)
[docs] def bind(self, values): """ Creates and returns a :class:`BoundStatement` instance using `values`. See :meth:`BoundStatement.bind` for rules on input ``values``. """ return BoundStatement(self).bind(values)
def is_routing_key_index(self, i): if self._routing_key_index_set is None: self._routing_key_index_set = set(self.routing_key_indexes) if self.routing_key_indexes else set() return i in self._routing_key_index_set def __str__(self): consistency = ConsistencyLevel.value_to_name.get(self.consistency_level, 'Not Set') return (u'<PreparedStatement query="%s", consistency=%s>' % (self.query_string, consistency)) __repr__ = __str__
[docs]class BoundStatement(Statement): """ A prepared statement that has been bound to a particular set of values. These may be created directly or through :meth:`.PreparedStatement.bind()`. """ prepared_statement = None """ The :class:`PreparedStatement` instance that this was created from. """ values = None """ The sequence of values that were bound to the prepared statement. """ def __init__(self, prepared_statement, retry_policy=None, consistency_level=None, routing_key=None, serial_consistency_level=None, fetch_size=FETCH_SIZE_UNSET, keyspace=None, custom_payload=None): """ `prepared_statement` should be an instance of :class:`PreparedStatement`. See :class:`Statement` attributes for a description of the other parameters. """ self.prepared_statement = prepared_statement self.retry_policy = prepared_statement.retry_policy self.consistency_level = prepared_statement.consistency_level self.serial_consistency_level = prepared_statement.serial_consistency_level self.fetch_size = prepared_statement.fetch_size self.custom_payload = prepared_statement.custom_payload self.is_idempotent = prepared_statement.is_idempotent self.values = [] meta = prepared_statement.column_metadata if meta: self.keyspace = meta[0].keyspace_name Statement.__init__(self, retry_policy, consistency_level, routing_key, serial_consistency_level, fetch_size, keyspace, custom_payload, prepared_statement.is_idempotent)
[docs] def bind(self, values): """ Binds a sequence of values for the prepared statement parameters and returns this instance. Note that `values` *must* be: * a sequence, even if you are only binding one value, or * a dict that relates 1-to-1 between dict keys and columns .. versionchanged:: 2.6.0 :data:`~.UNSET_VALUE` was introduced. These can be bound as positional parameters in a sequence, or by name in a dict. Additionally, when using protocol v4+: * short sequences will be extended to match bind parameters with UNSET_VALUE * names may be omitted from a dict with UNSET_VALUE implied. .. versionchanged:: 3.0.0 method will not throw if extra keys are present in bound dict (PYTHON-178) """ if values is None: values = () proto_version = self.prepared_statement.protocol_version col_meta = self.prepared_statement.column_metadata # special case for binding dicts if isinstance(values, dict): values_dict = values values = [] # sort values accordingly for col in col_meta: try: values.append(values_dict[]) except KeyError: if proto_version >= 4: values.append(UNSET_VALUE) else: raise KeyError( 'Column name `%s` not found in bound dict.' % ( value_len = len(values) col_meta_len = len(col_meta) if value_len > col_meta_len: raise ValueError( "Too many arguments provided to bind() (got %d, expected %d)" % (len(values), len(col_meta))) # this is fail-fast for clarity pre-v4. When v4 can be assumed, # the error will be better reported when UNSET_VALUE is implicitly added. if proto_version < 4 and self.prepared_statement.routing_key_indexes and \ value_len < len(self.prepared_statement.routing_key_indexes): raise ValueError( "Too few arguments provided to bind() (got %d, required %d for routing key)" % (value_len, len(self.prepared_statement.routing_key_indexes))) self.raw_values = values self.values = [] for value, col_spec in zip(values, col_meta): if value is None: self.values.append(None) elif value is UNSET_VALUE: if proto_version >= 4: self._append_unset_value() else: raise ValueError("Attempt to bind UNSET_VALUE while using unsuitable protocol version (%d < 4)" % proto_version) else: try: self.values.append(col_spec.type.serialize(value, proto_version)) except (TypeError, struct.error) as exc: actual_type = type(value) message = ('Received an argument of invalid type for column "%s". ' 'Expected: %s, Got: %s; (%s)' % (, col_spec.type, actual_type, exc)) raise TypeError(message) if proto_version >= 4: diff = col_meta_len - len(self.values) if diff: for _ in range(diff): self._append_unset_value() return self
def _append_unset_value(self): next_index = len(self.values) if self.prepared_statement.is_routing_key_index(next_index): col_meta = self.prepared_statement.column_metadata[next_index] raise ValueError("Cannot bind UNSET_VALUE as a part of the routing key '%s'" % self.values.append(UNSET_VALUE) @property def routing_key(self): if not self.prepared_statement.routing_key_indexes: return None if self._routing_key is not None: return self._routing_key routing_indexes = self.prepared_statement.routing_key_indexes if len(routing_indexes) == 1: self._routing_key = self.values[routing_indexes[0]] else: self._routing_key = b"".join(self._key_parts_packed(self.values[i] for i in routing_indexes)) return self._routing_key def __str__(self): consistency = ConsistencyLevel.value_to_name.get(self.consistency_level, 'Not Set') return (u'<BoundStatement query="%s", values=%s, consistency=%s>' % (self.prepared_statement.query_string, self.raw_values, consistency)) __repr__ = __str__
[docs]class BatchType(object): """ A BatchType is used with :class:`.BatchStatement` instances to control the atomicity of the batch operation. .. versionadded:: 2.0.0 """ LOGGED = None """ Atomic batch operation. """ UNLOGGED = None """ Non-atomic batch operation. """ COUNTER = None """ Batches of counter operations. """ def __init__(self, name, value): = name self.value = value def __str__(self): return def __repr__(self): return "BatchType.%s" % (, )
BatchType.LOGGED = BatchType("LOGGED", 0) BatchType.UNLOGGED = BatchType("UNLOGGED", 1) BatchType.COUNTER = BatchType("COUNTER", 2)
[docs]class BatchStatement(Statement): """ A protocol-level batch of operations which are applied atomically by default. .. versionadded:: 2.0.0 """ batch_type = None """ The :class:`.BatchType` for the batch operation. Defaults to :attr:`.BatchType.LOGGED`. """ serial_consistency_level = None """ The same as :attr:`.Statement.serial_consistency_level`, but is only supported when using protocol version 3 or higher. """ _statements_and_parameters = None _session = None def __init__(self, batch_type=BatchType.LOGGED, retry_policy=None, consistency_level=None, serial_consistency_level=None, session=None, custom_payload=None): """ `batch_type` specifies The :class:`.BatchType` for the batch operation. Defaults to :attr:`.BatchType.LOGGED`. `retry_policy` should be a :class:`~.RetryPolicy` instance for controlling retries on the operation. `consistency_level` should be a :class:`~.ConsistencyLevel` value to be used for all operations in the batch. `custom_payload` is a :ref:`custom_payload` passed to the server. Note: as Statement objects are added to the batch, this map is updated with any values found in their custom payloads. These are only allowed when using protocol version 4 or higher. Example usage: .. code-block:: python insert_user = session.prepare("INSERT INTO users (name, age) VALUES (?, ?)") batch = BatchStatement(consistency_level=ConsistencyLevel.QUORUM) for (name, age) in users_to_insert: batch.add(insert_user, (name, age)) session.execute(batch) You can also mix different types of operations within a batch: .. code-block:: python batch = BatchStatement() batch.add(SimpleStatement("INSERT INTO users (name, age) VALUES (%s, %s)"), (name, age)) batch.add(SimpleStatement("DELETE FROM pending_users WHERE name=%s"), (name,)) session.execute(batch) .. versionadded:: 2.0.0 .. versionchanged:: 2.1.0 Added `serial_consistency_level` as a parameter .. versionchanged:: 2.6.0 Added `custom_payload` as a parameter """ self.batch_type = batch_type self._statements_and_parameters = [] self._session = session Statement.__init__(self, retry_policy=retry_policy, consistency_level=consistency_level, serial_consistency_level=serial_consistency_level, custom_payload=custom_payload)
[docs] def clear(self): """ This is a convenience method to clear a batch statement for reuse. *Note:* it should not be used concurrently with uncompleted execution futures executing the same ``BatchStatement``. """ del self._statements_and_parameters[:] self.keyspace = None self.routing_key = None if self.custom_payload: self.custom_payload.clear()
[docs] def add(self, statement, parameters=None): """ Adds a :class:`.Statement` and optional sequence of parameters to be used with the statement to the batch. Like with other statements, parameters must be a sequence, even if there is only one item. """ if isinstance(statement, six.string_types): if parameters: encoder = Encoder() if self._session is None else self._session.encoder statement = bind_params(statement, parameters, encoder) self._add_statement_and_params(False, statement, ()) elif isinstance(statement, PreparedStatement): query_id = statement.query_id bound_statement = statement.bind(() if parameters is None else parameters) self._update_state(bound_statement) self._add_statement_and_params(True, query_id, bound_statement.values) elif isinstance(statement, BoundStatement): if parameters: raise ValueError( "Parameters cannot be passed with a BoundStatement " "to BatchStatement.add()") self._update_state(statement) self._add_statement_and_params(True, statement.prepared_statement.query_id, statement.values) else: # it must be a SimpleStatement query_string = statement.query_string if parameters: encoder = Encoder() if self._session is None else self._session.encoder query_string = bind_params(query_string, parameters, encoder) self._update_state(statement) self._add_statement_and_params(False, query_string, ()) return self
[docs] def add_all(self, statements, parameters): """ Adds a sequence of :class:`.Statement` objects and a matching sequence of parameters to the batch. Statement and parameter sequences must be of equal length or one will be truncated. :const:`None` can be used in the parameters position where are needed. """ for statement, value in zip(statements, parameters): self.add(statement, value)
def _add_statement_and_params(self, is_prepared, statement, parameters): if len(self._statements_and_parameters) >= 0xFFFF: raise ValueError("Batch statement cannot contain more than %d statements." % 0xFFFF) self._statements_and_parameters.append((is_prepared, statement, parameters)) def _maybe_set_routing_attributes(self, statement): if self.routing_key is None: if statement.keyspace and statement.routing_key: self.routing_key = statement.routing_key self.keyspace = statement.keyspace def _update_custom_payload(self, statement): if statement.custom_payload: if self.custom_payload is None: self.custom_payload = {} self.custom_payload.update(statement.custom_payload) def _update_state(self, statement): self._maybe_set_routing_attributes(statement) self._update_custom_payload(statement) def __len__(self): return len(self._statements_and_parameters) def __str__(self): consistency = ConsistencyLevel.value_to_name.get(self.consistency_level, 'Not Set') return (u'<BatchStatement type=%s, statements=%d, consistency=%s>' % (self.batch_type, len(self), consistency)) __repr__ = __str__
ValueSequence = cassandra.encoder.ValueSequence """ A wrapper class that is used to specify that a sequence of values should be treated as a CQL list of values instead of a single column collection when used as part of the `parameters` argument for :meth:`.Session.execute()`. This is typically needed when supplying a list of keys to select. For example:: >>> my_user_ids = ('alice', 'bob', 'charles') >>> query = "SELECT * FROM users WHERE user_id IN %s" >>> session.execute(query, parameters=[ValueSequence(my_user_ids)]) """ def bind_params(query, params, encoder): if six.PY2 and isinstance(query, six.text_type): query = query.encode('utf-8') if isinstance(params, dict): return query % dict((k, encoder.cql_encode_all_types(v)) for k, v in six.iteritems(params)) else: return query % tuple(encoder.cql_encode_all_types(v) for v in params)
[docs]class TraceUnavailable(Exception): """ Raised when complete trace details cannot be fetched from Cassandra. """ pass
[docs]class QueryTrace(object): """ A trace of the duration and events that occurred when executing an operation. """ trace_id = None """ :class:`uuid.UUID` unique identifier for this tracing session. Matches the ``session_id`` column in ``system_traces.sessions`` and ````. """ request_type = None """ A string that very generally describes the traced operation. """ duration = None """ A :class:`datetime.timedelta` measure of the duration of the query. """ client = None """ The IP address of the client that issued this request This is only available when using Cassandra 2.2+ """ coordinator = None """ The IP address of the host that acted as coordinator for this request. """ parameters = None """ A :class:`dict` of parameters for the traced operation, such as the specific query string. """ started_at = None """ A UTC :class:`datetime.datetime` object describing when the operation was started. """ events = None """ A chronologically sorted list of :class:`.TraceEvent` instances representing the steps the traced operation went through. This corresponds to the rows in ```` for this tracing session. """ _session = None _SELECT_SESSIONS_FORMAT = "SELECT * FROM system_traces.sessions WHERE session_id = %s" _SELECT_EVENTS_FORMAT = "SELECT * FROM WHERE session_id = %s" _BASE_RETRY_SLEEP = 0.003 def __init__(self, trace_id, session): self.trace_id = trace_id self._session = session
[docs] def populate(self, max_wait=2.0, wait_for_complete=True, query_cl=None): """ Retrieves the actual tracing details from Cassandra and populates the attributes of this instance. Because tracing details are stored asynchronously by Cassandra, this may need to retry the session detail fetch. If the trace is still not available after `max_wait` seconds, :exc:`.TraceUnavailable` will be raised; if `max_wait` is :const:`None`, this will retry forever. `wait_for_complete=False` bypasses the wait for duration to be populated. This can be used to query events from partial sessions. `query_cl` specifies a consistency level to use for polling the trace tables, if it should be different than the session default. """ attempt = 0 start = time.time() while True: time_spent = time.time() - start if max_wait is not None and time_spent >= max_wait: raise TraceUnavailable( "Trace information was not available within %f seconds. Consider raising Session.max_trace_wait." % (max_wait,)) log.debug("Attempting to fetch trace info for trace ID: %s", self.trace_id) session_results = self._execute( SimpleStatement(self._SELECT_SESSIONS_FORMAT, consistency_level=query_cl), (self.trace_id,), time_spent, max_wait) # PYTHON-730: There is race condition that the duration mutation is written before started_at the for fast queries is_complete = session_results and session_results[0].duration is not None and session_results[0].started_at is not None if not session_results or (wait_for_complete and not is_complete): time.sleep(self._BASE_RETRY_SLEEP * (2 ** attempt)) attempt += 1 continue if is_complete: log.debug("Fetched trace info for trace ID: %s", self.trace_id) else: log.debug("Fetching parital trace info for trace ID: %s", self.trace_id) session_row = session_results[0] self.request_type = session_row.request self.duration = timedelta(microseconds=session_row.duration) if is_complete else None self.started_at = session_row.started_at self.coordinator = session_row.coordinator self.parameters = session_row.parameters # since C* 2.2 self.client = getattr(session_row, 'client', None) log.debug("Attempting to fetch trace events for trace ID: %s", self.trace_id) time_spent = time.time() - start event_results = self._execute( SimpleStatement(self._SELECT_EVENTS_FORMAT, consistency_level=query_cl), (self.trace_id,), time_spent, max_wait) log.debug("Fetched trace events for trace ID: %s", self.trace_id) = tuple(TraceEvent(r.activity, r.event_id, r.source, r.source_elapsed, r.thread) for r in event_results) break
def _execute(self, query, parameters, time_spent, max_wait): timeout = (max_wait - time_spent) if max_wait is not None else None future = self._session._create_response_future(query, parameters, trace=False, custom_payload=None, timeout=timeout) # in case the user switched the row factory, set it to namedtuple for this query future.row_factory = named_tuple_factory future.send_request() try: return future.result() except OperationTimedOut: raise TraceUnavailable("Trace information was not available within %f seconds" % (max_wait,)) def __str__(self): return "%s [%s] coordinator: %s, started at: %s, duration: %s, parameters: %s" \ % (self.request_type, self.trace_id, self.coordinator, self.started_at, self.duration, self.parameters)
[docs]class TraceEvent(object): """ Representation of a single event within a query trace. """ description = None """ A brief description of the event. """ datetime = None """ A UTC :class:`datetime.datetime` marking when the event occurred. """ source = None """ The IP address of the node this event occurred on. """ source_elapsed = None """ A :class:`datetime.timedelta` measuring the amount of time until this event occurred starting from when :attr:`.source` first received the query. """ thread_name = None """ The name of the thread that this event occurred on. """ def __init__(self, description, timeuuid, source, source_elapsed, thread_name): self.description = description self.datetime = datetime.utcfromtimestamp(unix_time_from_uuid1(timeuuid)) self.source = source if source_elapsed is not None: self.source_elapsed = timedelta(microseconds=source_elapsed) else: self.source_elapsed = None self.thread_name = thread_name def __str__(self): return "%s on %s[%s] at %s" % (self.description, self.source, self.thread_name, self.datetime)