Remove threadlocal engine strategy, engine strategies pool threadlocal

The "threadlocal" execution strategy, deprecated in 1.3, has been
removed for 1.4, as well as the concept of "engine strategies" and the
``Engine.contextual_connect`` method.  The "strategy='mock'" keyword
argument is still accepted for now with a deprecation warning; use
:func:`.create_mock_engine` instead for this use case.

Fixes: #4632
Change-Id: I8a351f9fa1f7dfa2a56eec1cd2d1a4b9d65765a2
(cherry picked from commit b368c49b44c5716d93c7428ab22b6761c6ca7cf5)

1 files changed, 568 insertions, 0 deletions

diff --git a/lib/sqlalchemy/engine/create.py b/lib/sqlalchemy/engine/create.py
new file mode 100644
index 000000000..035953e99
--- /dev/null
+++ b/lib/sqlalchemy/engine/create.py
@@ -0,0 +1,568 @@
+# engine/create.py
+# Copyright (C) 2005-2019 the SQLAlchemy authors and contributors
+# <see AUTHORS file>
+#
+# This module is part of SQLAlchemy and is released under
+# the MIT License: http://www.opensource.org/licenses/mit-license.php
+
+
+from . import base
+from . import url as _url
+from .mock import create_mock_engine
+from .. import event
+from .. import exc
+from .. import pool as poollib
+from .. import util
+
+
+@util.deprecated_params(
+    strategy=(
+        "1.4",
+        "The :paramref:`.create_engine.strategy` keyword is deprecated, "
+        "and the only argument accepted is 'mock'; please use "
+        ":func:`.create_mock_engine` going forward.  For general "
+        "customization of create_engine which may have been accomplished "
+        "using strategies, see :class:`.CreateEnginePlugin`.",
+    )
+)
+def create_engine(url, **kwargs):
+    """Create a new :class:`.Engine` instance.
+
+    The standard calling form is to send the URL as the
+    first positional argument, usually a string
+    that indicates database dialect and connection arguments::
+
+
+        engine = create_engine("postgresql://scott:tiger@localhost/test")
+
+    Additional keyword arguments may then follow it which
+    establish various options on the resulting :class:`.Engine`
+    and its underlying :class:`.Dialect` and :class:`.Pool`
+    constructs::
+
+        engine = create_engine("mysql://scott:tiger@hostname/dbname",
+                                    encoding='latin1', echo=True)
+
+    The string form of the URL is
+    ``dialect[+driver]://user:password@host/dbname[?key=value..]``, where
+    ``dialect`` is a database name such as ``mysql``, ``oracle``,
+    ``postgresql``, etc., and ``driver`` the name of a DBAPI, such as
+    ``psycopg2``, ``pyodbc``, ``cx_oracle``, etc.  Alternatively,
+    the URL can be an instance of :class:`~sqlalchemy.engine.url.URL`.
+
+    ``**kwargs`` takes a wide variety of options which are routed
+    towards their appropriate components.  Arguments may be specific to
+    the :class:`.Engine`, the underlying :class:`.Dialect`, as well as the
+    :class:`.Pool`.  Specific dialects also accept keyword arguments that
+    are unique to that dialect.   Here, we describe the parameters
+    that are common to most :func:`.create_engine()` usage.
+
+    Once established, the newly resulting :class:`.Engine` will
+    request a connection from the underlying :class:`.Pool` once
+    :meth:`.Engine.connect` is called, or a method which depends on it
+    such as :meth:`.Engine.execute` is invoked.   The :class:`.Pool` in turn
+    will establish the first actual DBAPI connection when this request
+    is received.   The :func:`.create_engine` call itself does **not**
+    establish any actual DBAPI connections directly.
+
+    .. seealso::
+
+        :doc:`/core/engines`
+
+        :doc:`/dialects/index`
+
+        :ref:`connections_toplevel`
+
+    :param case_sensitive=True: if False, result column names
+       will match in a case-insensitive fashion, that is,
+       ``row['SomeColumn']``.
+
+    :param connect_args: a dictionary of options which will be
+        passed directly to the DBAPI's ``connect()`` method as
+        additional keyword arguments.  See the example
+        at :ref:`custom_dbapi_args`.
+
+    :param convert_unicode=False: if set to True, causes
+        all :class:`.String` datatypes to act as though the
+        :paramref:`.String.convert_unicode` flag has been set to ``True``,
+        regardless of a setting of ``False`` on an individual :class:`.String`
+        type.  This has the effect of causing all :class:`.String` -based
+        columns to accommodate Python Unicode objects directly as though the
+        datatype were the :class:`.Unicode` type.
+
+        .. deprecated:: 1.3
+
+            The :paramref:`.create_engine.convert_unicode` parameter
+            is deprecated and will be removed in a future release.
+            All modern DBAPIs now support Python Unicode directly and this
+            parameter is unnecessary.
+
+    :param creator: a callable which returns a DBAPI connection.
+        This creation function will be passed to the underlying
+        connection pool and will be used to create all new database
+        connections. Usage of this function causes connection
+        parameters specified in the URL argument to be bypassed.
+
+    :param echo=False: if True, the Engine will log all statements
+        as well as a ``repr()`` of their parameter lists to the default log
+        handler, which defaults to ``sys.stdout`` for output.   If set to the
+        string ``"debug"``, result rows will be printed to the standard output
+        as well. The ``echo`` attribute of ``Engine`` can be modified at any
+        time to turn logging on and off; direct control of logging is also
+        available using the standard Python ``logging`` module.
+
+        .. seealso::
+
+            :ref:`dbengine_logging` - further detail on how to configure
+            logging.
+
+    :param echo_pool=False: if True, the connection pool will log
+        informational output such as when connections are invalidated
+        as well as when connections are recycled to the default log handler,
+        which defaults to ``sys.stdout`` for output.   If set to the string
+        ``"debug"``, the logging will include pool checkouts and checkins.
+        Direct control of logging is also available using the standard Python
+        ``logging`` module.
+
+        .. seealso::
+
+            :ref:`dbengine_logging` - further detail on how to configure
+            logging.
+
+
+    :param empty_in_strategy:  The SQL compilation strategy to use when
+        rendering an IN or NOT IN expression for :meth:`.ColumnOperators.in_`
+        where the right-hand side
+        is an empty set.   This is a string value that may be one of
+        ``static``, ``dynamic``, or ``dynamic_warn``.   The ``static``
+        strategy is the default, and an IN comparison to an empty set
+        will generate a simple false expression "1 != 1".   The ``dynamic``
+        strategy behaves like that of SQLAlchemy 1.1 and earlier, emitting
+        a false expression of the form "expr != expr", which has the effect
+        of evaluting to NULL in the case of a null expression.
+        ``dynamic_warn`` is the same as ``dynamic``, however also emits a
+        warning when an empty set is encountered; this because the "dynamic"
+        comparison is typically poorly performing on most databases.
+
+        .. versionadded:: 1.2  Added the ``empty_in_strategy`` setting and
+           additionally defaulted the behavior for empty-set IN comparisons
+           to a static boolean expression.
+
+    :param encoding: Defaults to ``utf-8``.  This is the string
+        encoding used by SQLAlchemy for string encode/decode
+        operations which occur within SQLAlchemy, **outside of
+        the DBAPI.**  Most modern DBAPIs feature some degree of
+        direct support for Python ``unicode`` objects,
+        what you see in Python 2 as a string of the form
+        ``u'some string'``.  For those scenarios where the
+        DBAPI is detected as not supporting a Python ``unicode``
+        object, this encoding is used to determine the
+        source/destination encoding.  It is **not used**
+        for those cases where the DBAPI handles unicode
+        directly.
+
+        To properly configure a system to accommodate Python
+        ``unicode`` objects, the DBAPI should be
+        configured to handle unicode to the greatest
+        degree as is appropriate - see
+        the notes on unicode pertaining to the specific
+        target database in use at :ref:`dialect_toplevel`.
+
+        Areas where string encoding may need to be accommodated
+        outside of the DBAPI include zero or more of:
+
+        * the values passed to bound parameters, corresponding to
+          the :class:`.Unicode` type or the :class:`.String` type
+          when ``convert_unicode`` is ``True``;
+        * the values returned in result set columns corresponding
+          to the :class:`.Unicode` type or the :class:`.String`
+          type when ``convert_unicode`` is ``True``;
+        * the string SQL statement passed to the DBAPI's
+          ``cursor.execute()`` method;
+        * the string names of the keys in the bound parameter
+          dictionary passed to the DBAPI's ``cursor.execute()``
+          as well as ``cursor.setinputsizes()`` methods;
+        * the string column names retrieved from the DBAPI's
+          ``cursor.description`` attribute.
+
+        When using Python 3, the DBAPI is required to support
+        *all* of the above values as Python ``unicode`` objects,
+        which in Python 3 are just known as ``str``.  In Python 2,
+        the DBAPI does not specify unicode behavior at all,
+        so SQLAlchemy must make decisions for each of the above
+        values on a per-DBAPI basis - implementations are
+        completely inconsistent in their behavior.
+
+    :param execution_options: Dictionary execution options which will
+        be applied to all connections.  See
+        :meth:`~sqlalchemy.engine.Connection.execution_options`
+
+    :param implicit_returning=True: When ``True``, a RETURNING-
+        compatible construct, if available, will be used to
+        fetch newly generated primary key values when a single row
+        INSERT statement is emitted with no existing returning()
+        clause.  This applies to those backends which support RETURNING
+        or a compatible construct, including PostgreSQL, Firebird, Oracle,
+        Microsoft SQL Server.   Set this to ``False`` to disable
+        the automatic usage of RETURNING.
+
+    :param isolation_level: this string parameter is interpreted by various
+        dialects in order to affect the transaction isolation level of the
+        database connection.   The parameter essentially accepts some subset of
+        these string arguments: ``"SERIALIZABLE"``, ``"REPEATABLE_READ"``,
+        ``"READ_COMMITTED"``, ``"READ_UNCOMMITTED"`` and ``"AUTOCOMMIT"``.
+        Behavior here varies per backend, and
+        individual dialects should be consulted directly.
+
+        Note that the isolation level can also be set on a
+        per-:class:`.Connection` basis as well, using the
+        :paramref:`.Connection.execution_options.isolation_level`
+        feature.
+
+        .. seealso::
+
+            :attr:`.Connection.default_isolation_level` - view default level
+
+            :paramref:`.Connection.execution_options.isolation_level`
+            - set per :class:`.Connection` isolation level
+
+            :ref:`SQLite Transaction Isolation <sqlite_isolation_level>`
+
+            :ref:`PostgreSQL Transaction Isolation <postgresql_isolation_level>`
+
+            :ref:`MySQL Transaction Isolation <mysql_isolation_level>`
+
+            :ref:`session_transaction_isolation` - for the ORM
+
+    :param label_length=None: optional integer value which limits
+        the size of dynamically generated column labels to that many
+        characters. If less than 6, labels are generated as
+        "_(counter)". If ``None``, the value of
+        ``dialect.max_identifier_length`` is used instead.
+
+    :param listeners: A list of one or more
+        :class:`~sqlalchemy.interfaces.PoolListener` objects which will
+        receive connection pool events.
+
+    :param logging_name:  String identifier which will be used within
+        the "name" field of logging records generated within the
+        "sqlalchemy.engine" logger. Defaults to a hexstring of the
+        object's id.
+
+    :param max_overflow=10: the number of connections to allow in
+        connection pool "overflow", that is connections that can be
+        opened above and beyond the pool_size setting, which defaults
+        to five. this is only used with :class:`~sqlalchemy.pool.QueuePool`.
+
+    :param module=None: reference to a Python module object (the module
+        itself, not its string name).  Specifies an alternate DBAPI module to
+        be used by the engine's dialect.  Each sub-dialect references a
+        specific DBAPI which will be imported before first connect.  This
+        parameter causes the import to be bypassed, and the given module to
+        be used instead. Can be used for testing of DBAPIs as well as to
+        inject "mock" DBAPI implementations into the :class:`.Engine`.
+
+    :param paramstyle=None: The `paramstyle <http://legacy.python.org/dev/peps/pep-0249/#paramstyle>`_
+        to use when rendering bound parameters.  This style defaults to the
+        one recommended by the DBAPI itself, which is retrieved from the
+        ``.paramstyle`` attribute of the DBAPI.  However, most DBAPIs accept
+        more than one paramstyle, and in particular it may be desirable
+        to change a "named" paramstyle into a "positional" one, or vice versa.
+        When this attribute is passed, it should be one of the values
+        ``"qmark"``, ``"numeric"``, ``"named"``, ``"format"`` or
+        ``"pyformat"``, and should correspond to a parameter style known
+        to be supported by the DBAPI in use.
+
+    :param pool=None: an already-constructed instance of
+        :class:`~sqlalchemy.pool.Pool`, such as a
+        :class:`~sqlalchemy.pool.QueuePool` instance. If non-None, this
+        pool will be used directly as the underlying connection pool
+        for the engine, bypassing whatever connection parameters are
+        present in the URL argument. For information on constructing
+        connection pools manually, see :ref:`pooling_toplevel`.
+
+    :param poolclass=None: a :class:`~sqlalchemy.pool.Pool`
+        subclass, which will be used to create a connection pool
+        instance using the connection parameters given in the URL. Note
+        this differs from ``pool`` in that you don't actually
+        instantiate the pool in this case, you just indicate what type
+        of pool to be used.
+
+    :param pool_logging_name:  String identifier which will be used within
+       the "name" field of logging records generated within the
+       "sqlalchemy.pool" logger. Defaults to a hexstring of the object's
+       id.
+
+    :param pool_pre_ping: boolean, if True will enable the connection pool
+        "pre-ping" feature that tests connections for liveness upon
+        each checkout.
+
+        .. versionadded:: 1.2
+
+        .. seealso::
+
+            :ref:`pool_disconnects_pessimistic`
+
+    :param pool_size=5: the number of connections to keep open
+        inside the connection pool. This used with
+        :class:`~sqlalchemy.pool.QueuePool` as
+        well as :class:`~sqlalchemy.pool.SingletonThreadPool`.  With
+        :class:`~sqlalchemy.pool.QueuePool`, a ``pool_size`` setting
+        of 0 indicates no limit; to disable pooling, set ``poolclass`` to
+        :class:`~sqlalchemy.pool.NullPool` instead.
+
+    :param pool_recycle=-1: this setting causes the pool to recycle
+        connections after the given number of seconds has passed. It
+        defaults to -1, or no timeout. For example, setting to 3600
+        means connections will be recycled after one hour. Note that
+        MySQL in particular will disconnect automatically if no
+        activity is detected on a connection for eight hours (although
+        this is configurable with the MySQLDB connection itself and the
+        server configuration as well).
+
+        .. seealso::
+
+            :ref:`pool_setting_recycle`
+
+    :param pool_reset_on_return='rollback': set the
+        :paramref:`.Pool.reset_on_return` parameter of the underlying
+        :class:`.Pool` object, which can be set to the values
+        ``"rollback"``, ``"commit"``, or ``None``.
+
+        .. seealso::
+
+            :paramref:`.Pool.reset_on_return`
+
+    :param pool_timeout=30: number of seconds to wait before giving
+        up on getting a connection from the pool. This is only used
+        with :class:`~sqlalchemy.pool.QueuePool`.
+
+    :param pool_use_lifo=False: use LIFO (last-in-first-out) when retrieving
+        connections from :class:`.QueuePool` instead of FIFO
+        (first-in-first-out). Using LIFO, a server-side timeout scheme can
+        reduce the number of connections used during non- peak   periods of
+        use.   When planning for server-side timeouts, ensure that a recycle or
+        pre-ping strategy is in use to gracefully   handle stale connections.
+
+          .. versionadded:: 1.3
+
+          .. seealso::
+
+            :ref:`pool_use_lifo`
+
+            :ref:`pool_disconnects`
+
+    :param plugins: string list of plugin names to load.  See
+        :class:`.CreateEnginePlugin` for background.
+
+        .. versionadded:: 1.2.3
+
+
+    """  # noqa
+
+    if "strategy" in kwargs:
+        strat = kwargs.pop("strategy")
+        if strat == "mock":
+            return create_mock_engine(url, **kwargs)
+        else:
+            raise exc.ArgumentError("unknown strategy: %r" % strat)
+
+    # create url.URL object
+    u = _url.make_url(url)
+
+    plugins = u._instantiate_plugins(kwargs)
+
+    u.query.pop("plugin", None)
+    kwargs.pop("plugins", None)
+
+    entrypoint = u._get_entrypoint()
+    dialect_cls = entrypoint.get_dialect_cls(u)
+
+    if kwargs.pop("_coerce_config", False):
+
+        def pop_kwarg(key, default=None):
+            value = kwargs.pop(key, default)
+            if key in dialect_cls.engine_config_types:
+                value = dialect_cls.engine_config_types[key](value)
+            return value
+
+    else:
+        pop_kwarg = kwargs.pop
+
+    dialect_args = {}
+    # consume dialect arguments from kwargs
+    for k in util.get_cls_kwargs(dialect_cls):
+        if k in kwargs:
+            dialect_args[k] = pop_kwarg(k)
+
+    dbapi = kwargs.pop("module", None)
+    if dbapi is None:
+        dbapi_args = {}
+        for k in util.get_func_kwargs(dialect_cls.dbapi):
+            if k in kwargs:
+                dbapi_args[k] = pop_kwarg(k)
+        dbapi = dialect_cls.dbapi(**dbapi_args)
+
+    dialect_args["dbapi"] = dbapi
+
+    for plugin in plugins:
+        plugin.handle_dialect_kwargs(dialect_cls, dialect_args)
+
+    # create dialect
+    dialect = dialect_cls(**dialect_args)
+
+    # assemble connection arguments
+    (cargs, cparams) = dialect.create_connect_args(u)
+    cparams.update(pop_kwarg("connect_args", {}))
+    cargs = list(cargs)  # allow mutability
+
+    # look for existing pool or create
+    pool = pop_kwarg("pool", None)
+    if pool is None:
+
+        def connect(connection_record=None):
+            if dialect._has_events:
+                for fn in dialect.dispatch.do_connect:
+                    connection = fn(dialect, connection_record, cargs, cparams)
+                    if connection is not None:
+                        return connection
+            return dialect.connect(*cargs, **cparams)
+
+        creator = pop_kwarg("creator", connect)
+
+        poolclass = pop_kwarg("poolclass", None)
+        if poolclass is None:
+            poolclass = dialect_cls.get_pool_class(u)
+        pool_args = {"dialect": dialect}
+
+        # consume pool arguments from kwargs, translating a few of
+        # the arguments
+        translate = {
+            "logging_name": "pool_logging_name",
+            "echo": "echo_pool",
+            "timeout": "pool_timeout",
+            "recycle": "pool_recycle",
+            "events": "pool_events",
+            "reset_on_return": "pool_reset_on_return",
+            "pre_ping": "pool_pre_ping",
+            "use_lifo": "pool_use_lifo",
+        }
+        for k in util.get_cls_kwargs(poolclass):
+            tk = translate.get(k, k)
+            if tk in kwargs:
+                pool_args[k] = pop_kwarg(tk)
+
+        for plugin in plugins:
+            plugin.handle_pool_kwargs(poolclass, pool_args)
+
+        pool = poolclass(creator, **pool_args)
+    else:
+        if isinstance(pool, poollib.dbapi_proxy._DBProxy):
+            pool = pool.get_pool(*cargs, **cparams)
+        else:
+            pool = pool
+
+        pool._dialect = dialect
+
+    # create engine.
+    engineclass = base.Engine
+    engine_args = {}
+    for k in util.get_cls_kwargs(engineclass):
+        if k in kwargs:
+            engine_args[k] = pop_kwarg(k)
+
+    _initialize = kwargs.pop("_initialize", True)
+
+    # all kwargs should be consumed
+    if kwargs:
+        raise TypeError(
+            "Invalid argument(s) %s sent to create_engine(), "
+            "using configuration %s/%s/%s.  Please check that the "
+            "keyword arguments are appropriate for this combination "
+            "of components."
+            % (
+                ",".join("'%s'" % k for k in kwargs),
+                dialect.__class__.__name__,
+                pool.__class__.__name__,
+                engineclass.__name__,
+            )
+        )
+
+    engine = engineclass(pool, dialect, u, **engine_args)
+
+    if _initialize:
+        do_on_connect = dialect.on_connect()
+        if do_on_connect:
+
+            def on_connect(dbapi_connection, connection_record):
+                conn = getattr(
+                    dbapi_connection, "_sqla_unwrap", dbapi_connection
+                )
+                if conn is None:
+                    return
+                do_on_connect(conn)
+
+            event.listen(pool, "first_connect", on_connect)
+            event.listen(pool, "connect", on_connect)
+
+        def first_connect(dbapi_connection, connection_record):
+            c = base.Connection(
+                engine, connection=dbapi_connection, _has_events=False
+            )
+            c._execution_options = util.immutabledict()
+            dialect.initialize(c)
+            dialect.do_rollback(c.connection)
+
+        event.listen(pool, "first_connect", first_connect, once=True)
+
+    dialect_cls.engine_created(engine)
+    if entrypoint is not dialect_cls:
+        entrypoint.engine_created(engine)
+
+    for plugin in plugins:
+        plugin.engine_created(engine)
+
+    return engine
+
+
+def engine_from_config(configuration, prefix="sqlalchemy.", **kwargs):
+    """Create a new Engine instance using a configuration dictionary.
+
+    The dictionary is typically produced from a config file.
+
+    The keys of interest to ``engine_from_config()`` should be prefixed, e.g.
+    ``sqlalchemy.url``, ``sqlalchemy.echo``, etc.  The 'prefix' argument
+    indicates the prefix to be searched for.  Each matching key (after the
+    prefix is stripped) is treated as though it were the corresponding keyword
+    argument to a :func:`.create_engine` call.
+
+    The only required key is (assuming the default prefix) ``sqlalchemy.url``,
+    which provides the :ref:`database URL <database_urls>`.
+
+    A select set of keyword arguments will be "coerced" to their
+    expected type based on string values.    The set of arguments
+    is extensible per-dialect using the ``engine_config_types`` accessor.
+
+    :param configuration: A dictionary (typically produced from a config file,
+        but this is not a requirement).  Items whose keys start with the value
+        of 'prefix' will have that prefix stripped, and will then be passed to
+        :ref:`create_engine`.
+
+    :param prefix: Prefix to match and then strip from keys
+        in 'configuration'.
+
+    :param kwargs: Each keyword argument to ``engine_from_config()`` itself
+        overrides the corresponding item taken from the 'configuration'
+        dictionary.  Keyword arguments should *not* be prefixed.
+
+    """
+
+    options = dict(
+        (key[len(prefix) :], configuration[key])
+        for key in configuration
+        if key.startswith(prefix)
+    )
+    options["_coerce_config"] = True
+    options.update(kwargs)
+    url = options.pop("url")
+    return create_engine(url, **options)