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Please note that this patch does not change the use of database session in MBS. So, in the frontend, the database session is still managed by Flask-SQLAlchemy, that is the db.session. And the backend, running event handlers, has its own database session created from SQLAclehmy session API directly. This patch aims to reduce the number of scoped_session created when call original function make_db_session. For technical detailed information, please refer to SQLAlchemy documentation Contextual/Thread-local Sessions. As a result, a global scoped_session is accessible from the code running inside backend, both the event handlers and functions called from handlers. The library code shared by frontend and backend, like resolvers, has no change. Similarly, db.session is only used to recreate database for every test. Signed-off-by: Chenxiong Qi <cqi@redhat.com>
76 lines
2.8 KiB
Python
76 lines
2.8 KiB
Python
# -*- coding: utf-8 -*-
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# SPDX-License-Identifier: MIT
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import sqlalchemy.event
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from sqlalchemy.orm import scoped_session, sessionmaker
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from sqlalchemy.pool import NullPool
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from module_build_service import conf
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from module_build_service.models import session_before_commit_handlers
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__all__ = ("db_session",)
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def _setup_event_listeners(db_session):
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"""
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Starts listening for events related to the database session.
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"""
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if not sqlalchemy.event.contains(db_session, "before_commit", session_before_commit_handlers):
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sqlalchemy.event.listen(db_session, "before_commit", session_before_commit_handlers)
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# initialize DB event listeners from the monitor module
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from module_build_service.monitor import db_hook_event_listeners
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db_hook_event_listeners(db_session.bind.engine)
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def apply_engine_options(conf):
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options = {
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"configuration": {"sqlalchemy.url": conf.sqlalchemy_database_uri},
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}
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if conf.sqlalchemy_database_uri.startswith("sqlite://"):
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options.update({
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# For local module build, MBS is actually a multi-threaded
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# application. The command submitting a module build runs in its
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# own thread, and the backend build workflow, implemented as a
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# fedmsg consumer on top of fedmsg-hub, runs in separate threads.
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# So, disable this option in order to allow accessing data which
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# was written from another thread.
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"connect_args": {"check_same_thread": False},
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# Both local module build and running tests requires a file-based
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# SQLite database, we do not use a connection pool for these two
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# scenarios.
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"poolclass": NullPool,
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})
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else:
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# TODO - we could use ZopeTransactionExtension() here some day for
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# improved safety on the backend.
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pool_options = {}
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# Apply pool options SQLALCHEMY_* set in MBS config.
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# Abbrev sa stands for SQLAlchemy.
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def apply_mbs_option(mbs_config_key, sa_config_key):
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value = getattr(conf, mbs_config_key, None)
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if value is not None:
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pool_options[sa_config_key] = value
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apply_mbs_option("sqlalchemy_pool_size", "pool_size")
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apply_mbs_option("sqlalchemy_pool_timeout", "pool_timeout")
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apply_mbs_option("sqlalchemy_pool_recycle", "pool_recycle")
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apply_mbs_option("sqlalchemy_max_overflow", "max_overflow")
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options.update(pool_options)
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return options
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engine_opts = apply_engine_options(conf)
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engine = sqlalchemy.engine_from_config(**engine_opts)
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session_factory = sessionmaker(bind=engine)
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# This is the global, singleton database Session that could be used to operate
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# database queries.
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db_session = scoped_session(session_factory)
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_setup_event_listeners(db_session)
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