Thank you. My use case didn't permit me to use your examples but, based on your advice, I ended up using "after_flush_postexec" event. Any consequences from doing this? Seems to work fine for now.
On Wednesday, March 11, 2020 at 12:34:12 PM UTC-5, Mike Bayer wrote: > > > > On Wed, Mar 11, 2020, at 12:44 PM, Colton Allen wrote: > > Hi, > > Before we talk about the read-replica, let's talk about the test suite as > it is. I have a sessionmaker in my test suite configured to use an > external transaction. Basically identical to this: > https://docs.sqlalchemy.org/en/13/orm/session_transaction.html#joining-a-session-into-an-external-transaction-such-as-for-test-suites > > . This is great for performance and I have no complaints about it. > > To integrate a "read-replica" in my test suite I'm very clever. I just > say "master = master_connection" and "slave = master_connection". The test > suite has no idea there is a read-replica at all. > > Unfortunately, the coverage I get is not comprehensive. Because a "slave" > connection in this context could write to the database and cause errors in > production. So I need some way to differentiate the connections without > breaking the external transaction. Any thoughts on how I could do this? > Any argument I can pass to the sessionmaker to make it read-only while > still making the data in the transaction available to each? > > > IIUC you want an engine to fail a test if a write operation attempts to > proceed upon it. lots of ways to do this: > > 1. set logging_name on create_engine(), then use a session before_flush() > handler to check the engine's logging_name (e.g. > session.connection().engine.logging_name == 'readonly'), or use more > connection local events like before_insert, before_update, before_delete > https://docs.sqlalchemy.org/en/13/orm/events.html > > 2. use a checkout event on the read-only engine ( > https://docs.sqlalchemy.org/en/13/core/events.html#sqlalchemy.events.PoolEvents.checkout) > > <https://docs.sqlalchemy.org/en/13/core/events.html#sqlalchemy.events.PoolEvents.checkout> > > put a token in the connection's info dictionary, then use the above > techniques > > 3. intercept INSERT/UPDATE/DELETE directly using cursor_execute() events: > https://docs.sqlalchemy.org/en/13/core/events.html#sqlalchemy.events.ConnectionEvents.before_cursor_execute > > > basically use events to intercept operations and check the connection / > engine in use. > > > > > Thanks! > > > -- > SQLAlchemy - > The Python SQL Toolkit and Object Relational Mapper > > http://www.sqlalchemy.org/ > > To post example code, please provide an MCVE: Minimal, Complete, and > Verifiable Example. See http://stackoverflow.com/help/mcve for a full > description. > --- > You received this message because you are subscribed to the Google Groups > "sqlalchemy" group. > To unsubscribe from this group and stop receiving emails from it, send an > email to sqlal...@googlegroups.com <javascript:>. > To view this discussion on the web visit > https://groups.google.com/d/msgid/sqlalchemy/a83a28d9-0982-4686-928e-a451f60ee791%40googlegroups.com > > <https://groups.google.com/d/msgid/sqlalchemy/a83a28d9-0982-4686-928e-a451f60ee791%40googlegroups.com?utm_medium=email&utm_source=footer> > . > > > -- SQLAlchemy - The Python SQL Toolkit and Object Relational Mapper http://www.sqlalchemy.org/ To post example code, please provide an MCVE: Minimal, Complete, and Verifiable Example. See http://stackoverflow.com/help/mcve for a full description. --- You received this message because you are subscribed to the Google Groups "sqlalchemy" group. To unsubscribe from this group and stop receiving emails from it, send an email to sqlalchemy+unsubscr...@googlegroups.com. To view this discussion on the web visit https://groups.google.com/d/msgid/sqlalchemy/c8399b15-3a40-41d9-b78a-4166f446c097%40googlegroups.com.
