This adds quite a lot of OpenTracing decoration for database activity. Specifically it adds tracing at four different levels:
* emit a span for each "interaction" - ie, the top level database function that we tend to call "transaction", but isn't really, because it can end up as multiple transactions.
* emit a span while we hold a database connection open
* emit a span for each database transaction - actual actual transaction.
* emit a span for each database query.
I'm aware this might be quite a lot of overhead, but even just running it on a local Synapse it looks really interesting, and I hope the overhead can be offset just by turning down the sampling frequency and finding other ways of tracing requests of interest (eg, the `force_tracing_for_users` setting).
This fixes a regression where the logging context for runWithConnection
was reported as runWithConnection instead of the connection name,
e.g. "POST-XYZ".
I went through and removed a bunch of cruft that was lying around for compatibility with old Python versions. This PR also will now prevent Synapse from starting unless you're running Python 3.6+.
Part of #9744
Removes all redundant `# -*- coding: utf-8 -*-` lines from files, as python 3 automatically reads source code as utf-8 now.
`Signed-off-by: Jonathan de Jong <jonathan@automatia.nl>`
Split off from https://github.com/matrix-org/synapse/pull/9491
Adds a storage method for getting the current presence of all local users, optionally excluding those that are offline. This will be used by the code in #9491 when a PresenceRouter module informs Synapse that a given user should have `"ALL"` user presence updates routed to them. Specifically, it is used here: b588f16e39/synapse/handlers/presence.py (L1131-L1133)
Note that there is a `get_all_presence_updates` function just above. That function is intended to walk up the table through stream IDs, and is primarily used by the presence replication stream. I could possibly make use of it in the PresenceRouter-related code, but it would be a bit of a bodge.
The idea here is to stop people forgetting to call `check_consistency`. Folks can still just pass in `None` to the new args in `build_sequence_generator`, but hopefully they won't.
- Update black version to the latest
- Run black auto formatting over the codebase
- Run autoformatting according to [`docs/code_style.md
`](80d6dc9783/docs/code_style.md)
- Update `code_style.md` docs around installing black to use the correct version
`adbapi.ConnectionPool` let's you turn on auto reconnect of DB connections. This is off by default.
As far as I can tell if its not enabled dead connections never get removed from the pool.
Maybe helps #8574
This allows trailing commas in multi-line arg lists.
Minor, but we might as well keep our formatting current with regard to
our minimum supported Python version.
Signed-off-by: Dan Callahan <danc@element.io>
Autocommit means that we don't wrap the functions in transactions, and instead get executed directly. Introduced in #8456. This will help:
1. reduce the number of `could not serialize access due to concurrent delete` errors that we see (though there are a few functions that often cause serialization errors that we don't fix here);
2. improve the DB performance, as it no longer needs to deal with the overhead of `REPEATABLE READ` isolation levels; and
3. improve wall clock speed of these functions, as we no longer need to send `BEGIN` and `COMMIT` to the DB.
Some notes about the differences between autocommit mode and our default `REPEATABLE READ` transactions:
1. Currently `autocommit` only applies when using PostgreSQL, and is ignored when using SQLite (due to silliness with [Twisted DB classes](https://twistedmatrix.com/trac/ticket/9998)).
2. Autocommit functions may get retried on error, which means they can get applied *twice* (or more) to the DB (since they are not in a transaction the previous call would not get rolled back). This means that the functions need to be idempotent (or otherwise not care about being called multiple times). Read queries, simple deletes, and updates/upserts that replace rows (rather than generating new values from existing rows) are all idempotent.
3. Autocommit functions no longer get executed in [`REPEATABLE READ`](https://www.postgresql.org/docs/current/transaction-iso.html) isolation level, and so data can change queries, which is fine for single statement queries.
We call `_update_stream_positions_table_txn` a lot, which is an UPSERT
that can conflict in `REPEATABLE READ` isolation level. Instead of doing
a transaction consisting of a single query we may as well run it outside
of a transaction.
This is so we can tell what is going on when things are taking a while to start up.
The main change here is to ensure that transactions that are created during startup get correctly logged like normal transactions.
The bg update never managed to complete, because it kept being interrupted by
transactions which want to take a lock.
Just doing it in the foreground isn't that bad, and is a good deal simpler.
