While working on https://github.com/matrix-org/synapse/issues/5665 I found myself digging into the `Ratelimiter` class and seeing that it was both:
* Rather undocumented, and
* causing a *lot* of config checks
This PR attempts to refactor and comment the `Ratelimiter` class, as well as encourage config file accesses to only be done at instantiation.
Best to be reviewed commit-by-commit.
* Expose `return_html_error`, and allow it to take a Jinja2 template instead of a raw string
* Clean up exception handling in SAML2ResponseResource
* use the existing code in `return_html_error` instead of re-implementing it
(giving it a jinja2 template rather than inventing a new form of template)
* do the exception-catching in the REST layer rather than in the handler
layer, to make sure we catch all exceptions.
It looks like `user_device_resync` was ignoring cross-signing keys from the results received from the remote server. This patch fixes this, by processing these keys using the same process `_handle_signing_key_updates` does (and effectively factor that part out of that function).
The query keeps showing up in my slow query log.
This changes the plan under the top-level Sort node from
```
WindowAgg (cost=280335.88..292963.15 rows=561212 width=80) (actual time=138.651..160.562 rows=27112 loops=1)
-> Sort (cost=280335.88..281738.91 rows=561212 width=84) (actual time=138.597..140.622 rows=27112 loops=1)
Sort Key: state_groups_state.type, state_groups_state.state_key, state_groups_state.state_group
Sort Method: quicksort Memory: 4581kB
-> Nested Loop (cost=2.83..226745.22 rows=561212 width=84) (actual time=21.548..47.657 rows=27112 loops=1)
-> HashAggregate (cost=2.27..3.28 rows=101 width=8) (actual time=21.526..21.535 rows=20 loops=1)
Group Key: state.state_group
-> CTE Scan on state (cost=0.00..2.02 rows=101 width=8) (actual time=21.280..21.493 rows=20 loops=1)
-> Index Scan using state_groups_state_type_idx on state_groups_state (cost=0.56..2189.40 rows=5557 width=84) (actual time=0.005..0.991 rows=1356 loops=20)
Index Cond: (state_group = state.state_group)
```
to
```
Nested Loop (cost=2.83..226745.22 rows=561212 width=84) (actual time=24.194..52.834 rows=27112 loops=1)
-> HashAggregate (cost=2.27..3.28 rows=101 width=8) (actual time=24.130..24.138 rows=20 loops=1)
Group Key: state.state_group
-> CTE Scan on state (cost=0.00..2.02 rows=101 width=8) (actual time=23.887..24.113 rows=20 loops=1)
-> Index Scan using state_groups_state_type_idx on state_groups_state (cost=0.56..2189.40 rows=5557 width=84) (actual time=0.016..1.159 rows=1356 loops=20)
Index Cond: (state_group = state.state_group)
```
This cuts the execution time from ~190ms to ~130ms, i.e. a reduction
of ~30%.
The full plans are visualised at https://explain.depesz.com/s/WpbT and
https://explain.depesz.com/s/KlEk
Signed-off-by: Dagfinn Ilmari Mannsåker <ilmari@ilmari.org>
Without this patch, if an error happens which isn't caught by `user_device_resync`, then `_maybe_retry_device_resync` would fail, without retrying the next users in the iteration. This patch fixes this so that it now only logs an error in this case.
==============================
Bugfixes
--------
- Fix cache config to not apply cache factor to event cache. Regression in v1.14.0rc1. ([\#7578](https://github.com/matrix-org/synapse/issues/7578))
- Fix bug where `ReplicationStreamer` was not always started when replication was enabled. Bug introduced in v1.14.0rc1. ([\#7579](https://github.com/matrix-org/synapse/issues/7579))
- Fix specifying individual cache factors for caches with special characters in their name. Regression in v1.14.0rc1. ([\#7580](https://github.com/matrix-org/synapse/issues/7580))
Improved Documentation
----------------------
- Fix the OIDC `client_auth_method` value in the sample config. ([\#7581](https://github.com/matrix-org/synapse/issues/7581))
-----BEGIN PGP SIGNATURE-----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=BVTL
-----END PGP SIGNATURE-----
Merge tag 'v1.14.0rc2' into develop
Synapse 1.14.0rc2 (2020-05-27)
==============================
Bugfixes
--------
- Fix cache config to not apply cache factor to event cache. Regression in v1.14.0rc1. ([\#7578](https://github.com/matrix-org/synapse/issues/7578))
- Fix bug where `ReplicationStreamer` was not always started when replication was enabled. Bug introduced in v1.14.0rc1. ([\#7579](https://github.com/matrix-org/synapse/issues/7579))
- Fix specifying individual cache factors for caches with special characters in their name. Regression in v1.14.0rc1. ([\#7580](https://github.com/matrix-org/synapse/issues/7580))
Improved Documentation
----------------------
- Fix the OIDC `client_auth_method` value in the sample config. ([\#7581](https://github.com/matrix-org/synapse/issues/7581))
'client_auth_method' commented out value was erronously 'client_auth_basic',
when code and docstring says it should be 'client_secret_basic'.
Signed-off-by: Jason Robinson <jasonr@matrix.org>
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.
A couple of changes of significance:
* remove the `_last_ack < federation_position` condition, so that
updates will still be correctly processed after restart
* Correctly wire up send_federation_ack to the right class.
we can use `make_in_list_sql_clause` rather than doing our own half-baked
equivalent, which has the benefit of working just fine with empty lists.
(This has quite a lot of tests, so I think it's pretty safe)
The idea here is that if an instance persists an event via the replication HTTP API it can return before we receive that event over replication, which can lead to races where code assumes that persisting an event immediately updates various caches (e.g. current state of the room).
Most of Synapse doesn't hit such races, so we don't do the waiting automagically, instead we do so where necessary to avoid unnecessary delays. We may decide to change our minds here if it turns out there are a lot of subtle races going on.
People probably want to look at this commit by commit.
Instead of doing a complicated dance of deleting and moving aliases one
by one, which sends a canonical alias update into the old room for each
one, lets do it all in one go.
This also changes the function to move *all* local alias events to the new
room, however that happens later on anyway.
PyPy's gc.get_stats() returns an object containing detailed allocator statistics
which could be beneficial to collect as metrics.
Signed-off-by: Ivan Shapovalov <intelfx@intelfx.name>
When a call to `user_device_resync` fails, we don't currently mark the remote user's device list as out of sync, nor do we retry to sync it.
https://github.com/matrix-org/synapse/pull/6776 introduced some code infrastructure to mark device lists as stale/out of sync.
This commit uses that code infrastructure to mark device lists as out of sync if processing an incoming device list update makes the device handler realise that the device list is out of sync, but we can't resync right now.
It also adds a looping call to retry all failed resync every 30s. This shouldn't cause too much spam in the logs as this commit also removes the "Failed to handle device list update for..." warning logs when catching `NotRetryingDestination`.
Fixes#7418
We don't really make any promises about returning accurate presence data when
presence is disabled, so we may as well just return a static response, rather
than making the master handle a request.
`_is_server_still_joined` will throw if it is given state updates with non-user ID state keys with local user leaves. This is actually rarely a problem since local leaves almost always get persisted by themselves.
(I discovered this on a branch that was otherwise broken, so I haven't seen this in the wild)
Bugfixes:
- Hash passwords as early as possible during registration. #7523
-----BEGIN PGP SIGNATURE-----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=lpDI
-----END PGP SIGNATURE-----
Merge tag 'v1.13.0rc3' into develop
Synapse 1.13.0rc3 (2020-05-18)
Bugfixes:
- Hash passwords as early as possible during registration. #7523
Make sure that the AccountDataStream presents complete updates, in the right
order.
This is much the same fix as #7337 and #7358, but applied to a different stream.
This is required as both event persistence and the background update needs access to this function. It should be perfectly safe for two workers to write to that table at the same time.
This allows us to have the logic on both master and workers, which is necessary to move event persistence off master.
We also combine the instantiation of ID generators from DataStore and slave stores to the base worker stores. This allows us to select which process writes events independently of the master/worker splits.
==============================
Bugfixes
--------
- Fix a long-standing bug which could cause messages not to be sent over federation, when state events with state keys matching user IDs (such as custom user statuses) were received. ([\#7376](https://github.com/matrix-org/synapse/issues/7376))
- Restore compatibility with non-compliant clients during the user interactive authentication process, fixing a problem introduced in v1.13.0rc1. ([\#7483](https://github.com/matrix-org/synapse/issues/7483))
Internal Changes
----------------
- Fix linting errors in new version of Flake8. ([\#7470](https://github.com/matrix-org/synapse/issues/7470))
-----BEGIN PGP SIGNATURE-----
iQEzBAABCAAdFiEEv27Axt/F4vrTL/8QOSor00I9eP8FAl69IQ8ACgkQOSor00I9
eP87lAf8DK+v6cs2U0BoD5opzQ7ZazJT6JYTmnMBaTzHU6Wx20V2ttkF7Vpwm3WU
Zsz0048tdYtHFyYBQ1kF5RNIBBJwV8SA/QUcPkR7FVpwZMLR2q4aJn0EE7kC9OMf
tYsmdbHeBdyfLXpXzazxWlgHquLyEIt52ykAcCphjx/Jl2fAExFEhtfsxpECoJ2f
8Dqhjg3WFjd6QWU6AFkElbwHUYCdIWdJOcsC8N1p8OvBmDz5QXv/RlYipHE00Cpx
QQQOgEjdRc6dlz2mbetMklnfII3p2kO9bzNdmEpOzT0Zt7nFaGdntW4I1QA0yJfa
gows9bYMzhqYk7YSiyTYOZ4qyavVtw==
=N/zZ
-----END PGP SIGNATURE-----
Merge tag 'v1.13.0rc2' into develop
Synapse 1.13.0rc2 (2020-05-14)
==============================
Bugfixes
--------
- Fix a long-standing bug which could cause messages not to be sent over federation, when state events with state keys matching user IDs (such as custom user statuses) were received. ([\#7376](https://github.com/matrix-org/synapse/issues/7376))
- Restore compatibility with non-compliant clients during the user interactive authentication process, fixing a problem introduced in v1.13.0rc1. ([\#7483](https://github.com/matrix-org/synapse/issues/7483))
Internal Changes
----------------
- Fix linting errors in new version of Flake8. ([\#7470](https://github.com/matrix-org/synapse/issues/7470))
Fix a bug where the `get_joined_users` cache could be corrupted by custom
status events (or other state events with a state_key matching the user ID).
The bug was introduced by #2229, but has largely gone unnoticed since then.
Fixes#7099, #7373.
The aim here is to get to a stage where we have a `PersistEventStore` that holds all the write methods used during event persistence, so that we can take that class out of the `DataStore` mixin and instansiate it separately. This will allow us to instansiate it on processes other than master, while also ensuring it is only available on processes that are configured to write to events stream.
This is a bit of an architectural change, where we end up with multiple classes per data store (rather than one per data store we have now). We end up having:
1. Storage classes that provide high level APIs that can talk to multiple data stores.
2. Data store modules that consist of classes that must point at the same database instance.
3. Classes in a data store that can be instantiated on processes depending on config.
Before all streams were only written to from master, so only master needed to respond to `REPLICATE` commands.
Before all instances wrote to the cache invalidation stream, but didn't respond to `REPLICATE`. This was a bug, which could lead to missed rows from cache invalidation stream if an instance is restarted, however all the caches would be empty in that case so it wasn't a problem.
Proactively send out `POSITION` commands (as if we had just received a `REPLICATE`) when we connect to Redis. This is important as other instances won't notice we've connected to issue a `REPLICATE` command (unlike for direct TCP connections). This is only currently an issue if master process reconnects without restarting (if it restarts then it won't have written anything and so other instances probably won't have missed anything).
* release-v1.13.0:
Don't UPGRADE database rows
RST indenting
Put rollback instructions in upgrade notes
Fix changelog typo
Oh yeah, RST
Absolute URL it is then
Fix upgrade notes link
Provide summary of upgrade issues in changelog. Fix )
Move next version notes from changelog to upgrade notes
Changelog fixes
1.13.0rc1
Documentation on setting up redis (#7446)
Rework UI Auth session validation for registration (#7455)
Fix errors from malformed log line (#7454)
Drop support for redis.dbid (#7450)
For the record, the reason we need this is as follows:
each RDATA command comes down the redis pipe as a subscription message. txredisapi as written needs at least three reactor ticks to read each subscription message from the tcp buffer. Hence, once the process gets loaded, it starts getting behind, and eventually redis knifes the connection. it then takes ages for the master to work its way through the backlog, before it reconnects again, during which any commands from any workers are dropped.
We forgot to set the password on the subscriber connection, as well as
not calling super methods for overridden connectionMade/connectionLost
functions.
For in memory streams when fetching updates on workers we need to query the source of the stream, which currently is hard coded to be master. This PR threads through the source instance we received via `POSITION` through to the update function in each stream, which can then be passed to the replication client for in memory streams.
We move the processing of typing and federation replication traffic into their handlers so that `Stream.current_token()` points to a valid token. This allows us to remove `get_streams_to_replicate()` and `stream_positions()`.
By persisting the user interactive authentication sessions to the database, this fixes
situations where a user hits different works throughout their auth session and also
allows sessions to persist through restarts of Synapse.
This is primarily for allowing us to send those commands from workers, but for now simply allows us to ignore echoed RDATA/POSITION commands that we sent (we get echoes of sent commands when using redis). Currently we log a WARNING on the master process every time we receive an echoed RDATA.
For direct TCP connections we need the master to relay REMOTE_SERVER_UP
commands to the other connections so that all instances get notified
about it. The old implementation just relayed to all connections,
assuming that sending back to the original sender of the command was
safe. This is not true for redis, where commands sent get echoed back to
the sender, which was causing master to effectively infinite loop
sending and then re-receiving REMOTE_SERVER_UP commands that it sent.
The fix is to ensure that we only relay to *other* connections and not
to the connection we received the notification from.
Fixes#7334.
* Factor out functions for injecting events into database
I want to add some more flexibility to the tools for injecting events into the
database, and I don't want to clutter up HomeserverTestCase with them, so let's
factor them out to a new file.
* Rework TestReplicationDataHandler
This wasn't very easy to work with: the mock wrapping was largely superfluous,
and it's useful to be able to inspect the received rows, and clear out the
received list.
* Fix AssertionErrors being thrown by EventsStream
Part of the problem was that there was an off-by-one error in the assertion,
but also the limit logic was too simple. Fix it all up and add some tests.
If the admin adds a `.yaml` file that's either empty or doesn't parse into a dict to a config directory (e.g. `conf.d` for debs installs), stuff like https://github.com/matrix-org/synapse/issues/7322 would happen. This PR checks that the file is correctly parsed into a dict, or ignores it with a warning if it parses into any other type (including `None` for empty files).
Fixes https://github.com/matrix-org/synapse/issues/7322
Figuring out how to correctly limit updates from this stream without dropping
entries is far more complicated than just counting the number of rows being
returned. We need to consider each query separately and, if any one query hits
the limit, truncate the results from the others.
I think this also fixes some potentially long-standing bugs where events or
state changes could get missed if we hit the limit on either query.
Long story short: if we're handling presence on the current worker, we shouldn't be sending USER_SYNC commands over replication.
In an attempt to figure out what is going on here, I ended up refactoring some bits of the presencehandler code, so the first 4 commits here are non-functional refactors to move this code slightly closer to sanity. (There's still plenty to do here :/). Suggest reviewing individual commits.
Fixes (I hope) #7257.
==============================
Features
--------
- Always send users their own device updates. ([\#7160](https://github.com/matrix-org/synapse/issues/7160))
- Add support for handling GET requests for `account_data` on a worker. ([\#7311](https://github.com/matrix-org/synapse/issues/7311))
Bugfixes
--------
- Fix a bug that prevented cross-signing with users on worker-mode synapses. ([\#7255](https://github.com/matrix-org/synapse/issues/7255))
- Do not treat display names as globs in push rules. ([\#7271](https://github.com/matrix-org/synapse/issues/7271))
- Fix a bug with cross-signing devices belonging to remote users who did not share a room with any user on the local homeserver. ([\#7289](https://github.com/matrix-org/synapse/issues/7289))
-----BEGIN PGP SIGNATURE-----
iQEzBAABCAAdFiEEv27Axt/F4vrTL/8QOSor00I9eP8FAl6gS+IACgkQOSor00I9
eP8CTwf+KLehHQMcrz0yoHN+/O86mpNv3Uz83BJ0qDIgezVbtqT7+ZwnK2Jb8dwM
zTcGRq5a6V+JLdfSTnXfrPzvAPt0WLaEENSAEGwZ6unqqxcG2PgATkRb0XtY8Rzh
Feu8WgJTnORbiiM3sBLI8toZMxal3X3ZcftPEAan1SaoyqLPQ2s14edDwgx64S5e
rBGzPDNSxZU1McNBq7Q11QTg3zgBUF+TYwyhnLbC5X1RdDwQpKhNZhwhYBS1yOD6
TsPjtlixC+HXb21Rmob7XY8VFxTBSBdUdtVQKAT4h3+l9bNFQLpBfDSVc7xkPiLt
/Gj+PL+YgY9xQDvHO2fVw8m4ololZw==
=p53e
-----END PGP SIGNATURE-----
Merge tag 'v1.12.4rc1' into develop
Synapse 1.12.4rc1 (2020-04-22)
==============================
Features
--------
- Always send users their own device updates. ([\#7160](https://github.com/matrix-org/synapse/issues/7160))
- Add support for handling GET requests for `account_data` on a worker. ([\#7311](https://github.com/matrix-org/synapse/issues/7311))
Bugfixes
--------
- Fix a bug that prevented cross-signing with users on worker-mode synapses. ([\#7255](https://github.com/matrix-org/synapse/issues/7255))
- Do not treat display names as globs in push rules. ([\#7271](https://github.com/matrix-org/synapse/issues/7271))
- Fix a bug with cross-signing devices belonging to remote users who did not share a room with any user on the local homeserver. ([\#7289](https://github.com/matrix-org/synapse/issues/7289))
First some background: StreamChangeCache is used to keep track of what "entities" have
changed since a given stream ID. So for example, we might use it to keep track of when the last
to-device message for a given user was received [1], and hence whether we need to pull any to-device messages from the database on a sync [2].
Now, it turns out that StreamChangeCache didn't support more than one thing being changed at
a given stream_id (this was part of the problem with #7206). However, it's entirely valid to send
to-device messages to more than one user at a time.
As it turns out, this did in fact work, because *some* methods of StreamChangeCache coped
ok with having multiple things changing on the same stream ID, and it seems we never actually
use the methods which don't work on the stream change caches where we allow multiple
changes at the same stream ID. But that feels horribly fragile, hence: let's update
StreamChangeCache to properly support this, and add some typing and some more tests while
we're at it.
[1]: https://github.com/matrix-org/synapse/blob/release-v1.12.3/synapse/storage/data_stores/main/deviceinbox.py#L301
[2]: https://github.com/matrix-org/synapse/blob/release-v1.12.3/synapse/storage/data_stores/main/deviceinbox.py#L47-L51
Splitting based on the response code means we can avoid double logging here and identical information from line 164 while still logging at info if we don't get a good response and need to retry.
Other parts of the code (such as the StreamChangeCache) assume that there will
not be multiple changes with the same stream id.
This code was introduced in #7024, and I hope this fixes#7206.
Add changelog
Save retrieved keys to the db
lint
Fix and de-brittle remote result dict processing
Use query_user_devices instead, assume only master, self_signing key types
Make changelog more useful
Remove very specific exception handling
Wrap get_verify_key_from_cross_signing_key in a try/except
Note that _get_e2e_cross_signing_verify_key can raise a SynapseError
lint
Add comment explaining why this is useful
Only fetch master and self_signing key types
Fix log statements, docstrings
Remove extraneous items from remote query try/except
lint
Factor key retrieval out into a separate function
Send device updates, modeled after SigningKeyEduUpdater._handle_signing_key_updates
Update method docstring
The general idea here is to get rid of the type: ignore annotations on all of the current_token and update_function assignments, which would have caught #7290.
After a bit of experimentation, it seems like the least-awful way to do this is to pass the offending functions in as parameters to the Stream constructor. Unfortunately that means that the concrete implementations no longer have the same constructor signature as Stream itself, which means that it gets hard to correctly annotate STREAMS_MAP.
I've also introduced a couple of new types, to take out some duplication.
Some of the query functions return generators rather than lists, so we can't
index into the result. Happily we already have a copy of the results.
(think this was introduced in #7024)
I don't really remember why this was so complicated; I think it dates
back to the time when we had to instantiate the Config classes before
we could call `add_arguments` - ie before #5597. In any case, I don't
think there's a good reason for it any more, and the impact of it
being complicated is that `--help` doesn't work correctly.
`REPLICATE` is now a valid command, and it's nice if you can issue it from the
console without remembering to call it `REPLICATE ` with a trailing space.
Separate `SimpleCommand` from `Command`, so that things which don't want to use
the `data` property don't have to, and thus fix the warnings PyCharm was giving
me about not calling `__init__` in the base class.
The aim here is to move the command handling out of the TCP protocol classes and to also merge the client and server command handling (so that we can reuse them for redis protocol). This PR simply moves the client paths to the new `ReplicationCommandHandler`, a future PR will move the server paths too.
Fixes#6815
Before figuring out whether we should alert a user on MAU, we call get_notice_room_for_user to get some info on the existing server notices room for this user. This function, if the room doesn't exist, creates it and invites the user in it. This means that, if we decide later that no server notice is needed, the user gets invited in a room with no message in it. This happens at every restart of the server, since the room ID returned by get_notice_room_for_user is cached.
This PR fixes that by moving the inviting bit to a dedicated function, that's only called when the server actually needs to send a notice to the user. A potential issue with this approach is that the room that's created by get_notice_room_for_user doesn't match how that same function looks for an existing room (i.e. it creates a room that doesn't have an invite or a join for the current user in it, so it could lead to a new room being created each time a user syncs), but I'm not sure this is a problem given it's cached until the server restarts, so that function won't run very often.
It also renames get_notice_room_for_user into get_or_create_notice_room_for_user to make what it does clearer.
Occasionally we could get a federation device list update transaction which
looked like:
```
[
{'edu_type': 'm.device_list_update', 'content': {'user_id': '@user:test', 'device_id': 'D2', 'prev_id': [], 'stream_id': 12, 'deleted': True}},
{'edu_type': 'm.device_list_update', 'content': {'user_id': '@user:test', 'device_id': 'D1', 'prev_id': [12], 'stream_id': 11, 'deleted': True}},
{'edu_type': 'm.device_list_update', 'content': {'user_id': '@user:test', 'device_id': 'D3', 'prev_id': [11], 'stream_id': 13, 'deleted': True}}
]
```
Having `stream_ids` which are lower than `prev_ids` looks odd. It might work
(I'm not actually sure), but in any case it doesn't seem like a reasonable
thing to expect other implementations to support.
