Synapse supports PostgreSQL versions 10 or later.
Install postgres client libraries
Synapse will require the python postgres client library in order to connect to a postgres database.
If you are using the matrix.org debian/ubuntu packages, the necessary python library will already be installed, but you will need to ensure the low-level postgres library is installed, which you can do with
apt install libpq5.
For other pre-built packages, please consult the documentation from the relevant package.
If you installed synapse in a virtualenv, you can install the library with:
~/synapse/env/bin/pip install "matrix-synapse[postgres]"
(substituting the path to your virtualenv for
~/synapse/env, if you used a different path). You will require the postgres development files. These are in the
libpq-devpackage on Debian-derived distributions.
Set up database
Assuming your PostgreSQL database user is called
postgres, first authenticate as the database user with:
su - postgres # Or, if your system uses sudo to get administrative rights sudo -u postgres bash
Then, create a postgres user and a database with:
# this will prompt for a password for the new user createuser --pwprompt synapse_user createdb --encoding=UTF8 --locale=C --template=template0 --owner=synapse_user synapse
The above will create a user called
synapse_user, and a database called
Note that the PostgreSQL database must have the correct encoding set (as shown above), otherwise it will not be able to store UTF8 strings.
You may need to enable password authentication so
connect to the database. See
When you are ready to start using PostgreSQL, edit the
section in your config file to match the following lines:
database: name: psycopg2 args: user: <user> password: <pass> database: <db> host: <host> cp_min: 5 cp_max: 10
All key, values in
args are passed to the
function, except keys beginning with
cp_, which are consumed by the
twisted adbapi connection pool. See the libpq
for a list of options which can be passed.
You should consider tuning the
args.keepalives_* options if there is any danger of
the connection between your homeserver and database dropping, otherwise Synapse
may block for an extended period while it waits for a response from the
database server. Example values might be:
database: args: # ... as above # seconds of inactivity after which TCP should send a keepalive message to the server keepalives_idle: 10 # the number of seconds after which a TCP keepalive message that is not # acknowledged by the server should be retransmitted keepalives_interval: 10 # the number of TCP keepalives that can be lost before the client's connection # to the server is considered dead keepalives_count: 3
The default settings should be fine for most deployments. For larger scale deployments tuning some of the settings is recommended, details of which can be found at https://wiki.postgresql.org/wiki/Tuning_Your_PostgreSQL_Server.
In particular, we've found tuning the following values helpful for performance:
Note that the appropriate values for those fields depend on the amount of free memory the database host has available.
Additionally, admins of large deployments might want to consider using huge pages
to help manage memory, especially when using large values of
can read more about that here.
Porting from SQLite
synapse_port_db allows porting an existing synapse server
backed by SQLite to using PostgreSQL. This is done in as a two phase
- Copy the existing SQLite database to a separate location and run the port script against that offline database.
- Shut down the server. Rerun the port script to port any data that has come in since taking the first snapshot. Restart server against the PostgreSQL database.
The port script is designed to be run repeatedly against newer snapshots of the SQLite database file. This makes it safe to repeat step 1 if there was a delay between taking the previous snapshot and being ready to do step 2.
It is safe to at any time kill the port script and restart it.
Note that the database may take up significantly more (25% - 100% more) space on disk after porting to Postgres.
Using the port script
Firstly, shut down the currently running synapse server and copy its
database file (typically
homeserver.db) to another location. Once the
copy is complete, restart synapse. For instance:
synctl stop cp homeserver.db homeserver.db.snapshot synctl start
Copy the old config file into a new config file:
cp homeserver.yaml homeserver-postgres.yaml
Edit the database section as described in the section Synapse config
above and with the SQLite snapshot located at
synapse_port_db --sqlite-database homeserver.db.snapshot \ --postgres-config homeserver-postgres.yaml
--curses displays a coloured curses progress UI.
If the script took a long time to complete, or time has otherwise passed since the original snapshot was taken, repeat the previous steps with a newer snapshot.
To complete the conversion shut down the synapse server and run the port
script one last time, e.g. if the SQLite database is at
synapse_port_db --sqlite-database homeserver.db \ --postgres-config homeserver-postgres.yaml
Once that has completed, change the synapse config to point at the
PostgreSQL database configuration file
synctl stop mv homeserver.yaml homeserver-old-sqlite.yaml mv homeserver-postgres.yaml homeserver.yaml synctl start
Synapse should now be running against PostgreSQL.
Alternative auth methods
If you get an error along the lines of
FATAL: Ident authentication failed for user "synapse_user", you may need to use an authentication method other than
synapse_useruser has a password, add the password to the
homeserver.yaml. Then add the following to
host synapse synapse_user ::1/128 md5 # or `scram-sha-256` instead of `md5` if you use that
synapse_useruser does not have a password, then a password doesn't have to be added to
homeserver.yaml. But the following does need to be added to
host synapse synapse_user ::1/128 trust
Note that line order matters in
pg_hba.conf, so make sure that if you do add a
new line, it is inserted before:
host all all ::1/128 ident
Synapse will refuse to set up a new database if it has the wrong values of
CTYPE set. Synapse will also refuse to start an existing database with incorrect values
CTYPE unless the config flag
allow_unsafe_locale, found in the
database section of the config, is set to true. Using different locales can cause issues if the locale library is updated from
underneath the database, or if a different version of the locale is used on any
If you have a databse with an unsafe locale, the safest way to fix the issue is to dump the database and recreate it with
the correct locale parameter (as shown above). It is also possible to change the
parameters on a live database and run a
REINDEX on the entire database,
however extreme care must be taken to avoid database corruption.
Note that the above may fail with an error about duplicate rows if corruption has already occurred, and such duplicate rows will need to be manually removed.
Fixing inconsistent sequences error
Synapse uses Postgres sequences to generate IDs for various tables. A sequence and associated table can get out of sync if, for example, Synapse has been downgraded and then upgraded again.
To fix the issue shut down Synapse (including any and all workers) and run the SQL command included in the error message. Once done Synapse should start successfully.