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Worker-based setup
Very busy servers are brought down because a single thread can't keep up with the load. So you want to create several threads for different types of work.
See this Matrix blog for some background information.
Redis
First step is to install Redis.
apt install redis-server
For less overhead we use a UNIX socket instead of a network connection to
localhost. Disable the TCP listener and enable the socket in
/etc/redis/redis.conf:
port 0
unixsocket /run/redis/redis-server.sock
unixsocketperm 770
Our matrix user (matrix-synapse) has to be able to read from and write to
that socket, which is created by Redis and owned by redis:redis, so we add
user matrix-synapse to the group redis.
adduser matrix-synapse redis
Restart Redis for these changes to take effect. Check if port 6379 is no
longer active, and if the socketfile /run/redis/redis-server.sock exists.
Synapse
First, create the directory where all the socket files for workers will come, and give it the correct user, group and permission:
mkdir /run/matrix-synapse
dpkg-statoverride --add --update matrix-synapse matrix-synapse 0770 /run/matrix-synapse
Add a replication listener:
listeners:
...
- path: /run/matrix-synapse/replication.sock
mode: 0660
type: http
resources:
- names:
- replication
Check if the socket is created and has the correct permissions. Now point
Synapse at Redis in conf.d/redis.yaml:
redis:
enabled: true
path: /run/redis/redis-server.sock
Check if Synapse can connect to Redis via the socket, you should find log entries like this:
synapse.replication.tcp.redis - 292 - INFO - sentinel - Connecting to redis server UNIXAddress('/run/redis/redis-server.sock')
synapse.util.httpresourcetree - 56 - INFO - sentinel - Attaching <synapse.replication.http.ReplicationRestResource object at 0x7f95f850d150> to path b'/_synapse/replication'
synapse.replication.tcp.redis - 126 - INFO - sentinel - Connected to redis
synapse.replication.tcp.redis - 138 - INFO - subscribe-replication-0 - Sending redis SUBSCRIBE for ['matrix.example.com/USER_IP', 'matrix.example.com']
synapse.replication.tcp.redis - 141 - INFO - subscribe-replication-0 - Successfully subscribed to redis stream, sending REPLICATE command
synapse.replication.tcp.redis - 146 - INFO - subscribe-replication-0 - REPLICATE successfully sent
Workers
Workers are Synapse instances that perform a single job (or a set of jobs).
Their configuration goes into /etc/matrix-synapse/workers, which we have to
create first.
Create a worker for
Preparing for sockets
Because we use sockets for speed, we should make sure only those programs that need access to those sockets get it.
Create a new group and add the users that need access to it:
addgroup --system clubmatrix
addgroup matrix-synapse clubmatrix
addgroup www-data clubmatrix
Create one systemd service file for all workers:
[Unit]
Description=Synapse %i
AssertPathExists=/etc/matrix-synapse/workers/%i.yaml
# This service should be restarted when the synapse target is restarted.
PartOf=matrix-synapse.target
ReloadPropagatedFrom=matrix-synapse.target
# if this is started at the same time as the main, let the main process start
# first, to initialise the database schema.
After=matrix-synapse.service
[Service]
Type=notify
NotifyAccess=main
User=matrix-synapse
WorkingDirectory=/var/lib/matrix-synapse
EnvironmentFile=-/etc/default/matrix-synapse
ExecStart=/opt/venvs/matrix-synapse/bin/python -m synapse.app.generic_worker --config-path=/etc/matrix-synapse/homeserver.yaml --config-path=/etc/matrix-synapse/conf.d/ --config-path=/etc/matrix-synapse/workers/%i.yaml
ExecReload=/bin/kill -HUP $MAINPID
Restart=always
RestartSec=3
SyslogIdentifier=matrix-synapse-%i
[Install]
WantedBy=matrix-synapse.target
And create the matrix-synapse.target, which combines all Synapse parts into
one systemd target:
[Unit]
Description=Matrix Synapse with all its workers
After=network.target
[Install]
WantedBy=multi-user.target