Merge pull request #456 from eMPee584/synapse-workers

Synapse workers

docs/configuring-playbook-synapse.md

@@ -18,6 +18,35 @@ Alternatively, **if there is no pre-defined variable** for a Synapse setting you
 - or, if extending the configuration is still not powerful enough for your needs, you can **override the configuration completely** using `matrix_synapse_configuration` (or `matrix_synapse_configuration_yaml`). You can find information about this in [`roles/matrix-synapse/defaults/main.yml`](../roles/matrix-synapse/defaults/main.yml).
 
 
+## Load balancing with workers
+
+To have Synapse gracefully handle thousands of users, worker support should be enabled. It factors out some homeserver tasks and spreads the load of incoming client and server-to-server traffic between multiple processes. More information can be found in the [official Synapse workers documentation](https://github.com/matrix-org/synapse/blob/master/docs/workers.md).
+
+To enable Synapse worker support, update your `inventory/host_vars/matrix.DOMAIN/vars.yml` file:
+
+```yaml
+matrix_synapse_workers_enabled: true
+```
+
+We support a few configuration presets (`matrix_synapse_workers_preset: one-of-each` being the default configuration):
+- `little-federation-helper` - a very minimal worker configuration to improve federation performance
+- `one-of-each` - one worker of each supported type
+
+If you'd like more customization power, you can start with one of the presets and tweak various `matrix_synapse_workers_*_count` variables manually.
+
+If you increase worker counts too much, you may need to increase the maximum number of Postgres connections too (example):
+
+```yaml
+matrix_postgres_process_extra_arguments: [
+  "-c 'max_connections=200'"
+]
+```
+
+If you're using the default setup (the `matrix-nginx-proxy` webserver being enabled) or you're using your own `nginx` server (which imports the configuration files generated by the playbook), you're good to go. If you use some other webserver, you may need to tweak your reverse-proxy setup manually to forward traffic to the various workers.
+
+In case any problems occur, make sure to have a look at the [list of synapse issues about workers](https://github.com/matrix-org/synapse/issues?q=workers+in%3Atitle) and your `journalctl --unit 'matrix-*'`.
+
+
 ## Synapse Admin
 
 Certain Synapse administration tasks (managing users and rooms, etc.) can be performed via a web user-interace, if you install [Synapse Admin](configuring-playbook-synapse-admin.md).