dendrite/docs/FAQ.md

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FAQ

Why does Dendrite exist?

Dendrite aims to provide a matrix compatible server that has low resource usage compared to Synapse. It also aims to provide more flexibility when scaling either up or down. Dendrite's code is also very easy to hack on which makes it suitable for experimenting with new matrix features such as peer-to-peer.

Is Dendrite stable?

Mostly, although there are still bugs and missing features. If you are a confident power user and you are happy to spend some time debugging things when they go wrong, then please try out Dendrite. If you are a community, organisation or business that demands stability and uptime, then Dendrite is not for you yet - please install Synapse instead.

Is Dendrite feature-complete?

No, although a good portion of the Matrix specification has been implemented. Mostly missing are client features - see the readme at the root of the repository for more information.

Why doesn't Dendrite have "x" yet?

Dendrite development is currently supported by a small team of developers and due to those limited resources, the majority of the effort is focused on getting Dendrite to be specification complete. If there are major features you're requesting (e.g. new administration endpoints), we'd like to strongly encourage you to join the community in supporting the development efforts through contributing.

Is there a migration path from Synapse to Dendrite?

No, not at present. There will be in the future when Dendrite reaches version 1.0. For now it is not possible to migrate an existing Synapse deployment to Dendrite.

Can I use Dendrite with an existing Synapse database?

No, Dendrite has a very different database schema to Synapse and the two are not interchangeable.

Can I configure which port Dendrite listens on?

Yes, use the cli flag -http-bind-address.

I've installed Dendrite but federation isn't working

Check the Federation Tester. You need at least:

• A valid DNS name
• A valid TLS certificate for that DNS name
• Either DNS SRV records or well-known files

Whenever I try to connect from Element it says unable to connect to homeserver

Check that your dendrite instance is running. Otherwise this is most likely due to a reverse proxy misconfiguration.

Does Dendrite work with my favourite client?

It should do, although we are aware of some minor issues:

• Element Android: registration does not work, but logging in with an existing account does
• Hydrogen: occasionally sync can fail due to gaps in the since parameter, but clearing the cache fixes this

Is there a public instance of Dendrite I can try out?

Use dendrite.matrix.org which we officially support.

Does Dendrite support Space Summaries?

Yes, Space Summaries were merged into the Matrix Spec as of 2022-01-17 however, they are still treated as an MSC (Matrix Specification Change) in Dendrite. In order to enable Space Summaries in Dendrite, you must add the MSC to the MSC configuration section in the configuration YAML. If the MSC is not enabled, a user will typically see a perpetual loading icon on the summary page. See below for a demonstration of how to add to the Dendrite configuration:

mscs:
  mscs:
    - msc2946

Similarly, msc2836 would need to be added to mscs configuration in order to support Threading. Other MSCs are not currently supported.

Please note that MSCs should be considered experimental and can result in significant usability issues when enabled. If you'd like more details on how MSCs are ratified or the current status of MSCs, please see the Matrix specification documentation on the subject.

Does Dendrite support push notifications?

Yes, we have experimental support for push notifications. Configure them in the usual way in your Matrix client.

Does Dendrite support application services/bridges?

Possibly - Dendrite does have some application service support but it is not well tested. Please let us know by raising a GitHub issue if you try it and run into problems.

Bridges known to work (as of v0.5.1):

• Telegram
• WhatsApp
• Signal
• probably all other mautrix bridges

Remember to add the config file(s) to the app_service_api section of the config file.

Is it possible to prevent communication with the outside world?

Yes, you can do this by disabling federation - set disable_federation to true in the global section of the Dendrite configuration file.

How can I migrate a room in order to change the internal ID?

This can be done by performing a room upgrade. Use the command /upgraderoom <version> in Element to do this.

How do I reset somebody's password on my server?

Use the admin endpoint resetpassword

Should I use PostgreSQL or SQLite for my databases?

Please use PostgreSQL wherever possible, especially if you are planning to run a homeserver that caters to more than a couple of users.

What data needs to be kept if transferring/backing up Dendrite?

The list of files that need to be stored is:

• matrix-key.pem
• dendrite.yaml
• the postgres or sqlite DB
• the media store
• the search index (although this can be regenerated)

Note that this list may change / be out of date. We don't officially maintain instructions for migrations like this.

How can I prepare enough storage for media caches?

This might be what you want: matrix-media-repo We don't officially support this or any other dedicated media storage solutions.

Is there an upgrade guide for Dendrite?

Run a newer docker image. We don't officially support deployments other than Docker. Most of the time you should be able to just

• stop
• replace binary
• start

Dendrite is using a lot of CPU

Generally speaking, you should expect to see some CPU spikes, particularly if you are joining or participating in large rooms. However, constant/sustained high CPU usage is not expected - if you are experiencing that, please join #dendrite-dev:matrix.org and let us know what you were doing when the CPU usage shot up, or file a GitHub issue. If you can take a CPU profile then that would be a huge help too, as that will help us to understand where the CPU time is going.

Dendrite is using a lot of RAM

As above with CPU usage, some memory spikes are expected if Dendrite is doing particularly heavy work at a given instant. However, if it is using more RAM than you expect for a long time, that's probably not expected. Join #dendrite-dev:matrix.org and let us know what you were doing when the memory usage ballooned, or file a GitHub issue if you can. If you can take a memory profile then that would be a huge help too, as that will help us to understand where the memory usage is happening.

Do I need to generate the self-signed certificate if I'm going to use a reverse proxy?

No, if you already have a proper certificate from some provider, like Let's Encrypt, and use that on your reverse proxy, and the reverse proxy does TLS termination, then you’re good and can use HTTP to the dendrite process.

Dendrite is running out of PostgreSQL database connections

You may need to revisit the connection limit of your PostgreSQL server and/or make changes to the max_connections lines in your Dendrite configuration. Be aware that each Dendrite component opens its own database connections and has its own connection limit, even in monolith mode!

VOIP and Video Calls don't appear to work on Dendrite

There is likely an issue with your STUN/TURN configuration on the server. If you believe your configuration to be correct, please see the troubleshooting for troubleshooting recommendations.

What is being reported when enabling phone-home statistics?

Phone-home statistics contain your server's domain name, some configuration information about your deployment and aggregated information about active users on your deployment. They are sent to the endpoint URL configured in your Dendrite configuration file only. The following is an example of the data that is sent:

{
    "cpu_average": 0,
    "daily_active_users": 97,
    "daily_e2ee_messages": 0,
    "daily_messages": 0,
    "daily_sent_e2ee_messages": 0,
    "daily_sent_messages": 0,
    "daily_user_type_bridged": 2,
    "daily_user_type_native": 97,
    "database_engine": "Postgres",
    "database_server_version": "11.14 (Debian 11.14-0+deb10u1)",
    "federation_disabled": false,
    "go_arch": "amd64",
    "go_os": "linux",
    "go_version": "go1.16.13",
    "homeserver": "my.domain.com",
    "log_level": "trace",
    "memory_rss": 93452,
    "monolith": true,
    "monthly_active_users": 97,
    "nats_embedded": true,
    "nats_in_memory": true,
    "num_cpu": 8,
    "num_go_routine": 203,
    "r30v2_users_all": 0,
    "r30v2_users_android": 0,
    "r30v2_users_electron": 0,
    "r30v2_users_ios": 0,
    "r30v2_users_web": 0,
    "timestamp": 1651741851,
    "total_nonbridged_users": 97,
    "total_room_count": 0,
    "total_users": 99,
    "uptime_seconds": 30,
    "version": "0.8.2"
}