External Component Configuration
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## External Component Configuration

Tigase can connect to external components, this guide will show you how this can be accomplished.

Configuration follows the same standards as all other components. It is also much more powerful as a single Tigase instance can control many TCP/IP ports and many external components on each port and even allows for multiple connections for the same component. It supports both XEP-0114 and XEP-0225 with protocol auto-detection mechanisms. Protocols are pluggable so more protocols can be supported or custom extensions to existing protocols can be added.

The implementation also supports a scripting API and new domains with passwords can be added at run-time using ad-hoc commands. New scripts can be loaded to even further control all connected external components.

Pages in this guide describe in details all the administration aspects of setting up and managing external components.

- External Component Configuration
- Tigase as an External Component
- Load Balancing External Components in Cluster Mode

### External Component Configuration

As for all Tigase components you can load and configure external components via the `config.tdsl` file described in details in the DSL configuration section. This document describes how to enable the component and set the initial configuration to accept or initiate connections for an external component.

First thing to do is to specify the component class and the component name which must be unique within the Tigase installation. The most commonly name used is `ext` and the class is `tigase.server.ext.ComponentProtocol` (class doesn’t have to be specified when using default name).

The following line in the `config.tdsl` will load the component during the server startup time:

    ext (class: tigase.server.ext.ComponentProtocol) {}

While this would load the component, without any additional configurations provided, the component would be practically useless. It is necessary to configure the virtual host domains of the external component during run-time via ad-hoc commands to make use of this component.

You may additionally configure the `bind-ext-hostnames` property.

To configure external component connections using Admin UI you need to open Admin UI web page (if you are logged in the same computer on which Tigase XMPP Server is running by default it should be available at http://localhost:8080/admin/). Then you should click on `Configuration` on the left side of the Admin UI web page and then select `Add new item` on `ext` component or by execution corresponding ad-hoc command on `ext` component using ad-hoc capable XMPP client, ie. Psi.

You will be presented with a form which you should fill to configure external component connection details:

- Domain name - external component domain name (`muc.devel.tigase.org`)
- Domain password - password for authentication of the external component connection (`muc-pass`)
- Connection type - `accept` to make component wait for connection or `connect` force component to connect to the server (`connect`)
- Port number - port on which component should wait for connection or on which it try to connect (`5270`)
- Remote host - host to connect to (`devel.tigase.org`) (may be left blank if component will only accept connections)

- Protocol - id of protocol used for establishing connection

  - if connection type is `connect`:

    - `XEP-0114: Jabber Component Protocol (accept)` - for XEP-0114: Jabber Component Protocol
    - `XEP-0225: Component Connections` - for XEP-0225: Component Connections

  - if connection type is `accept`:

    - `Autodetect` - for automatic detection of protocol used by incoming connection (recommended)
    - `XEP-0114: Jabber Component Protocol (accept)` - for XEP-0114: Jabber Component Protocol
    - `XEP-0225: Component Connections` - for XEP-0225: Component Connections

Additional options may be left with defaults.

Later on if you would like to modify this values, you can do that using Admin UI by clicking on `Configuration` and `Remove an item` or `Update item configuration` at `ext` component or by execution corresponding ad-hoc commands on `ext` component using ad-hoc capable XMPP client, ie. Psi.

### Tigase as an External Component

There are cases when you want to deploy one or more Tigase components separately from the main server, or perhaps you want to run some Tigase components connecting to a different XMPP server, or perhaps you work on a component and you do not want to restart the main server every time you make a change.

There is a way to run the Tigase server in external component mode. In fact you can run any of Tigase’s components as an external component and connect them to the main XMPP server either via XEP-0114 or XEP-0225 connection.

Let’s look at the examples…​

#### Usage with shared database (since version 8.0.0)

When you are using Tigase server 8.0.0 or newer in the "external component mode" while using shared default "user repository" and you have main server also running Tigase XMPP Server 8.0.0 or newer, then you can benefit from the remote management of the component connections from the main server. To use that, you need to enable external component and external component manager on the main server by adding following line to the config file:

    'ext' () {}
    'ext-man' () {}

With that in place you can use Admin UI or ad-hoc commands available at `ext-man` component of the main server to configure connection details of the servers running in the `component` mode.

In Admin UI you click on `Configuration` section and select `Add new item` at the `ext-man` component, which will present you with a following form to fill in external component connectivity details:

##### A Simple Case - MUC as an External Component

A few assumptions:

1. We want to run a MUC component for a domain: `muc.devel.tigase.org` and password `muc-pass`
2. The main server works at an address: devel.tigase.org and for the same virtual domain
3. We want to connect to the server using XEP-0114 protocol and port `5270`.

There is a special configuration type for this case which simplifies setting needed to run Tigase as an external component:

    'config-type' = 'component'

Knowing that we can now create simple configuration file for Tigase XMPP Server:

    admins = [ 'admin@devel.tigase.org' ]
    'config-type' = 'component'
    debug = [ 'server' ]
    'default-virtual-host' = [ 'devel.tigase.org' ]
    dataSource {
        default () {
            uri = 'master_server_default_database_url'
        }
    }
    userRepository {
        default () {}
    }
    authRepository {
        default () {}
    }
    muc (class: tigase.muc.MUCComponent) {}
    ext () {
    }

where `master_server_default_database_url` is the same URL as the one used on the main server for default data source.

With that in place we can use ad-hoc commands or Admin UI on the main server to configure Tigase XMPP Server to accept external component connections and to connect from the external component to the master server.

Adding external component connection settings to the manager (ext-man) using Admin UI.

You need to pass:

- Domain name - external component domain name (`muc.devel.tigase.org`)
- Domain password - password for authentication of the external component connection (`muc-pass`)
- Connection type - `accept` to make component wait for connection or `connect` force component to connect to the server (`connect`)
- Port number - port on which component should wait for connection or on which it try to connect (`5270`)
- Remote host - host to connect to (`devel.tigase.org`)

- Protocol - id of protocol used for establishing connection

  - `XEP-0114: Jabber Component Protocol (accept)` - establish connection using XEP-0114: Jabber Component Protocol
  - `XEP-0225: Component Connections` - establish connection using XEP-0225: Component Connections

Additional options may be left with defaults.

##### More Components

Suppose you want to run more than one component as an external components within one Tigase instance. Let’s add another - PubSub component to the configuration above and see how to set it up.

The most straightforward way is just to add another component to the server running in the component mode for the component domain

    admins = [ 'admin@devel.tigase.org' ]
    'config-type' = 'component'
    debug = [ 'server' ]
    'default-virtual-host' = [ 'devel.tigase.org' ]
    dataSource {
        default () {
            uri = 'jdbc:derby:/tigasedb'
        }
    }
    userRepository {
        default () {}
    }
    authRepository {
        default () {}
    }
    muc (class: tigase.muc.MUCComponent) {}
    pubsub (class: tigase.pubsub.PubSubComponent) {}
    ext () {}

and then to add new connection domain to the main server external component settings and to the external component manager settings. You basically do the same thing as you did while adding only MUC component as the external component.

Please note however that we are opening two connections to the same server. This can waste resources and over-complicate the system. For example, what if we want to run even more components? Opening a separate connection for each component is a tad overkill.

In fact there is a way to reuse the same connection for all component domains running as an external component. The property `bind-ext-hostnames` contains a comma separated list of all hostnames (external domains) which should reuse the existing connection.

There is one catch however. Since you are reusing connections (hostname binding is defined in XEP-0225 only), you must use this protocol for the functionality.

Here is an example configuration with a single connection over the XEP-0225 protocol used by both external domains:

    admins = [ 'admin@devel.tigase.org' ]
    'bind-ext-hostnames' = [ 'pubsub.devel.tigase.org' ]
    'config-type' = 'component'
    debug = [ 'server' ]
    'default-virtual-host' = [ 'devel.tigase.org' ]
    dataSource {
        default () {
            uri = 'jdbc:derby:/tigasedb'
        }
    }
    ext () {
    }
    userRepository {
        default () {}
    }
    authRepository {
        default () {}
    }
    muc (class: tigase.muc.MUCComponent) {}
    pubsub (class: tigase.pubsub.PubSubComponent) {}

With this configuration you do not need to configure entries in `ext-man` for PubSub component, only for MUC component but you need to user `client` as the value for protocol field.

#### Usage with a separate database

##### A Simple Case - MUC as an External Component

A few assumptions:

1. We want to run a MUC component for a domain: `muc.devel.tigase.org` and password `muc-pass`
2. The main server works at an address: devel.tigase.org and for the same virtual domain
3. We want to connect to the server using XEP-0114 protocol and port `5270`.

There is a special configuration type for this case which simplifies setting needed to run Tigase as an external component:

    'config-type' = 'component'

This generates a configuration for Tigase with only one component loaded by default - the component used for external component connection. If you use this configuration type, your `config.tdsl` file may look like this:

    admins = [ 'admin@devel.tigase.org' ]
    'config-type' = 'component'
    debug = [ 'server' ]
    'default-virtual-host' = [ 'devel.tigase.org' ]
    dataSource {
        default () {
            uri = 'jdbc:derby:/tigasedb'
        }
    }
    userRepository {
        default () {}
    }
    authRepository {
        default () {}
    }
    muc (class: tigase.muc.MUCComponent) {}
    ext () {
    }

To make this new instance connect to the Tigase XMPP Server, you need to create one more file with external connection configuration at `etc/externalComponentItems` which will be loaded to the local database and then removed.

    muc.devel.tigase.org:muc-pass:connect:5270:devel.tigase.org:accept

### Warning

While loading configuration from `etc/externalComponentItems` file is supported, we recommend usage of shared database if possible. In future this method may be deprecated.

##### More Components

Suppose you want to run more than one component as an external components within one Tigase instance. Let’s add another - PubSub component to the configuration above and see how to set it up.

The most straightforward way is just to add another external component connection to the main server for the component domain using Admin UI or ad-hoc command on the main server.

Then we can use following configuration on the server running in the `component` mode:

    admins = [ 'admin@devel.tigase.org' ]
    'config-type' = 'component'
    debug = [ 'server' ]
    'default-virtual-host' = [ 'devel.tigase.org' ]
    dataSource {
        default () {
            uri = 'jdbc:derby:/tigasedb'
        }
    }
    userRepository {
        default () {}
    }
    authRepository {
        default () {}
    }
    muc (class: tigase.muc.MUCComponent) {}
    pubsub (class: tigase.pubsub.PubSubComponent) {}
    ext () {
    }

and we need to create a file with configuration for external component connection which will be loaded to the internal database:

    muc.devel.tigase.org:muc-pass:connect:5270:devel.tigase.org:accept
    pubsub.devel.tigase.org:pubsub-pass:connect:5270:devel.tigase.org:accept

Please note however that we are opening two connections to the same server. This can waste resources and over-complicate the system. For example, what if we want to run even more components? Opening a separate connection for each component is a tad overkill.

In fact there is a way to reuse the same connection for all component domains running as an external component. The property `bind-ext-hostnames` contains a comma separated list of all hostnames (external domains) which should reuse the existing connection.

There is one catch however. Since you are reusing connections (hostname binding is defined in XEP-0225 only), you must use this protocol for the functionality.

Here is an example configuration with a single connection over the XEP-0225 protocol used by both external domains:

    admins = [ 'admin@devel.tigase.org' ]
    'bind-ext-hostnames' = [ 'pubsub.devel.tigase.org' ]
    'config-type' = 'component'
    debug = [ 'server' ]
    'default-virtual-host' = [ 'devel.tigase.org' ]
    dataSource {
        default () {
            uri = 'jdbc:derby:/tigasedb'
        }
    }
    ext () {
    }
    userRepository {
        default () {}
    }
    authRepository {
        default () {}
    }
    muc (class: tigase.muc.MUCComponent) {}
    pubsub (class: tigase.pubsub.PubSubComponent) {}

and example of the external connections configuration file:

    muc.devel.tigase.org:muc-pass:connect:5270:devel.tigase.org:client

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