|
6 | 6 | Applications |
7 | 7 | ============ |
8 | 8 |
|
9 | | -A NS8 application is implemented by a unit called *module*. It is usually |
10 | | -composed of one or more Linux containers and a user interface for its |
11 | | -configuration. |
12 | | - |
13 | | -The terms *application* and *module* are almost synonims in the context of |
14 | | -NethServer 8, however there can be modules that actually do not implement |
15 | | -applications because they are just services for other modules, so they do |
16 | | -not provide any user configuration interface at all. |
17 | | - |
18 | | -Every time a module instance is added to the cluster, the new instance is |
19 | | -named like the module itself followed by a progressive number starting |
20 | | -from 1. Given a module named ``myapp``, instances will be named |
21 | | -``myapp1``, ``myapp2`` and so on. It is possible to set a more meaningful |
22 | | -name for the instance from the :ref:`software_center-section` page. |
23 | | - |
24 | | -Some applications or modules require specific resources that cannot be |
25 | | -shared among instances installed on the same cluster node. As an example, |
26 | | -the Mail application needs to reserve SMTP and IMAP well-known TCP ports. |
27 | | -You can install only one instance per node of this kind of applications. |
28 | | - |
29 | | -On the contrary, applications that do not require exclusive access to |
30 | | -resources can be installed multiple times on the same node. As an example, |
31 | | -you can install multiple Nextcloud applications on a single node. |
| 9 | +The ``Applications`` page lists the applications installed in the cluster. |
| 10 | +The list can be filtered by: |
| 11 | + |
| 12 | +- ``Type``, for example to list only Nextcloud applications. |
| 13 | +- ``Node``, to limit the list to applications installed on a specific |
| 14 | + cluster node. |
| 15 | +- Free text, to display only applications matching a certain string. |
| 16 | + |
| 17 | +A single click on the application **name** opens its configuration page. |
| 18 | + |
| 19 | +A click on the application **type** shows detailed information about the |
| 20 | +application itself. This information, including the **version**, is also |
| 21 | +available from the :ref:`Software center <software_center-section>` page. |
| 22 | + |
| 23 | +Each item in the list has a **three-dots menu** with the available |
| 24 | +**actions** for that application. |
| 25 | + |
| 26 | +.. |bento| image:: _static/bento.png |
| 27 | + :alt: application drawer |
| 28 | + |
| 29 | +Installed applications are also listed in the **application drawer**, by |
| 30 | +clicking the |bento| menu in the top-right corner of the screen. The |
| 31 | +drawer shows only installed applications, not those available for |
| 32 | +installation. |
| 33 | + |
| 34 | +The application name |
| 35 | +==================== |
| 36 | + |
| 37 | +Every time an application is added to the cluster, it is uniquely |
| 38 | +identified by its name followed by a sequential number. Given the |
| 39 | +application *Myapp*, installed instances will be named ``myapp1``, |
| 40 | +``myapp2`` and so on. |
| 41 | + |
| 42 | +This internal, unique identifier is assigned by the cluster and cannot be |
| 43 | +changed, but the ``Edit label`` action allows assigning a custom label. |
| 44 | + |
| 45 | +Furthermore, a small text note can be attached to the application with the |
| 46 | +``Edit note`` action. When an application has an attached note, a small |
| 47 | +circled *i* with a tooltip appears next to the application name. |
| 48 | + |
| 49 | + |
| 50 | +.. _move_clone-section: |
| 51 | + |
| 52 | +Clone and move |
| 53 | +============== |
| 54 | + |
| 55 | +The ``Clone`` and ``Move`` actions create a **destination** application |
| 56 | +that is a copy of the **source** one. |
| 57 | + |
| 58 | +The cluster node where the destination runs can be the same as the source. |
| 59 | +Instead, when moving an application, you must select a target node |
| 60 | +different from the one where the source is currently running. |
| 61 | + |
| 62 | +Generally, there are no limitations on running multiple applications of |
| 63 | +the same type on the same node. However, in some cases, cloning or moving |
| 64 | +to certain nodes may be restricted due to application policies, node |
| 65 | +resource limits (CPU, memory), or because the application requires |
| 66 | +exclusive access to a system resource, such as binding a fixed TCP port. |
| 67 | + |
| 68 | +Once started, ``Clone`` and ``Move`` actions run through these steps: |
| 69 | + |
| 70 | +1. Create the destination application. |
| 71 | +2. Start the data transfer between source and destination. During this |
| 72 | + step, the source remains up and running. |
| 73 | +3. Briefly stop the source application (when required by its data |
| 74 | + synchronization strategy). |
| 75 | +4. Execute the final data synchronization. |
| 76 | +5. The final step differs between the two actions: |
| 77 | + |
| 78 | + - *For Clone*, start both the source and the destination applications. |
| 79 | + |
| 80 | + - *For Move*, **start the destination** application and **remove the |
| 81 | + source** one. |
| 82 | + |
| 83 | +If the moved application is referenced by a fully qualified domain name |
| 84 | +(FQDN), ensure that external DNS records are updated to point to the |
| 85 | +target node. The cluster reverse proxy is automatically reconfigured. |
| 86 | + |
| 87 | +Restart application |
| 88 | +=================== |
| 89 | + |
| 90 | +The ``Restart`` action fully stops the application and starts its services |
| 91 | +again, performing the same operations normally executed at node boot time. |
| 92 | + |
| 93 | +This action should be used sparingly and preferably during non-working |
| 94 | +hours, as it interrupts application operation with unpredictable effects on |
| 95 | +the end-user experience. |
| 96 | + |
| 97 | +Some unpredictable events, such as lack of disk space or memory |
| 98 | +exhaustion, may degrade application functionality. In these situations, |
| 99 | +``Restart`` may resolve the issue, provided that sufficient resources are |
| 100 | +available again. |
| 101 | + |
| 102 | +Core apps |
| 103 | +========= |
| 104 | + |
| 105 | +From the ``Applications`` page, select the :guilabel:`Core apps` button to |
| 106 | +see a full list of installed Core applications and their versions. Core |
| 107 | +updates, when available, are always applied at the same time. |
| 108 | + |
| 109 | +The *module* term |
| 110 | +================= |
| 111 | + |
| 112 | +The *module* term is often used by developers. An NS8 application is |
| 113 | +implemented by a unit called a *module*. It is usually composed of one or |
| 114 | +more Linux containers and a user interface for its configuration. A module |
| 115 | +is the deployable unit managed by the cluster orchestrator. |
| 116 | + |
| 117 | +The terms *application* and *module* are almost synonyms in the context of |
| 118 | +NS8. However, some modules provide services to other modules and do not |
| 119 | +include a configuration UI. For example, Core components such as |
| 120 | +:ref:`Loki <logs-persistence-section>` and :ref:`Grafana |
| 121 | +<grafana_access-section>` are implemented as modules running on the leader |
| 122 | +node. |
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