path: root/docs/1-afm-daemons.md

# The application framework daemons

## Foreword

This document describes application framework daemons
FCS (Fully Conform to Specification) implementation is still under development.
It may happen that current implementation somehow diverges with specifications.

## Introduction

Daemons ***afm-user-daemon*** and ***afm-system-daemon*** handle applications
life.
Understand that they will manage operations like:

- ***installation***
- ***uninstallation***
- ***running***
- ***suspend***
- ***inventory***
- ...

In addition, they ensure that operations use the security framework as needed
and that applications are executed in the correct context.

***D-Bus*** is in charge of transmitting orders to the appropriate daemon
depending upon ***D-Bus*** destination.

The figure below summarizes the situation of both **afm-system-daemon** and
**afm-user-daemon** in the system.

![afm-daemons][afm-daemons]{:: style="width:65%;"}

## The D-Bus interface

### Overview of the dbus interface

The ***afm daemons*** takes theirs orders from the session instance
of D-Bus.
The use of D-Bus is great because it allows to implement
discovery and signaling.

The dbus session is by default addressed by environment
variable *DBUS_SESSION_BUS_ADDRESS*. Using **systemd**
variable *DBUS_SESSION_BUS_ADDRESS* is automatically set for
user sessions.

They are listening with the destination name ***org.AGL.afm.[user|system]***
at the object of path ***/org/AGL/afm/[user|system]*** on the interface
***org.AGL.afm.[user|system]***  for the below detailed members for the
***afm-system-daemon***:

- ***install***
- ***uninstall***

And for ***afm-user-daemon***:

- ***runnables***
- ***detail***
- ***start***
- ***once***
- ***terminate***
- ***pause***
- ***resume***
- ***runners***
- ***state***
- ***install***
- ***uninstall***

D-Bus is mainly used for signaling and discovery.
Its optimized typed protocol is not used except for transmitting
 only one string in both directions.

The client and the service are using JSON serialization to
exchange data.
Signature of any member of the D-Bus interface is
***string -> string*** for ***JSON -> JSON***.
This is the normal case, if there is an error, current implementation
returns a dbus error that is a string.

Here are examples using *dbus-send*, here to install an application from a
widget file:

```bash
dbus-send --session --print-reply \
    --dest=org.AGL.afm.system \
    /org/AGL/afm/system \
    org.AGL.afm.system.install string:"/tmp/appli.wgt"
```

And here, to query data on installed applications that can be run:

```bash
dbus-send --session --print-reply \
    --dest=org.AGL.afm.user \
    /org/AGL/afm/user \
    org.AGL.afm.user.runnables string:true
```

### The protocol over D-Bus

On all following sub-chapters we assume that we talk about either
***afm-system-daemon*** or ***afm-user-daemon***. Method and D-Bus parameters
are considered as self-explanatory.

The D-Bus interface is defined by:

- **DESTINATION**: org.AGL.afm.[user|system]
- **PATH**: /org/AGL/afm/[user|system]
- **INTERFACE**: org.AGL.afm.[user|system]

#### Method org.AGL.afm.system.install

**Description**: Install an application from a widget file.

When an application with the same *id* and *version* already exists. Outside of
using *force=true* the application is not reinstalled.

Applications are installed the subdirectories of applications common directory.
If *root* is specified, the application is installed under the
sub-directories of the *root* defined.

Note that this methods is a simple accessor method of
***org.AGL.afm.system.install*** from ***afm-system-daemon***.

After the installation and before returning to the sender,
***afm-system-daemon*** sends a signal ***org.AGL.afm.system.changed***.

**Input**: The *path* of the widget file to install and, optionally,
a flag to *force* reinstallation, and, optionally, a *root* directory.

Either just a string being the absolute path of the widget file:

```bash
"/a/path/driving/to/the/widget"
```

Or an object:

```json
{
  "wgt": "/a/path/to/the/widget",
  "force": false,
  "root": "/a/path/to/the/root"
}
```

"wgt" and "root" must be absolute paths.

**output**: An object with the field "added" being the string for
the id of the added application.

```json
{"added":"appli@x.y"}
```

---

#### Method org.AGL.afm.system.uninstall

**Description**: Uninstall an application from its id.

Note that this methods is a simple method accessor of
***org.AGL.afm.system.uninstall*** from ***afm-system-daemon***.

After the uninstallation and before returning to the sender,
***afm-system-daemon*** sends a signal ***org.AGL.afm.system.changed***.

**Input**: the *id* of the application and optionally the application *root* path.

Either a string:

```bash
"appli@x.y"
```

Or an object:

```json
{
  "id": "appli@x.y",
  "root": "/a/path/to/the/root"
}
```

**output**: the value 'true'.

---

#### Method org.AGL.afm.user.detail

**Description**: Get details about an application from its id.

**Input**: the id of the application as below.

Either just a string:

```bash
"appli@x.y"
```

Or an object having the field "id" of type string:

```json
{"id":"appli@x.y"}
```

**Output**: A JSON object describing the application containing
the fields described below.

```json
{
  "id":          string, the application id (id@version)
  "version":     string, the version of the application
  "width":       integer, requested width of the application
  "height":      integer, requested height of the application
  "name":        string, the name of the application
  "description": string, the description of the application
  "shortname":   string, the short name of the application
  "author":      string, the author of the application
}
```

---

#### Method org.AGL.afm.user.runnables

**Description**: Get the list of applications that can be run.

**Input**: any valid json entry, can be anything except null.

**output**: An array of description of the runnable applications.
Each item of the array contains an object containing the detail of
an application as described above for the method
*org.AGL.afm.user.detail*.

---

#### Method org.AGL.afm.user.install

**Description**: Install an application from its widget file.

If an application of the same *id* and *version* exists, it is not
reinstalled except when *force=true*.

Applications are installed in the subdirectories of the common directory
reserved for applications.
If *root* is specified, the application is installed under
sub-directories of defined *root*.

Note that this methods is a simple accessor to the method
***org.AGL.afm.system.install*** of ***afm-system-daemon***.

After the installation and before returning to the sender,
***afm-user-daemon*** sends the signal ***org.AGL.afm.user.changed***.

**Input**: The *path* of widget file to be installed. Optionally,
a flag to *force* reinstallation and/or a *root* directory.

Simple form a simple string containing the absolute widget path:

```bash
"/a/path/driving/to/the/widget"
```

Or an object:

```json
{
  "wgt": "/a/path/to/the/widget",
  "force": false,
  "root": "/a/path/to/the/root"
}
```

***wgt*** and ***root*** MUST be absolute paths.

**output**: An object containing field "added" to use as application ID.

```json
{"added":"appli@x.y"}
```

---

#### Method org.AGL.afm.user.uninstall

**Description**: Uninstall an application from its id.

Note that this methods is a simple accessor to
***org.AGL.afm.system.uninstall*** method from ***afm-system-daemon***.

After the uninstallation and before returning to the sender,
***afm-user-daemon*** sends the signal ***org.AGL.afm.user.changed***.

**Input**: the *id* of the application and, optionally, the path to
application *root*.

Either a string:

```bash
"appli@x.y"
```

Or an object:

```json
{
  "id": "appli@x.y",
  "root": "/a/path/to/the/root"
}
```

**output**: the value 'true'.

---

#### Method org.AGL.afm.user.start

**Description**:

**Input**: the *id* of the application and, optionally, the
start *mode* as below.

Either just a string:

```bash
"appli@x.y"
```

Or an object containing field "id" of type string and
optionally a field mode:

```json
{"id":"appli@x.y","mode":"local"}
```

The field "mode" is a string equal to either "local" or "remote".

[Currently the mode is not available in the systemd version]

**output**: The *runid* of the application launched. *runid* is an integer.

---

#### Method org.AGL.afm.user.once

**Description**:

**Input**: the *id* of the application

Either just a string:

```bash
"appli@x.y"
```

Or an object containing field "id" of type string.

```json
{"id":"appli@x.y"}
```

**output**: The *state* of the application retrieved or launched.
See *org.AGL.afm.user.state* to get a description of the returned
object.

---

#### Method org.AGL.afm.user.terminate

**Description**: Terminates the application attached to *runid*.

**Input**: The *runid* (an integer) of running instance to terminate.

**output**: the value 'true'.

---

#### Method org.AGL.afm.user.stop

Obsolete since 8th November 2016 (2016/11/08).
Kept for compatibility.

Use **org.AGL.afm.user.pause** instead.

---

#### Method org.AGL.afm.user.continue

Obsolete since 8th November 2016 (2016/11/08).
Kept for compatibility.

Use **org.AGL.afm.user.resume** instead.

---

#### Method org.AGL.afm.user.pause

[Currently not available in the systemd version]

**Description**: Pauses the application attached to *runid* until terminate or resume.

**Input**: The *runid* (integer) of the running instance to pause.

**output**: the value 'true'.

---

#### Method org.AGL.afm.user.resume

[Currently not available in the systemd version]

**Description**: Resumes the application attached to *runid* previously paused.

**Input**: The *runid* (integer) of the running instance to resume.

**output**: the value 'true'.

---

#### Method org.AGL.afm.user.state

**Description**: Get information about a running instance of *runid*.

**Input**: The *runid* (integer) of the running instance inspected.

**output**: An object describing instance state.
It contains:

- the runid (integer)
- the pids of the processes as an array starting
- with the group leader
- the id of the running application (string)
- the state of the application (string either: "starting", "running", "paused").

Example of returned state:

```json
    {
      "runid": 2,
      "pids": [ 435, 436 ],
      "state": "running",
      "id": "appli@x.y"
    }
```

---

#### Method org.AGL.afm.user.runners

**Description**: Get the list of currently running instances.

**Input**: anything.

**output**: An array of states, one per running instance, as returned by
the method ***org.AGL.afm.user.state***.

## Starting **afm daemons**

***afm-system-daemon*** and ***afm-user-daemon*** are launched as systemd
services attached to system and user respectively.
Normally, service files are locatedat */lib/systemd/system/afm-system-daemon.service* and
*/usr/lib/systemd/user/afm-user-daemon.service*.

### ***afm-system-daemon*** options

The options for launching **afm-system-daemon** are:

```bash
    -r
    --root directory

         Set the root application directory.

         Note that the default root directory is defined
         to be /usr/share/afm/applications (may change).

    -d
    --daemon

         Daemonizes the process. It is not needed by systemd.

    -q
    --quiet

         Reduces the verbosity (can be repeated).

    -v
    --verbose

         Increases the verbosity (can be repeated).

    -h
    --help

         Prints a short help.
```

### ***afm-user-daemon*** options

The options for launching **afm-user-daemon** are:

```bash
    -a
    --application directory

         [Currently not available in the systemd version]

         Includes the given application directory to
         the database base of applications.

         Can be repeated.

    -r
    --root directory

         [Currently not available in the systemd version]

         Includes root application directory or directories when
         passing multiple rootdir to
         applications database.

         Note that default root directory for
         applications is always added. In current version
         /usr/share/afm/applications is used as default.

    -m
    --mode (local|remote)

         [Currently not available in the systemd version]

         Set the default launch mode.
         The default value is 'local'

    -d
    --daemon

         Daemonizes the process. It is not needed by systemd.

    -q
    --quiet

         Reduces the verbosity (can be repeated).

    -v
    --verbose

         Increases the verbosity (can be repeated).

    -h
    --help

         Prints a short help.
```

## Tasks of **afm-user-daemon**

### Maintaining list of applications

At start **afm-user-daemon** scans the directories containing
applications and load in memory a list of available applications
accessible by current user.

When **afm-system-daemon** installs or removes an application.
On success it sends the signal *org.AGL.afm.system.changed*.
When receiving such a signal, **afm-user-daemon** rebuilds its
applications list.

**afm-user-daemon** provides the data it collects about
applications to its clients.
Clients may either request the full list
of available applications or a more specific information about a
given application.

### Launching application

**afm-user-daemon** launches application by using systemd.
Systemd builds a secure environment for the application
before starting it.

Once launched, running instances of application receive
a runid that identify them.
To make interface with systemd evident, the pid is the runid.

### Managing instances of running applications

**afm-user-daemon** manages the list of applications
that it launched.

When owning the right permissions, a client can get the list
of running instances and details about a specific
running instance.
It can also terminate a given application.

### Installing and uninstalling applications

If the client own the right permissions,
**afm-user-daemon** delegates that task
to **afm-system-daemon**.

## Using ***afm-util***

The command line tool ***afm-util*** uses dbus-send to send
orders to **afm-user-daemon**.
This small scripts allows to send command to ***afm-user-daemon*** either
interactively at shell prompt or scriptically.

The syntax is simple:

- it accept a command and when requires attached arguments.

Here is the summary of ***afm-util***:

- **afm-util runnables      **:
  list the runnable widgets installed

- **afm-util install    wgt **:
  install the wgt file

- **afm-util uninstall  id  **:
  remove the installed widget of id

- **afm-util detail     id  **:
  print detail about the installed widget of id

- **afm-util runners        **:
  list the running instance

- **afm-util start      id  **:
  start an instance of the widget of id

- **afm-util once      id  **:
  run once an instance of the widget of id

- **afm-util terminate  rid **:
  terminate the running instance rid

- **afm-util state      rid **:
  get status of the running instance rid

Here is how to list applications using ***afm-util***:

```bash
    afm-util runnables
```

[afm-daemons]: pictures/afm-daemons.svg