The application framework daemons ================================= Foreword -------- This document describes application framework daemons FCF (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] 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: 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: 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: "/a/path/driving/to/the/widget" Or an object: { "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. {"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: "appli@x.y" Or an object: { "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: "appli@x.y" Or an object having the field "id" of type string: {"id":"appli@x.y"} **Output**: A JSON object describing the application containing the fields described below. { "id": string, the application id (id@version) "version": string, the version of the application "width": integer, requested width of the application "height": integer, resqueted 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: "/a/path/driving/to/the/widget" Or an object: { "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. {"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: "appli@x.y" Or an object: { "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: "appli@x.y" Or an object containing field "id" of type string and optionally a field mode: {"id":"appli@x.y","mode":"local"} The field "mode" is a string equal to either "local" or "remote". **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: "appli@x.y" Or an object containing field "id" of type string. {"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 **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 **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 informations 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: { "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 */lib/systemd/user/afm-user-daemon.service*. ### ***afm-system-daemon*** options The options for launching **afm-system-daemon** are: -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 sytemd. -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: -a --application directory Includes the given application directory to the database base of applications. Can be repeated. -r --root directory 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) Set the default launch mode. The default value is 'local' -d --daemon Daemonizes the process. It is not needed by sytemd. -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 avaliable 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 avaliable applications or a more specific information about a given application. ### Launching application **afm-user-daemon** launches application. Its builds a secure environment for the application before starting it within a secured environment. Different kind of applications can be launched. This is set using a configuration file that describes how to launch an application of a given kind within a given mode. There is two launching modes: local or remote. Launching an application locally means that the application and its binder are launched together. Launching application remotely translates in only launching the application binder. The UI by itself has to be activated remotely by the requested (ie: HTML5 homescreen in a browser) Once launched, running instances of application receive a runid that identify them. ### 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, pause or resume a given application. ### Installing and uninstalling applications If the client own the right permissions, **afm-user-daemon** delegates that task to **afm-system-daemon**. Launcher Configuration ---------------------- It contains rules for launching applications. When **afm-user-daemon** has to launch an application, it looks for launch mode (local or remote), as well as for the type of application describe in ***config.xml*** widget configuration file. This tuple mode+type allows to select the adequate rule. Configuration file is **/etc/afm/afm-launch.conf**. It contains sections and rules. It can also contain comments and empty lines to improve readability. The separators are space and tabulation, any other character should have a meaning. The format is line oriented. The new line character separate the lines. Lines having only separators are blank lines and ignored. Line having character #(sharp) at first position are comment lines and ignored. Lines not starting with a separator are different from lines starting with a separator character. The grammar of the configuration file is defined below: CONF: *COMMENT *SECTION SECTION: MODE *RULE RULE: +TYPE VECTOR ?VECTOR MODE: 'mode' +SEP ('local' | 'remote') *SEP EOL TYPE: DATA *SEP EOL VECTOR: +SEP DATA *(+SEP NDATA) *SEP EOL DATA: CHAR *NCHAR NDATA: +NCHAR EOL: NL *COMMENT COMMENT: *SEP CMT *(SEP | NCHAR) NL NL: '\x0a' SEP: '\x20' | '\x09' CMT: '#' CHAR: '\x00'..'\x08' | '\x0b'..'\x1f' | '\x21' | '\x22' | '\x24'..'\xff' NCHAR: CMT | CHAR Here is a sample of configuration file for defining how to launch an application of types *application/x-executable*, *text/x-shellscript* and *text/html* in local mode: mode local application/x-executable text/x-shellscript %r/%c text/html /usr/bin/afb-daemon --mode=local --readyfd=%R --alias=/icons:%I --port=%P --rootdir=%r --token=%S --sessiondir=%D/.afb-daemon /usr/bin/web-runtime http://localhost:%P/%c?token=%S This shows that: - within a section, several rules can be defined - within a rule, several types can be defined - within a rule, one or two vectors can be defined - vectors are using %substitution - launched binaries must be defined with their full path ### mode local Within this mode, the launchers have either one or two description vectors. All of those vectors are treated as programs and are executed with 'execve' system call. The first vector is the leader vector and it defines the process group. The second vector (if any) is attached to the group defined by this first vector. ### mode remote Within this mode, the launchers have either one or two vectors describing them. The first vector is process as a program and is executed with system call 'execve'. The second vector (if any) defines a text that is returned to the caller. This mechanism can be used to return a uri for remote UI to connect on the newly launched application. The daemon ***afm-user-daemon*** allocates a port for each new remote application. The current implementation port allocation is incremental. A smarter (cacheable and discoverable) allocation should be defined. ### %substitutions Vectors can include sequences of 2 characters that have a special meaning. These sequences are named *%substitution* because their first character is the percent sign (%) and because each occurrence of the sequence is replaced, at launch time, by the value associated to sequences. Here is the list of *%substitutions*: - ***%%***: %. This simply emits the percent sign % - ***%a***: appid Holds application Id of launched application. Defined by the attribute **id** of the element **<widget>** of **config.xml**. - ***%b***: bindings In the future should represent the list of bindings and bindings directory separated by ','. Warning: not supported in current version. - ***%c***: content The file within the widget directory that is the entry point. For HTML applications, it represents the relative path to main page (aka index.html). Defined by attribute **src** of the element **<content>** within **config.xml**. - ***%D***: datadir Path of the directory where the application runs (cwd) and stores its data. It is equal to %h/%a. - ***%H***: height Requested height for the widget. Defined by the attribute **height** of the element **<widget>** of **config.xml**. - ***%h***: homedir Path of the home directory for all applications. It is generally equal to $HOME/app-data - ***%I***: icondir Path of the directory were the icons of the applications can be found. - ***%m***: mime-type Mime type of the launched application. Defined by the attribute **type** of the element **<content>** of **config.xml**. - ***%n***: name Name of the application as defined by the content of the element **<name>** of **config.xml**. - ***%P***: port A port to use. It is currently a kind of random port. The precise model is to be defined later. - ***%R***: readyfd Number of file descriptor to use for signaling readiness of launched process. - ***%r***: rootdir Path of directory containing the widget and its data. - ***%S***: secret An hexadecimal number that can be used to initialize pairing of client and application binder. - ***%W***: width Requested width for the widget. Defined by the attribute **width** of the element **<widget>** of **config.xml**. 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 pause rid **: pause the running instance rid - **afm-util resume rid **: resume the previously paused rid - **afm-util state rid **: get status of the running instance rid Here is how to list applications using ***afm-util***: afm-util runnables [afm-daemons]: pictures/afm-daemons.svg