[[PageOutline(1-3,Table of Contents,inline)]]

= Introduction =

== Architectural Overview ==
[[Image(arhi.png, center)]]

The Check architecture consists of the following entities:
 * WSN Island: Sensor nodes organize into a multi-hop wireless network with tree topology in which some nodes act as routers for the end node leaves.
 * Edge Router: An embedded network coordinator. Acts as a sink to the sensor node data and routes the island network traffic to an IPv6 network.
 * Gateway: Binary Web Services (COAP) running on a machine in the same network with the Edge Router.
 * Check Services: Self-healing, Task Scheduling and Monitoring Framework. 

== Software Architecture ==
[[Image(sensei+rum.png, center)]]
= Monitoring and reprogramming=

== Reprogramming - Gateway Watchdog ==

The SENSEI Gateway Watchdog is a monitoring and control service for the SENSEI Gateway. It allows for remote starting, stoping and updating the gateway code and can report the version string and uptime of the currently running gateway binary.

=== Software Requirements ===

Installing the Gateway Watchdog requires the following software packages:

 * [http://www.ubuntu.com/ Linux PC (Ubuntu)] 
 * g++, make
 * [http://www.alhem.net/Sockets/ Sockets C++ library] (Also included in lib/Sockets-2.3.7; make clean; make; make install)
 * libxml2, libxml2-dev
 * libssl, libssl-dev

=== Project Organization ===

The watchdog shares its code with the gateway implementation and can be found in the [https://ncit-cluster.grid.pub.ro/trac/Sensei-WP5/browser/gateway /gateway] folder in the SVN.

 * [https://ncit-cluster.grid.pub.ro/trac/Sensei-WP5/browser/gateway/bin /bin] executables
 * [https://ncit-cluster.grid.pub.ro/trac/Sensei-WP5/browser/gateway/src /src] Gateway and Watchdog Code
 * [https://ncit-cluster.grid.pub.ro/trac/Sensei-WP5/browser/gateway/xml /xml] Location of resource descriptions
 * [https://ncit-cluster.grid.pub.ro/trac/Sensei-WP5/browser/gateway/lib /lib] Sockets++ library
 * [https://ncit-cluster.grid.pub.ro/trac/Sensei-WP5/browser/gateway/config /config] Configuration files (unused)
 * [https://ncit-cluster.grid.pub.ro/trac/Sensei-WP5/browser/gateway/log /log] Log files (unused)

=== Compiling the Gateway Watchdog ===

Some packages are required to be installed prior to the compilation of the Gateway Watchdog. Please install the following packages from the Ubuntu repository if you did not do already so.

{{{
$ sudo apt-get install gcc g++ libssl-dev libxml2-dev
}}}

Sockets library also needs to be installed:

{{{
$ cd ./lib/Sockets-2.3.7
$ make clean
$ make
$ sudo make install
}}}

The top-level Makefile will build everything with the following, which places the executables in ./bin.

{{{
make
}}}

To clean everything do

{{{
make clean
}}}

=== Running the Gateway Watchdog ===

The watchdog must be run from the root of the project

{{{
./bin/watchdog
}}}

Available command line options are:
-p HTTPD port (default: 9000) [[BR]]
-s HTTPD hostname for inserting in resource desciption (default: localhost) [[BR]]
-d domain name inserted in resource description (default: example.com) [[BR]]
-w WSAN island name inserted in resource description (default: Example) [[BR]]
-f folder where the gateway binary can be found (default: ./) [[BR]]
-c gateway binary filename (default: sensei-gateway) [[BR]]
-cert ssl certificate filename, also enables https operation [[BR]]
-pass ssl certificate passphrase, necessary if the certificate file is encrypted [[BR]]

The SENSEI Gateway Watchdog server runs by default on port 9000. It exposes the following URIs:
 * /start - a POST request starts the gateway if not already started
 * /stop - a POST request stops the gateway
 * /update - a POST request with a form that has a 'file' field named 'code' updates the gateway binary, a 'text' field named 'version' can also be sent as the version string for the newly uploaded binary, otherwise version string will be taken from the uploaded file
 * /uptime - a GET request returns the uptime of the gateway in seconds or -1 if the gateway is not started
 * /version - a GET request returns the gateway version string, if one is available.

For the /start, /stop and /uptime urls GET requests are also accepted. They return an HTML page that allows easy access to the operations from a browser.

=== Test demo ===

The Gateway Watchdog provides monitoring and control of the SENSEI Gateway. To run a demo, please start the Watchdog service by giving the following commands in a console:

{{{
$ make
$ ./bin/watchdog -f bin/ -c sensei-gateway -d pub.ro -w test
}}}

This will start the Gateway Watchdog which runs an http server at '''localhost:9000'''. You will be able to see the registered gateway watchdog URIs by querying the Resource Directory at http://sensei-dev1.grid.pub.ro:8184/rd. A possible response from the Resource directory is shown below.

[[Image(rd.png, center)]]

The watchdog service will now accept requests at the following URIs:

 * Start Gateway         http://localhost:9000/start
 * Stop Gateway          http://localhost:9000/stop
 * Update Gateway code   http://localhost:9000/update
 * Gateway uptime        http://localhost:9000/uptime
 * Gateway version       http://localhost:9000/version

As an example, by pointing your browser to the [http://localhost:9000/start Start Gateway] URI you should see following response

[[Image(start.png, center)]]

Clicking the Start button will start the gateway if it is not already started. You can check that the gateway is running by clicking the following link http://localhost:8000

By pointing your browser to the [http://localhost:9000/stop Stop Gateway] URI you should see the following response

[[Image(stop.png, center)]]

Clicking the Stop button will stop the gateway.

By pointing your browser to the [http://localhost:9000/update Update Gateway code] URI you will be able to upload a new binary to the gateway and, optionally, specify a version string for this binary, as shown bellow.

[[Image(update2.png, center)]]

Note that to run the new gateway code you have to stop and then start the gateway.

= Scheduling =
= Self-healing =