COHORTE system is composed of several Nodes. Only one node is specified to be Top Composer. It manages the components distribution among the available participating nodes.
In this chapter, we will detail how to create and start COHORTE Nodes using simple command lines.
To create COHORTE node, you have to use the provided
Ensure to have installed COHORTE on your system and that the COHORTE_HOME environment variable is set to the installation path of COHORTE (see setup guide).
This command has the following arguments :
-h, --help show this help message and exit -n NODE_NAME, --name NODE_NAME Name of the node -c COMPOSITION_NAME, --composition-name COMPOSITION_NAME application's composition name -a APP_ID, --app-id APP_ID application's ID
You should at least provide
NODE_NAME (node name).
COMPOSITION_NAME is a symbolic name given to your application’s composition (set of components of your application that will be instantiated by Cohorte), and the
APP_ID is you application’s secret token that will be shared between the different nodes of your application. You can set it at startup time if you need (see further).
It is the
APP_ID which allows the different nodes of your application to be discovered automatically while rejecting other nodes with different specified
This command will create a directory containing the following structure:
- mynode corresponds to the provided name by the user using the
- run is the startup script. It will be detailed in the next section (Starting nodes)
- repo is a directory where user provided bundles should be placed.
- conf is a directory containing configuration files. Only two configuration files are created initially (composition.js and run.js), other files will be generated in this directory when starting the node using the
Here is the content of the generated
conf/composition.jsfile. You should add component descriptions on the indicated zone (see Composition Specification).
composition.js template is generated only when the --composition-name option is set. This is the case of a Top Composer Node which will be responsible for controlling the instantion of component on the different Nodes.
conf/run.js file contain the initial startup arguments. Here is its content :
The next section will give more information about the startup options.
To start a COHORTE node, you have to use the generated
run command (this command calls
cohorte-start-node internal command).
There are different kind of arguments depending on the use of the actual node.
-a APP_ID, --app-id APP_ID Application's ID
All the nodes participating for a given application should have the same
Startup configuration options
--use-config CONFIG_FILE Configuration file to use for starting cohorte node. By default the conf/run.js file is used if available --update-config Update startup configuration file with provided options --show-config Show startup configuration file content -i INTERPRETER, --interpreter INTERPRETER Path to Python interpreter to use (python2 or python3) -b BASE_ABSOLUTE_PATH, --base BASE_ABSOLUTE_PATH absolute file path of the node's directory
We can write the startup configurations in a separate JSON file (see How to use startup configuration files section). This options will simplify the command options list and allows sharing the same startup configurations between several nodes.
Information about the node to start
-n NODE_NAME, --node NODE_NAME Node name --top-composer IS_TOP_COMPOSER Flag indicating that this node is a Top Composer --composition-file COMPOSITION_FILE Composition file (by default 'composition.js'). All composition files should be placed on 'conf' directory --auto-start AUTO_START Auto-start the composition if this node is a Top Composer --http-port HTTP_PORT Node HTTP port --shell-port SHELL_PORT Node Remote Shell port --use-cache USE_CACHE Use cache to accelerate startup time (experimental) --recomposition-delay RECOMPOSITION_DELAY Delay in seconds between two recomposition tentatives
We can provide a different node name than the already provided when the node is created (by using
--node argument). One important option of cohorte nodes is the
--top-composer. If set, the node will be considered as a Top Composer (manages all the distribution of components among the available nodes). Users can also provide customised informations such as the http port to use for the web-admin component (see monitoring chapter), or the port to use for the remote shell-admin component.
--transport TRANSPORT_MODES Transport mode (http and/or xmpp - seperated by comma)
--transport option allow the user to choose which transport protocol to use between the actual node and the other nodes participating in the same application. You can provide a common seperated list of the supported protocols (
xmpp for the moment). Each protocol needs additional configuration options that should be provided seperataly using dedicated options.
HTTP options :
--http-ipv HTTP_IPV HTTP IP version to use (4 or 6)
XMPP options :
--xmpp-server XMPP_SERVER XMPP server --xmpp-port XMPP_PORT XMPP server port --xmpp-user-jid XMPP_JID XMPP User jid (not yet implemented - annonymous mode only) --xmpp-user-password XMPP_PASSWORD XMPP User password
If the XMPP server accepts
anonymous connections, you can connect to it without a JID. However, in any cases, the server should accept multi-user chat.
How to use startup configuration files
To avoid re-typing the same options each time a node is started, or to share the same configuration between several nodes, you can provide a startup configuration file which contains such startup configurations. En complet exemple of such file is given hereafter.
- To show the content of the startup configuration file :
- To use other configuration file than the default run.js file :
- Update the startup configuration using command options (–some-configuration should be replaced with a supported options list):
This will update all the provided options within the startup configuration file (run.js).
The discovery is done using TCP multi-caste feature. This limits the scope of the discovered COHORET nodes to only available at a local network area LAN. To deploy you COHORTE nodes at the Internet level, you should use XMPP mode.
You need to start the Top Composer with the following at least configurations :
You can use the two transport protocols in the same time. At runtime, only one is used, if it does not work COHORTE choose the other one.
Herald, the framework used as discovery and transport layer in COHORTE, has a generic architecture allowing it to add more discovery and transport protocols. Other connection modes are under development and will be released in future version of COHORTE.