Application Flow

The application workflow is as follows:

First, a user enters the following at the CLI command prompt:

> configure
# set sync helloworld  message "Hello SDK World!"

To initialize itself on the Routing Engine, the application next begins a series of steps in main(), culminating in a call to the junos_app_init() function:

• Call junos_create_app_ctx() to create a context object

• Call junos_set_app_cb_config_read() to set up the callback helloworld_config_read(), which will read the configuration settings

• Call junos_set_app_cb_init() to set up the callback helloworld_init(), which will perform additional initialization operations

• Call junos_app_init() to invoke the initialization process.

The code for this is as follows:

int
main (int argc, char ** argv)
{
    int ret = 0;
    junos_sdk_app_ctx_t ctx;

    /* Create an application context */
    ctx = junos_create_app_ctx(argc, argv, DNAME_HELLOWORLDD,
                               master_menu, PACKAGE_NAME, SEQUENCE_NUMBER);
    if (ctx == NULL) {
        return -1;
    }

    /* Set config read call back */
    if ((ret = junos_set_app_cb_config_read(ctx, helloworld_config_read))) {
        goto cleanup;
    }

    /* Set init call back */
    if ((ret = junos_set_app_cb_init(ctx, helloworld_init))) {
        goto cleanup;
    }

    /* Calling junos_app_init */
    ret = junos_app_init(ctx);

The system next executes the following operations:

1. Calls the helloworld_init() function to perform additional initialization needed by the daemon. (see Main Function: Performing Setup and Initializing the Daemon)

2. Opens the configuration database and calls the helloworld_config_read() function to read and apply the daemon's configuration. (see Creating the Tree and Adding Messages)

3. Converts the process into a daemon and enters the ISC event loop to wait for events or user commands.

The application sets up the menu of commands in the helloworld_ui.c file, which also includes the code to display the message; this commands menu is the array passed to junos_daemon_init() in the master_menu parameter. (See Creating the Commands Menu Array).

Loading and Reading the Message

To load the message into the configuration database, the application:

• Initializes a patricia tree data structure to store the message
• Clears any previously stored messages
• When it finds the new message, adds it to the tree.

For more information, see Creating the Tree and Adding Messages.

Displaying a Message

Assume that the user now enters the following command:

#exit
>show sync helloworld message

The daemon fetches the message (see Reading the Configuration ) and then uses ODL to format and display the message (see Coding, Fetching, and Displaying the Output.)

Contents of this Topic

This topic continues with the following sections:

• Main Function: Performing Setup and Initializing the Daemon

• Creating the Tree and Adding Messages

• Creating the User Interface

• Creating the Commands Menu Array

• Defining the Input Command Hierarchy, Reading the Configuration, and Adding the Message

• Coding, Fetching, and Displaying the Output

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