Developing Shiny Web Applications

Preamble

The following environment variables must be set before developing a shiny web application within the CSIAPPS ecosystem:

• CSIAPPS_CLIENT_ID: The client ID for the application registered in CSIAPPS.
• CSIAPPS_CLIENT_SECRET: The client secret for the application registered in CSIAPPS.
• CSIAPPS_REDIRECT_URL: The URL to which the application will redirect after authentication.
• CSIAPPS_SCOPE: (optional) The scope of the authentication request.

Example

Suppose that you have the following shiny web application:

library(shiny)

df = faithful[, 2]

ui <- fluidPage(

    titlePanel("Old Faithful Geyser Data"),

    sidebarLayout(
        sidebarPanel(
            sliderInput("bins",
                        "Number of bins:",
                        min = 1,
                        max = 50,
                        value = 30)
        ),

        mainPanel(
           plotOutput("distPlot")
        )
    )
)

server <- function(input, output) {

    output$distPlot <- renderPlot({
        bins <- seq(min(df), max(df), length.out = input$bins + 1)

        hist(df, breaks = bins, col = 'darkgray', border = 'white',
             xlab = 'Waiting time to next eruption (in mins)',
             main = 'Histogram of waiting times')
    })
}

shinyApp(ui = ui, server = server)

To migrate this app within the CSIAPPS ecosystem, we can leverage several functions provided by csiapps.

1. set_institute()

We specify which institute internal API calls should be made for (such as authentication redirects) by the application using set_institute().

# institute can be set to one of "csiontario" or "csipacific"
csiapps::set_institute("csiontario")

2. check_secrets()

We then run check_secrets() to ensure that all environment variables required have been set. The verbose argument, which is FALSE by default, can be set to TRUE to print out the values of the environment variables that are being checked. check_secrets() will throw an error if any of the required environment variables are not present, making it useful for debugging.

csiapps::check_secrets(verbose = FALSE)

3. global_wrapper()

For code defined outside but used within the server function, we use global_wrapper() to ensure that it is accessible by internal helper functions.

csiapps::global_wrapper({
  df = faithful[, 2]
})

4. ui_wrapper() and server_wrapper()

The ui page and server function can simply be wrapped by ui_wrapper() and server_wrapper(), respectively. These convenience functions include additional code to redirect the application to CSIAPPS for user authentication and provide aesthetic formatting.

# original code

ui <- ...

server <- ...

shinyApp(ui = ui, server = server)

# wrapped code

shinyApp(ui = csiapps::ui_wrapper(ui), server = csiapps::server_wrapper(server))

Summary

Therefore, the full code for the app, after migration, would look like this:

library(shiny)
library(csiapps)

# CSIAPPS Setup
set_institute("csiontario")
check_secrets()

global_wrapper({
  df = faithful[, 2]
})

# Define UI for application that draws a histogram
ui <- fluidPage(

    titlePanel("Old Faithful Geyser Data"),

    sidebarLayout(
        sidebarPanel(
            sliderInput("bins",
                        "Number of bins:",
                        min = 1,
                        max = 50,
                        value = 30)
        ),

        mainPanel(
           plotOutput("distPlot")
        )
    )
)

# Define server logic required to draw a histogram
server <- function(input, output) {

    output$distPlot <- renderPlot({
        bins <- seq(min(df), max(df), length.out = input$bins + 1)

        # draw the histogram with the specified number of bins
        hist(df, breaks = bins, col = 'darkgray', border = 'white',
             xlab = 'Waiting time to next eruption (in mins)',
             main = 'Histogram of waiting times')
    })
}

# Run the application 
shinyApp(ui = ui_wrapper(ui), server = server_wrapper(server))