Troubleshooting HTTP Request Failures in shinyapps.io

Issue/Error

When deploying a Shiny application to shinyapps.io, you may encounter the following error:

Warning: Error in curl::curl_fetch_memory: Failed sending HTTP request

Description

This error typically occurs when your Shiny application is attempting to make HTTP requests to external servers but encounters connectivity issues. This can happen due to several reasons:

• The external server is not responding or is blocking requests
• There are issues with the HTTP request configuration
• Rate limiting from the external API
• Network connectivity problems
• Malformed request headers

Solution

To resolve HTTP request failures in your shinyapps.io deployment, try the following steps:

1. Verify your HTTP request configuration:
   • Check for duplicate headers (especially Content-Type headers)
   • Ensure all URLs are properly formatted and accessible
   • Verify any authentication tokens or credentials are valid
2. Implement error handling:

   tryCatch({
     response <- curl::curl_fetch_memory(="curl::curl_fetch_memory(" https:="https:" api-endpoint.com="api-endpoint.com" )=")" #="#" handle="Handle" the="the" response="response" here="here" },="}," error="function(e)" {="{" message(="message(" failed="Failed" to="to" fetch="fetch" url:="URL:" ,="," e$message)="e$message)" implement="Implement" fallback="fallback" behavior="behavior" })="})">

3. Optimize request timing:
   • Avoid making requests during app startup if possible
   • Consider caching responses for frequently accessed data
   • Implement request throttling if dealing with rate limits
4. Test the external service availability:
   • Verify the API endpoint is accessible from your local machine
   • Check if the service has any known outages or maintenance windows
   • Confirm your access permissions to the external service

If you're still having issues, you can reach out to Support by opening a ticket here.