Why can't I catch the following error?

New to Julia
1

I have created a simple web server using HTTP.jl for handling high-volume, low-latency simple requests. For performance, I spawn a separate thread on :default for each request.

Everything runs fine but after running tests using 200 concurrent connections, I get the following error when the requester stops sending requests:

┌ Error: handle_connection handler error.
│
│ ===========================
│ HTTP Error message:
│
│ ERROR: IOError: write: connection reset by peer (ECONNRESET)
│ Stacktrace:
│ [1] uv_write(s::Sockets.TCPSocket, p::Ptr{UInt8}, n::UInt64)
---- removed as forum software thought I was posting links
│
│ “”"
└ @ HTTP.Servers ~/usr/local/julia/reg/packages/HTTP/sJD5V/src/Servers.jl:483

I am not so concerned about the error itself as it could be that the test tool is dropping the connection. However, I am trying to catch these errors so it doesn’t clutter my logs, since this application could have thousands of connections. Here is the basic structure of the app:

function main()
global server_ready, http_server_port, http_max_conns, http_readtimeout
try
server_ready = true
HTTP.serve(ROUTER, “0.0.0.0”, http_server_port, stream=true, max_connections=http_max_conns, readtimeout=http_readtimeout)
catch
if isa(e, Base.IOError) && e.code == Base.UV_EPIPE
println(“Broken Pipe Error - Ignored”)
else
rethrow()
end
end
end

try
main()
catch e
println(“Error in main server loop”)
showerror(stdout, e)
end

However, when the connection reset error occurs, it is not caught by my exception handling code, regardless of how I structure it.

2

Hi and welcome to the forum :wave:

Please consider wrapping your code and terminal output in backticks (as described here: Please read: make it easier to help you ) for easier readability :slight_smile:

Regarding your actual problem:

  • What exactly is your desired output? If I understand correctly, your code should print "Broken Pipe Error - Ignored" if you encounter the error you mentioned, but keep running? What is the behavior you see instead? (exception/no exception; exact error message)
  • I think your code as-is should probably throw an UndefVarError if the HTTP error occurs because your catch block inside main() doesn’t assign the variable e. Are there some parts of the code missing?
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3

Thanks for the reply. I will pay more attention to formatting in future posts.

You are correct with what I am looking to see but what I get is either the handle connection error I posted or an equivalent Broken Pipe error.

Your second point is also correct (thanks!) but reinforces the idea that the exception isn’t being caught by my try/catch. I have fixed it and will test again to see if the try/catch was being ignored because of this.

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4

Errors that are wrapped in a bracket like that probably come from the @error logging macros. The underlying exception is handled and logged by the underlying library and not available to the calling code. There’s presumably a non-exception-handling way to retrieve the status for an HTTP error for programmatic handling of the error.

EDIT: And also probably a way to control the logging of said errors.

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5

I figured out that HTTP.jl uses LoggingExtras. I was able to suppress these error messages using an ActiveFilteredLogger.

Thanks for the help.

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