Under what circumstances will request_uri() return an "error" string?

[xt1234567]

i use the function _M.request_uri(self, uri, params) in http.lua file, the error message it returns is the "error" string. I would like to ask whether this is a problem on the requesting side or a problem returned by the responding side. If in request side,
What is the possible root cause?

[pintsized]

It can be either. A badly formed request may return nil, err -- for example if the URI cannot be parsed correctly -- before attempting to make a connection. But also an upstream connection error, or a send / read timeout can return nil, err.

The contents of the error string should make this obvious, but please post an example if it is not.

[xt1234567]

thank you for your reply！
In my scenario, local resp, err = request_uri(url, req_params)
if not resp, i will retry it and print the err content.
First，the content of err is just a string "error", this is where I'm confused.
Second, I retried the request and it succeeded, so it don't like the uri can't be parsed.

[pintsized]

That is odd, but I am quite certain the error string "error" could not be generated here. Note that in many cases we simply pass on the error message from the underlying cosocket.

You could try calling httpc.debug(true) globally. This will print noisy details about the generated request to your log, and so you can compare what this library is trying to do with something like curl, for example.

Please post a minimal yet complete working example that reproduces the issue if you need more help. I am guessing otherwise.