How to get upstream information inside serverless-pre-function?

[rohitkrishna-marneni]

Consider this snippet that I have for my apisix route configuration

        plugins:
          serverless-pre-function:
            functions:
              - |-
                return function(conf, ctx)
                    local cookie = ngx.var.cookie_sticky_session
                    local upstream_addr = ngx.var.upstream_addr

                    ngx.log(ngx.ERR, "Checking sticky_session cookie", upstream_addr) 
                    if not cookie then
                        -- Randomly assign box1 or box2
                        local value = (math.random(2) == 1) and "box1" or "box2"
                        ngx.log(ngx.ERR, "Setting sticky_session cookie to: " .. value)
                        ngx.header["Set-Cookie"] = "sticky_session=" .. value .. "; Path=/; HttpOnly; Max-Age=36000"
                    else
                        ngx.log(ngx.ERR, "sticky_session cookie already set: " .. cookie)
                    end
                    --ngx.log(ngx.ERR, "Request handled by upstream: " .. upstream_addr .. " with sticky_session: " .. (cookie or "nil"))
                end
            phase: rewrite

The upstream_addr is always nil for some reason. And I also want to find upstream_host and other upstream related details here. Is it possible to perhaps pull upstream_addr, upstream_uri, upstream_host from conf or ctx parameters? Or maybe the phase attribute of rewrite is wrong? I tried the same config above with phase as access and it also gave upstream_addr as nil

[dosubot[bot]]

I found a similar unsolved discussion titled "how do I get upstream host in serverless-pre-function?" which might be relevant to your query ^[1].

Regarding your question, the upstream_addr and other upstream-related variables like upstream_host are typically populated later in the request lifecycle, often after the access phase. In the rewrite and access phases, these variables might not be available yet, which is why you're seeing nil.

Unfortunately, there isn't a straightforward way to access these upstream details in the serverless-pre-function plugin during the rewrite or access phases. The upstream information is usually set during the proxying phase, which occurs after these phases.

If you need to work with upstream information, you might need to consider a different approach or phase where this information is available. However, based on the current capabilities, accessing upstream details directly in the serverless-pre-function during the rewrite or access phases is not feasible.

To continue talking to Dosu, mention @dosu.

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