Openresty: Make an http call with lua and return its parsed result

Question

My problem

I am using openresty to build a simple server.

Upon calling this server, it should make another call to a different server, fetch a JSON result, process it and return the parsed result.

The server should be implemented in openresty for reasons beyond the scope if this question.

Code

error_log /dev/stdout info;

events {
    worker_connections  14096;
}

http {
    access_log off;
    lua_package_path ";;/usr/local/openresty/nginx/?.lua;";

    server {
        keepalive_requests 100000;
        proxy_http_version 1.1;
        keepalive_timeout 10;

        location / {
        content_by_lua_block {
                res = ngx.location.capture('http://localhost:8080/functions.json')
                ngx.say(res.body)
            }
        }

        location /functions {
            root /usr/local/openresty/nginx/html/;
        }

        listen 0.0.0.0:80 default_server;
    }
}

Error log

2017/09/11 08:27:49 [error] 7#7: *1 open() "/usr/local/openresty/nginx/htmlhttp://localhost:8080/functions.json" failed (2: No such file or directory), client: 172.17.0.1, server: , request: "GET / HTTP/1.1", subrequest: "http://localhost:8080/functions.json", host: "localhost:8080"

My question

How can I make an HTTP GET request from within a Lua content block in nginx openresty?

score 6 · Answer 1 · answered Sep 11 '17 at 09:09

6

Capture will allow you to capture internal nginx locations and not absolute urls

error_log /dev/stdout info;

events {
    worker_connections  14096;
}

http {
    access_log off;
    lua_package_path ";;/usr/local/openresty/nginx/?.lua;";

    server {
        keepalive_requests 100000;
        proxy_http_version 1.1;
        keepalive_timeout 10;

        location / {
        content_by_lua_block {
                res = ngx.location.capture('/functions.json')
                ngx.say(res.body)
            }
        }
        location /functions.json {
            proxy_pass http://localhost:8080/functions.json;
        }

        location /functions {
            root /usr/local/openresty/nginx/html/;
        }

        listen 0.0.0.0:80 default_server;
    }
}

answered Sep 11 '17 at 09:09

Tarun Lalwani

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I tried `capture` in my code, but it was treated as a local file (see logs). – Adam Matan Sep 11 '17 at 10:02
Earlier or now? also try using `location = /functions.json {` instead if mine didn't work for you – Tarun Lalwani Sep 11 '17 at 10:04
Thanks, I solved it using a third-party http library: https://github.com/pintsized/lua-resty-http – Adam Matan Sep 11 '17 at 16:17
1

Yes you can do that, but this is recommended method from the author of the nginx lua module. See issue https://github.com/openresty/lua-nginx-module/issues/160 – Tarun Lalwani Sep 11 '17 at 16:26

score 5 · Answer 2 · answered Sep 11 '17 at 16:20

Solved using the lua-resty-http package. Copied the library to the nginx openresty root, and :

local http = require "resty.http"
local httpc = http.new()

local res, err = httpc:request_uri("http://127.0.0.1/functions.json", { method = "GET" })
// Use res.body to access the response

Openresty: Make an http call with lua and return its parsed result

My problem

Code

Error log

My question

2 Answers2