there is an openresty load balancer in front of several instances of container app, the load balancer will use round robbin to route traffic to each app instance.
Is there a way I can record the paired backend server IP address into redis? the upstream is fixed, it is dynamic.
I tried to use upstream but it seems only work with fixed upstream {}, not dynamic one
docker-compose up --scale nginx_html_app=2
-- this is docker-compose.yml
nginx_html_app:
build: nginx_html_app
proxy:
build: proxy
ports:
- "9000:80"
-- this is proxy.conf
server{
listen 80;
set $upstream http://nginx_html_app
location / {
some_lua_block{
# get paired backend IP, eg: 172.18.0.3 (nginx_html_app 1)
# save to redis (know how to do this)
}
proxy_pass $upstream
}
}
Upstream IP and port are available in ngx.var.upstream_addr variable, in header_filter_by_lua and log_by_lua. But logging in the first place will make requests wait on your writes to complete, and in the second one network sockets aren't available, so you need to queue your logging and fire it in a timer.
Something like that (untested but should help you to get the idea):
app.lua - separate file, we need it so that global state will be cached:
M = {}
local queue = {}
function M.init()
ngx.timer.every(1.0, function(premature)
if premature then return end
-- push queue to redis and clear it
end)
end
function M.log()
queue[#queue+1] = ngx.var.upstream_addr
end
return M
nginx:
init_worker_by_lua_block { require('app.lua').init() }
log_by_lua_block { -- or header_filter_by_lua_block
require('app.lua').log()
}
I have an openresty nginx to proxy elasticsearch. So the grafana client contacts nginx and nginx in return fetches the response from elasticsearch. The goal is to change the http status to 504 if the response body from the elasticsearch contains the key "timedout": true
The response body is read using body_by_filter_lua_block but this directive doesn't support to change the http status.
http {
lua_need_request_body on;
server {
listen 8000;
location / {
proxy_pass "http://localhost:9200"
header_filter_by_lua_block {
ngx.header.content_length = nil
}
body_filter_by_lua_block {
if string.find(ngx.arg[1], "\"timedout\":true") then
ngx.arg[1] = nil
}
}
}
}
The above code just makes the response body nil . But Is there a way to change the http status ? Or if it's not supported in nginx , is there any other proxy server which can do this job ?
Any help would be appreciated.
You cannot change a status within body_filter_by_lua_block, because at this moment all response headers already sent downstream.
If you definitely need it - don't use proxy_pass.
Instead use content_by_lua_block and within it use lua-resty-http to issue a request, read full body, analyze it and respond with any status code you want.
This approach is full buffered and may have significant performance implication for big responses.
Also you should keep in mind that body may be compressed.
I use nginx to proxy and hold persistent connections to far away servers for me.
I have configured about 15 blocks similar to this example:
upstream rinu-test {
server test.rinu.test:443;
keepalive 20;
}
server {
listen 80;
server_name test.rinu.test;
location / {
proxy_pass https://rinu-test;
proxy_http_version 1.1;
proxy_set_header Connection "";
proxy_set_header Host $http_host;
}
}
The problem is if the hostname can not be resolved in one or more of the upstream blocks, nginx will not (re)start. I can't use static IPs either, some of these hosts explicitly said not to do that because IPs will change. Every other solution I've seen to this error message says to get rid of upstream and do everything in the location block. That it not possible here because keepalive is only available under upstream.
I can temporarily afford to lose one server but not all 15.
Edit:
Turns out nginx is not suitable for this use case. An alternative backend (upstream) keepalive proxy should be used. A custom Node.js alternative is in my answer. So far I haven't found any other alternatives that actually work.
Earlier versions of nginx (before 1.1.4), which already powered a huge number of the most visited websites worldwide (and some still do even nowdays, if the server headers are to be believed), didn't even support keepalive on the upstream side, because there is very little benefit for doing so in the datacentre setting, unless you have a non-trivial latency between your various hosts; see https://serverfault.com/a/883019/110020 for some explanation.
Basically, unless you know you specifically need keepalive between your upstream and front-end, chances are it's only making your architecture less resilient and worse-off.
(Note that your current solution is also wrong because a change in the IP address will likewise go undetected, because you're doing hostname resolution at config reload only; so, even if nginx does start, it'll basically stop working once IP addresses of the upstream servers do change.)
Potential solutions, pick one:
The best solution would seem to just get rid of upstream keepalive as likely unnecessary in a datacentre environment, and use variables with proxy_pass for up-to-date DNS resolution for each request (nginx is still smart-enough to still do the caching of such resolutions)
Another option would be to get a paid version of nginx through a commercial subscription, which has a resolve parameter for the server directive within the upstream context.
Finally, another thing to try might be to use a set variable and/or a map to specify the servers within upstream; this is neither confirmed nor denied to have been implemented; e.g., it may or may not work.
Your scenario is very similar to the one when using aws ELB as uptreams in where is critical to resolve the proper IP of the defined domain.
The first thing you need to do and ensure is that the DNS servers you are using can resolve to your domains, then you could create your config like this:
resolver 10.0.0.2 valid=300s;
resolver_timeout 10s;
location /foo {
set $foo_backend_servers foo_backends.example.com;
proxy_pass http://$foo_backend_servers;
}
location /bar {
set $bar_backend_servers bar_backends.example.com;
proxy_pass http://$bar_backend_servers;
}
Notice the resolver 10.0.0.2 it should be IP of the DNS server that works and answer your queries, depending on your setup this could be a local cache service like unbound. and then just use resolve 127.0.0.1
Now, is very important to use a variable to specify the domain name, from the docs:
When you use a variable to specify the domain name in the proxy_pass directive, NGINX re‑resolves the domain name when its TTL expires.
You could check your resolver by using tools like dig for example:
$ dig +short stackoverflow.com
In case is a must to use keepalive in the upstreams, and if is not an option to use Nginx +, then you could give a try to openresty balancer, you will need to use/implement lua-resty-dns
A one possible solution is to involve a local DNS cache. It can be a local DNS server like Bind or Dnsmasq (with some crafty configuration, note that nginx can also use specified dns server in place of the system default), or just maintaining the cache in hosts file.
It seems that using hosts file with some scripting is quite straightforward way. The hosts file should be spitted into the static and dynamic parts (i.e. cat hosts.static hosts.dynamic > hosts), and the dynamic part should be generated (and updated) automatically by a script.
Perhaps it make sense to check from time to time the hostnames for changing IPs, and update hosts file and reload configuration in nginx on changes. In case of some hostname cannot be resolved the old IP or some default IP (like 127.0.1.9) should be used.
If you don't need the hostnames in the nginx config file (i.e., IPs are enough), the upstream section with IPs (resolved hostnames) can be generated by a script and included into nginx config — and no need to touch the hosts file in such case.
I put the resolve parameter on server and you need to set the Nginx Resolver in nginx.conf as below:
/etc/nginx/nginx.conf:
http {
resolver 192.168.0.2 ipv6=off valid=40s; # The DNS IP server
}
Site.conf:
upstream rinu-test {
server test.rinu.test:443;
keepalive 20;
}
My problem was container related. I'm using docker compose to create the nginx container, plus the app container. When setting network_mode: host in the app container config in docker-compose.yml, nginx was unable to find the upstream app container. Removing this fixed the problem.
we can resolve it temporarily
cd /etc
sudo vim resolv.conf
i
nameserver 8.8.8.8
:wq
then do sudo nginx -t
restart nginx it will work for the momment
An alternative is to write a new service that only does what I want. The following replaces nginx for proxying https connections using Node.js
const http = require('http');
const https = require('https');
const httpsKeepAliveAgent = new https.Agent({ keepAlive: true });
http.createServer(onRequest).listen(3000);
function onRequest(client_req, client_res) {
https.pipe(
protocol.request({
host: client_req.headers.host,
port: 443,
path: client_req.url,
method: client_req.method,
headers: client_req.headers,
agent: httpsKeepAliveAgent
}, (res) => {
res.pipe(client_res);
}).on('error', (e) => {
client_res.end();
})
);
}
Example usage:
curl http://localhost:3000/request_uri -H "Host: test.rinu.test"
which is equivalent to:
curl https://test.rinu.test/request_uri
I'm trying to configure SSL-passthrough for multiple webapps using the same nginx server (nginx version: nginx/1.13.6), but when restarting the nginx server, I get an error complaining that
nginx: [emerg] "stream" directive is duplicate
The configuration I have is the following:
2 files for the ssl passthrough that look like this:
server1.conf:
stream {
upstream workers {
server 192.168.1.10:443;
server 192.168.1.11:443;
server 192.168.1.12:443;
}
server {
listen server1.com:8443;
proxy_pass workers;
}
}
and server2.conf:
stream {
upstream workers {
server 192.168.1.20:443;
server 192.168.1.21:443;
server 192.168.1.22:443;
}
server {
listen server2.com:8443;
proxy_pass workers;
}
}
If I remove one of the two files, then nginx starts correctly.
How can this be achieved?
Thanks,
Cristi
Streams work on Layer 5, and cannot read encrypted traffic (which is Layer 6 on the OSI model), and thus cannot tell apart requests hitting server1.com and server2.com unless they are pointing to different IPs.
This can be solved by one of the following solutions
Decrypt the traffic on nginx, then proxy-pass it to backend processes/wockers using HTTP.
Bind server1.com to a port that is different to server2.com.
Get an additional IP address and bind server2.com on that.
Get an additional load balancer and move server2.com there.
I'm looking for a way to specify a port range in the nginx upstream block.
Is there a way to turn this:
upstream backend {
least_conn;
server 127.0.0.1:3000;
server 127.0.0.1:3001;
server 127.0.0.1:3002;
server 127.0.0.1:3003;
server 127.0.0.1:3004;
server 127.0.0.1:3005;
}
into something like this?:
upstream backend {
least_conn;
server 127.0.0.1:[3000:3005]
}
One way to approach to operate host with Openresty which is based on Nginx and is capable of running Lua plugins. The snippet of code to make it work would look like this
upstream backend {
balancer_by_lua_block {
local balancer = require "ngx.balancer"
local start_port=3000
local max_port=start_port+5
repeat
local ok, err = balancer.set_current_peer('127.0.0.1', start_port)
if not ok then
ngx.log(ngx.ERR, "failed to set the current peer: ", err)
return ngx.exit(500)
end
start_port=start_port+1
until start_port>max_port
}