CODEWITHSUNDEEP
dockernginxdns
Y Talansky
Y Talansky

Reputation: 401

Nginx caching DNS look ups and ignoring my resolver settings

I am using docker swarm. I placed an nginx container in front of my API for caching purposes. Since every time I deploy my API it creates a new internal IP I am using the name of my service tasks.api as per swarm documentation. Below is my location block

proxy_cache_path /var/cache/nginx/ta_api levels=1:2 keys_zone=api_cache:10m max_size=10g
                  inactive=60m use_temp_path=off;

server {
    listen       80;
    server_name  localhost;

    location / {
      proxy_pass http://tasks.api:10010;
      proxy_http_version 1.1;
      proxy_set_header Upgrade $http_upgrade;
      proxy_set_header Connection 'upgrade';
      proxy_set_header Host $host;
      proxy_buffering on;
      proxy_cache api_cache;
      proxy_cache_bypass $http_upgrade;
      # Add header to see if response was cached
      add_header X-Cache-Status $upstream_cache_status;

      # Allow one cache-update request at a time sent to an origin server.
      proxy_cache_lock on;
      # Permit revalidation of stale cached responses.
      proxy_cache_revalidate on;

      # proxy_cache_valid 200 1d;
      # Delivering Cached Content When the Origin is Down
      proxy_cache_use_stale error timeout invalid_header updating
                            http_500 http_502 http_503 http_504;

      # Do all updates in background. With proxy_cache_use_stale, allows stale
      # cached responses to be served.
      proxy_cache_background_update on;
    }
}

I also added resolver 127.0.0.11 ipv6=off valid=15s; to my http block. However, when I redeploy my API and it gets a new API nginx still attempts to send to the old IP.

I am running an nginx container tag nginx:1.15.12-alpine when I install bind-tools on the nginx container I can see that I am getting the new IPs using dig tasks.api

I am at a loss what to try next. I can hardcode private IPs, but that is not the docker way...

Upvotes: 7

Views: 11419

Answers (1)

JamesJJ
JamesJJ

Reputation: 954

NGINX will only do DNS lookups at startup and cache forever for fixed hostnames. To enable DNS lookup during runtime, you need to change the fixed hostname to a dynamic variable. So in the OP case, change the original proxy_pass line to:

set $target_host tasks.api ;
proxy_pass http://$target_host:10010;

Upvotes: 15

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