5.7. Lab 6 - File IO

1. Start an NGINX docker instance with the file_io app by running the following commands: This places the file_io.conf file and file_io.js files into the running NGINX instance.

   EXAMPLE=file_io
   docker run --rm --name njs_example  -v $(pwd)/conf/$EXAMPLE.conf:/etc/nginx/nginx.conf:ro  -v $(pwd)/njs/$EXAMPLE.js:/etc/nginx/example.js:ro -p 80:80 -p 8090:8090 -d nginx
   

   The nginx.conf will be as follows, for the /version it returns a version from the njs, /push will add info, /flush will remove info, /read will output the info.

   ...
   
   http {
      js_include example.js;
   
      server {
           listen 80;
   
           location /version {
               js_content version;
           }
   
           location /push {
               js_content push;
           }
   
           location /flush {
               js_content flush;
           }
   
           location /read {
               js_content read;
           }
      }
    }
   

   The njs code has 3 functions, push to store data in a file, flush to empty the data in file, read to output the data in file.

   var fs = require('fs');
   var STORAGE = "/tmp/njs_storage"
   
   function push(r) {
      fs.appendFileSync(STORAGE, r.requestBody);
      r.return(200);
   }
   
   function flush(r) {
      fs.writeFileSync(STORAGE, "");
      r.return(200);
   }
   
   function read(r) {
      var data = "";
      try {
          data = fs.readFileSync(STORAGE);
      } catch (e) {
      }
   
      r.return(200, data);
   }
   

2. To show this run the following commands:

   curl http://localhost/read
   200 <empty reply>
   
   curl http://localhost/push -X POST --data 'AAA'
   200
   
   curl http://localhost/push -X POST --data 'BBB'
   200
   
   curl http://localhost/push -X POST --data 'CCC'
   200
   
   curl http://localhost/read
   200 AAABBBCCC
   
   curl http://localhost/flush -X POST
   200
   
   curl http://localhost/read
   200 <empty reply>
   
   docker stop njs_example