Log Format with $request_body Not working

I am trying to log the incomming HTTP Request with the below given
log_fromat. It is logging only ‘-’. could you please help what I am
doing
wrong.

Thanks in advance.

nginx.conf

http {
include mime.types;
default_type application/octet-stream;
log_format postdata $request_body;
types_hash_bucket_size 64;
server_names_hash_bucket_size 128;

server {
listen 9080;
server_name X1n2d23;

  location / {
        proxy_set_header X-Forwarded-For $proxy_add_x_forwarded_for;
          proxy_set_header X-Real-IP $remote_addr;
          proxy_set_header Host $http_host;
          proxy_redirect off;
          proxy_pass http://www.google.com;
        access_log  /nginx/install/log/nginx/log_server.log postdata 

;
}
}
}

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