Export shows badgateway in nginx

`I am using an import-export model in my Django admin panel it works very well...if the records goes more means on that time also i am export means it gives an error like Bad Gateway...if i click export it asks what format it wants like that then it takes too much of timing and gives an Bad Gateway.I don't Know why

class SongListAdmin(ImportExportModelAdmin):
      list_display = ('article_title','song_views','date_posted','date_updated','listview')
      search_fields=('article_title','Tags__tag_name')

this is my code...In my SongList table having an record 16,000 if i click export from my admin panel means it goes an Bad Gateway....why

If i export i need to 16,000 records but it does'nt comes the actual result it goes an an badgateway in nginx why``