content_by_lua_block deletes request body

[Coshgun Huseynov]

Hello. I wanted to make some changes on existing nginx configuration. My previous configuration was like this:

Then I added content_by_lua_block as below:

My /serviceprovider actually accepts JSON request in POST. When I send request after adding lua block I get error message "Invalid JSON: Empty string", but It writes request body to file successfully. 

I think this lua block deletes request body after writing it to file. I only want that location block worked as usual but in addition to write request body to a file.