can't print the response header Set-Cookie in log

[tjliupeng]

Hi,

I try to print the response header Set-Cookie to log by:

header_filter_by_lua_block {
ngx.log(ngx.WARN, "Set-Cookie %s", ngx.resp.get_headers()['Set-Cookie'] or "None")
}

But I get nothing in access.log or error.log.

Thanks

[detailyang]

check the docs

Syntax: error_log file [level];
Default:    
error_log logs/error.log error;
Context:    main, http, mail, stream, server, location

the log level can be debug, info, notice, warn, error, crit, alert, or emerg. And level is error at default, your are using ngx.WARN to logging so it will be ignored. you can use ngx.ERR or set error_log level to warn

[tjliupeng]

Thanks. I change to ngx.ERR and something is printed in error.log. But it fail to get the Set-Cookie header as follow. If I change Set-Cookie to Connection, it can print the value of Connection. Seems 'or None' does not work.

2016/08/23 14:05:58 [error] 22020#22020: 1 failed to run header_filter_by_lua: header_filter_by_lua:2: bad argument #2 to 'log' (expected table to have __tostring metamethod)
stack traceback:
[C]: in function 'log'
header_filter_by_lua:2: in function <header_filter_by_lua:1> while reading response header from upstream, client: 15.107.4.15, server: 16.165.217.31, request: "POST /SM/ui HTTP/1.1", upstream: "http://15.107.4.15:13080/SM/ui", host: "16.165.217.31"
2016/08/23 14:05:58 [error] 22020#22020: 3 failed to run header_filter_by_lua: header_filter_by_lua:2: bad argument #2 to 'log' (expected table to have __tostring metamethod)
stack traceback:
[C]: in function 'log'
header_filter_by_lua:2: in function <header_filter_by_lua:1> while reading response header from upstream, client: 15.107.4.15, server: 16.165.217.31, request: "POST /SM/ui HTTP/1.1", upstream: "http://15.107.4.15:13081/SM/ui", host: "16.165.217.31"

[detailyang]

the error as the following:

header_filter_by_lua:2: bad argument #2 to 'log' (expected table to have __tostring metamethod)

it means your ngx.resp.get_headers()['Set-Cookie'] argument is table . you cannot log table directly unless you have __tostring metamethod.

I guess you upstream return more than set-cookie header. you can check this docs carefully

[tjliupeng]

@detailyang , you are right. Thanks.