ngx.flush throws runtime error

[tokers]

Hi!

I found ngx.flush throws a Lua runtime error after the ngx.print was called by accident.

you can reproduce the problem by the following nginx configuration.

server {
    listen 8081;
    server_name _;
    location / {
        content_by_lua_block {
            ngx.say("Hello, World!")
            ngx.flush()
        }
    }
}

curl -v http://127.0.0.1:8081/ -H 'If-Unmodified-Since: Mon, 17 Apr 2006 03:10:35 GMT'

Then you will see something like this in the corresponding error.log:

2017/08/02 16:37:50 [error] 21399#21399: *3 lua entry thread aborted: runtime error: content_by_lua(nginx.conf:42):3: no request ctx found
stack traceback:
coroutine 0:
        [C]: in function 'flush'
        content_by_lua(nginx.conf:42):3: in function <content_by_lua(nginx.conf:42):1>, client: 127.0.0.1, server: _, request: "GET / HTTP/1.1", host: "127.0.0.1:8081"

After reading the related codes, i find the problem is caused by ngx_http_not_modified_header_filter at the earliest, which jumps to ngx_http_filter_finalize_request when ngx_http_test_if_unmodified returns 0, and ngx_http_filter_finalize_request cleans ctx of all the http modules, sets r->filter_finalize to 1.

Then we calling ngx.flush, we will get the provious runtime error because the ctx of ngx_lua is cleaned.

Maybe we should set the ctx of ngx_lua when r->filter_finalize is equal to 1 in ngx_http_lua_ngx_flush, like ngx_http_lua_handle_exit and others? Or we can mark it in the doc?

openresty version in my local machine:

nginx version: openresty/1.11.2.4
built by gcc 7.1.1 20170526 (Red Hat 7.1.1-2) (GCC)
built with OpenSSL 1.0.2k  26 Jan 2017
TLS SNI support enabled
configure arguments: --prefix=/usr/local/openresty/nginx --with-cc-opt='-O2
-I/usr/local/openresty/zlib/include -I/usr/local/openresty/pcre/include
-I/usr/local/openresty/openssl/include' --add-module=../ngx_devel_kit-0.3.0
--add-module=../echo-nginx-module-0.60 --add-module=../xss-nginx-module-0.05
--add-module=../ngx_coolkit-0.2rc3 --add-module=../set-misc-nginx-module-0.31
--add-module=../form-input-nginx-module-0.12
--add-module=../encrypted-session-nginx-module-0.06
--add-module=../srcache-nginx-module-0.31 --add-module=../ngx_lua-0.10.8
--add-module=../ngx_lua_upstream-0.06 --add-module=../headers-more-nginx-module-0.32
--add-module=../array-var-nginx-module-0.05 --add-module=../memc-nginx-module-0.18
--add-module=../redis2-nginx-module-0.14 --add-module=../redis-nginx-module-0.3.7
--with-ld-opt='-Wl,-rpath,/usr/local/openresty/luajit/lib -L/usr/local/openresty/zlib/lib
-L/usr/local/openresty/pcre/lib -L/usr/local/openresty/openssl/lib -Wl,
-rpath,/usr/local/openresty/zlib/lib:/usr/local/openresty/pcre/lib:/usr/local/openresty/openssl/lib'
--with-pcre-jit --with-ipv6 --with-stream --with-stream_ssl_module --with-http_v2_module
--without-mail_pop3_module --without-mail_imap_module --without-mail_smtp_module
--with-http_stub_status_module --with-http_realip_module --with-http_addition_module
--with-http_auth_request_module --with-http_secure_link_module
--with-http_random_index_module --with-http_gzip_static_module --with-http_sub_module
--with-http_dav_module --with-http_flv_module --with-http_mp4_module
--with-http_gunzip_module --with-threads --with-file-aio --with-dtrace-probes
--with-http_ssl_module

uname -a

Linux Fedora26-64 4.11.11-300.fc26.x86_64 #1 SMP Mon Jul 17 16:32:11 UTC 2017 x86_64 x86_64 x86_64 GNU/Linux

I am sorry if something i describe is not clear.

[agentzh]

@tokers Thanks for the detailed analysis. Sounds reasonable to me. Will you please contribute a pull request for this issue? Thanks!

[tokers]

@agentzh I will try!

[tokers]

Sorry, any plan for this issue?