Opened 2 years ago

Closed 2 years ago

#1591 closed defect (invalid)

Reload signal does not show error for failed bind

Reported by: Sebastian Owned by:
Priority: minor Milestone:
Component: nginx-core Version: 1.15.x
Keywords: Cc:
uname -a: Linux host 3.16.0-6-amd64 #1 SMP Debian 3.16.56-1+deb8u1 (2018-05-08) x86_64 GNU/Linux
nginx -V: nginx version: nginx/1.15.1
built by gcc 4.9.2 (Debian 4.9.2-10+deb8u1)
built with OpenSSL 1.0.1t 3 May 2016 (running with OpenSSL 1.0.2l 25 May 2017)
TLS SNI support enabled
configure arguments: --prefix=/etc/nginx --sbin-path=/usr/sbin/nginx --modules-path=/usr/lib/nginx/modules --conf-path=/etc/nginx/nginx.conf --error-log-path=/var/log/nginx/error.log --http-log-path=/var/log/nginx/access.log --pid-path=/var/run/nginx.pid --lock-path=/var/run/nginx.lock --http-client-body-temp-path=/var/cache/nginx/client_temp --http-proxy-temp-path=/var/cache/nginx/proxy_temp --http-fastcgi-temp-path=/var/cache/nginx/fastcgi_temp --http-uwsgi-temp-path=/var/cache/nginx/uwsgi_temp --http-scgi-temp-path=/var/cache/nginx/scgi_temp --user=nginx --group=nginx --with-compat --with-file-aio --with-threads --with-http_addition_module --with-http_auth_request_module --with-http_dav_module --with-http_flv_module --with-http_gunzip_module --with-http_gzip_static_module --with-http_mp4_module --with-http_random_index_module --with-http_realip_module --with-http_secure_link_module --with-http_slice_module --with-http_ssl_module --with-http_stub_status_module --with-http_sub_module --with-http_v2_module --with-mail --with-mail_ssl_module --with-stream --with-stream_realip_module --with-stream_ssl_module --with-stream_ssl_preread_module --with-cc-opt='-g -O2 -fstack-protector-strong -Wformat -Werror=format-security -Wp,-D_FORTIFY_SOURCE=2 -fPIC' --with-ld-opt='-Wl,-z,relro -Wl,-z,now -Wl,--as-needed -pie'

Description

Under normal circumstances, when nginx is signalled to reload (nginx -s reload) and there is an error in the configuration, the error is returned:

# nginx -s reload
nginx: [emerg] unknown directive "testtest" in /etc/nginx/conf.d/default.conf:3

However, when the configuration specifies to bind to a non-bindable (non-existant) IP, the reload signal returns as OK, while nginx doesn't actually reload. The workers don't get respawned.

server {
    listen       1.2.3.4:80;
...

(assume 1.2.3.4 isn't assigned to any interface on the system)

# pidof nginx
8192 8182
# nginx -s reload
# echo $?
0
# pidof nginx
8192 8182

Stopping, then starting the process shows the error correctly:

# nginx
nginx: [emerg] bind() to 1.2.3.4:80 failed (99: Cannot assign requested address)

Change History (1)

comment:1 by Maxim Dounin, 2 years ago

Resolution: invalid
Status: newclosed

The nginx -s reload command is just a way to send a signal to a running nginx master process. Just a way to do kill -HUP <nginx-master-pid>, introduced to make it possible to send control signals to nginx on Windows. It cannot and not expected to provide any information about results of processing a particular signal - in particular, whether the configuration reload was successful or not. It simply do not have this information, much like kill -HUP <nginx-master-pid> do not have any information about the signal processing.

When there is a syntax error in the configuration, nginx -s reload fails because it cannot parse the configuration to find out where nginx's pid file resides. This is actually a limitation compared to kill, because there are cases when it should be possible to send signals regardless of the current configuration state - see ticket #724 for detailed explanation.

To check if a reload was successful or not, you are expected to look into error log and/or check running nginx processes.

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