Docker Networking - nginx: [emerg] host not found in upstream - nginx

Question

I have recently started migrating to Docker 1.9 and Docker-Compose 1.5's networking features to replace using links.
So far with links there were no problems with nginx connecting to my php5-fpm fastcgi server located in a different server in one group via docker-compose. Newly though when I run docker-compose --x-networking up my php-fpm, mongo and nginx containers boot up, however nginx quits straight away with [emerg] 1#1: host not found in upstream "waapi_php_1" in /etc/nginx/conf.d/default.conf:16
However, if I run the docker-compose command again while the php and mongo containers are running (nginx exited), nginx starts and works fine from then on.
This is my docker-compose.yml file:
nginx:
image: nginx
ports:
- "42080:80"
volumes:
- ./config/docker/nginx/default.conf:/etc/nginx/conf.d/default.conf:ro
php:
build: config/docker/php
ports:
- "42022:22"
volumes:
- .:/var/www/html
env_file: config/docker/php/.env.development
mongo:
image: mongo
ports:
- "42017:27017"
volumes:
- /var/mongodata/wa-api:/data/db
command: --smallfiles
This is my default.conf for nginx:
server {
listen 80;
root /var/www/test;
error_log /dev/stdout debug;
access_log /dev/stdout;
location / {
# try to serve file directly, fallback to app.php
try_files $uri /index.php$is_args$args;
}
location ~ ^/.+\.php(/|$) {
# Referencing the php service host (Docker)
fastcgi_pass waapi_php_1:9000;
fastcgi_split_path_info ^(.+\.php)(/.*)$;
include fastcgi_params;
# We must reference the document_root of the external server ourselves here.
fastcgi_param SCRIPT_FILENAME /var/www/html/public$fastcgi_script_name;
fastcgi_param HTTPS off;
}
}
How can I get nginx to work with only a single docker-compose call?

Answer 1

This can be solved with the mentioned depends_on directive since it's implemented now (2016):
version: '2'
services:
nginx:
image: nginx
ports:
- "42080:80"
volumes:
- ./config/docker/nginx/default.conf:/etc/nginx/conf.d/default.conf:ro
depends_on:
- php
php:
build: config/docker/php
ports:
- "42022:22"
volumes:
- .:/var/www/html
env_file: config/docker/php/.env.development
depends_on:
- mongo
mongo:
image: mongo
ports:
- "42017:27017"
volumes:
- /var/mongodata/wa-api:/data/db
command: --smallfiles
Successfully tested with:
$ docker-compose version
docker-compose version 1.8.0, build f3628c7
Find more details in the documentation.
There is also a very interesting article dedicated to this topic: Controlling startup order in Compose

Answer 2

There is a possibility to use "volumes_from" as a workaround until depends_on feature (discussed below) is introduced. All you have to do is change your docker-compose file as below:
nginx:
image: nginx
ports:
- "42080:80"
volumes:
- ./config/docker/nginx/default.conf:/etc/nginx/conf.d/default.conf:ro
volumes_from:
- php
php:
build: config/docker/php
ports:
- "42022:22"
volumes:
- .:/var/www/html
env_file: config/docker/php/.env.development
mongo:
image: mongo
ports:
- "42017:27017"
volumes:
- /var/mongodata/wa-api:/data/db
command: --smallfiles
One big caveat in the above approach is that the volumes of php are exposed to nginx, which is not desired. But at the moment this is one docker specific workaround that could be used.
depends_on feature
This probably would be a futuristic answer. Because the functionality is not yet implemented in Docker (as of 1.9)
There is a proposal to introduce "depends_on" in the new networking feature introduced by Docker. But there is a long running debate about the same # https://github.com/docker/compose/issues/374 Hence, once it is implemented, the feature depends_on could be used to order the container start-up, but at the moment, you would have to resort to one of the following:
make nginx retry until the php server is up - I would prefer this one
use volums_from workaround as described above - I would avoid using this, because of the volume leakage into unnecessary containers.

Answer 3

If you are so lost for read the last comment. I have reached another solution.
The main problem is the way that you named the services names.
In this case, if in your docker-compose.yml, the service for php are called "api" or something like that, you must ensure that in the file nginx.conf the line that begins with fastcgi_pass have the same name as the php service. i.e fastcgi_pass api:9000;
Lets say the php service name is php_service then the code will be:
In the file docker-compose.yml
php_service:
build:
dockerfile: ./docker/php/Dockerfile
In the file nginx.conf
location ~ \.php$ {
fastcgi_pass php_service:9000;
fastcgi_param SCRIPT_FILENAME$document_root$fastcgi_script_name;
include fastcgi_params;
}

Answer 4

You can set the max_fails and fail_timeout directives of nginx to indicate that the nginx should retry the x number of connection requests to the container before failing on the upstream server unavailability.
You can tune these two numbers as per your infrastructure and speed at which the whole setup is coming up. You can read more details about the health checks section of the below URL:
http://nginx.org/en/docs/http/load_balancing.html
Following is the excerpt from http://nginx.org/en/docs/http/ngx_http_upstream_module.html#server
max_fails=number
sets the number of unsuccessful attempts to communicate with the
server that should happen in the duration set by the fail_timeout
parameter to consider the server unavailable for a duration also set
by the fail_timeout parameter. By default, the number of unsuccessful
attempts is set to 1. The zero value disables the accounting of
attempts. What is considered an unsuccessful attempt is defined by the
proxy_next_upstream, fastcgi_next_upstream, uwsgi_next_upstream,
scgi_next_upstream, and memcached_next_upstream directives.
fail_timeout=time
sets the time during which the specified number of unsuccessful
attempts to communicate with the server should happen to consider the
server unavailable; and the period of time the server will be
considered unavailable. By default, the parameter is set to 10
seconds.
To be precise your modified nginx config file should be as follows (this script is assuming that all the containers are up by 25 seconds at least, if not, please change the fail_timeout or max_fails in below upstream section):
Note: I didn't test the script myself, so you could give it a try!
upstream phpupstream {
server waapi_php_1:9000 fail_timeout=5s max_fails=5;
}
server {
listen 80;
root /var/www/test;
error_log /dev/stdout debug;
access_log /dev/stdout;
location / {
# try to serve file directly, fallback to app.php
try_files $uri /index.php$is_args$args;
}
location ~ ^/.+\.php(/|$) {
# Referencing the php service host (Docker)
fastcgi_pass phpupstream;
fastcgi_split_path_info ^(.+\.php)(/.*)$;
include fastcgi_params;
# We must reference the document_root of the external server ourselves here.
fastcgi_param SCRIPT_FILENAME /var/www/html/public$fastcgi_script_name;
fastcgi_param HTTPS off;
}
}
Also, as per the following Note from docker (https://github.com/docker/docker.github.io/blob/master/compose/networking.md#update-containers), it is evident that the retry logic for checking the health of the other containers is not docker's responsibility and rather the containers should do the health check themselves.
Updating containers
If you make a configuration change to a service and run docker-compose
up to update it, the old container will be removed and the new one
will join the network under a different IP address but the same name.
Running containers will be able to look up that name and connect to
the new address, but the old address will stop working.
If any containers have connections open to the old container, they
will be closed. It is a container's responsibility to detect this
condition, look up the name again and reconnect.

Answer 5

My problem was that I forgot to specify network alias in
docker-compose.yml in php-fpm
networks:
- u-online
It is works well!
version: "3"
services:
php-fpm:
image: php:7.2-fpm
container_name: php-fpm
volumes:
- ./src:/var/www/basic/public_html
ports:
- 9000:9000
networks:
- u-online
nginx:
image: nginx:1.19.2
container_name: nginx
depends_on:
- php-fpm
ports:
- "80:8080"
- "443:443"
volumes:
- ./docker/data/etc/nginx/conf.d/default.conf:/etc/nginx/conf.d/default.conf
- ./docker/data/etc/nginx/nginx.conf:/etc/nginx/nginx.conf
- ./src:/var/www/basic/public_html
networks:
- u-online
#Docker Networks
networks:
u-online:
driver: bridge

Answer 6

I believe Nginx dont take in account Docker resolver (127.0.0.11), so please, can you try adding:
resolver 127.0.0.11
in your nginx configuration file?

Answer 7

I had the same problem because there was two networks defined in my docker-compose.yml: one backend and one frontend.
When I changed that to run containers on the same default network everything started working fine.

Answer 8

I found solution for services, that may be disabled for local development. Just use variables, that prevents emergency shutdown and works after service is available.
server {
location ^~ /api/ {
# other config entries omitted for breavity
set $upstream http://api.awesome.com:9000;
# nginx will now start if host is not reachable
fastcgi_pass $upstream;
fastcgi_index index.php;
}
}
source: https://sandro-keil.de/blog/let-nginx-start-if-upstream-host-is-unavailable-or-down/

Answer 9

Had the same problem and solved it. Please add the following line to docker-compose.yml nginx section:
links:
- php:waapi_php_1
Host in nginx config fastcgi_pass section should be linked inside docker-compose.yml nginx configuration.

Answer 10

At the first glance, I missed, that my "web" service didn't actually start, so that's why nginx couldn't find any host
web_1 | python3: can't open file '/var/www/app/app/app.py': [Errno 2] No such file or directory
web_1 exited with code 2
nginx_1 | [emerg] 1#1: host not found in upstream "web:4044" in /etc/nginx/conf.d/nginx.conf:2

Answer 11

Two things worth to mention:
Using same network bridge
Using links to add hosts resol
My example:
version: '3'
services:
mysql:
image: mysql:5.7
restart: always
container_name: mysql
volumes:
- ./mysql-data:/var/lib/mysql
environment:
MYSQL_ROOT_PASSWORD: tima#123
network_mode: bridge
ghost:
image: ghost:2
restart: always
container_name: ghost
depends_on:
- mysql
links:
- mysql
environment:
database__client: mysql
database__connection__host: mysql
database__connection__user: root
database__connection__password: xxxxxxxxx
database__connection__database: ghost
url: https://www.itsfun.tk
volumes:
- ./ghost-data:/var/lib/ghost/content
network_mode: bridge
nginx:
image: nginx
restart: always
container_name: nginx
depends_on:
- ghost
links:
- ghost
ports:
- "80:80"
- "443:443"
volumes:
- ./nginx/nginx.conf:/etc/nginx/nginx.conf
- ./nginx/conf.d:/etc/nginx/conf.d
- ./nginx/letsencrypt:/etc/letsencrypt
network_mode: bridge
If you don't specify a special network bridge, all of them will use the same default one.

Answer 12

Add the links section to your nginx container configuration.
You have to make visible the php container to the nginx container.
nginx:
image: nginx
ports:
- "42080:80"
volumes:
- ./config/docker/nginx/default.conf:/etc/nginx/conf.d/default.conf:ro
links:
- php:waapi_php_1

Answer 13

With links there is an order of container startup being enforced. Without links the containers can start in any order (or really all at once).
I think the old setup could have hit the same issue, if the waapi_php_1 container was slow to startup.
I think to get it working, you could create an nginx entrypoint script that polls and waits for the php container to be started and ready.
I'm not sure if nginx has any way to retry the connection to the upstream automatically, but if it does, that would be a better option.

Answer 14

You have to use something like docker-gen to dynamically update nginx configuration when your backend is up.
See:
https://hub.docker.com/r/jwilder/docker-gen/
https://github.com/jwilder/nginx-proxy
I believe Nginx+ (premium version) contains a resolve parameter too (http://nginx.org/en/docs/http/ngx_http_upstream_module.html#upstream)

Answer 15

Perhaps the best choice to avoid linking containers issues are the docker networking features
But to make this work, docker creates entries in the /etc/hosts for each container from assigned names to each container.
with docker-compose --x-networking -up is something like
[docker_compose_folder]-[service]-[incremental_number]
To not depend on unexpected changes in these names you should use the parameter
container_name
in your docker-compose.yml as follows:
php:
container_name: waapi_php_1
build: config/docker/php
ports:
- "42022:22"
volumes:
- .:/var/www/html
env_file: config/docker/php/.env.development
Making sure that it is the same name assigned in your configuration file for this service. I'm pretty sure there are better ways to do this, but it is a good approach to start.

Answer 16

My Workaround (after much trial and error):
In order to get around this issue, I had to get the full name of the 'upstream' Docker container, found by running docker network inspect my-special-docker-network and getting the full name property of the upstream container as such:
"Containers": {
"39ad8199184f34585b556d7480dd47de965bc7b38ac03fc0746992f39afac338": {
"Name": "my_upstream_container_name_1_2478f2b3aca0",
Then used this in the NGINX my-network.local.conf file in the location block of the proxy_pass property: (Note the addition of the GUID to the container name):
location / {
proxy_pass http://my_upsteam_container_name_1_2478f2b3aca0:3000;
As opposed to the previously working, but now broken:
location / {
proxy_pass http://my_upstream_container_name_1:3000
Most likely cause is a recent change to Docker Compose, in their default naming scheme for containers, as listed here.
This seems to be happening for me and my team at work, with latest versions of the Docker nginx image:
I've opened issues with them on the docker/compose GitHub here

Answer 17

this error appeared to me because my php-fpm image enabled cron, and I have no idea why

Answer 18

In my case it was nginx: [emerg] host not found in upstream as well, so I managed to solve it, by adding depends_on directive to nginx service in docker-compose.yml file.

Answer 19

(new to nginx)
In my case it was wrong folder name
For config
upstream serv {
server ex2_app_1:3000;
}
make sure the app folder is in ex2 folder:
ex2/app/...