502 Bad Gateway - nginx/1.14.0 (Ubuntu): Impossibile trovare l'immagine localmente + Risposta di errore dal daemon

Recentemente ho spostato il mio server Dell da una posizione all’altra. Il suo sistema operativo principale/Gestore di VM è Proxmox VE 5.3. Ho una VM Nginx che fa da Reverse Proxy per diverse altre VM, una delle quali è una VM Discourse.

Dopo aver configurato il mio nuovo router, ho fatto sì che diverse delle mie VM si connettessero a Internet (senza nemmeno dover rinnovare i certificati SSL). Tuttavia, con Discourse, ricevo 502 Bad Gateway - nginx/1.14.0 (Ubuntu) quando provo ad accedere a Discourse da un browser.

Ho ricevuto questo errore in passato, ma di solito uno dei metodi seguenti lo risolve:

Riavvio della VM Discourse

Ancora 502 Bad Gateway - nginx/1.14.0 (Ubuntu) nel browser.

Cancellazione dei cookie del browser e prova con browser diversi

Solo per escludere che il problema sia dalla mia parte… no. Stesso 502 Bad Gateway - nginx/1.14.0 (Ubuntu) in vari browser.

Pulizia di Discourse e controllo dello spazio su disco

Inizialmente, durante la pulizia, sono stati rimossi circa 4 GB di dati. Sono rimasto molto sorpreso. Forse è quello che ha causato il problema in primo luogo? Comunque, ora quando provo a pulire Discourse:

> root@forum:/var/discourse# ./launcher cleanup
> WARNING! This will remove all stopped containers.
> Are you sure you want to continue? [y/N] y
> Total reclaimed space: 0B
> WARNING! This will remove all images without at least one container associated to them.
> Are you sure you want to continue? [y/N] y
> Total reclaimed space: 0B

Voglio anche ribadire che non sono a corto di spazio su disco:

Git Pull

È aggiornato all’ultima versione.

> root@forum:/var/discourse# git pull
> Already up to date.

Riavvio di Discourse

È qui che ho scoperto due errori che sto ricevendo:

> root@forum:/var/discourse# ./launcher restart app
> 
> WARNING: We are about to start downloading the Discourse base image
> This process may take anywhere between a few minutes to an hour, depending on your network speed
> 
> Please be patient
> 
> Unable to find image 'discourse/base:2.0.20191013-2320' locally
> /usr/bin/docker: Error response from daemon: Get https://registry-1.docker.io/v2/: net/http: request canceled while waiting for connection (Client.Timeout exceeded while awaiting headers).
> See '/usr/bin/docker run --help'.
> Your Docker installation is not working correctly
> 
> See: `https://meta.discourse.org/t/docker-error-on-bootstrap/13657/18?u=sam`

Ho controllato il link suggerito. Raccomanda un Git Pull e di Ricostruire Discourse (come vedrai più avanti). Suggerisce anche di eseguire un comando Docker “Hello World”. Funziona (anche se sembra avere alcuni problemi?):

> root@forum:/var/discourse# docker run -it --rm hello-world
> Unable to find image 'hello-world:latest' locally
> latest: Pulling from library/hello-world
> 1b930d010525: Pull complete
> Digest: sha256:c3b4ada4687bbaa170745b3e4dd8ac3f194ca95b2d0518b417fb47e5879d9b5f
> Status: Downloaded newer image for hello-world:latest
> 
> Hello from Docker!
> This message shows that your installation appears to be working correctly.
> 
> To generate this message, Docker took the following steps:
>  1. The Docker client contacted the Docker daemon.
>  2. The Docker daemon pulled the "hello-world" image from the Docker Hub.
>     (amd64)
>  3. The Docker daemon created a new container from that image which runs the
>     executable that produces the output you are currently reading.
>  4. The Docker daemon streamed that output to the Docker client, which sent it
>     to your terminal.
> 
> To try something more ambitious, you can run an Ubuntu container with:
>  $ docker run -it ubuntu bash
> 
> Share images, automate workflows, and more with a free Docker ID:
>  https://hub.docker.com/
> 
> For more examples and ideas, visit:
>  https://docs.docker.com/get-started/
> 
> failed to resize tty, using default size

Bene, dopo ho provato Ubuntu Bash… ed errore:

> root@forum:/var/discourse# docker run -it ubuntu bash
> Unable to find image 'ubuntu:latest' locally
> docker: Error response from daemon: Get https://registry-1.docker.io/v2/library/ubuntu/manifests/latest: Get https://auth.docker.io/token?scope=repository%3Alibrary%2Fubuntu%3Apull&service=registry.docker.io: net/http: request canceled while waiting for connection (Client.Timeout exceeded while awaiting headers).
> See 'docker run --help'.

È il momento di passare ad altri metodi che conosco:

Arresto e avvio di Discourse

Ricevo la stessa cosa che con il Riavvio:

> root@forum:/var/discourse# ./launcher stop app
> 
> WARNING: We are about to start downloading the Discourse base image
> This process may take anywhere between a few minutes to an hour, depending on your network speed
> 
> Please be patient
> 
> Unable to find image 'discourse/base:2.0.20191013-2320' locally
> /usr/bin/docker: Error response from daemon: Get https://registry-1.docker.io/v2/: net/http: request canceled while waiting for connection (Client.Timeout exceeded while awaiting headers).
> See '/usr/bin/docker run --help'.
> Your Docker installation is not working correctly
> 
> See: `https://meta.discourse.org/t/docker-error-on-bootstrap/13657/18?u=sam`
> 
> root@forum:/var/discourse# ./launcher start app
> 
> WARNING: We are about to start downloading the Discourse base image
> This process may take anywhere between a few minutes to an hour, depending on your network speed
> 
> Please be patient
> 
> Unable to find image 'discourse/base:2.0.20191013-2320' locally
> /usr/bin/docker: Error response from daemon: Get https://registry-1.docker.io/v2/discourse/base/manifests/2.0.20191013-2320: Get https://auth.docker.io/token?scope=repository%3Adiscourse%2Fbase%3Apull&service=registry.docker.io: net/http: request canceled while waiting for connection (Client.Timeout exceeded while awaiting headers).
> See '/usr/bin/docker run --help'.
> Your Docker installation is not working correctly
> 
> See: `https://meta.discourse.org/t/docker-error-on-bootstrap/13657/18?u=sam`

Ricostruzione di Discourse

E ricevo di nuovo gli stessi due errori.

> root@forum:/var/discourse# ./launcher rebuild app
> 
> WARNING: We are about to start downloading the Discourse base image
> This process may take anywhere between a few minutes to an hour, depending on your network speed
> 
> Please be patient
> 
> Unable to find image 'discourse/base:2.0.20191013-2320' locally
> /usr/bin/docker: Error response from daemon: Get https://registry-1.docker.io/v2/: net/http: request canceled while waiting for connection (Client.Timeout exceeded while awaiting headers).
> See '/usr/bin/docker run --help'.
> Your Docker installation is not working correctly
> 
> See: https://meta.discourse.org/t/docker-error-on-bootstrap/13657/18?u=sam

Ripristino da un backup precedente

Ho uno snapshot di un periodo precedente allo spostamento del server e alla pulizia (che, come detto, ha rimosso circa 4 GB di file). Ho riprovato tutti i metodi sopra… e la stessa cosa (esclusa la Pulizia), oltre al 502 Bad Gateway - nginx/1.14.0 (Ubuntu) nel browser. Quindi forse non c’entra nulla con la pulizia?

In tutto il tempo che uso Discourse, non mi sono mai imbattuto in nessuno di questi errori. Qualche suggerimento su cosa posso fare per risolvere questi errori e far funzionare Discourse nel browser?

Your server can’t connect to the docker hub in order to download large images, only the small hello world succeeded.

So how do I remedy this? I don’t have much experience using Docker, so I don’t know where to start.

The only Docker stuff I know is the commands the Discourse Install included (along with modifications of course, since Discourse is installed on a VM on a Server of mine as opposed to a Third Party Cloud).

Which docker version are you running (docker info)?

Can you check your network stack for problems stablishing connections to https://registry-1.docker.io/v2/ ?

Here is my Docker info:

root@forum:/var/discourse# docker info
Containers: 1
Running: 1
Paused: 0
Stopped: 0
Images: 3
Server Version: 18.09.5
Storage Driver: overlay2
Backing Filesystem: extfs
Supports d_type: true
Native Overlay Diff: true
Logging Driver: json-file
Cgroup Driver: cgroupfs
Plugins:
Volume: local
Network: bridge host macvlan null overlay
Log: awslogs fluentd gcplogs gelf journald json-file local logentries splunk syslog
Swarm: inactive
Runtimes: runc
Default Runtime: runc
Init Binary: docker-init
containerd version: bb71b10fd8f58240ca47fbb579b9d1028eea7c84
runc version: 2b18fe1d885ee5083ef9f0838fee39b62d653e30
init version: fec3683
Security Options:
apparmor
seccomp
Profile: default
Kernel Version: 4.15.0-69-generic
Operating System: Ubuntu 18.04.2 LTS
OSType: linux
Architecture: x86_64
CPUs: 2
Total Memory: 6.805GiB
Name: forum
ID: 2RRX:ZQIT:R5AK:WNPR:VJ6Z:2EBY:PFOL:W5RD:GL3X:RUQM:YLJ4:2L2X
Docker Root Dir: /var/lib/docker
Debug Mode (client): false
Debug Mode (server): false
Registry: https://index.docker.io/v1/
Labels:
Experimental: false
Insecure Registries:
127.0.0.0/8
Live Restore Enabled: false
Product License: Community Engine

WARNING: No swap limit support

As for your question:

How do I do this?

@Falco So I’ve been trying to Troubleshoot this problem further, and I’m even more confused now. Good News and Bad News:

Good News

After performing several Discourse Rebuilds (./launcher rebuild app), I no longer receive the Unable to find image or Error response from daemon errors! When I Start/Restart Discourse, I see no errors:

> root@forum:/var/discourse# ./launcher start app
> 
> .+ /usr/bin/docker run --shm-size=512m -d --restart=always -e LANG=en_US.UTF-8 -e RAILS_ENV=production -e UNICORN_WORKERS=4 -e UNICORN_SIDEKIQS=1 -e RUBY_GLOBAL_METHOD_CACHE_SIZE=131072 -e RUBY_GC_HEAP_GROWTH_MAX_SLOTS=40000 -e RUBY_GC_HEAP_INIT_SLOTS=400000 -e RUBY_GC_HEAP_OLDOBJECT_LIMIT_FACTOR=1.5 -e DISCOURSE_DB_SOCKET=/var/run/postgresql -e DISCOURSE_DB_HOST= -e DISCOURSE_DB_PORT= -e DISCOURSE_HOSTNAME=discourse.example.com -e DISCOURSE_DEVELOPER_EMAILS=admin@example.com,postmaster@example.com -e DISCOURSE_SMTP_ADDRESS=smtp.sparkpostmail.com -e DISCOURSE_SMTP_PORT=587 -e DISCOURSE_SMTP_USER_NAME=SMTP_Injection -e DISCOURSE_SMTP_PASSWORD=<HIDING-FOR-PRICACY> -e LETSENCRYPT_ACCOUNT_EMAIL=admin@example.com -h forum-app -e DOCKER_HOST_IP=100.17.0.1 --name app -t -p 8080:80 -p 8443:443 -p 2222:22 -v /var/discourse/shared/standalone:/shared -v /var/discourse/shared/standalone/log/var-log:/var/log --mac-address 02:96:f3:e6:e7:14 local_discourse/app /sbin/boot
> cebe89493bc79dab2c1716599629adfe3dc571c8659367e6ffa0d39b0e6d47af
> root@forum:/var/discourse# ./launcher restart app
> .+ /usr/bin/docker stop -t 10 app
> app
> 
> starting up existing container
> .+ /usr/bin/docker start app
> app

Docker is also running:
> root@forum:/var/discourse# systemctl status docker.service
> ● docker.service - Docker Application Container Engine
>    Loaded: loaded (/lib/systemd/system/docker.service; enabled; vendor preset: enabled)
>    Active: active (running) since Thu 2019-11-14 03:00:54 UTC; 17h ago
>      Docs: https://docs.docker.com
>  Main PID: 18721 (dockerd)
>     Tasks: 31
>    CGroup: /system.slice/docker.service
>            ├─ 1375 /usr/bin/docker-proxy -proto tcp -host-ip 0.0.0.0 -host-port 8443 -container-ip 172.17.0.2 -container-port 443
>            ├─ 1387 /usr/bin/docker-proxy -proto tcp -host-ip 0.0.0.0 -host-port 8080 -container-ip 172.17.0.2 -container-port 80
>            ├─ 1399 /usr/bin/docker-proxy -proto tcp -host-ip 0.0.0.0 -host-port 2222 -container-ip 172.17.0.2 -container-port 22
>            └─18721 /usr/bin/dockerd -H fd:// --containerd=/run/containerd/containerd.sock
> 
> Nov 14 20:13:26 forum dockerd[18721]: time="2019-11-14T20:13:26.430856242Z" level=info msg="ignoring event" module=libcontainerd namespace=moby topic=/tasks/delete type="*events.TaskDelete"
> Nov 14 20:13:28 forum dockerd[18721]: time="2019-11-14T20:13:28.597999379Z" level=info msg="ignoring event" module=libcontainerd namespace=moby topic=/tasks/delete type="*events.TaskDelete"
> Nov 14 20:13:30 forum dockerd[18721]: time="2019-11-14T20:13:30.862158413Z" level=info msg="ignoring event" module=libcontainerd namespace=moby topic=/tasks/delete type="*events.TaskDelete"
> Nov 14 20:13:32 forum dockerd[18721]: time="2019-11-14T20:13:32.978285148Z" level=info msg="ignoring event" module=libcontainerd namespace=moby topic=/tasks/delete type="*events.TaskDelete"
> Nov 14 20:13:35 forum dockerd[18721]: time="2019-11-14T20:13:35.105130149Z" level=info msg="ignoring event" module=libcontainerd namespace=moby topic=/tasks/delete type="*events.TaskDelete"
> Nov 14 20:13:37 forum dockerd[18721]: time="2019-11-14T20:13:37.151466214Z" level=info msg="ignoring event" module=libcontainerd namespace=moby topic=/tasks/delete type="*events.TaskDelete"
> Nov 14 20:13:39 forum dockerd[18721]: time="2019-11-14T20:13:39.024948159Z" level=info msg="ignoring event" module=libcontainerd namespace=moby topic=/tasks/delete type="*events.TaskDelete"
> Nov 14 20:14:05 forum dockerd[18721]: time="2019-11-14T20:14:05.179759938Z" level=info msg="ignoring event" module=libcontainerd namespace=moby topic=/tasks/delete type="*events.TaskDelete"
> Nov 14 20:14:16 forum dockerd[18721]: time="2019-11-14T20:14:16.078334393Z" level=info msg="Container cebe89493bc79dab2c1716599629adfe3dc571c8659367e6ffa0d39b0e6d47af failed to exit within
> Nov 14 20:14:16 forum dockerd[18721]: time="2019-11-14T20:14:16.281731176Z" level=info msg="ignoring event" module=libcontainerd namespace=moby topic=/tasks/delete type="*events.TaskDelete"

Bad News

Still receiving the 502 Bad Gateway - nginx/1.14.0 (Ubuntu) error when I try to open the site in various Browser. I’ve cleared their caches and tried multiple Browsers just in case. No go.

One thing I have noticed is if I try a Discourse Cleanup, it wipes quite a few Containers:

> root@forum:/var/discourse# ./launcher cleanup
> WARNING! This will remove all stopped containers.
> Are you sure you want to continue? [y/N] y
> Total reclaimed space: 0B
> WARNING! This will remove all images without at least one container associated to them.
> Are you sure you want to continue? [y/N] y
> Deleted Images:
> untagged: hello-world:latest
> untagged: hello-world@sha256:c3b4ada4687bbaa170745b3e4dd8ac3f194ca95b2d0518b417fb47e5879d9b5f
> deleted: sha256:fce289e99eb9bca977dae136fbe2a82b6b7d4c372474c9235adc1741675f587e
> deleted: sha256:af0b15c8625bb1938f1d7b17081031f649fd14e6b233688eea3c5483994a66a3
> untagged: discourse/base:2.0.20191013-2320
> untagged: discourse/base@sha256:77e010342aa5111c8c3b81d80de7d4bdb229793d595bbe373992cdb8f86ef41f
> deleted: sha256:53b44681b65ee5e9a9cadc6bd34c6aa6f6bcbbbe6270e61669c50bcd655c6898
> deleted: sha256:939a3ac6d5627270ae02a9f9ea05c580589cec0afa019b7f296fdd43157dd3a0
> 
> Total reclaimed space: 452.2MB

Now anytime I try to start/restart … the errors are back! I’ve rolled back to when the Unable to find image or Error response from daemon error messages stopped showing up. Clearly Containers were rebuilt, and clearing the image containers causes issues.

If your docker is broken (aka docker run ubuntu fails) Discourse most certainly won’t work.

To get Docker specific Docker support you may try posting https://forums.docker.com/

@Falco Yeah, I’m getting the Unable to find image locally and Error response from daemon errors as I was getting before when I run that command.

So as per your suggestion, I’ve started a topic over in the Docker forums. No response yet unfortunately.

So some more news:

Good News

I’m not receiving the /usr/bin/docker: Error response from daemon: Get https://registry-1.docker.io/v2/: net/http: request canceled while waiting for connection (Client.Timeout exceeded while awaiting headers). anymore!

docker run ubuntu no longer reports an error. @Falco is there supposed to be any output I should be seeing?

root@forum:/var/discourse# docker run ubuntu
root@forum:/var/discourse#

So what have I done that resolves the error? I replaced the nameserver (DNS) used on this VM by the Google Public DNS service:
echo "nameserver 8.8.8.8">/etc/resolv.conf

I have to run the above command every time after the VM is restarted though (so it seems to just be temporary), or I will get the two errors when I try to run any ./launcher commands. Afterwards though, only one of the errors (Unable to find image 'discourse/base:2.0.20191013-2320' locally) comes up, but the command looks to resolve:

root@forum:/var/discourse# ./launcher start app

WARNING: We are about to start downloading the Discourse base image
This process may take anywhere between a few minutes to an hour, depending on your network speed

Please be patient

Unable to find image 'discourse/base:2.0.20191013-2320' locally
2.0.20191013-2320: Pulling from discourse/base
Digest: sha256:77e010342aa5111c8c3b81d80de7d4bdb229793d595bbe373992cdb8f86ef41f
Status: Downloaded newer image for discourse/base:2.0.20191013-2320

starting up existing container
+ /usr/bin/docker start app
app

I look to also be able to do a ./launcher rebuild app without errors. Here is the last thing the output of the command shows (hiding URLs and MAC Address):

+ /usr/bin/docker run --shm-size=512m -d --restart=always -e LANG=en_US.UTF-8 -e RAILS_ENV=production -e UNICORN_WORKERS=4 -e UNICORN_SIDEKIQS=1 -e RUBY_GLOBAL_METHOD_CACHE_SIZE=131072 -e RUBY_GC_HEAP_GROWTH_MAX_SLOTS=40000 -e RUBY_GC_HEAP_INIT_SLOTS=400000 -e RUBY_GC_HEAP_OLDOBJECT_LIMIT_FACTOR=1.5 -e DISCOURSE_DB_SOCKET=/var/run/postgresql -e DISCOURSE_DB_HOST= -e DISCOURSE_DB_PORT= -e DISCOURSE_HOSTNAME=discourse.domain.com -e DISCOURSE_DEVELOPER_EMAILS=admin@domain.com,postmaster@domain.com -e DISCOURSE_SMTP_ADDRESS=smtp.sparkpostmail.com -e DISCOURSE_SMTP_PORT=587 -e DISCOURSE_SMTP_USER_NAME=SMTP_Injection -e DISCOURSE_SMTP_PASSWORD=0d431cd177ce3d35833aa823d498eb57c7c4e99c -e LETSENCRYPT_ACCOUNT_EMAIL=admin@domain.com -h forum-app -e DOCKER_HOST_IP=172.17.0.1 --name app -t -p 8080:80 -p 8443:443 -p 2222:22 -v /var/discourse/shared/standalone:/shared -v /var/discourse/shared/standalone/log/var-log:/var/log --mac-address 00:00:00:00:00:01 local_discourse/app /sbin/boot
abb788d4a6fd301d88f129189a07a19c4a6bfc8554d43c555d3e3cd126374736

Bad News

I am still getting the 502 Bad Gateway - nginx/1.14.0 (Ubuntu) error when I try going to the page.

What else could be the issue? Any suggestions?

I resolved my issue! My Discourse Forum shows up now in a Browser!

Well, to be more specific, Francis Day over on the Nginx Forums resolved my issue! It was indeed Nginx all along. Here is what I did:

  1. Logged into my Nginx VM.
  2. VIMed Discourse CONF file: vim /etc/nginx/sites-available/discourse.conf
  3. Here is what my Discourse CONF file looked like (obviously not using the Domain Name I would normally use, and where 192.168.0.101 = Nginx VM and 192.168.0.104 = Discourse VM).
  4. I only made one change: I changed proxy_pass http://discourse.domainame.com:8080/; to proxy_pass 192.168.0.104:8080/;. So proxy_pass is set to the Discourse VM’s Local IP instead of the Hostname.
  5. Save the CONF file, and then Reloaded (systemctl reload nginx.service) and Restarted (systemctl restart nginx.service) Nginx.
  6. Viola! I refresh the Discourse URL, and it comes up! Didn’t even need to Restart/Rebuild Discourse!

I hope someone finds what I’ve written here useful, as reverse proxying Discourse through Nginx can be really tricky.