java.net.SocketTimeoutException: Read timed out while downloading libraries.

[KS-HTK]

I get this Issue:

java.net.SocketTimeoutException: Read timed out
        at java.net.SocketInputStream.socketRead0(Native Method)
        at java.net.SocketInputStream.socketRead(SocketInputStream.java:116)
        at java.net.SocketInputStream.read(SocketInputStream.java:171)
        at java.net.SocketInputStream.read(SocketInputStream.java:141)
        at sun.security.ssl.InputRecord.readFully(InputRecord.java:465)
        at sun.security.ssl.InputRecord.read(InputRecord.java:503)
        at sun.security.ssl.SSLSocketImpl.readRecord(SSLSocketImpl.java:975)
        at sun.security.ssl.SSLSocketImpl.performInitialHandshake(SSLSocketImpl.java:1367)
        at sun.security.ssl.SSLSocketImpl.startHandshake(SSLSocketImpl.java:1395)
        at sun.security.ssl.SSLSocketImpl.startHandshake(SSLSocketImpl.java:1379)
        at sun.net.www.protocol.https.HttpsClient.afterConnect(HttpsClient.java:559)
        at sun.net.www.protocol.https.AbstractDelegateHttpsURLConnection.connect(AbstractDelegateHttpsURLConnection.java:185)
        at sun.net.www.protocol.http.HttpURLConnection.getInputStream0(HttpURLConnection.java:1564)
        at sun.net.www.protocol.http.HttpURLConnection.getInputStream(HttpURLConnection.java:1492)
        at java.net.HttpURLConnection.getResponseCode(HttpURLConnection.java:480)
        at sun.net.www.protocol.https.HttpsURLConnectionImpl.getResponseCode(HttpsURLConnectionImpl.java:347)
        at net.minecraftforge.installer.DownloadUtils.getConnection(DownloadUtils.java:202)
        at net.minecraftforge.installer.DownloadUtils.downloadMirrors(DownloadUtils.java:252)
        at net.minecraftforge.installer.json.Install.getMirror(Install.java:116)
        at net.minecraftforge.installer.actions.ServerInstall.run(ServerInstall.java:53)
        at net.minecraftforge.installer.SimpleInstaller.main(SimpleInstaller.java:127)

While trying to install a CurseForge Modpack using following Docker Compose:

version: '3.6'
services:
  minecraft:
    container_name: val3
    image: itzg/minecraft-server:java8
    ports:
      - "25566:25565"
    environment:
      EULA: "TRUE"
      VIEW_DISTANCE: "12"
      MOTD: "Valhelsia 3 Server"

      TYPE: "CURSEFORGE"
      VERSION: "1.16.5"
      CF_SERVER_MOD: "/modpacks/valhelsia3-server.zip"
      CF_BASE_DIR: "/data"
      FORCE_REDOWNLOAD: "true"
      REMOVE_OLD_MODS: "true"
      ENABLE_AUTOPAUSE: "true"
      AUTOPAUSE_TIMEOUT_EST: "7200"
      AUTOPAUSE_TIMEOUT_KN: "240"
      TZ: "Europe/Berlin"
      MEMORY: "10G"
      USE_AIKAR_FLAGS: "true"
    volumes:
      - "~/val3/data:/data"
      - "~/modpacks:/modpacks"
    restart: always

[itzg]

I'm afraid that's not something I can fix from the the image. As you've probably the noticed the failure is within the forge installer and is somehow influenced by network connectivity towards their library repo.

[itzg]

If you don't mind, I can convert this issue to a discussion to see if others have encountered and fixed this scenario.

[KS-HTK]

Thank you for the Info, changing this into a Discussion seems to be a good Idea.
I had tried to find a solution and have not found anything helpfull yet.
If terminating the docker-compose and then starting the docker container it just errors out saying to rerun the install script.
Is it possible to start the ServerStart.sh from within the Container?
Or is that what docker start is doing?

I was able to run the ServerStart.bat locally and did not run into this issue. It seems that the response to the first library download takes a lot longer than any subsequent ones. Is there a way to set a higher timeout for downloads or would the script of the Modpack have to do that?

[itzg]

Is it possible to start the ServerStart.sh from within the Container?
Or is that what docker start is doing?

Yes, that's what it already does.

So, again, the start script provided by the modpack is beyond my control via the image.

Modpack scripts are inconsistent and some are broken, so you could also try

https://github.com/itzg/docker-minecraft-server#buggy-start-scripts

[KS-HTK]

This seems to be some other issue as curl is unable to download the forge files aswell.
I have created a test container running this compose:

version: '3.6'
services:
  minecraft:
    container_name: test
    image: itzg/minecraft-server
    ports:
      - "25566:25565"
    environment:
      EULA: "TRUE"

      TYPE: "FORGE"
      VERSION: "1.16.5"
      FORGEVERSION: "36.2.2"
      FORGE_INSTALLER_URL: "https://maven.minecraftforge.net/net/minecraftforge/forge/1.16.5-36.2.2/forge-1.16.5-36.2.2-installer.jar"
      TZ: "Europe/Berlin"
      MAX_MEMORY: "4G"
      INIT_MEMORY: "1G"
    volumes:
      - "~/test/data:/data"
    restart: always

BTW: Not specifying the Download URL results in the non functioning URL: https://maven.minecraftforge.net/net/minecraftforge/forge/1.16.5-36.2.2-1.16.5/forge-1.16.5-36.2.2-1.16.5-installer.jar

I have experimented around a bit more. But I cant seem to pinpoint the problem.
First I tought it was the container networking. But attaching a praqma/network-multitool container to the test_default network seemd to be able to resolv hostnames and obtain files using curl.

The Out put of the test continer:

[init] Running as uid=1000 gid=1000 with /data as 'drwxrwxr-x 2 1000 1000 4096 Aug 16 21:14 /data'
[init] Resolved version given 1.16.5 into 1.16.5
[init] Resolving type given FORGE
[init] **********************************************************************
[init] WARNING: The image tag itzg/minecraft-server:java8 is recommended
[init]          since some mods require Java 8
[init]          Exception traces reporting ClassCastException: class jdk.internal.loader.ClassLoaders$AppClassLoader
[init]          can be fixed with java8
[init] **********************************************************************
[init] Downloading https://maven.minecraftforge.net/net/minecraftforge/forge/1.16.5-36.2.2/forge-1.16.5-36.2.2-installer.jar ...
curl: (6) Could not resolve host: maven.minecraftforge.net
[init] Failed to download from given location https://maven.minecraftforge.net/net/minecraftforge/forge/1.16.5-36.2.2/forge-1.16.5-36.2.2-installer.jar

So this seems to be a Issue with the docker Image? That seems odd. It did not resolve by removing the Image and redownloading.
I did try that.

[KS-HTK]

Did a lot more digging. I have come to the conclusion this must be somehow related to the container image.
But since I do not know much about docker images I can't continue debugging from this point on.

@itzg Here is what I have found out so far.

1. As mentioned before: The generated Forge download links are wrong. Having an additional version number in them:
   https://maven.minecraftforge.net/net/minecraftforge/forge/1.16.5-36.2.2-1.16.5/forge-1.16.5-36.2.2-1.16.5-installer.jar
   This also applies to the 1.17.1 link generated by the container.
2. Something is wrong with file downloading in general.

Downloading the minecraft server jar from mojang works fine.
Running this compose is flawless.

version: '3.6'
services:
  minecraft:
    container_name: test
    image: itzg/minecraft-server
    ports:
      - 25565:25565
    environment:
      EULA: "true"
    volumes:
      - "~/test/data:/data"
    restart: unless-stopped

Running this compose fails to download even the Forge installer even if provided with the correct link.

version: '3.6'
services:
  minecraft:
    container_name: test2
    image: itzg/minecraft-server
    ports:
      - "25565:25565"
    environment:
      EULA: "TRUE"
      TYPE: "FORGE"
      VERSION: "1.17.1"
      FORGEVERSION: "37.0.48"
      FORGE_INSTALLER: "https://maven.minecraftforge.net/net/minecraftforge/forge/1.17.1-37.0.48/forge-1.17.1-37.0.48-installer.jar"
    volumes:
      - "~/test2/data:/data"
    restart: unless-stopped

Recreating test2 ... done
Attaching to test2
test2        | [init] Running as uid=1000 gid=1000 with /data as 'drwxrwxr-x 2 1000 1000 4096 Aug 31 10:25 /data'
test2        | [init] Resolved version given 1.17.1 into 1.17.1
test2        | [init] Resolving type given FORGE
test2        | [init] ERROR: the given Forge installer doesn't exist : https://maven.minecraftforge.net/net/minecraftforge/forge/1.17.1-37.0.48/forge-1.17.1-37.0.48-installer.jar
test exited with code 2

I am not sure if the fix for this is also the solution for the original problem. But since I have the same Issue on different operating systems it seems to be related to the container.

[KS-HTK]

OK, I finally figured this Issue out.

After playing around with the network-test container a bit more I found a error establishing an ssl connection.
This lead me to an article regarding the network mtu. https://mlohr.com/docker-mtu/
And this was the problem causing all the issues.
So what might have caused the issue is that the server provider changed the mtu on the physical link in the datacenter and this caused the issue with docker. Docker does not set the mtu of its bridge networks according to the mtu of the actual link.
Setting this manually according to the linked article solved the connectivity issues.

Why this was only an issue on some downloads is unclear to me, but it might be related to the package size sent by the server.