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Pixelmon Server Crashing? Troubleshooting and Solutions for Server Stability

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Running a Pixelmon server can be an incredibly rewarding experience, bringing together Minecraft and Pokémon fans in a unique and engaging way. However, server crashes can quickly disrupt this fun, leading to frustration for both server owners and players. If you’re experiencing persistent crashes on your Pixelmon server, understanding the causes and how to address them is crucial. This guide will walk you through analyzing a crash report and provide actionable steps to improve your Pixelmon server’s stability.

Let’s dive into a real-world example of a Pixelmon server crash and explore how to diagnose and potentially fix the issue.

Analyzing a Pixelmon Server Crash Report

Crash reports are your best friend when troubleshooting server issues. They provide valuable insights into what went wrong and can point you directly to the problem area. Let’s examine a sample crash report to understand how to interpret it.

---- Minecraft Crash Report ----

WARNING: coremods are present: SpongeCoremod (spongeforge-1.12.2-2768-7.1.6-RC3686 (2).jar) Contact their authors BEFORE contacting forge

// Who set us up the TNT?

Time: 6/9/19 4:39 AM
Description: Watching Server

java.lang.Error: ServerHangWatchdog detected that a single server tick took 6.00 seconds (should be max 0.05)
    at java.io.FileOutputStream.write(Native Method)
    at java.io.FileOutputStream.write(FileOutputStream.java:290)
    at java.io.DataOutputStream.writeInt(DataOutputStream.java:200)
    at net.minecraft.nbt.NBTTagInt.func_74734_a(SourceFile:25)
    at net.minecraft.nbt.NBTTagCompound.func_150298_a(NBTTagCompound.java:474)
    at net.minecraft.nbt.NBTTagCompound.func_74734_a(NBTTagCompound.java:35)
    at net.minecraft.nbt.NBTTagCompound.func_150298_a(NBTTagCompound.java:474)
    at net.minecraft.nbt.NBTTagCompound.func_74734_a(NBTTagCompound.java:35)
    at net.minecraft.nbt.NBTTagCompound.func_150298_a(NBTTagCompound.java:474)
    at net.minecraft.nbt.NBTTagCompound.func_74734_a(NBTTagCompound.java:35)
    at net.minecraft.nbt.CompressedStreamTools.func_150663_a(CompressedStreamTools.java:112)
    at net.minecraft.nbt.CompressedStreamTools.func_74800_a(CompressedStreamTools.java:102)
    at com.pixelmonmod.pixelmon.storage.FileStorage.writeComputerData(FileStorage.java:108)
    at com.pixelmonmod.pixelmon.storage.StorageAdapter.saveComputerStorage(StorageAdapter.java:31)
    at com.pixelmonmod.pixelmon.storage.ComputerManager.savePlayer(ComputerManager.java:106)
    at com.pixelmonmod.pixelmon.storage.ComputerManager.saveAll(ComputerManager.java:98)
    at com.pixelmonmod.pixelmon.storage.ComputerManager.onWorldSave(ComputerManager.java:114)
    at net.minecraftforge.fml.common.eventhandler.ASMEventHandler_58_ComputerManager_onWorldSave_Save.invoke(.dynamic)
    at net.minecraftforge.fml.common.eventhandler.ASMEventHandler.invoke(ASMEventHandler.java:90)
    at net.minecraftforge.fml.common.eventhandler.EventBus.post(EventBus.java:746)
    at org.spongepowered.mod.event.SpongeToForgeEventFactory.createAndPostWorldSaveEvent(SpongeToForgeEventFactory.java:936)
    at org.spongepowered.mod.event.SpongeToForgeEventFactory.createAndPostForgeEvent(SpongeToForgeEventFactory.java:287)
    at org.spongepowered.mod.event.SpongeModEventManager.post(SpongeModEventManager.java:340)
    at org.spongepowered.mod.event.SpongeModEventManager.extendedPost(SpongeModEventManager.java:450)
    at org.spongepowered.mod.event.SpongeModEventManager.post(SpongeModEventManager.java:419)
    at org.spongepowered.common.event.SpongeEventManager.post(SpongeEventManager.java:465)
    at net.minecraft.world.WorldServer.func_73044_a(WorldServer.java:2638)
    at org.spongepowered.common.world.WorldManager.saveWorld(WorldManager.java:555)
    at net.minecraft.server.MinecraftServer.func_71267_a(MinecraftServer.java:3894)
    at net.minecraft.server.MinecraftServer.constant$getSaveTickInterval$zjo000(MinecraftServer.java:3847)
    at net.minecraft.server.MinecraftServer.func_71217_p(MinecraftServer.java:687)
    at net.minecraft.server.MinecraftServer.run(MinecraftServer.java:526)
    at java.lang.Thread.run(Thread.java:748)


## A detailed walkthrough of the error, its code path and all known details is as follows:

-- Head --
Thread: Server Watchdog
Stacktrace:
    at java.io.FileOutputStream.write(Native Method)
    at java.io.FileOutputStream.write(FileOutputStream.java:290)
    at java.io.DataOutputStream.writeInt(DataOutputStream.java:200)
    at net.minecraft.nbt.NBTTagInt.func_74734_a(SourceFile:25)
    at net.minecraft.nbt.NBTTagCompound.func_150298_a(NBTTagCompound.java:474)
    at net.minecraft.nbt.NBTTagCompound.func_74734_a(NBTTagCompound.java:35)
    at net.minecraft.nbt.NBTTagCompound.func_150298_a(NBTTagCompound.java:474)
    at net.minecraft.nbt.NBTTagCompound.func_74734_a(NBTTagCompound.java:35)
    at net.minecraft.nbt.NBTTagCompound.func_150298_a(NBTTagCompound.java:474)
    at net.minecraft.nbt.NBTTagCompound.func_74734_a(NBTTagCompound.java:35)
    at net.minecraft.nbt.CompressedStreamTools.func_150663_a(CompressedStreamTools.java:112)
    at net.minecraft.nbt.CompressedStreamTools.func_74800_a(CompressedStreamTools.java:102)
    at com.pixelmonmod.pixelmon.storage.FileStorage.writeComputerData(FileStorage.java:108)
    at com.pixelmonmod.pixelmon.storage.StorageAdapter.saveComputerStorage(StorageAdapter.java:31)
    at com.pixelmonmod.pixelmon.storage.ComputerManager.savePlayer(ComputerManager.java:106)
    at com.pixelmonmod.pixelmon.storage.ComputerManager.saveAll(ComputerManager.java:98)
    at com.pixelmonmod.pixelmon.storage.ComputerManager.onWorldSave(ComputerManager.java:114)
    at net.minecraftforge.fml.common.eventhandler.ASMEventHandler_58_ComputerManager_onWorldSave_Save.invoke(.dynamic)
    at net.minecraftforge.fml.common.eventhandler.ASMEventHandler.invoke(ASMEventHandler.java:90)
    at net.minecraftforge.fml.common.eventhandler.EventBus.post(EventBus.java:746)
    at org.spongepowered.mod.event.SpongeToForgeEventFactory.createAndPostWorldSaveEvent(SpongeToForgeEventFactory.java:936)
    at org.spongepowered.mod.event.SpongeToForgeEventFactory.createAndPostForgeEvent(SpongeToForgeEventFactory.java:287)
    at org.spongepowered.mod.event.SpongeModEventManager.post(SpongeModEventManager.java:340)
    at org.spongepowered.mod.event.SpongeModEventManager.extendedPost(SpongeModEventManager.java:450)
    at org.spongepowered.mod.event.SpongeModEventManager.post(SpongeModEventManager.java:419)
    at org.spongepowered.common.event.SpongeEventManager.post(SpongeEventManager.java:465)
    at net.minecraft.world.WorldServer.func_73044_a(WorldServer.java:2638)
    at org.spongepowered.common.world.WorldManager.saveWorld(WorldManager.java:555)

-- Sponge PhaseTracker --
Details:
    Phase Stack:
        /*****************************************************/
        /* - Phase: PluginPhase{}{EventListenerPhaseState}  */
        /*   Context:                                        */
        /*     - Source: FMLMod:pixelmon{2.6.2}              */
        /*     - Listener: null                               */
        /*     - CapturePlayer: CapturePlayer{player=null}    */
        /*****************************************************/

Stacktrace:
    at net.minecraft.server.MinecraftServer.handler$onCrashReport$zjo000(MinecraftServer.java:3975)
    at net.minecraft.server.MinecraftServer.func_71230_b(MinecraftServer.java:889)
    at net.minecraft.server.dedicated.DedicatedServer.func_71230_b(DedicatedServer.java:371)
    at net.minecraft.server.dedicated.ServerHangWatchdog.run(ServerHangWatchdog.java:61)
    at java.lang.Thread.run(Thread.java:748)

-- Thread Dump --
Details:

Key Information from the Crash Report

  • ServerHangWatchdog: The description clearly states “ServerHangWatchdog detected that a single server tick took 6.00 seconds (should be max 0.05)”. This is a crucial indicator. The Watchdog is designed to detect when the server is unresponsive, usually due to being overloaded or stuck in a loop. A server tick taking 6 seconds when it should be 0.05 is a massive lag spike.
  • File Output Stream Write Error: The error originates in java.io.FileOutputStream.write. This suggests an issue writing data to a file.
  • NBT Data and Pixelmon Storage: The stack trace goes through Minecraft’s NBT (Named Binary Tag) system, used for saving game data, and then specifically points to com.pixelmonmod.pixelmon.storage.FileStorage.writeComputerData and com.pixelmonmod.pixelmon.storage.ComputerManager. This strongly indicates the crash is related to Pixelmon’s storage system, specifically when saving data, potentially related to the Pokémon PC.
  • SpongeForge and Pixelmon Version: The warning at the top mentions SpongeCoremod and the “Sponge PhaseTracker” section appears later. The Pixelmon mod version is also mentioned in the PhaseTracker: FMLMod:pixelmon{2.6.2}. This tells us the server is using SpongeForge and Pixelmon 2.6.2. Compatibility issues between these or with other mods could be at play.

Potential Causes for Pixelmon Server Crashes

Based on the crash report and common Pixelmon server issues, here are potential causes:

  1. Pixelmon Mod Issues:

    • Bugs in Pixelmon Version: Version 2.6.2 might have known bugs related to data saving or PC storage. Outdated or corrupted mod files can also cause problems.
    • Data Corruption: Issues during world saving or unexpected server shutdowns can corrupt Pixelmon data files, leading to crashes when the server tries to access or write to these files.

  2. Server Resource Overload:

    • Insufficient RAM or CPU: Saving large amounts of Pixelmon data, especially with many players online, can be resource-intensive. If the server doesn’t have enough RAM or CPU power, it can hang and crash during save operations.
    • Disk I/O Bottleneck: Slow disk write speeds can exacerbate the issue. If the server’s hard drive is slow or overloaded, writing player and Pixelmon data can take too long, triggering the ServerHangWatchdog.

  3. Mod or Plugin Conflicts:

    • Incompatible Mods/Plugins: Conflicts between Pixelmon, SpongeForge, and other installed mods or plugins can lead to unexpected behavior and crashes. The warning about SpongeCoremod suggests potential interaction issues.
    • Outdated SpongeForge or Forge: Incompatibility between the versions of Forge, SpongeForge, and Pixelmon can cause instability.

  4. External Factors:

    • Java Version Issues: Using an outdated or incompatible Java version can cause various problems, including crashes.
    • Server Hosting Issues: Problems with the hosting provider’s hardware or network can sometimes manifest as server crashes.

Troubleshooting Steps for Pixelmon Server Crashes

Here are actionable steps to troubleshoot and potentially resolve the crashes:

  1. Update Pixelmon Mod:

    • Check for the latest stable version of Pixelmon Reforged. Newer versions often include bug fixes and performance improvements.
    • If already on the latest version, consider rolling back to a slightly older stable version if the crashes started after an update.

  2. Verify Server Resources:

    • RAM Allocation: Ensure your server has sufficient RAM allocated (at least 4-8GB for a moderately sized Pixelmon server, potentially more depending on player count and other mods).
    • CPU Performance: A dedicated CPU core or a powerful multi-core CPU is recommended for smooth Pixelmon server operation. Monitor CPU usage during peak times and save operations.
    • Disk Space and Speed: Make sure the server has enough free disk space. Consider using SSD storage for faster read/write speeds, which can significantly improve performance during data saving.

  3. Investigate Mod and Plugin Compatibility:

    • Check Mod/Plugin Versions: Ensure all mods and plugins are compatible with your Minecraft version (1.12.2 in this case), Forge version, and SpongeForge version.
    • Disable Recently Added Mods/Plugins: If the crashes started after adding new mods or plugins, temporarily disable them to see if they are the cause.
    • SpongeForge Compatibility: Verify you are using a compatible and stable version of SpongeForge for your Forge and Minecraft versions. Consider updating SpongeForge if an update is available.

  4. Examine Pixelmon Configuration:

    • Pixelmon Config Files: Check Pixelmon’s configuration files for any unusual or potentially problematic settings. Consult the Pixelmon documentation for default and recommended configurations.
    • PC Storage Settings: While less likely, investigate if there are any configurable options related to PC storage in Pixelmon’s configs that might be contributing to the issue.

  5. Check Java Version:

    • Ensure you are using a recommended Java version for Minecraft 1.12.2 and Forge. Java 8 is generally recommended for Minecraft 1.12.2.

  6. Review Server Logs (Besides Crash Reports):

    • Server Console Logs: Examine the regular server logs (not just crash reports) for any warnings or errors leading up to the crashes. These logs might provide additional context or clues.

  7. Seek Community Support:

    • Pixelmon Forums/Discord: Reach out to the Pixelmon community forums or Discord channels. Other server owners might have experienced similar issues and found solutions.
    • SpongeForge Community: If you suspect SpongeForge might be involved, consult the SpongeForge community for advice.

Preventing Future Pixelmon Server Crashes

Proactive measures can significantly reduce the likelihood of server crashes:

  • Regular Server Backups: Implement regular server backups. In case of data corruption or major issues, you can restore to a previous stable state.
  • Server Monitoring: Monitor server performance metrics (CPU, RAM, disk I/O) regularly. Identify potential bottlenecks before they lead to crashes.
  • Keep Mods and Plugins Updated: Stay up-to-date with the latest stable versions of Pixelmon, Forge, SpongeForge, and other mods/plugins.
  • Test Mod/Plugin Changes: Before adding new mods or plugins to your live server, test them thoroughly in a separate testing environment to identify potential conflicts.
  • Optimize Server Configuration: Fine-tune server settings (Minecraft server properties, Pixelmon configs, SpongeForge configs) for optimal performance and stability.

By systematically analyzing crash reports, understanding potential causes, and implementing these troubleshooting steps, you can effectively address Pixelmon server crashes and provide a stable and enjoyable experience for your players. Remember to approach troubleshooting methodically and test changes incrementally to pinpoint the exact cause and solution.

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