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blocks:server:mirror [2020-05-25 10:02]
admin updated date to 2020-05-25 		blocks:server:mirror [2025-02-13 20:01] (current)
admin Added Sync Errors note
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 ====== Blocks Mirroring Service ====== ====== Blocks Mirroring Service ======
  
-Our Linux-based Blocks server dated 2020-05-25 and later, running Ubuntu 20.04, supports a new redundancy feature for increased system reliability. While the Blocks server software is very robust, the complete system can never be more reliable than the hardware it runs on.+Our Linux-based server supports a hardware redundancy feature for increased system reliability. While the Blocks server software is very robust, the complete system can never be more reliable than the hardware it runs on.
  
 ===== Introduction ===== ===== Introduction =====
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   * Server Disk Space. Indicates the amount of free space on the Blocks Server itself. This also makes sens to keep an eye on – especially before adding a significant amount of new content.   * Server Disk Space. Indicates the amount of free space on the Blocks Server itself. This also makes sens to keep an eye on – especially before adding a significant amount of new content.
   * Server Time. Shows the current time of the clock in the Blocks Server. If your server has Internet access, this is generally adjusted automatically. If not, you may want to check this every few monts to make sure that it is reasonably accurate.   * Server Time. Shows the current time of the clock in the Blocks Server. If your server has Internet access, this is generally adjusted automatically. If not, you may want to check this every few monts to make sure that it is reasonably accurate.
 +  * Sync Errors. Cumulative count of data sync errors that have occurred, if any. Check the Mirror log file for details.
  
-The SYNCHRONIZE NOW button can be used to force a full synchronization. Use this after making manual changes to the files in the /home/pixi-server directory of the Blocks server, such as updating Blocks itself or the mirroring service (the files PIXILAN.jar and MIRROR.jar respectvely). Doing so pushes those changes over to the Mirror Server immediately rather than waiting for the next scheduled full synchronization.+The "Synchtronize Now" button can be used to force a full synchronization. Use this after making manual changes to the files in the /home/pixi-server directory of the Blocks server, such as updating Blocks itself or the mirroring service (the files PIXILAN.jar and MIRROR.jar respectvely). Doing so pushes those changes over to the Mirror Server immediately rather than waiting for the next scheduled full synchronization.
  
 ===== Testing the Mirror Server ===== ===== Testing the Mirror Server =====
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   * Set fullSyncOnStartup to //true// to run a full synchronization once when mirroring service is started.   * Set fullSyncOnStartup to //true// to run a full synchronization once when mirroring service is started.
   * Set java.util.logging.FileHandler.level to //ERROR// for less verbose logging, or //INFO// for more details (sometimes useful when troubleshooting).   * Set java.util.logging.FileHandler.level to //ERROR// for less verbose logging, or //INFO// for more details (sometimes useful when troubleshooting).
 +
 +The following additional, advanced settings are available in version 7.1 and later, then specified under the "mirror:" heading as shown above. 
 +
 +<code>
 +  interface: enp2s0
 +  subnet: 192.168.0.0/24
 +</code>
 +
 +:!: **NOTE**: There are two spaces at the beginning of each line, as required when used under the "mirror:" heading.
 +
 +  * The //interface// setting is useful if your computer have more than one network interface with link local addressing. If so, use this setting to specify the name of the desired synchronization backdoor network interface.
 +  * The //subnet// setting lets you specify a non link local subnet (in CIDR notation) for use as the data synchronization backdoor. This is useful in cases where you may want to use this interface for other purposes, such as remote management of the servers. You would then either set fixed addresses (within the specified subnet) or use dynamically assigned addresses (DHCP).
 +
  
 The settings under //logging// follow the java.util.logging standard, sometimes referred to as JUL, allowing you to use any settings available there, for example to log to an external log handler. The settings under //logging// follow the java.util.logging standard, sometimes referred to as JUL, allowing you to use any settings available there, for example to log to an external log handler.
  
  
 +=====Troubleshooting=====
 +Unless the advanced //subnet// setting is used (see above), the server-to-server backdoor connection assumes the use of self-assigned ("link local") addresses. Such adresses are in the 169.254.x.x address range. There must not be any additional network interfaces in either computer having such IP addresses. If there are, do either of the following:
 +  * Disable any such interface(s). in some cases this may need to be done in the computer's BIOS settings.
 +  * Change their addresses to keep them out of this address range.
 +  * Use the advanced //nic// setting to specify which interface to use. 
 + 
 +=== Verifying over SSH ===
 +The mirroring service shows its status window while running, as described above. If you're accessing your server using a terminal session over SSH, you can instead use this command to ascertain whether the mirroring service is running, while being logged in as the pixi-server user:
 +
 +<code>
 +systemctl --user status blocks.mirror
 +</code>
 +
 +
 +=====Implementation Notes=====
 +
 +These notes provide additional understanding of how the mirroring service works. While not generally something you need to know, these details may be of assistans in some installations or when troubleshooting a system.
 +
 +===Synchronized files===
 +The following directories and files are synchronized:
 +
 +  * /home/pixi-server/PIXILAB-BLOCKS-root/*
 +  * /home/pixi-server/native/*
 +  * /home/pixi-server/*.sh (e.g., the command-line start and stop scripts)
 +  * /home/pixi-server/PIXILAN.jar (the Blocks software)
 +  * /home/pixi-server/MIRROR.jar (the Mirroring software)
 +  * /home/pixi-server/PIXILAB-Blocks-config.yml (if it exists)
 +
 +:!: **NOTE:** Any additional files you want to synchronize, such as SSL certificates, must be placed inside the PIXILAB-BLOCKS-root
 +
 +===Starting/stopping Blocks===
 +The Linux [[https://en.wikipedia.org/wiki/Systemd|systemd]] feature is used to start and manage most programs that aren't started manually. This includes Blocks as well as the Mirroring service. You can see how this is done inside the start.sh and stop.sh scripts located in the home directory of the pixi-server user. When //not// using the mirroring service, //systemd// directly starts and manages Blocks. 
 +
 +However, when using the mirroring service, //systemd// starts the mirroring service (referred to by the name //blocks.mirror//). Then, when appropriate (i.e., when the license key is connected) the mirroring service starts Blocks. Likewise, if the license key is disconnected (e.g., to be moved to the other server), the mirroring service shuts down Blocks. Here, //systemd// isn't directly responsible for starting/stopping Blocks. Therefore, viewing its //systemd// status (e.g. using the //systemctl --user status blocks// command) will show its status as inactive, even though it's running. Other system commands can be used to look at running processes.
 +
 +The mirroring service also generates its own log, found in the logs directory inside your Blocks root directory. Check these log files if you encounter any problems related to the mirroring service.