Common issues with the Data Server

In this guide, you can find solutions to common issues that might occur with Flexmonster Data Server. See how to troubleshoot your issue if it is not listed here.

Issues with running the server

This section contains solutions to issues that can occur when running the Data Server.

Error: "Failed to bind to address http://[::]:<port number>: address already in use."

This issue occurs when you are trying to run the Data Server on a port used by another program.

To resolve this issue, do one of the following:

• Stop the program that uses the specified port.
• Run the Data Server on a different port. See how to set a port for the Data Server as a service or as a console application.

Issues with indexes and data sources

This section contains solutions to issues related to index configurations or data sources.

Errors: "Failed to connect using connection string: <connection string>", "Option <option name> not supported.", "Index <index name> cannot be loaded. Details: Cannot load data from database executing query <your query>. Please check query or connection string. Option <option name> not supported."

This error might be caused by one of the following:

• Incorrect option name in the connection string. Ensure that you have specified the option’s name correctly. 
• The password in your connection string contains unescaped special characters. See how to set passwords with special characters in the Data Server as a service, as a console application, or as a DLL.
• Bad formatting in the connection string. Ensure that your connection string is formatted correctly.

Error: "Cannot connect to the database using "Server=xxxx;Port=xxxx;Uid=xxxx;Pwd=xxxx;Database=xxxx". Please check connection string. Details: Exception while reading from stream."

This issue might occur when connecting to a secure PostgreSQL instance without making the necessary configurations. Learn more details in this support ticket.

Error: "Cannot connect to the database using "Server=(localdb)\\MSSQLLocalDB;Uid=root;Pwd=password;Database=database_name". Please check connection string. Details: Cannot connect to SQL Server Browser. Ensure SQL Server Browser has been started."

This error might appear when remotely connecting to an SQL Server instance without starting SQL Server Browser. See how to start SQL Server Browser. 

For more information on remote connections to SQL Server, refer to our guide.

Error: "Index <index name> cannot be loaded. Details: Cannot load data from database executing query <your query>. Please check query or connection string."

This issue might be caused by one of the following:

• Incorrect SQL syntax is used in your query. Use the correct syntax in the query depending on your database type:
  • MySQL
  • MariaDB
  • PostgreSQL
  • Microsoft SQL Server
  • Oracle
• Your query contains names with special characters. Enclose such names with backtick quotes. For example: SELECT * FROM `<table name>`.
• Your MySQL or MariaDB connection string requires additional options. Starting from version 2.9.1, the Data Server uses a new driver for MySQL and MariaDB databases. If you get this issue after updating from the Data Server 2.9.0, try adding the IgnorePrepare=true option to your connection string.

Error: "Index <index name> cannot be loaded. Details: Cannot load data from database executing query <your query>. Please check query or connection string. Exception of type 'System.OutOfMemoryException' was thrown."

This error occurs when Flexmonster Data Server does not have enough RAM to load an entire dataset.

To resolve this issue, do one of the following:

• Select only the necessary columns in the query. For example: `SELECT a,b,c FROM table`.
• Decrease the amount of used RAM by adjusting the configuration. Depending on how the Data Server is used, make the following changes:

  As a Windows/Unix service

  • Set the Cache size limit to 0.
  • Disable the Keep data on refresh configuration.

  As a console application

  • Set the CacheSizeLimit to 0.
  • Set the KeepDataOnRefresh to false.

  As a DLL

  • Set the CacheSizeLimit to 0.
  • Set the KeepDataOnRefresh to false.
• Run Flexmonster Data Server on a machine with more RAM.

Error: "Index <index name> cannot be loaded. Details: Cannot find file for index <index name>."

This error occurs when a JSON/CSV file specified in the index configuration cannot be found.

Ensure the file exists and the correct path to it is specified in the index. See how to specify path to a JSON/CSV file in the Data Server as a service, as a console application, or as a DLL.

Error: "Index <index name> cannot be loaded. Details: Cannot load data from <JSON/CSV> file at <file path>."

This error is caused by an invalid or corrupted JSON/CSV data source.

Ensure that data in the JSON/CSV file is valid and formatted in the way supported by Flexmonster Data Server. Learn more about supported formats:

• Supported JSON format
• Supported CSV format

Issues with HTTPS configuration

This section contains solutions to issues related to HTTPS configs.

Error: "Https configuration failed."

This issue might occur because of the following reasons:

• The certificate file cannot be found. Ensure the certificate file exists and the correct path to it is specified. See how to configure the certificate file in the Data Server as a service or as a console application.
• The certificate is invalid. Check if the certificate is configured correctly.
• The configuration file is corrupted. See how to resolve this issue.

Error: "ERR_HTTP2_INADEQUATE_TRANSPORT_SECURITY"

The main reason for this error is that HTTP/2 does not support the Data Server’s SSL certificate. See this thread to learn more.

One of the possible solutions to this error is to set the Protocols property to "Http1" in flexmonster-config.json:

"HTTPS": {
  "Enabled": true,
  "Protocols": "Http1",
  "Certificate": {
    // Your certificate
  }
}

Note If you are using the Data Server as a service, see where to find flexmonster-config.json.

Issues with the Admin Panel

This section contains solutions to issues related to the Admin Panel. 

Issue: The configuration file is corrupted, locked, or cannot be updated

Sometimes the configuration file might become corrupted or locked because of unsuccessful changes, interrupted saving, entering invalid values, etc.

Resolve issues with the configuration file in the following way:

Step 1. Open the Admin Panel.

Step 2. Click Stop server in the lower-left corner of the window.

Step 3. Rename the current Data Server configuration file (e.g., to flexmonster-config.old). 

Step 4. Choose if you want to use a previous config or revert to the default one:

Admin Panel error: "Server is unreachable"

This error might be caused by one of the following:

• The Data Server is not run as a Windows/Unix service. The Admin Panel works only with the Data Server as a service. Stop instances of the Data Server as a console application and ensure the Data Server is run as a service.
• Access to the Admin Panel's working directory is restricted. Make sure the following directory can be modified:
  • On Windows — C:/ProgramData/FlexmonsterDataServer/.
  • On macOS and Ubuntu/Linux — ~/.local/share/FlexmonsterDataServer/ (will resolve to /home/[current_user]/.local/share/FlexmonsterDataServer/).