MDB_READERS_FULL: Environment maxreaders limit reached

# Cause of failure

This issue primarily occurs in the following environments:

• Edge Node Version: Versions prior to 24.3.27-1
• Server Configuration: CPU core count exceeds 62 cores

This is caused by a known limitation in earlier versions when handling high-core-count servers.

# Impact of failure

This issue will result in:

• Edge Node process unable to start properly
• Complete service unavailability, severely affecting business availability

# Troubleshooting

# Emergency Support Contact

Please immediately contact the OpenResty Edge support team while following the emergency procedures below.

# Emergency Response Solutions

# Solution 1: Disable Cache Index

Applicable Condition: Error message contains cache index Example: cache index unable to start read transaction: MDB_READERS_FULL: Environment maxreaders limit reached

# 1. Disable cache index

Modify the configuration file /usr/local/oredge-node/conf/config.ini and add the following content:

[cache]
enabled = false

# 2. Clean up related configurations

sed -i '/\(cache_index_lmdb\|cache_index_max_readers\|cache_index on;\)/d' /usr/local/oredge-node/conf/nginx.conf

# 3. Restart the service

sudo systemctl start upgrade-oredge-node

# Solution 2: Upgrade Edge Node Version

Note: Newer versions of Edge Node are typically backward compatible with older versions of Edge Admin. Upgrading can completely resolve this issue.

# 1. Determine upgrade version

Choose the appropriate upgrade command based on your current Edge Node version:

Case 1: Current version < 24.3.27-1

Upgrade to version 24.3.27-1:

curl --compressed -SsLo openresty-edge-installer.sh \
  'https://openresty.com/client/oredge/openresty-edge-installer.sh' && \
sudo bash openresty-edge-installer.sh -a upgrade -c node -v 24.3.27-1

Case 2: Current version between 24.3.27-1 ~ 25.6.15-1

Upgrade to version 25.6.15-1:

curl --compressed -SsLo openresty-edge-installer.sh \
  'https://openresty.com/client/oredge/openresty-edge-installer.sh' && \
sudo bash openresty-edge-installer.sh -a upgrade -c node -v 25.6.15-1

# 2. Verify upgrade results

If the upgrade script fails, please check whether the new version has been successfully installed:

RPM systems (CentOS/RHEL/Fedora):

rpm -q openresty-edge-node

DEB systems (Ubuntu/Debian):

dpkg -l openresty-edge-node

# 3. Manual service restart (if needed)

If the new version is installed but the service hasn’t started properly, please follow these steps:

3.1 Stop the service

sudo systemctl stop oredge-node

3.2 Confirm process has completely exited

sudo systemctl status oredge-node

3.3 Configuration parameter adjustments

• Adjust cache_index_max_readers parameter:

  • If this parameter already exists in the configuration file, change its value to 516
  • If it doesn’t exist, execute the following command to add it:

    sudo sed -i '/cache_index_lmdb/a \    cache_index_max_readers 516;' /usr/local/oredge-node/conf/nginx.conf
    

• Adjust lua_config_max_readers parameter:

  • If this parameter already exists in the configuration file, change its value to 516
  • If it doesn’t exist, execute the following command to add it:

    sudo sed -i '/lua_config_map_size/a \lua_config_max_readers 516;' /usr/local/oredge-node/conf/nginx.conf
    

3.4 Start the service

sudo systemctl start oredge-node

3.5 Check service status

sudo systemctl status oredge-node

# Follow-up Actions

# If the issue remains unresolved

• Immediately contact the OpenResty Edge support team for further technical assistance

# If the issue has been resolved

• Recommend contacting the support team to learn about the latest stable version
• Develop an upgrade plan to prevent similar issues from recurring