# Postgres The Postgres service manages the connection and communication between the Chainlink node and its local or remote PostgreSQL database. ### \[ERROR] could not get advisory lock for classID The advisory lock provides a mechanism that locks the database as an application-oriented session without simultaneously preventing write operations (e.g. manual editing of the database). This means that other applications can be in the queue and have full access to the database as soon as the lock is released. It can be used for automated Chainlink node failover architectures by enabling a secondary node to wait for the lock to be released to jump in whenever the primary node fails (this practice is no longer recommended). This log indicates that the lock could not be closed. * Make sure that the `ETH_DATABASE_URL` environmental variables of the primary and secondary Chainlink nodes are identical * Check if the PostgeSQL database settings for the advisory lock is enabled ### \[WARN] Postgres event broadcaster: disconnected, trying to reconnect… The connection to the PostgreSQL database might have been interrupted and the Chainlink node tries to reconnect to resume the exchange with it. * Check the firewall settings of the Chainlink node’s host machine for outgoing traffic * Check the firewall settings of the PostgreSQL server for incoming traffic * Check the health and availability of the PostgreSQL server ### \[WARN] Postgres event broadcaster: reconnect attempt failed, trying again… The Chainlink node was not able to reconnect to the PostgreSQL database. It will produce this log until it can successfully reconnect. * Check the firewall settings of the Chainlink node’s host machine for outgoing traffic * Check the firewall settings of the PostgreSQL server for incoming traffic * Check the health and availability of the PostgreSQL server --- # Agent Instructions: Querying This Documentation If you need additional information that is not directly available in this page, you can query the documentation dynamically by asking a question. Perform an HTTP GET request on the current page URL with the `ask` query parameter: ``` GET https://www.oraclelabs.link/technical/chainlink-node-logs/postgres.md?ask= ``` The question should be specific, self-contained, and written in natural language. The response will contain a direct answer to the question and relevant excerpts and sources from the documentation. Use this mechanism when the answer is not explicitly present in the current page, you need clarification or additional context, or you want to retrieve related documentation sections.