Briefly, this error occurs when Elasticsearch tries to establish a connection to a node, but the channel (network connection) closes unexpectedly. This could be due to network issues, firewall restrictions, or the target node being unresponsive or overloaded. To resolve this, you can check the network connectivity between the nodes, ensure there are no firewall restrictions blocking the connection, and verify the target node’s health and load. If the target node is overloaded, consider adding more nodes to your cluster or increasing the resources of the existing nodes.
This guide will help you check for common problems that cause the log ” a channel closed while connecting ” to appear. To understand the issues related to this log, read the explanation below about the following Elasticsearch concepts: .
Log Context
Log “a channel closed while connecting” class name is ClusterConnectionManager.java. We extracted the following from Elasticsearch source code for those seeking an in-depth context :
connectionListener.onConnectionOpened(connection);
} finally {
connection.addCloseListener(ActionListener.running(() -> connectionListener.onConnectionClosed(connection)));
}
if (connection.isClosed()) {
throw new ConnectTransportException(node; "a channel closed while connecting");
}
return connection;
}));
}
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