Details
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Bug
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Status: Resolved
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Minor
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Resolution: Fixed
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1.1.0
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None
Description
The content of getActiveConnections() within AbstractGuacamoleTunnelService currently does the following:
- Check if there are zero active connections. If there aren't any, just return an empty set.
- Produce the set of connection identifiers associated with all active connections. <-- race condition
- Retrieve the subset of those connection identifiers that are actually readable.
There is a race condition here, as the set of active connections is a live, concurrently-modifiable map. If there are active connections at the beginning, but all of those connections disconnect prior to producing the set of connection identifiers, then the set of identifiers will be empty. When this empty set is passed to the selectReadable() query that follows, an internal error will result:
17:02:02.435 [http-nio-8080-exec-3] ERROR o.a.g.rest.RESTExceptionMapper - Unexpected internal error: ### Error querying database. Cause: com.mysql.jdbc.exceptions.jdbc4.MySQLSyntaxErrorException: You have an error in your SQL syntax; check the manual that corresponds to your MariaDB server version for the right syntax to use near 'AND ( guacamole_connection_permission.entity_id = 7 ' at line 19 ### The error may exist in org/apache/guacamole/auth/jdbc/connection/ConnectionMapper.xml ### The error may involve defaultParameterMap ### The error occurred while setting parameters ### SQL: SELECT guacamole_connection.connection_id, guacamole_connection.connection_name, parent_id, protocol, max_connections, max_connections_per_user, proxy_hostname, proxy_port, proxy_encryption_method, connection_weight, failover_only, MAX(start_date) AS last_active FROM guacamole_connection JOIN guacamole_connection_permission ON guacamole_connection_permission.connection_id = guacamole_connection.connection_id LEFT JOIN guacamole_connection_history ON guacamole_connection_history.connection_id = guacamole_connection.connection_id WHERE guacamole_connection.connection_id IN AND ( guacamole_connection_permission.entity_id = ? ) AND permission = 'READ' GROUP BY guacamole_connection.connection_id; SELECT primary_connection_id, guacamole_sharing_profile.sharing_profile_id FROM guacamole_sharing_profile JOIN guacamole_sharing_profile_permission ON guacamole_sharing_profile_permission.sharing_profile_id = guacamole_sharing_profile.sharing_profile_id WHERE primary_connection_id IN AND ( entity_id = ? ) AND permission = 'READ'; SELECT guacamole_connection_attribute.connection_id, attribute_name, attribute_value FROM guacamole_connection_attribute JOIN guacamole_connection_permission ON guacamole_connection_permission.connection_id = guacamole_connection_attribute.connection_id WHERE guacamole_connection_attribute.connection_id IN AND ( entity_id = ? ) AND permission = 'READ'; ### Cause: com.mysql.jdbc.exceptions.jdbc4.MySQLSyntaxErrorException: You have an error in your SQL syntax; check the manual that corresponds to your MariaDB server version for the right syntax to use near 'AND ( guacamole_connection_permission.entity_id = 7 ' at line 19
Though the above has been reported several times as a possible cause of failures to connect to remote desktops, this error does not actually result in connection failure. Its association with connection failures is a red herring, and it has been confirmed that intentionally causing this error will not result in an otherwise functional connection failing. It is simply more likely for this error to occur if connections are failing on their own.