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https://issues.apache.org/jira/browse/GUACAMOLE-942?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
]
Mike Jumper resolved GUACAMOLE-942.
-----------------------------------
Fix Version/s: 1.3.0
Resolution: Fixed
This should now be fixed on git master.
> Query may fail if all connections disconnect while listing active connections
> -----------------------------------------------------------------------------
>
> Key: GUACAMOLE-942
> URL: https://issues.apache.org/jira/browse/GUACAMOLE-942
> Project: Guacamole
> Issue Type: Bug
> Components: guacamole-auth-jdbc
> Affects Versions: 1.1.0
> Reporter: Stefan Bluhm
> Assignee: Mike Jumper
> Priority: Minor
> Fix For: 1.3.0
>
> Attachments: catalina.zip
>
>
> The content of [{{getActiveConnections()}} within
> {{AbstractGuacamoleTunnelService}}|https://github.com/apache/guacamole-client/blob/ae4361ab70dae4829b08f34a80b08fac885703ba/extensions/guacamole-auth-jdbc/modules/guacamole-auth-jdbc-base/src/main/java/org/apache/guacamole/auth/jdbc/tunnel/AbstractGuacamoleTunnelService.java#L623]
> 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. {color:red}<-- race condition{color}
> # 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:
> {code:none}
> 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
> {code}
> 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|https://issues.apache.org/jira/browse/GUACAMOLE-942?focusedCommentId=17150530&page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel#comment-17150530].
> It is simply more likely for this error to occur if connections are failing
> on their own.
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