The first step in troubleshooting the agent is finding out whether it is running or not. To do this see:
Some additional tips are:
To diagnose any issues with the agent, start by looking at the Logs link under the Settings tab, as described in Section 2.8.6, “Logs”. This page consolidates troubleshooting information across all the MySQL Enterprise Monitor components.
To run on start-up, the agent requires correct login
credentials for the monitored MySQL server. Log in to the
monitored MySQL server and check the agent's credentials.
Compare the values of the
fields in the
mysql.user table with the
values shown in the
[mysqld] section of the
If incorrect credentials are specified in the
ini file, simply correct them and restart
the agent. Remember, changes to the
file do not take effect until the agent is restarted.
The agent will not start up if incorrect credentials are
specified for the service manager login. Using incorrect
credentials for logging in to the service manager creates an
entry in the agent log file. For the location of this log file
see Section C.2.3, “Agent Log and
If the agent starts up but no server appears in the dashboard,
hostname specified in the
[mysql-proxy] portion of the
mysql-monitor-agent.ini file. Incorrect
credentials, IP address, or port will all cause the MySQL
server to fail to appear in the dashboard. Also, ensure that
the port specified in this file is not blocked on the machine
hosting the MySQL Enterprise Service Manager.
An easy way to confirm that the agent can log in to the
service manager is to type
into the address bar of your web browser, substituting the
appropriate host name and port. When the HTTP authentication
dialog box opens, enter the agent user name and password. The
following message indicates a successful login:
<exceptions> <error>E0401: NullAgentPayloadException: </error> </exceptions>
Despite the fact that the preceding listing shows an error, you have logged in successfully. This error appears because you have logged in but with no “payload”.
If you can log in successfully in the way described above and
the agent is running, then there are errors in the
mysql-monitor-agent.ini file. Compare the
host name, port, agent name, and password found in the
ini file with the values you entered into
the address bar of your web browser.
If HTTP authentication fails then you are using incorrect
credentials for the agent. Attempting to log in to the service
manager using incorrect credentials creates an entry in the
agent log file. For the location of this log file see
Section C.2.3, “Agent Log and
If no HTTP authentication dialog box appears, and you are
unable to connect at all, then the host name or port might be
specified incorrectly. Confirm the values you entered against
those described as the
Application hostname and
port: in the
configuration_report.txt file. Failure to
connect could also indicate that the port is blocked on the
machine hosting the MySQL Enterprise Service Manager.
To check if a blocked port is the problem, temporarily bring down your firewall. If the agent is then able to connect, open up the port specified during installation and restart the agent. If necessary you can monitor outside the firewall using an SSH tunnel. For more information, see Section 5.3.8, “Monitoring Outside the Firewall with an SSH Tunnel”.
You can also check the agent error log file to help determine any problems. An error such as the following might indicate a blocked port:
(critical) connection to merlin-server 'http://
agent:firstname.lastname@example.org:18080/heartbeat' failed: "connect() timed out!" error.
For the location of the agent error log file, see
Section C.2.3, “Agent Log and
log-level entry in your
ini file is also a good debugging
technique. For more information on this subject see,
Section C.2.1, “MySQL Enterprise Monitor Agent Configurable Options”.
Running the agent from the command line sometimes displays errors that fail to appear in the log file or on the screen when the agent is started from a menu option. To start the agent from the command line see the instructions given at the start of this section.
If you have more than one agent running on the same machine,
UUID must be unique and the
values must be different. For more information, see
Section C.2.2, “MySQL Server (
If the agent and the MySQL server it is monitoring are running
on different machines, ensure that the correct
host is specified for the agent account.
The correct port, typically 3306, must also be open for remote
login. For more information about remote monitoring see,
Section 5.3.7, “Configuring an Agent to Monitor a Remote MySQL Server”.
The MySQL Enterprise Monitor Agent and MySQL Enterprise Service Manager use the unique host ID,
stored within the
mysql.inventory table on
the monitored MySQL Server, to determine whether the instance
being monitored is a clone. The host ID of the current server
is checked against the stored value when the agent starts. If
the generated host ID and stored host ID do not match, you get
an error similar to the following in the agent log file:
%s: [%s] the hostid from mysql.inventory doesn't match our agent's host-id (%s != %s) We assume that this is a cloned host and shutdown now. Please TRUNCATE TABLE mysql.inventory on this mysql-instance and restart the agent. If this is a master for replication, please also run SET SQL_LOG_BIN = 0; first.
To fix the problem, connect to the MySQL server using the
credentials configured when you installed the agent, and then
mysql> TRUNCATE mysql.inventory;
Now restart the agent, which recreates the
mysql.inventory table with the updated
instance UUID and hostid information.
If the MySQL Enterprise Monitor Agent is restarted after being terminated
ungracefully (for example, by the kill
command), you might see a
DuplicateAgentUuidException error until the
original registration of the previous instance of the agent