The first step in troubleshooting the agent is finding out whether it is running or not. To do this see:
If incorrect credentials are specified for the agent login to the
MySQL server that it is monitoring, then the agent will not run on
start-up. Log in to the monitored MySQL server and check the
agent's credentials. Compare the values of the
Host
, User
, and
Password
fields in the
mysql.user
table with the values shown in the
[mysqld]
section of the
etc/instances/mysql/agent-instance.ini
. If
incorrect credentials are specified in the
ini
file, simply correct them and restart the
agent. Remember, changes to the ini
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 Agent Log and PID Files.
If the agent starts up but no server appears in the dashboard,
check the 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
http://
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. If you
log in successfully, you should see the following message:
Dashboard_Host:18080
/heartbeat
<exceptions> <error>E1031: Agent payload parameter NULL.</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 Agent Log and PID Files.
If no HTTP authentication dialog box appears, and you are unable
to connect at all, then you may have specified an incorrect host
name or port. 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 15.3.3.6.5, “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:test@172.11.1.1:18080
/heartbeat' failed:
"connect() timed out!" error.
For the location of the agent error log file see, Agent Log and PID Files.
Setting the log-level
entry in your
ini
file is also a good debugging technique.
For more information on this subject see,
Section 15.3.3.6.1, “MySQL Enterprise Monitor Agent (mysql-monitor-agent.ini
)
Configuration”.
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, the
UUID
must be unique and the
log-file
and pid-file
values
must be different. For more information, see
Section 15.3.3.6.2, “MySQL Server (agent-instance.ini
) Configuration”.
If the agent is not running on the same machine that hosts the
MySQL server it is monitoring, then you must 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 15.3.3.6.4, “Configuring an Agent to Monitor a Remote MySQL Server”.
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