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Troubleshooting

This document provides advice for troubleshooting problems with Ops Manager.

For resolutions to alert conditions, see also Alert Resolutions.

Getting Started Checklist

To begin troubleshooting, complete these tasks to check for common, easily fixed problems:

  1. Authentication Errors
  2. Check Agent Output or Log
  3. Ensure Connectivity Between Agent and Monitored Hosts
  4. Ensure Connectivity Between Agent and Ops Manager Server
  5. Allow Agent to Discover Hosts and Collect Initial Data

Authentication Errors

If your MongoDB instances run with authentication enabled, ensure Ops Manager has the MongoDB credentials. See Configure MongoDB Authentication and Authorization.

Check Agent Output or Log

If you continue to encounter problems, check the agent’s output for errors. See Agent Logs for more information.

Ensure Connectivity Between Agent and Monitored Hosts

Ensure the system running the agent can resolve and connect to the mongod processes. If you install multiple Monitoring Agents, ensure that each Monitoring Agent can reach every mongod process in the deployment.

To confirm, log into the system where the agent is running and issue a command in the following form:

mongo [hostname]:[port]

Replace [hostname] with the hostname and [port] with the port that the database is listening on.

Ops Manager does not support port forwarding.

Ensure Connectivity Between Agent and Ops Manager Server

Verify that the Monitoring Agent can connect on TCP port 8443 (outbound) to the Ops Manager server (i.e. api-agents.mongodb.com.)

Allow Agent to Discover Hosts and Collect Initial Data

Allow the agent to run for 5-10 minutes to allow host discovery and initial data collection.

Installation

The monitoring server does not start up successfully

Confirm the URI or IP address for the Ops Manager service is stored correctly in the mongo.mongoUri property in the <install_dir>/conf/conf-mms.properties file:

mongo.mongoUri=<SetToValidUri>

If you don’t set this property, Ops Manager will fail while trying to connect to the default 127.0.0.1:27017 URL.

If the URI or IP address of your service changes, you must update the property with the new address. For example, update the address if you deploy on a system without a static IP address, or if you deploy on EC2 without a fixed IP and then restart the EC2 instance.

If the URI or IP address changes, then each user who access the service must also update the address in the URL used to connect and in the client-side monitoring-agent.config files.

If you use the Ops Manager <install_dir>/bin/credentialstool to encrypt the password used in the mongo.mongoUri value, also add the mongo.encryptedCredentials key to the <install_dir>/conf/conf-mms.properties file and set the value for this property to true:

mongo.encryptedCredentials=true

Monitoring

Alerts

For resolutions to alert conditions, see also Alert Resolutions.

For information on creating and managing alerts, see Manage Alert Configurations and Manage Alerts.

Cannot Turn Off Email Notifications

There are at least two ways to turn off alert notifications:

Receive Duplicate Alerts

If the notification email list contains multiple email-groups, one or more people may receive multiple notifications of the same alert.

Receive “Host has low open file limits” or “Too many open files” error messages

These error messages appear on the Deployment page, under a host’s name. They appear if the number of available connections does not meet the Ops Manager-defined minimum value. These errors are not generated by the mongos instance and, therefore, will not appear in mongos log files.

On a host by host basis, the Monitoring Agent compares the number of open file descriptors and connections to the maximum connections limit. The max open file descriptors ulimit parameter directly affects the number of available server connections. The agent calculates whether or not enough connections exist to meet the Ops Manager-defined minimum value.

In ping documents, for each node and its serverStatus.connections values, if the sum of the current value plus the available value is less than the maxConns configuration value set for a monitored host, the Monitoring Agent will send a Host has low open file limits or Too many open files message to Ops Manager.

Ping documents are data sent by Monitoring Agents to Ops Manager. To view ping documents, click the Deployment page, then click the host’s name, and then click Last Ping.

To prevent this error, we recommend you set ulimit open files to 64000. We also recommend setting the maxConns command in the mongo shell to at least the recommended settings.

See the MongoDB ulimit reference page and the the MongoDB maxConns reference page for details.

Deployments

Deployment Hangs in In Progress

If you have added or restarted a deployment and the deployment remains in the In Progress state for several minutes, click View Agent Logs and look for any errors.

If you diagnose an error and need to correct the deployment configuration:

  1. Click Edit Configuration and then click Edit Configuration again.
  2. Reconfigure the deployment.
  3. When you complete your changes, click Review Changes and then Confirm & Deploy.

If you shut down the deployment and still cannot find a solution, remove the deployment from Ops Manager.

Monitoring Agent Fails to Collect Data

Possible causes for this state:

Hosts

Hosts are not Visible

Problems with the Monitoring Agent detecting hosts can be caused by a few factors.

Host not added: In Ops Manager, click Deployment, then click the Processes tab, then click the Add Host button. In the New Host window, specify the host type, internal hostname, and port. If appropriate, add the database username and password and whether or not Ops Manager should use SSL to connect with your Monitoring Agent. Note it is not necessary to restart your Monitoring Agent when adding (or removing) a host.

Accidental duplicate mongods If you add the host after a crash and restart the Monitoring Agent, you might not see the hostname on the Ops Manager Deployment page. Ops Manager detects the host as a duplicate and suppresses its data. To reset, click Settings, then Group Settings, then the Reset Duplicates button.

Monitoring Agents cannot detect hosts: If your hosts exist across multiple data centers, make sure that all of your hosts can be discovered by all of your Monitoring Agents.

Cannot Delete a Host

In rare cases, the mongod is brought down and the replica set is reconfigured. The down host cannot be deleted and returns an error message, “This host cannot be deleted because it is enabled for backup.” Contact MongoDB Support for help in deleting these hosts.

Groups

Additional Information on Groups

Create a group to monitor additional segregated systems or environments for servers, agents, users, and other resources. For example, your deployment might have two or more environments separated by firewalls. In this case, you would need two or more separate Ops Manager groups.

API and shared secret keys are unique to each group. Each group requires its own agent with the appropriate API and shared secret keys. Within each group, the agent needs to be able to connect to all hosts it monitors in the group.

For information on creating and managing groups, see Create a Group.

Munin

Important

munin-node is a third-party package. For problems related to installing munin-node, refer to the Munin Wiki.

Install and configure the munin-node service on the MongoDB server(s) to be monitored before starting Ops Manager monitoring. The Ops Manager agent README file provides guidelines to install munin-node.

See also

See Configure Hardware Monitoring with munin-node for details about monitoring hardware with munin-node.

Red Hat Enterprise Linux (RHEL 6, 7) can generate the following error messages.

No package munin-node is available Error

To correct this error:

  1. Follow the instructions on the Extra Packages for Enterprise Linux repository wiki page to install the epel-release rpm for your version of your enterprise Linux.

  2. After the package is installed, type this command to install munin-node and all of its dependencies:

    sudo yum install munin-node
    
  3. After the munin-node is installed, check to see if the munin-node service is running. If it is not, type these commands to start the munin- node service.

    service munin-node status
    service munin-node start
    

Non-localhost IP Addresses are Blocked

By default, munin blocks incoming connections from non-localhost IP addresses. The /var/log/munin/munin-node.log file will display a “Denying connection” error for your non-localhost IP address.

To fix this error, open the munin-node.conf configuration file and comment out these two lines:

allow ^127\.0\.0\.1$
allow ^::1$

Then add this line to the munin-node.conf configuration file with a pattern that matches your subnet:

cidr_allow 0.0.0.0/0

Restart munin-node after editing the configuration file for changes to take effect.

Verifying iostat and Other Plugins/Services Returns “# Unknown service” Error

The first step is to confirm there is a problem. Open a telnet session and connect to iostat, iostat_ios, and cpu:

telnet HOSTNAME 4949 <default/required munin port>
fetch iostat
fetch iostat_ios
fetch cpu

The iostat_ios plugin creates the iotime chart, and the cpu plugin creates the cputime chart.

If any of these telnet fetch commands returns an “# Unknown Service” error, create a link to the plugin or service in /etc/munin/plugins/ by typing these commands:

cd /etc/munin/plugins/
sudo ln -s /usr/share/munin/plugins/<service> <service>

Replace <service> with the name of the service that generates the error.

Disk names are not listed by Munin

In some cases, Munin will omit disk names with a dash between the name and a numerical prefix, for example, dm-0 or dm-1. There is a documented fix for Munin’s iostat plugin.

Authentication

Two-Factor Authentication

Missed SMS Authentication Tokens

Unfortunately SMS is not a 100% reliable delivery mechanism for messages, especially across international borders. The Google authentication option is 100% reliable. Unless you must use SMS for authentication, use the Google Authenticator application for two-factor authentication.

If you do not receive the SMS authentication tokens:

  1. Refer to the Settings page for more details about using two-factor authentication. This page includes any limitations which may affect SMS delivery times.
  2. Enter the SMS phone number with country code first followed by the area code and the phone number. Also try 011 first followed by the country code, then area code, and then the phone number.

If you do not receive the authentication token in a reasonable amount of time, contact your Ops Manager system administrator.

Delete or Reset Two-Factor Authentication

Contact your system administrator to remove or reset two-factor authentication on your account.

For administrative information on two-factor authentication, see Manage Two-Factor Authentication for Ops Manager.

LDAP

Forgot to Change MONGODB-CR Error

If your MongoDB deployment uses LDAP for authentication, and you find the following error message:

You forget to change "MONGODB-CR" to "LDAP (PLAIN)" since they both
take username/password.

Then make sure that you specified the LDAP (PLAIN) as is the authentication mechanism for both the Monitoring Agent and the Backup Agent. See Configure Backup Agent for LDAP Authentication and Configure Monitoring Agent for LDAP.

Backup

Logs Display MongodVersionException

The MongodVersionException can occur if the Backup Daemon’s host cannot access the internet to download the version or versions of MongoDB required for the backed-up databases. Each database requires a version of MongoDB that matches the database’s version. Specifically, for each instance you must run the latest stable release of that release series. For versions earlier than 2.4, the database requires the latest stable release of 2.4.

If the Daemon runs without access to the internet, you must manually download the required MongoDB versions, as described here:

  1. Go to the MongoDB downloads page and download the appropriate versions for your environment.

  2. Copy the download to the Daemon’s host.

  3. Decompress the download into the directory specified in the mongodb.release.directory setting in the Daemon’s conf-daemon.properties file. For the file’s location, see Ops Manager Configuration.

    Within the directory specified in the mongodb.release.directory setting, the folder structure for MongoDB should look like the following:

    <path-to-mongodb-release-directory>/
    |-- mongodb-<platform>
    |  |-- THIRD-PARTY-NOTICES
    |  |-- README
    |  |-- GNU-AGPL-3.0
    |  |-- bin
    |  |  |-- bsondump
    |  |  |-- mongo
    |  |  |-- mongod
    |  |  |-- mongodump
    |  |  |-- mongoexport
    |  |  |-- mongofiles
    |  |  |-- mongoimport
    |  |  |-- mongooplog
    |  |  |-- mongoperf
    |  |  |-- mongorestore
    |  |  |-- mongos
    |  |  |-- mongostat
    |  |  |-- mongotop
    

Insufficient Oplog Size Error

When using the Ops Manager interface to back up a MongoDB cluster, Ops Manager checks to see if the cluster’s oplogs are, based on their recent usage, large enough to hold a minimum of 3 hours worth of data based on the last 24 hours of usage patterns. If the oplogs are not large enough, it may be possible that the oplogs may have turned over multiple times, creating a gap between where a backup ends and an oplog starts.

If the oplog size check fails, the user cannot enable backups and is shown the warning:

Insufficient oplog size: The oplog window must be at least 3 hours
over the last 24 hours for all members of replica set <name>.
Please increase the oplog.

If possible, wait to start a backup until the oplog has had sufficient time to meet the size requirement.

If this is not possible, the minimum oplog size value can be changed. See mms.backup.minimumOplogWindowHours for how to set this value.

Warning

Do not change the minimum oplog size unless you are certain smaller backups still provide useful backups.

Important

MongoDB recommends only changing this value temporarily to permit a test backup job to execute. The minimum oplog size value should be reset to the default as soon as possible. If an oplog is set to too small of a value, it can result in a gap between a backup job and an oplog which makes the backup unusuable for restores. Stale backup jobs must be resynchronized before it can be used for restores.

Understanding the risks given, you can start backups using this changed minimum value. Once you pass the 24 hour mark, you should reset this minimum value to preserve the sanity check for the global Ops Manager installation going forward.

System

Logs Display OutOfMemoryError

If your logs display OutOfMemoryError, ensure you are running with sufficient ulimits and RAM.

Increase Ulimits

For the recommended ulimit setting, see the FAQ on Receive “Host has low open file limits” or “Too many open files” error messages.

Ops Manager infers the host’s ulimit setting using the total number of available and current connections. For more information about ulimits in MongoDB, see the UNIX ulimit Settings reference page.

Ensure Sufficient RAM for All Components

  • Ensure that each server has enough RAM for the components it runs. If a server runs multiple components, its RAM must be at least the sum of the required amount of RAM for each component.

    For the individual RAM requirements for the Ops Manager Application server, Ops Manager Application Database, Backup Daemon server, and Backup Database, see Ops Manager System Requirements.

Obsolete Config Settings

Ops Manager will fail to start if there are obsolete configuration settings set in the conf-mms.properties file. If there is an obsolete setting, the log lists an “Obsolete Setting” error as in the following:

[OBSOLETE SETTING] Remove "mms.multiFactorAuth.require" or replace "mms.multiFactorAuth.require" with "mms.multiFactorAuth.level".

You will need to remove or replace the obsolete property in the conf-mms.properties file before you can start Ops Manager.

Automation Checklist

Ops Manager Automation allows you to deploy, configure, and manage MongoDB deployments with the Ops Manager UI. Ops Manager Automation relies on an Automation Agent, which must be installed on every server in the deployment. The Automation Agents periodically poll the Ops Manager service to determine the current goal, and continually report their status to Ops Manager.

To use Automation, you must install the Automation Agent on each server that you want Ops Manager to manage.

Automation Runs Only on 64-bit Architectures

Ops Manager provides only 64-bit downloads of the Automation Agent.

Using Own Hardware

  • If you deploy Automation manually, ensure that you have one Automation Agent on every server.

  • If you deploy the agent manually, you must create MongoDB’s dbpath and the directory for the MongoDB binaries and ensure that the user running the agent owns these directories.

    If you install using the rpm package, the agent runs as the mongod user; if using the deb package, the agent runs as the mongodb user. If you install using the tar.gz archive file, you can run the agent as any user.

Networking

All hosts must be able to allow communication between MongoDB ports. The default is 27017, but you can configure alternate port ranges in the Ops Manager interface.

The Automation Agent must be able to connect to Ops Manager on port 8443 (i.e. https). For more information on access to ports and IP addresses, see Security Overview.

Automation Configuration

After completing the automation configuration, always ensure that the deployment plan satisfies the needs of your deployment. Always double check hostnames and ports before confirming the deployment.

Sizing

  • Ensure that you provision machines with enough space to run MongoDB and support the requirements of your data set.
  • Ensure that you provision sufficient machines to run your deployment. Each mongod should run on its own host.

Frequent Connection Timeouts

The Automation Agent may frequently time out of connections for one or more of the following reasons:

  • High network latency
  • High server load
  • Large SSL keys
  • Lack of SSL accelerator
  • Insufficient CPU speed

By default, connections time out after 40 seconds. MongoDB recommends gradually increasing the value of the dialTimeoutSeconds Automation Agent configuration setting to prevent frequent premature connection timeouts. However, increasing this value also increases the time required to deploy future configuration changes. Experiment with small, incremental increases until you determine the optimum value for your deployment. See dialTimeoutSeconds in Connection Settings at Automation Agent Configuration for more information.