Central Logging in Kolla

Central Logging in Kolla

An OpenStack deployment generates vast amounts of log data. In order to successfully monitor this and use it to diagnose problems, the standard “ssh and grep” solution quickly becomes unmanageable.

Preparation and deployment

Modify the configuration file /etc/kolla/globals.yml and change the following:

enable_central_logging: "yes"

Elasticsearch

Kolla deploys Elasticsearch as part of the E*K stack to store, organize and make logs easily accessible.

By default Elasticsearch is deployed on port 9200.

Note

Elasticsearch stores a lot of logs, so if you are running centralized logging, remember to give /var/lib/docker an adequate space.

Kibana

Kolla deploys Kibana as part of the E*K stack in order to allow operators to search and visualise logs in a centralised manner.

After successful deployment, Kibana can be accessed using a browser on <kolla_external_vip_address>:5601.

The default username is kibana, the password can be located under <kibana_password> in /etc/kolla/passwords.yml.

Search logs - Discover tab

Operators can create and store searches based on various fields from logs, for example, “show all logs marked with ERROR on nova-compute”.

To do this, click the Discover tab. Fields from the logs can be filtered by hovering over entries from the left hand side, and clicking add or remove. Add the following fields:

  • Hostname
  • Payload
  • severity_label
  • programname

This yields an easy to read list of all log events from each node in the deployment within the last 15 minutes. A “tail like” functionality can be achieved by clicking the clock icon in the top right hand corner of the screen, and selecting Auto-refresh.

Logs can also be filtered down further. To use the above example, type programname:nova-compute in the search bar. Click the drop-down arrow from one of the results, then the small magnifying glass icon from beside the programname field. This should now show a list of all events from nova-compute services across the cluster.

The current search can also be saved by clicking the Save Search icon available from the menu on the right hand side.

Example: using Kibana to diagnose a common failure

The following example demonstrates how Kibana can be used to diagnose a common OpenStack problem, where an instance fails to launch with the error ‘No valid host was found’.

First, re-run the server creation with --debug:

openstack --debug server create --image cirros --flavor m1.tiny \
--key-name mykey --nic net-id=00af016f-dffe-4e3c-a9b8-ec52ccd8ea65 \
demo1

In this output, look for the key X-Compute-Request-Id. This is a unique identifier that can be used to track the request through the system. An example ID looks like this:

X-Compute-Request-Id: req-c076b50a-6a22-48bf-8810-b9f41176a6d5

Taking the value of X-Compute-Request-Id, enter the value into the Kibana search bar, minus the leading req-. Assuming some basic filters have been added as shown in the previous section, Kibana should now show the path this request made through the OpenStack deployment, starting at a nova-api on a control node, through the nova-scheduler, nova-conductor, and finally nova-compute. Inspecting the Payload of the entries marked ERROR should quickly lead to the source of the problem.

While some knowledge is still required of how Nova works in this instance, it can still be seen how Kibana helps in tracing this data, particularly in a large scale deployment scenario.

Visualize data - Visualize tab

In the visualization tab a wide range of charts is available. If any visualization has not been saved yet, after choosing this tab Create a new visualization panel is opened. If a visualization has already been saved, after choosing this tab, lately modified visualization is opened. In this case, one can create a new visualization by choosing add visualization option in the menu on the right. In order to create new visualization, one of the available options has to be chosen (pie chart, area chart). Each visualization can be created from a saved or a new search. After choosing any kind of search, a design panel is opened. In this panel, a chart can be generated and previewed. In the menu on the left, metrics for a chart can be chosen. The chart can be generated by pressing a green arrow on the top of the left-side menu.

Note

After creating a visualization, it can be saved by choosing save visualization option in the menu on the right. If it is not saved, it will be lost after leaving a page or creating another visualization.

Organize visualizations and searches - Dashboard tab

In the Dashboard tab all of saved visualizations and searches can be organized in one Dashboard. To add visualization or search, one can choose add visualization option in the menu on the right and then choose an item from all saved ones. The order and size of elements can be changed directly in this place by moving them or resizing. The color of charts can also be changed by checking a colorful dots on the legend near each visualization.

Note

After creating a dashboard, it can be saved by choosing save dashboard option in the menu on the right. If it is not saved, it will be lost after leaving a page or creating another dashboard.

If a Dashboard has already been saved, it can be opened by choosing open dashboard option in the menu on the right.

Exporting and importing created items - Settings tab

Once visualizations, searches or dashboards are created, they can be exported to a JSON format by choosing Settings tab and then Objects tab. Each of the item can be exported separately by selecting it in the menu. All of the items can also be exported at once by choosing export everything option. In the same tab (Settings - Objects) one can also import saved items by choosing import option.

Custom log forwarding

In some scenarios it may be useful to forward logs to a logging service other than elasticsearch. This can be done by configuring custom fluentd outputs.

Configuration of custom fluentd outputs is possible by placing output configuration files in /etc/kolla/config/fluentd/output/*.conf on the control host.

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