Latest revision as of 20:07, 18 August 2017

Logging

Where Are the Logs?

Most services use the convention of writing their log files to subdirectories of the /var/log directory, as listed in table_log_locations.

Reading the Logs

OpenStack services use the standard logging levels, at increasing severity: TRACE, DEBUG, INFO, AUDIT, WARNING, ERROR, and CRITICAL. That is, messages only appear in the logs if they are more "severe" than the particular log level, with DEBUG allowing all log statements through. For example, TRACE is logged only if the software has a stack trace, while INFO is logged for every message including those that are only for information.

To disable DEBUG-level logging, edit /etc/nova/nova.conf file as follows:

debug=false

Keystone is handled a little differently. To modify the logging level, edit the /etc/keystone/logging.conf file and look at the logger_root and handler_file sections.

Logging for horizon is configured in /etc/openstack_dashboard/local_settings.py. Because horizon is a Django web application, it follows the Django Logging framework conventions.

The first step in finding the source of an error is typically to search for a CRITICAL, or ERROR message in the log starting at the bottom of the log file.

Here is an example of a log message with the corresponding ERROR (Python traceback) immediately following:

2017-01-18 15:54:00.467 32552 ERROR oslo_messaging.rpc.server [req-c0b38ace-2586-48ce-9336-6233efa1f035 6c9808c2c5044e1388a83a74da9364d5 e07f5395c
2eb428cafc41679e7deeab1 - default default] Exception during message handling
2017-01-18 15:54:00.467 32552 ERROR oslo_messaging.rpc.server Traceback (most recent call last):
2017-01-18 15:54:00.467 32552 ERROR oslo_messaging.rpc.server   File "/openstack/venvs/cinder-14.0.0/lib/python2.7/site-packages/oslo_messaging/rpc/server.py", line 133, in _process_incoming
2017-01-18 15:54:00.467 32552 ERROR oslo_messaging.rpc.server     res = self.dispatcher.dispatch(message)
2017-01-18 15:54:00.467 32552 ERROR oslo_messaging.rpc.server   File "/openstack/venvs/cinder-14.0.0/lib/python2.7/site-packages/oslo_messaging/rpc/dispatcher.py", line 150, in dispatch
2017-01-18 15:54:00.467 32552 ERROR oslo_messaging.rpc.server     return self._do_dispatch(endpoint, method, ctxt, args)
2017-01-18 15:54:00.467 32552 ERROR oslo_messaging.rpc.server   File "/openstack/venvs/cinder-14.0.0/lib/python2.7/site-packages/oslo_messaging/rpc/dispatcher.py", line 121, in _do_dispatch
2017-01-18 15:54:00.467 32552 ERROR oslo_messaging.rpc.server     result = func(ctxt, **new_args)
2017-01-18 15:54:00.467 32552 ERROR oslo_messaging.rpc.server   File "/openstack/venvs/cinder-14.0.0/lib/python2.7/site-packages/cinder/volume/manager.py", line 4366, in create_volume
2017-01-18 15:54:00.467 32552 ERROR oslo_messaging.rpc.server     allow_reschedule=allow_reschedule, volume=volume)
2017-01-18 15:54:00.467 32552 ERROR oslo_messaging.rpc.server   File "/openstack/venvs/cinder-14.0.0/lib/python2.7/site-packages/cinder/volume/manager.py", line 634, in create_volume
2017-01-18 15:54:00.467 32552 ERROR oslo_messaging.rpc.server     _run_flow()
2017-01-18 15:54:00.467 32552 ERROR oslo_messaging.rpc.server   File "/openstack/venvs/cinder-14.0.0/lib/python2.7/site-packages/cinder/volume/manager.py", line 626, in _run_flow
2017-01-18 15:54:00.467 32552 ERROR oslo_messaging.rpc.server     flow_engine.run()
2017-01-18 15:54:00.467 32552 ERROR oslo_messaging.rpc.server   File "/openstack/venvs/cinder-14.0.0/lib/python2.7/site-packages/taskflow/engines/action_engine/engine.py", line 247, in run
2017-01-18 15:54:00.467 32552 ERROR oslo_messaging.rpc.server     for _state in self.run_iter(timeout=timeout):
2017-01-18 15:54:00.467 32552 ERROR oslo_messaging.rpc.server   File "/openstack/venvs/cinder-14.0.0/lib/python2.7/site-packages/taskflow/engines/action_engine/engine.py", line 340, in run_iter
2017-01-18 15:54:00.467 32552 ERROR oslo_messaging.rpc.server     failure.Failure.reraise_if_any(er_failures)
2017-01-18 15:54:00.467 32552 ERROR oslo_messaging.rpc.server   File "/openstack/venvs/cinder-14.0.0/lib/python2.7/site-packages/taskflow/types/failure.py", line 336, in reraise_if_any
2017-01-18 15:54:00.467 32552 ERROR oslo_messaging.rpc.server     failures[0].reraise()
2017-01-18 15:54:00.467 32552 ERROR oslo_messaging.rpc.server   File "/openstack/venvs/cinder-14.0.0/lib/python2.7/site-packages/taskflow/types/failure.py", line 343, in reraise

In this example, cinder-volumes failed to start and has provided a stack trace, since its volume back end has been unable to set up the storage volume—probably because the LVM volume that is expected from the configuration does not exist.

Here is an example error log:

2013-02-25 20:26:33 6619 ERROR nova.openstack.common.rpc.common [-] AMQP server on localhost:5672 is unreachable:
 [Errno 111] ECONNREFUSED. Trying again in 23 seconds.

In this error, a nova service has failed to connect to the RabbitMQ server because it got a connection refused error.

Tracing Instance Requests

When an instance fails to behave properly, you will often have to trace activity associated with that instance across the log files of various nova-* services and across both the cloud controller and compute nodes.

The typical way is to trace the UUID associated with an instance across the service logs.

Consider the following example:

$ openstack server list
+--------------------------------+--------+--------+--------------------------+------------+
| ID                             | Name   | Status | Networks                 | Image Name |
+--------------------------------+--------+--------+--------------------------+------------+
| fafed8-4a46-413b-b113-f1959ffe | cirros | ACTIVE | novanetwork=192.168.100.3| cirros     |
+--------------------------------------+--------+--------+--------------------+------------+

Here, the ID associated with the instance is faf7ded8-4a46-413b-b113-f19590746ffe. If you search for this string on the cloud controller in the /var/log/nova-*.log files, it appears in nova-api.log and nova-scheduler.log. If you search for this on the compute nodes in /var/log/nova-*.log, it appears in nova-compute.log. If no ERROR or CRITICAL messages appear, the most recent log entry that reports this may provide a hint about what has gone wrong.

Adding Custom Logging Statements

If there is not enough information in the existing logs, you may need to add your own custom logging statements to the nova-* services.

The source files are located in /usr/lib/python2.7/dist-packages/nova.

To add logging statements, the following line should be near the top of the file. For most files, these should already be there:

from nova.openstack.common import log as logging
LOG = logging.getLogger(__name__)

To add a DEBUG logging statement, you would do:

LOG.debug("This is a custom debugging statement")

You may notice that all the existing logging messages are preceded by an underscore and surrounded by parentheses, for example:

LOG.debug(_("Logging statement appears here"))

This formatting is used to support translation of logging messages into different languages using the gettext internationalization library. You don't need to do this for your own custom log messages. However, if you want to contribute the code back to the OpenStack project that includes logging statements, you must surround your log messages with underscores and parentheses.

RabbitMQ Web Management Interface or rabbitmqctl

Aside from connection failures, RabbitMQ log files are generally not useful for debugging OpenStack related issues. Instead, we recommend you use the RabbitMQ web management interface. Enable it on your cloud controller:

# /usr/lib/rabbitmq/bin/rabbitmq-plugins enable rabbitmq_management

# service rabbitmq-server restart

The RabbitMQ web management interface is accessible on your cloud controller at *[[1]].

note
Ubuntu 12.04 installs RabbitMQ version 2.7.1, which uses port 55672. RabbitMQ versions 3.0 and above use port 15672 instead. You can check which version of RabbitMQ you have running on your local Ubuntu machine by doing:
$ dpkg -s rabbitmq-server | grep "Version:"
Version: 2.7.1-0ubuntu4

An alternative to enabling the RabbitMQ web management interface is to use the rabbitmqctl commands. For example, rabbitmqctl list_queues| grep cinder displays any messages left in the queue. If there are messages, it's a possible sign that cinder services didn't connect properly to rabbitmq and might have to be restarted.

Items to monitor for RabbitMQ include the number of items in each of the queues and the processing time statistics for the server.

Centrally Managing Logs

Because your cloud is most likely composed of many servers, you must check logs on each of those servers to properly piece an event together. A better solution is to send the logs of all servers to a central location so that they can all be accessed from the same area.

The choice of central logging engine will be dependent on the operating system in use as well as any organizational requirements for logging tools.

Syslog choices

There are a large number of syslogs engines available, each have differing capabilities and configuration requirements.

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