Chapter 13. Logging and Monitoring

As an OpenStack cloud is composed of so many different services, there are a large number of log files. This chapter aims to assist you in locating and working with them and describes other ways to track the status of your deployment.

 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 13.1, “OpenStack log locations”.

Table 13.1. OpenStack log locations
Node type Service Log location

Cloud controller

nova-*

/var/log/nova

Cloud controller

glance-*

/var/log/glance

Cloud controller

cinder-*

/var/log/cinder

Cloud controller

keystone-*

/var/log/keystone

Cloud controller

neutron-*

/var/log/neutron

Cloud controller

horizon

/var/log/apache2/

All nodes

misc (swift, dnsmasq)

/var/log/syslog

Compute nodes

libvirt

/var/log/libvirt/libvirtd.log

Compute nodes

Console (boot up messages) for VM instances:

/var/lib/nova/instances/instance-<instance id>/console.log

Block Storage nodes

cinder-volume

/var/log/cinder/cinder-volume.log

 Reading the Logs

OpenStack services use the standard logging levels, at increasing severity: DEBUG, INFO, AUDIT, WARNING, ERROR, CRITICAL, and TRACE. 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 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, TRACE, or ERROR message in the log starting at the bottom of the log file.

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

2013-02-25 21:05:51 17409 CRITICAL cinder [-] Bad or unexpected response from the storage volume backend API: volume group
 cinder-volumes doesn't exist
2013-02-25 21:05:51 17409 TRACE cinder Traceback (most recent call last):
2013-02-25 21:05:51 17409 TRACE cinder File "/usr/bin/cinder-volume", line 48, in <module>
2013-02-25 21:05:51 17409 TRACE cinder service.wait()
2013-02-25 21:05:51 17409 TRACE cinder File "/usr/lib/python2.7/dist-packages/cinder/service.py", line 422, in wait
2013-02-25 21:05:51 17409 TRACE cinder _launcher.wait()
2013-02-25 21:05:51 17409 TRACE cinder File "/usr/lib/python2.7/dist-packages/cinder/service.py", line 127, in wait
2013-02-25 21:05:51 17409 TRACE cinder service.wait()
2013-02-25 21:05:51 17409 TRACE cinder File "/usr/lib/python2.7/dist-packages/eventlet/greenthread.py", line 166, in wait
2013-02-25 21:05:51 17409 TRACE cinder return self._exit_event.wait()
2013-02-25 21:05:51 17409 TRACE cinder File "/usr/lib/python2.7/dist-packages/eventlet/event.py", line 116, in wait
2013-02-25 21:05:51 17409 TRACE cinder return hubs.get_hub().switch()
2013-02-25 21:05:51 17409 TRACE cinder File "/usr/lib/python2.7/dist-packages/eventlet/hubs/hub.py", line 177, in switch
2013-02-25 21:05:51 17409 TRACE cinder return self.greenlet.switch()
2013-02-25 21:05:51 17409 TRACE cinder File "/usr/lib/python2.7/dist-packages/eventlet/greenthread.py", line 192, in main
2013-02-25 21:05:51 17409 TRACE cinder result = function(*args, **kwargs)
2013-02-25 21:05:51 17409 TRACE cinder File "/usr/lib/python2.7/dist-packages/cinder/service.py", line 88, in run_server
2013-02-25 21:05:51 17409 TRACE cinder server.start()
2013-02-25 21:05:51 17409 TRACE cinder File "/usr/lib/python2.7/dist-packages/cinder/service.py", line 159, in start
2013-02-25 21:05:51 17409 TRACE cinder self.manager.init_host()
2013-02-25 21:05:51 17409 TRACE cinder File "/usr/lib/python2.7/dist-packages/cinder/volume/manager.py", line 95,
 in init_host
2013-02-25 21:05:51 17409 TRACE cinder self.driver.check_for_setup_error()
2013-02-25 21:05:51 17409 TRACE cinder File "/usr/lib/python2.7/dist-packages/cinder/volume/driver.py", line 116,
 in check_for_setup_error
2013-02-25 21:05:51 17409 TRACE cinder raise exception.VolumeBackendAPIException(data=exception_message)
2013-02-25 21:05:51 17409 TRACE cinder VolumeBackendAPIException: Bad or unexpected response from the storage volume
 backend API: volume group cinder-volumes doesn't exist
2013-02-25 21:05:51 17409 TRACE cinder

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.

 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 http://localhost:55672.

[Note]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.

Ubuntu uses rsyslog as the default logging service. Since it is natively able to send logs to a remote location, you don't have to install anything extra to enable this feature, just modify the configuration file. In doing this, consider running your logging over a management network or using an encrypted VPN to avoid interception.

 rsyslog Server Configuration

Designate a server as the central logging server. The best practice is to choose a server that is solely dedicated to this purpose. Create a file called /etc/rsyslog.d/server.conf with the following contents:

# Enable UDP
$ModLoad imudp
# Listen on 192.168.1.10 only
$UDPServerAddress 192.168.1.10
# Port 514
$UDPServerRun 514

# Create logging templates for nova
$template NovaFile,"/var/log/rsyslog/%HOSTNAME%/nova.log"
$template NovaAll,"/var/log/rsyslog/nova.log"

# Log everything else to syslog.log
$template DynFile,"/var/log/rsyslog/%HOSTNAME%/syslog.log"
*.* ?DynFile

# Log various openstack components to their own individual file
local0.* ?NovaFile
local0.* ?NovaAll
& ~

This example configuration handles the nova service only. It first configures rsyslog to act as a server that runs on port 514. Next, it creates a series of logging templates. Logging templates control where received logs are stored. Using the last example, a nova log from c01.example.com goes to the following locations:

  • /var/log/rsyslog/c01.example.com/nova.log

  • /var/log/rsyslog/nova.log

This is useful, as logs from c02.example.com go to:

  • /var/log/rsyslog/c02.example.com/nova.log

  • /var/log/rsyslog/nova.log

You have an individual log file for each compute node as well as an aggregated log that contains nova logs from all nodes.

 Monitoring

There are two types of monitoring: watching for problems and watching usage trends. The former ensures that all services are up and running, creating a functional cloud. The latter involves monitoring resource usage over time in order to make informed decisions about potential bottlenecks and upgrades.

 Process Monitoring

A basic type of alert monitoring is to simply check and see whether a required process is running. For example, ensure that the nova-api service is running on the cloud controller:

# ps aux | grep nova-api
nova 12786 0.0 0.0 37952 1312 ? Ss Feb11 0:00 su -s /bin/sh -c exec nova-api
--config-file=/etc/nova/nova.conf nova
nova 12787 0.0 0.1 135764 57400 ? S Feb11 0:01 /usr/bin/python
 /usr/bin/nova-api --config-file=/etc/nova/nova.conf
nova 12792 0.0 0.0 96052 22856 ? S Feb11 0:01 /usr/bin/python
/usr/bin/nova-api --config-file=/etc/nova/nova.conf
nova 12793 0.0 0.3 290688 115516 ? S Feb11 1:23 /usr/bin/python
/usr/bin/nova-api --config-file=/etc/nova/nova.conf
nova 12794 0.0 0.2 248636 77068 ? S Feb11 0:04 /usr/bin/python
/usr/bin/nova-api --config-file=/etc/nova/nova.conf
root 24121 0.0 0.0 11688 912 pts/5 S+ 13:07 0:00 grep nova-api

You can create automated alerts for critical processes by using Nagios and NRPE. For example, to ensure that the nova-compute process is running on compute nodes, create an alert on your Nagios server that looks like this:

define service {
    host_name c01.example.com
    check_command check_nrpe_1arg!check_nova-compute
    use generic-service
    notification_period 24x7
    contact_groups sysadmins
    service_description nova-compute
}

Then on the actual compute node, create the following NRPE configuration:

\command[check_nova-compute]=/usr/lib/nagios/plugins/check_procs -c 1: \
-a nova-compute

Nagios checks that at least one nova-compute service is running at all times.

 StackTach

StackTach is a tool that collects and reports the notifications sent by nova. Notifications are essentially the same as logs but can be much more detailed. Nearly all OpenStack components are capable of generating notifications when significant events occur. Notifications are messages placed on the OpenStack queue (generally RabbitMQ) for consumption by downstream systems. An overview of notifications can be found at System Usage Data.

To enable nova to send notifications, add the following to nova.conf:

notification_topics=monitor
notification_driver=messagingv2

Once nova is sending notifications, install and configure StackTach. StackTach workers for Queue consumption and pipeling processing are configured to read these notifications from RabbitMQ servers and store them in a database. Users can inquire on instances, requests and servers by using the browser interface or command line tool, Stacky. Since StackTach is relatively new and constantly changing, installation instructions quickly become outdated. Please refer to the StackTach Git repo for instructions as well as a demo video. Additional details on the latest developments can be discovered at theofficial page

 Logstash

Logstash is a high performance indexing and search engine for logs. Logs from Jenkins test runs are sent to logstash where they are indexed and stored. Logstash facilitates reviewing logs from multiple sources in a single test run, searching for errors or particular events within a test run, and searching for log event trends across test runs.

There are four major layers in Logstash setup which are

  • Log Pusher

  • Log Indexer

  • ElasticSearch

  • Kibana

Each layer scales horizontally. As the number of logs grows you can add more log pushers, more Logstash indexers, and more ElasticSearch nodes.

Logpusher is a pair of Python scripts which first listens to Jenkins build events and converts them into Gearman jobs. Gearman provides a generic application framework to farm out work to other machines or processes that are better suited to do the work. It allows you to do work in parallel, to load balance processing, and to call functions between languages.Later Logpusher performs Gearman jobs to push log files into logstash. Logstash indexer reads these log events, filters them to remove unwanted lines, collapse multiple events together, and parses useful information before shipping them to ElasticSearch for storage and indexing. Kibana is a logstash oriented web client for ElasticSearch.

 OpenStack Telemetry

An integrated OpenStack project (code-named ceilometer) collects metering and event data relating to OpenStack services. Data collected by the Telemetry service could be used for billing. Depending on deployment configuration, collected data may be accessible to users based on the deployment configuration. The Telemetry service provides a REST API documented at http://developer.openstack.org/api-ref-telemetry-v2.html. You can read more about the module in the OpenStack Administrator Guide or in the developer documentation.

 OpenStack-Specific Resources

Resources such as memory, disk, and CPU are generic resources that all servers (even non-OpenStack servers) have and are important to the overall health of the server. When dealing with OpenStack specifically, these resources are important for a second reason: ensuring that enough are available to launch instances. There are a few ways you can see OpenStack resource usage. The first is through the nova command:

# nova usage-list

This command displays a list of how many instances a tenant has running and some light usage statistics about the combined instances. This command is useful for a quick overview of your cloud, but it doesn't really get into a lot of details.

Next, the nova database contains three tables that store usage information.

The nova.quotas and nova.quota_usages tables store quota information. If a tenant's quota is different from the default quota settings, its quota is stored in the nova.quotas table. For example:

mysql> select project_id, resource, hard_limit from quotas;
+----------------------------------+-----------------------------+------------+
| project_id                       | resource                    | hard_limit |
+----------------------------------+-----------------------------+------------+
| 628df59f091142399e0689a2696f5baa | metadata_items              | 128        |
| 628df59f091142399e0689a2696f5baa | injected_file_content_bytes | 10240      |
| 628df59f091142399e0689a2696f5baa | injected_files              | 5          |
| 628df59f091142399e0689a2696f5baa | gigabytes                   | 1000       |
| 628df59f091142399e0689a2696f5baa | ram                         | 51200      |
| 628df59f091142399e0689a2696f5baa | floating_ips                | 10         |
| 628df59f091142399e0689a2696f5baa | instances                   | 10         |
| 628df59f091142399e0689a2696f5baa | volumes                     | 10         |
| 628df59f091142399e0689a2696f5baa | cores                       | 20         |
+----------------------------------+-----------------------------+------------+

The nova.quota_usages table keeps track of how many resources the tenant currently has in use:

mysql> select project_id, resource, in_use from quota_usages where project_id like '628%';
+----------------------------------+--------------+--------+
| project_id                       | resource     | in_use |
+----------------------------------+--------------+--------+
| 628df59f091142399e0689a2696f5baa | instances    | 1      |
| 628df59f091142399e0689a2696f5baa | ram          | 512    |
| 628df59f091142399e0689a2696f5baa | cores        | 1      |
| 628df59f091142399e0689a2696f5baa | floating_ips | 1      |
| 628df59f091142399e0689a2696f5baa | volumes      | 2      |
| 628df59f091142399e0689a2696f5baa | gigabytes    | 12     |
| 628df59f091142399e0689a2696f5baa | images       | 1      |
+----------------------------------+--------------+--------+

By comparing a tenant's hard limit with their current resource usage, you can see their usage percentage. For example, if this tenant is using 1 floating IP out of 10, then they are using 10 percent of their floating IP quota. Rather than doing the calculation manually, you can use SQL or the scripting language of your choice and create a formatted report:

+----------------------------------+------------+-------------+---------------+
| some_tenant                                                                 |
+-----------------------------------+------------+------------+---------------+
| Resource                          | Used       | Limit      |               |
+-----------------------------------+------------+------------+---------------+
| cores                             | 1          | 20         |           5 % |
| floating_ips                      | 1          | 10         |          10 % |
| gigabytes                         | 12         | 1000       |           1 % |
| images                            | 1          | 4          |          25 % |
| injected_file_content_bytes       | 0          | 10240      |           0 % |
| injected_file_path_bytes          | 0          | 255        |           0 % |
| injected_files                    | 0          | 5          |           0 % |
| instances                         | 1          | 10         |          10 % |
| key_pairs                         | 0          | 100        |           0 % |
| metadata_items                    | 0          | 128        |           0 % |
| ram                               | 512        | 51200      |           1 % |
| reservation_expire                | 0          | 86400      |           0 % |
| security_group_rules              | 0          | 20         |           0 % |
| security_groups                   | 0          | 10         |           0 % |
| volumes                           | 2          | 10         |          20 % |
+-----------------------------------+------------+------------+---------------+

The preceding information was generated by using a custom script that can be found on GitHub.

[Note]Note

This script is specific to a certain OpenStack installation and must be modified to fit your environment. However, the logic should easily be transferable.

 Intelligent Alerting

Intelligent alerting can be thought of as a form of continuous integration for operations. For example, you can easily check to see whether the Image service is up and running by ensuring that the glance-api and glance-registry processes are running or by seeing whether glace-api is responding on port 9292.

But how can you tell whether images are being successfully uploaded to the Image service? Maybe the disk that Image service is storing the images on is full or the S3 back end is down. You could naturally check this by doing a quick image upload:

#!/bin/bash
#
# assumes that reasonable credentials have been stored at
# /root/auth


. /root/openrc
wget http://download.cirros-cloud.net/0.3.4/cirros-0.3.4-x86_64-disk.img
glance image-create --name='cirros image' --is-public=true
--container-format=bare --disk-format=qcow2 < cirros-0.3.4-x8
6_64-disk.img

By taking this script and rolling it into an alert for your monitoring system (such as Nagios), you now have an automated way of ensuring that image uploads to the Image Catalog are working.

[Note]Note

You must remove the image after each test. Even better, test whether you can successfully delete an image from the Image Service.

Intelligent alerting takes considerably more time to plan and implement than the other alerts described in this chapter. A good outline to implement intelligent alerting is:

  • Review common actions in your cloud.

  • Create ways to automatically test these actions.

  • Roll these tests into an alerting system.

Some other examples for Intelligent Alerting include:

  • Can instances launch and be destroyed?

  • Can users be created?

  • Can objects be stored and deleted?

  • Can volumes be created and destroyed?

 Trending

Trending can give you great insight into how your cloud is performing day to day. You can learn, for example, if a busy day was simply a rare occurrence or if you should start adding new compute nodes.

Trending takes a slightly different approach than alerting. While alerting is interested in a binary result (whether a check succeeds or fails), trending records the current state of something at a certain point in time. Once enough points in time have been recorded, you can see how the value has changed over time.

All of the alert types mentioned earlier can also be used for trend reporting. Some other trend examples include:

As an example, recording nova-api usage can allow you to track the need to scale your cloud controller. By keeping an eye on nova-api requests, you can determine whether you need to spawn more nova-api processes or go as far as introducing an entirely new server to run nova-api. To get an approximate count of the requests, look for standard INFO messages in /var/log/nova/nova-api.log:

# grep INFO /var/log/nova/nova-api.log | wc

You can obtain further statistics by looking for the number of successful requests:

# grep " 200 " /var/log/nova/nova-api.log | wc

By running this command periodically and keeping a record of the result, you can create a trending report over time that shows whether your nova-api usage is increasing, decreasing, or keeping steady.

A tool such as collectd can be used to store this information. While collectd is out of the scope of this book, a good starting point would be to use collectd to store the result as a COUNTER data type. More information can be found in collectd's documentation.

 Summary

For stable operations, you want to detect failure promptly and determine causes efficiently. With a distributed system, it's even more important to track the right items to meet a service-level target. Learning where these logs are located in the file system or API gives you an advantage. This chapter also showed how to read, interpret, and manipulate information from OpenStack services so that you can monitor effectively.

Questions? Discuss on ask.openstack.org
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