Logging¶

Logging module¶

Logging behavior can be changed by creating a configuration file. To specify the configuration file, add this line to the /etc/nova/nova.conf file:

log-config=/etc/nova/logging.conf

To change the logging level, add DEBUG, INFO, WARNING, or ERROR as a parameter.

The logging configuration file is an INI-style configuration file, which must contain a section called logger_nova. This controls the behavior of the logging facility in the nova-* services. For example:

[logger_nova]
level = INFO
handlers = stderr
qualname = nova

This example sets the debugging level to INFO (which is less verbose than the default DEBUG setting).

For more about the logging configuration syntax, including the handlers and qualname variables, see the Python documentation on logging configuration files.

For an example of the logging.conf file with various defined handlers, see the Example Configuration File for nova.

Syslog¶

OpenStack Compute services can send logging information to syslog. This is useful if you want to use rsyslog to forward logs to a remote machine. Separately configure the Compute service (nova), the Identity service (keystone), the Image service (glance), and, if you are using it, the Block Storage service (cinder) to send log messages to syslog. Open these configuration files:

• /etc/nova/nova.conf
• /etc/keystone/keystone.conf
• /etc/glance/glance-api.conf
• /etc/glance/glance-registry.conf
• /etc/cinder/cinder.conf

In each configuration file, add these lines:

debug = False
use_syslog = True
syslog_log_facility = LOG_LOCAL0

In addition to enabling syslog, these settings also turn off debugging output from the log.

Rsyslog¶

rsyslog is useful for setting up a centralized log server across multiple machines. This section briefly describe the configuration to set up an rsyslog server. A full treatment of rsyslog is beyond the scope of this book. This section assumes rsyslog has already been installed on your hosts (it is installed by default on most Linux distributions).

This example provides a minimal configuration for /etc/rsyslog.conf on the log server host, which receives the log files

# provides TCP syslog reception
$ModLoad imtcp
$InputTCPServerRun 1024

Add a filter rule to /etc/rsyslog.conf which looks for a host name. This example uses COMPUTE_01 as the compute host name:

:hostname, isequal, "COMPUTE_01" /mnt/rsyslog/logs/compute-01.log

On each compute host, create a file named /etc/rsyslog.d/60-nova.conf, with the following content:

# prevent debug from dnsmasq with the daemon.none parameter
*.*;auth,authpriv.none,daemon.none,local0.none -/var/log/syslog
# Specify a log level of ERROR
local0.error    @@172.20.1.43:1024

Once you have created the file, restart the rsyslog service. Error-level log messages on the compute hosts should now be sent to the log server.

Serial console¶

The serial console provides a way to examine kernel output and other system messages during troubleshooting if the instance lacks network connectivity.

Read-only access from server serial console is possible using the os-GetSerialOutput server action. Most cloud images enable this feature by default. For more information, see Common errors and fixes for Compute.

OpenStack Juno and later supports read-write access using the serial console using the os-GetSerialConsole server action. This feature also requires a websocket client to access the serial console.

Configuring read-write serial console access

1. On a compute node, edit the /etc/nova/nova.conf file:

   In the [serial_console] section, enable the serial console:

   [serial_console]
   # ...
   enabled = true
   

2. In the [serial_console] section, configure the serial console proxy similar to graphical console proxies:

   [serial_console]
   # ...
   base_url = ws://controller:6083/
   listen = 0.0.0.0
   proxyclient_address = MANAGEMENT_INTERFACE_IP_ADDRESS
   

   The base_url option specifies the base URL that clients receive from the API upon requesting a serial console. Typically, this refers to the host name of the controller node.

   The listen option specifies the network interface nova-compute should listen on for virtual console connections. Typically, 0.0.0.0 will enable listening on all interfaces.

   The proxyclient_address option specifies which network interface the proxy should connect to. Typically, this refers to the IP address of the management interface.

   When you enable read-write serial console access, Compute will add serial console information to the Libvirt XML file for the instance. For example:

   <console type='tcp'>
     <source mode='bind' host='127.0.0.1' service='10000'/>
     <protocol type='raw'/>
     <target type='serial' port='0'/>
     <alias name='serial0'/>
   </console>
   

Accessing the serial console on an instance

1. Use the nova get-serial-proxy command to retrieve the websocket URL for the serial console on the instance:

   $ nova get-serial-proxy INSTANCE_NAME
   

   Type	Url
   serial	ws://127.0.0.1:6083/?token=18510769-71ad-4e5a-8348-4218b5613b3d

   Alternatively, use the API directly:

   $ curl -i 'http://<controller>:8774/v2.1/<tenant_uuid>/servers/<instance_uuid>/action' \
     -X POST \
     -H "Accept: application/json" \
     -H "Content-Type: application/json" \
     -H "X-Auth-Project-Id: <project_id>" \
     -H "X-Auth-Token: <auth_token>" \
     -d '{"os-getSerialConsole": {"type": "serial"}}'
   

2. Use Python websocket with the URL to generate .send, .recv, and .fileno methods for serial console access. For example:

   import websocket
   ws = websocket.create_connection(
       'ws://127.0.0.1:6083/?token=18510769-71ad-4e5a-8348-4218b5613b3d',
       subprotocols=['binary', 'base64'])
   

Alternatively, use a Python websocket client.