openstack/octavia
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0aef474cd9
octavia/doc/source/admin/guides/operator-maintenance.rst
Gregory Thiemonge be91493332 Retry to set loadbalancer prov status on failures 
In case of DB outages when a flow is running, an exception is caught and
the flow is reverted. In most of the flows, the revert function of the
first task's (the last to be reverted) unlocks the load balancer by
setting its provisioning status (to ERROR or ACTIVE, depending on the
flow), but it fails if the DB is not reachable, leaving the LB in
a PENDING_* state.
This commit adds tenacity.retry to those functions, Octavia retries to
set the status during ~2h45 (2000 attempts, 1 sec initial delay, 5 sec
max delay).

Closes-Bug: #2036952
Change-Id: I458dd6d6f5383edc24116ea0fa27e3a593044146
2023-10-03 06:13:34 -04:00

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..
Copyright (c) 2017 Rackspace
Licensed under the Apache License, Version 2.0 (the "License"); you may
not use this file except in compliance with the License. You may obtain
a copy of the License at
http://www.apache.org/licenses/LICENSE-2.0
Unless required by applicable law or agreed to in writing, software
distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
License for the specific language governing permissions and limitations
under the License.
======================================
Operator Maintenance Guide
======================================
This document is intended for operators. For a developer guide see the
:doc:`../../contributor/guides/dev-quick-start` in this documentation
repository. For an end-user guide, please see the
:doc:`../../user/guides/basic-cookbook` in this documentation repository.
Monitoring
==========
Monitoring Load Balancer Amphora
--------------------------------
Octavia will monitor the load balancing amphorae itself and initiate failovers
and/or replacements if they malfunction. Therefore, most installations won't
need to monitor the amphorae running the load balancer.
Octavia will log each failover to the corresponding health manager logs. It is
advisable to use log analytics to monitor failover trends to notice problems in
the OpenStack installation early. We have seen neutron (network) connectivity
issues, Denial of Service attacks, and nova (compute) malfunctions lead to a
higher than normal failover rate. Alternatively, the monitoring of the other
services showed problems as well, so depending on your overall monitoring
strategy this might be optional.
If additional monitoring is necessary, review the corresponding calls on
the amphora agent REST interface (see
:doc:`../../contributor/api/haproxy-amphora-api`)
Monitoring Pool Members
-----------------------
Octavia will use the health information from the underlying load balancing
subsystems to determine the health of members. This information will be
streamed to the Octavia database and made available via the status
tree or other API methods. For critical applications we recommend to
poll this information in regular intervals.
Monitoring Load Balancers
-------------------------
You should monitor the provisioning status of a load balancer, and send alerts
if the provisioning status is not ACTIVE. Alerts should not be triggered when
an application is making regular changes to the pool and enters several PENDING
stages.
The provisioning status of load balancer objects reflect the status of the
control plane being able to contact and successfully provision a create,
update, and delete request. The operating status of a load balancer object
reports on the current functional status of the load balancer.
For example, a load balancer might have a provisioning status of ERROR, but an
operating status of ONLINE. This could be caused by a neutron networking
failure that blocked that last requested update to the load balancer
configuration from successfully completing. In this case the load balancer is
continuing to process traffic through the load balancer, but might not have
applied the latest configuration updates yet.
A load balancer in a PENDING provisioning status is immutable, it cannot be
updated or deleted by another process, this PENDING status acts as a lock on
the resource.
If a database outage occurs while a load balancer is deleted, created or
updated, the Octavia control plane will try to remove the PENDING status and
set it to ERROR during a long period of time (around 2h45min with the default
settings), to prevent the resource from remaining immutable.
Monitoring load balancer functionality
--------------------------------------
You can monitor the operational status of your load balancer using the
`openstack loadbalancer status show` command. It reports the current operation
status of the load balancer and its child objects.
You might also want to use an external monitoring service that connects to your
load balancer listeners and monitors them from outside of the cloud. This type
of monitoring indicates if there is a failure outside of Octavia that might
impact the functionality of your load balancer, such as router failures,
network connectivity issues, and so on.
.. _Monasca Octavia plugin: https://github.com/openstack/monasca-agent/blob/master/monasca_setup/detection/plugins/octavia.py
Monitoring Octavia Control Plane
--------------------------------
To monitor the Octavia control plane we recommend process monitoring of the
main Octavia processes:
* octavia-api
* octavia-worker
* octavia-health-manager
* octavia-housekeeping
The Monasca project has a plugin for such monitoring (see
`Monasca Octavia plugin`_).
Please refer to this project for further information.
Octavia's control plane components are shared nothing and can be scaled
linearly. For high availability of the control plane we recommend to run at
least one set of components in each availability zone. Furthermore, the
octavia-api endpoint could be behind a load balancer or other HA technology.
That said, if one or more components fail the system will still be available
(though potentially degraded). For instance if you have installed one set of
components in each of the three availability zones even if you lose a whole
zone Octavia will still be responsive and available - only if you lose the
Octavia control plane in all three zones will the service be unavailable.
Please note this only addresses control plane availability; the availability of
the load balancing function depends highly on the chosen topology and the
anti-affinity settings. See our forthcoming HA guide for more details.
Additionally, we recommend to monitor the Octavia API endpoint(s). There
currently is no special url to use so just polling the root URL in regular
intervals is sufficient.
There is a host of information in the log files which can be used for log
analytics. A few examples of what could be monitored are:
* Amphora Build Rate - to determine load of the system
* Amphora Build Time - to determine how long it takes to build an amphora
* Failures/Errors - to be notified of system problems early
.. _rotating_amphora:
Rotating the Amphora Images
===========================
Octavia will start load balancers with a pre-built image which contain the
amphora agent, a load balancing application, and are seeded with cryptographic
certificates through the config drive at start up.
Rotating the image means making a load balancer amphora running with an old
image failover to an amphora with a new image. This should be without any
measurable interruption in the load balancing functionality when using
ACTIVE/STANDBY topology. Standalone load balancers might experience a short
outage.
Here are some reasons you might need to rotate the amphora image:
* There has been a (security) update to the underlying operating system
* You want to deploy a new version of the amphora agent or haproxy
* The cryptographic certificates and/or keys on the amphora have been
compromised.
* Though not related to rotating images, this procedure might be invoked if you
are switching to a different flavor for the underlying virtual machine.
Preparing a New Amphora Image
-----------------------------
To prepare a new amphora image you will need to use diskimage-create.sh as
described in the README in the diskimage-create directory.
For instance, in the ``octavia/diskimage-create`` directory, run:
.. code-block:: bash
./diskimage-create.sh
Once you have created a new image you will need to upload it into glance. The
following shows how to do this if you have set the image tag in the
Octavia configuration file. Make sure to use a user with the same tenant as
the Octavia service account:
.. code-block:: bash
openstack image create --file amphora-x64-haproxy.qcow2 \
--disk-format qcow2 --tag <amphora-image-tag> --private \
--container-format bare /var/lib/octavia/amphora-x64-haproxy.qcow2
If you didn't configure image tags and instead configured an image id, you
will need to update the Octavia configuration file with the new id and restart
the Octavia services (except octavia-api).
Generating a List of Load Balancers to Rotate
---------------------------------------------
The easiest way to generate a list, is to just list the IDs of all
load balancers:
.. code-block:: bash
openstack loadbalancer list -c id -f value
Take note of the IDs.
Rotating a Load Balancer
------------------------
Octavia has an API call to initiate the failover of a load balancer:
.. code-block:: bash
openstack loadbalancer failover <loadbalancer id>
You can observe the failover by querying octavia ``openstack load balancer
show <loadbalancer id>`` until the load balancer goes ``ACTIVE`` again.
.. _best_practice:
Best Practices/Optimizations
----------------------------
Since a failover puts significant load on the OpenStack installation by
creating new virtual machines and ports, it should either be done at a very
slow pace, during a time with little load, or with the right throttling
enabled in Octavia. The throttling will make sure to prioritize failovers
higher than other operations and depending on how many failovers are
initiated this might crowd out other operations.
Rotating Cryptographic Certificates
===================================
Octavia secures the communication between the amphora agent and the control
plane with two-way SSL encryption. To accomplish that, several certificates
are distributed in the system:
* Control plane:
* Amphora certificate authority (CA) certificate: Used to validate
amphora certificates if Octavia acts as a Certificate Authority to
issue new amphora certificates
* Client certificate: Used to authenticate with the amphora
* Amphora:
* Client CA certificate: Used to validate control plane
client certificate
* Amphora certificate: Presented to control plane processes to prove amphora
identity.
The heartbeat UDP packets emitted from the amphora are secured with a
symmetric encryption key. This is set by the configuration option
`heartbeat_key` in the `health_manager` section. We recommend setting it to a
random string of a sufficient length.
.. _rotate-amphora-certs:
Rotating Amphora Certificates
-----------------------------
For the server part Octavia will act as a certificate authority itself to
issue amphora certificates to be used by each amphora. Octavia will also
monitor those certificates and refresh them before they expire.
There are three ways to initiate a rotation manually:
* Change the expiration date of the certificate in the database. Octavia
will then rotate the amphora certificates with newly issued ones. This
requires the following:
* Client CA certificate hasn't expired or the
corresponding client certificate on the control plane hasn't been issued by
a different client CA (in case the authority was
compromised)
* The Amphora CA certificate on the control plane didn't
change in any way which jeopardizes validation of the amphora certificate
(e.g. the certificate was reissued with a new private/public key)
* If the amphora CA changed in a way which jeopardizes
validation of the amphora certificate an operator can manually upload newly
issued amphora certificates by switching off validation of the old amphora
certificate. This requires a client certificate which can be validated by the
client CA file on the amphora. Refer to
:doc:`../../contributor/api/haproxy-amphora-api` for more details.
* If the client certificate on the control plane changed in a way that it can't
be validated by the client certificate authority certificate on the amphora,
a failover (see :ref:`rotate-amphora-certs`) of all amphorae needs to be
initiated. Until the failover is completed the amphorae can't be controlled
by the control plane.
Rotating the Certificate Authority Certificates
-----------------------------------------------
If there is a compromise of the certificate authorities' certificates, or they
expired, new ones need to be installed into the system. If Octavia is
not acting as the certificate authority only the certificate authority's
cert needs to be changed in the system so amphora can be authenticated again.
* Issue new certificates (see the script in the bin folder of Octavia if
Octavia is acting as the certificate authority) or follow the instructions
of the third-party certificate authority. Copy the certificate and the
private key (if Octavia acts as a certificate authority) where Octavia can
find them.
* If the previous certificate files haven't been overridden, adjust the paths
to the new certs in the configuration file and restart all Octavia services
(except octavia-api).
Review :ref:`rotate-amphora-certs` above to determine if and how the
amphora certificates needs to be rotated.
Rotating Client Certificates
----------------------------
If the client certificates expired new ones need to be issued and installed on
the system:
* Issue a new client certificate (see the script in the bin folder of Octavia
if self signed certificates are used) or use the ones provided to you by
your certificate authority.
* Copy the new cert where Octavia can find it.
* If the previous certificate files haven't been overridden, adjust the paths
to the new certs in the configuration file. In all cases restart all Octavia
services except octavia-api.
If the client CA certificate has been replaced in addition to
rotating the client certificate the new client CA
certificate needs to be installed in the system. After that initiate a
failover of all amphorae to distribute the new client CA
cert. Until the failover is completed the amphorae can't be controlled by the
control plane.
Changing The Heartbeat Encryption Key
-------------------------------------
Special caution needs to be taken to replace the heartbeat encryption key.
Once this is changed Octavia can't read any heartbeats and will assume
all amphora are in an error state and initiate an immediate failover.
In preparation, read the chapter on :ref:`best_practice` in
the Failover section.
Given the risks involved with changing this key it should not be changed
during routine maintenance but only when a compromise is strongly suspected.
.. note::
For future versions of Octavia an "update amphora" API is planned which
will allow this key to be changed without failover. At that time there would
be a procedure to halt health monitoring while the keys are rotated and then
resume health monitoring.
Handling a VM Node Failure
--------------------------
If a node fails which is running amphora, Octavia will automatically failover
the amphora to a different node (capacity permitting). In some cases, the
node can be recovered (e.g. through a hard reset) and the hypervisor might
bring back the amphora vms. In this case, an operator should manually delete
all amphora on this specific node since Octavia assumes they have been
deleted as part of the failover and will not touch them again.
.. note::
As a safety measure an operator can, prior to deleting, manually check if
the VM is in use. First, use the Amphora API to obtain the current list of
amphorae, then match the nova instance ID to the compute_id column in the
amphora API response (it is not currently possible to filter amphora by
compute_id). If there are any matches where the amphora status is not
'DELETED', the amphora is still considered to be in use.
Evacuating a Specific Amphora from a Host
-----------------------------------------
In some cases an amphora needs to be evacuated either because the host is being
shutdown for maintenance or as part of a failover. Octavia has a rich amphora
API to do that.
First use the amphora API to find the specific amphora. Then, if not already
performed, disable scheduling to this host in nova. Lastly, initiate a failover
of the specific amphora with the failover command on the amphora API.
Alternatively, a live migration might also work if it happens quick enough for
Octavia not to notice a stale amphora (the default configuration is 60s).
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