Merge "Terraform Infra-driver for Insta/Termi"
This commit is contained in:
Zuul
Gerrit Code Review
commit
c36317e842
427
specs/2023.2/terraform-infra-driver.rst
Normal file
427
specs/2023.2/terraform-infra-driver.rst
Normal file
@ -0,0 +1,427 @@
|
||||
..
|
||||
This work is licensed under a Creative Commons Attribution 3.0 Unported
|
||||
License.
|
||||
|
||||
http://creativecommons.org/licenses/by/3.0/legalcode
|
||||
|
||||
|
||||
============================================================
|
||||
Terraform Infra-driver for VNF Instantiation and Termination
|
||||
============================================================
|
||||
|
||||
This specification describes Terraform Infra-driver in Tacker. The scope of the
|
||||
present document includes VNF instantiation and termination with this new
|
||||
infra-driver, using AWS as an example NFVI.
|
||||
|
||||
https://blueprints.launchpad.net/tacker/+spec/terraform-infra-driver
|
||||
|
||||
|
||||
Problem description
|
||||
===================
|
||||
|
||||
Tacker is designed as a G-VNFM that supports both VNF and CNF LCM. However,
|
||||
OpenStack is the only platform where Tacker can deploy VNF among the variety of
|
||||
cloud platforms. Given the recent multi-cloud trends in cloud computing, Tacker
|
||||
have to overcome this potential disadvantage by implementing additional
|
||||
infra-driver.
|
||||
|
||||
|
||||
Proposed change
|
||||
===============
|
||||
|
||||
This spec proposes to support Terraform infra-driver. Terraform [#terraform]_
|
||||
is the de-facto standard in the IaC area, it's platform-agnostic, declarative
|
||||
and open source. Using Terraform as a backend tool enables Tacker to create
|
||||
virtual resources on several platforms that Terraform has already supported,
|
||||
such as AWS. Terraform has its own configuration language to define virtual
|
||||
resources, like manifest in Kubernetes or Helm chart in Helm. Users can easily
|
||||
create VNF packages for Terraform infra-driver by including the configuration.
|
||||
|
||||
For this to happen, the following items have to be implemented.
|
||||
|
||||
* VNF Instantiation with Terraform Infra-driver
|
||||
* VNF Termination with Terraform Infra-driver
|
||||
* Adding DB table/field to store Terraform state (optional)
|
||||
* Sample VNF packages for Terraform infra-driver
|
||||
* Updating user document
|
||||
|
||||
Terraform
|
||||
---------
|
||||
|
||||
HashiCorp Terraform is an infrastructure as code tool that lets you define both
|
||||
cloud and on-prem resources in human-readable configuration files that you can
|
||||
version, reuse, and share. Put simply, you can see Terraform as generic
|
||||
OpenStack Heat that can be used among several cloud platforms. Terraform
|
||||
supports a number of cloud infrastructure providers such as:
|
||||
|
||||
* Amazon Web Services
|
||||
* Cloudflare
|
||||
* Microsoft Azure
|
||||
* IBM Cloud
|
||||
* Serverspace
|
||||
* Google Cloud Platform
|
||||
* DigitalOcean
|
||||
* Oracle Cloud Infrastructure
|
||||
* Yandex.Cloud
|
||||
* VMware vSphere
|
||||
* OpenStack
|
||||
* Kubernetes
|
||||
* Helm
|
||||
|
||||
Terraform uses declarative configuration to describe the desired final state
|
||||
and its client-side is provided only a CLI tool, similar to Helm. Therefore,
|
||||
the basic architecture of Terraform infra-driver can be similar to Helm
|
||||
infra-driver.
|
||||
|
||||
The following are the characteristics of Terraform:
|
||||
|
||||
#. Configuration file
|
||||
Terraform has its own language HCL for the resource definition. The files
|
||||
containing Terraform code are often called configuration files. These files
|
||||
correspond to the Helm chart in Helm.
|
||||
#. Variables
|
||||
Terraform allows users to define variables in configuration files.
|
||||
Variables can be set as a file or parameters of Terraform CLI. This is a
|
||||
similar mechanism to the values in Helm.
|
||||
#. State file and state lock file
|
||||
Terraform creates a state file and a state lock file [#tf_state]_ when
|
||||
Terraform creates actual resources. This might be the biggest difference
|
||||
from Helm. This state file records the information of resources created by
|
||||
Terraform. The state lock file prevents others from acquiring the lock and
|
||||
potentially corrupting your state in the case where multiple users manage
|
||||
the same resources with Terraform in different places.
|
||||
|
||||
.. note:: In Kubernetes, the state file corresponds to the resources on
|
||||
Kubernetes worker nodes which store all information of actual resources
|
||||
managed by Kubernetes. As there's no entity corresponding to the worker
|
||||
nodes, Terraform creates state files.
|
||||
|
||||
This figure shows the overview of the operation of Terraform, and input/output
|
||||
files.
|
||||
|
||||
.. uml::
|
||||
|
||||
@startuml
|
||||
|
||||
|
||||
actor "User" as user
|
||||
component "Terraform CLI" as cli
|
||||
component "Terraform" as tf
|
||||
component "Configuration file" as config
|
||||
component "Variables file" as vars
|
||||
component "Target Service" as svc
|
||||
file "State file" as state
|
||||
file "State lock file" as statelock
|
||||
|
||||
'# Relationships
|
||||
user --> config: 1. Create Configuration file
|
||||
user --> vars: 1. Create Variables file
|
||||
user -> cli
|
||||
cli -> tf: 2. Init Terraform\n with configuration file\n and variables file
|
||||
tf --> statelock: 3. Create state lock file
|
||||
cli -> tf: 4. Apply Configuration file
|
||||
tf -> svc: 5. Call APIs
|
||||
tf --> state: 6. Create state file
|
||||
|
||||
@enduml
|
||||
|
||||
|
||||
Terraform Infra-driver
|
||||
----------------------
|
||||
|
||||
This figure shows an overview of Instantiate VNF with the Terraform
|
||||
infra-driver. Terminate VNF is omitted as it is almost the same as the
|
||||
Instantiate VNF.
|
||||
|
||||
Instantiate VNF consist of the following steps:
|
||||
|
||||
#. Request create VNF
|
||||
Users request create VNF with a VNF package that contains Terraform config
|
||||
and variable files in addition to VNFD.
|
||||
#. Request instantiate VNF
|
||||
Users request instantiate VNF with an instantiate parameters that can
|
||||
overrides variables defined in Terraform variables file.
|
||||
#. Execute Terraform command
|
||||
Terraform infra-driver executes terraform command to apply configuration
|
||||
files to Terraform.
|
||||
#. Call target service API
|
||||
Terraform calls target service APIs according to the configuration file.
|
||||
#. Create VM(s)
|
||||
Target service (e.g., OpenStack Nova, AWS EC2, etc) creates VM(s).
|
||||
|
||||
.. uml::
|
||||
|
||||
@startuml
|
||||
|
||||
frame "python-tackerclient" {
|
||||
component "tacker-client" as client {
|
||||
package "VNF Package" as vnfpkg {
|
||||
file "VNFD" as vnfd
|
||||
file "Terraform\nconfiguration" as tffile
|
||||
file "Terraform\nvariables\nfile" as tfvar
|
||||
}
|
||||
file "Instantiate\nparameters" as inst_param
|
||||
}
|
||||
}
|
||||
|
||||
vnfd -[hidden]> tffile
|
||||
tffile-[hidden]> tfvar
|
||||
|
||||
frame "tacker" {
|
||||
component "tacker-server" {
|
||||
component "server" as serv
|
||||
}
|
||||
component "tacker-conductor" {
|
||||
component "conductor" as cond
|
||||
component "Terraform\ninfra-driver" as infra
|
||||
}
|
||||
}
|
||||
|
||||
node "Terraform"
|
||||
|
||||
node "Target Service" as ts
|
||||
cloud "Hardware Resources" as hw {
|
||||
node "VM" as ins1
|
||||
}
|
||||
|
||||
'# Relationships
|
||||
vnfpkg --> serv: 1. Request\n create VNF
|
||||
inst_param --> serv: 2. Request\n instantiate VNF
|
||||
serv --> cond
|
||||
cond --> infra
|
||||
infra --> Terraform: 3. Execute Terraform command
|
||||
Terraform -right-> ts: 4. Call target\n service API
|
||||
ts --> ins1: 5. Create VM(s)
|
||||
|
||||
@enduml
|
||||
|
||||
|
||||
|
||||
State file management
|
||||
`````````````````````
|
||||
|
||||
Given that terraform config file is located in VNF packages, state files are
|
||||
created and managed for each VNF instance. Terraform provides several options
|
||||
(i.e., backend) to store the state file [#tf_state_backend]_. Based on the
|
||||
available backend, the available options for Tacker are the following:
|
||||
|
||||
#. Store state files as a local file
|
||||
#. Store state files in InstantiatedVnfInfo
|
||||
#. Store state files in a new DB table/field
|
||||
#. Store state files in Kubernetes Secret
|
||||
#. Store state files in PostgresDB
|
||||
|
||||
The first option is the easiest way. As Tacker extracts a VNF package into a
|
||||
local directory, we can place a state file in that local directory. However,
|
||||
this makes creating more than one VNF instance from one VNF package almost
|
||||
impossible. Thus, practically, we need to create another directory for each VNF
|
||||
instance, copy all contents of a VNF package and keep the state file there.
|
||||
|
||||
If the first option is not possible, for example, there is no way to create
|
||||
temporal directories, we can manage the state file on the InstantiatedVnfInfo
|
||||
field. Since the data type of this field is structure [#sol003]_ and the state
|
||||
file is written in JSON, we can directly store the state file in that field.
|
||||
This field is also suitable in the sense that the lifecycle of the state file
|
||||
matches that of the VNF Instance.
|
||||
|
||||
The rest of the options are not recommended as it incurs changes on the data
|
||||
model of Tacker or requires another component to manage the state file.
|
||||
|
||||
This figure shows the basic idea of the first option.
|
||||
|
||||
.. uml::
|
||||
|
||||
@startuml
|
||||
|
||||
left to right direction
|
||||
|
||||
component "Terraform infra-driver" as tfid
|
||||
folder "VNF Package A" as pkga
|
||||
folder "VNF Package B" as pkgb
|
||||
folder "Directory for VNF Instance A" as da {
|
||||
file "Configuration" as ca
|
||||
file "Variables" as va
|
||||
file "State file A" as statea
|
||||
file "State lock file A" as statelocka
|
||||
}
|
||||
folder "Directory for VNF Instance B" as db {
|
||||
file "Configuration" as cb
|
||||
file "Variables" as vb
|
||||
file "State lock file B" as statelockb
|
||||
file "State file B" as stateb
|
||||
}
|
||||
folder "Directory for VNF Instance C" as dc {
|
||||
file "Configuration" as cc
|
||||
file "Variables" as vc
|
||||
file "State lock file C" as statelockc
|
||||
file "State file C" as statec
|
||||
}
|
||||
dc -[hidden]> db
|
||||
db -[hidden]> da
|
||||
component "Terraform" as tf
|
||||
|
||||
'# Relationships
|
||||
tfid -> tf: Execute
|
||||
tfid <-up- pkga: Download
|
||||
tfid <-up- pkgb: Download
|
||||
tfid ---> da: Copy VNF Package A
|
||||
tfid ---> db: Copy VNF Package A
|
||||
tfid ---> dc: Copy VNF Package B
|
||||
tf --> statea: Create
|
||||
tf --> statelocka: Create
|
||||
tf --> stateb: Create
|
||||
tf --> statelockb: Create
|
||||
tf --> statec: Create
|
||||
tf --> statelockc: Create
|
||||
|
||||
|
||||
|
||||
@enduml
|
||||
|
||||
State lock file management
|
||||
``````````````````````````
|
||||
|
||||
Ideally, we can disable generating state lock files [#tf_lock]_ as Tacker is
|
||||
only the entity that manages the resources associated with the instantiated
|
||||
VNF. If we need to use the lock file, we have the similar options as the state
|
||||
file as follows:
|
||||
|
||||
#. Store state files as a local file
|
||||
#. Store state files in InstantiatedVnfInfo
|
||||
#. Store state files in a new DB table/field
|
||||
|
||||
Alternatives
|
||||
------------
|
||||
|
||||
Implementing infra-driver for individual platform can be an alternative.
|
||||
|
||||
Data model impact
|
||||
-----------------
|
||||
|
||||
None. One possible reason for data model changes is to make new table/field to
|
||||
store state and state lock files. As described in the State file management
|
||||
section, we have several alternative ways.
|
||||
|
||||
REST API impact
|
||||
---------------
|
||||
|
||||
None.
|
||||
|
||||
Security impact
|
||||
---------------
|
||||
|
||||
Terraform uses sensitive data in some scenes. For example, Terraform requires
|
||||
credentials to make API requests. In general, we can avoid exposure of
|
||||
sensitive data by using environment variables. However, at the same time, we
|
||||
need to carefully make configuration files.
|
||||
|
||||
Potential risks are listed as follows, but there can be more:
|
||||
|
||||
* Hardcoded credentials for the target services
|
||||
* Hardcoded credentials for the backend of the state file [#tf_state_sec]_
|
||||
|
||||
See the best practice for details [#tf_sec]_
|
||||
|
||||
Notifications impact
|
||||
--------------------
|
||||
|
||||
None. However, if state files are stored in InstantiatedVnfInfo, they can be
|
||||
omitted from LcmOpOccNotification.
|
||||
|
||||
Other end user impact
|
||||
---------------------
|
||||
|
||||
None.
|
||||
|
||||
Performance Impact
|
||||
------------------
|
||||
|
||||
None. Terraform itself and the state file (might be located on DB) might use
|
||||
storage, but it is negligibly small. As the infra-drivers are abstracted by
|
||||
Tacker's VNF LCM driver, Terraform infra-driver does not affect to the overall
|
||||
performance.
|
||||
|
||||
|
||||
Other deployer impact
|
||||
---------------------
|
||||
|
||||
After merging this feature, the following points must be considered:
|
||||
|
||||
* Users need to install Terraform when using Terraform infra-driver
|
||||
* Tacker community should add installation of Terraform in Zuul to tests
|
||||
Terraform infra-driver
|
||||
|
||||
No effects on existing deployments as this is a new feature independent of the
|
||||
existing ones.
|
||||
|
||||
Developer impact
|
||||
----------------
|
||||
|
||||
* Developers may need to update Terraform infra-driver according to the update
|
||||
of Terraform.
|
||||
* Developers may need to fix bugs of Terraform infra-driver caused by the
|
||||
Terraform.
|
||||
* Developers may need to be careful to change other components than Terraform
|
||||
infra-driver, such as VNF package format, controllers, conductor, etc, so
|
||||
that it works in Terraform infra-driver.
|
||||
|
||||
Implementation
|
||||
==============
|
||||
|
||||
Assignee(s)
|
||||
-----------
|
||||
|
||||
Primary assignee:
|
||||
* Hiromu Asahina (hiromu) <hiromu.asahina@ntt.com> <hiromu.a5a@gmail.com>
|
||||
|
||||
Other contributors:
|
||||
* TBD
|
||||
|
||||
Work Items
|
||||
----------
|
||||
|
||||
* VNF Instantiation with Terraform Infra-driver
|
||||
* VNF Termination with Terraform Infra-driver
|
||||
* Adding DB table/field to store Terraform state (optional)
|
||||
* Sample VNF packages for Terraform infra-driver
|
||||
* Updating user document
|
||||
|
||||
|
||||
Dependencies
|
||||
============
|
||||
|
||||
* Terraform v1.4.0 or later
|
||||
|
||||
Testing
|
||||
=======
|
||||
|
||||
Terraform supports several providers including OpenStack [#tf_os]_, Kubernetes
|
||||
[#tf_k8s]_, Docker [#tf_local]_ and local files [#tf_docker]_. The easiest way
|
||||
is to use OpenStack in the functional tests. As terraform infra-driver is
|
||||
transparent for VNF packages, its normality must not be affected by the
|
||||
difference of used providers. In this sense, we can test its normality with
|
||||
other available providers, such as Kubernetes, docker or local provider.
|
||||
|
||||
Alternatively, we can use LocalStack [#localstack]_ that acts as a stub of AWS
|
||||
services.
|
||||
|
||||
Documentation Impact
|
||||
====================
|
||||
|
||||
Need to explain the use cases of Terraform infra-driver.
|
||||
|
||||
References
|
||||
==========
|
||||
|
||||
.. [#terraform] https://www.terraform.io/
|
||||
.. [#tf_state] https://developer.hashicorp.com/terraform/language/state
|
||||
.. [#tf_state_backend] https://developer.hashicorp.com/terraform/language/settings/backends/configuration#available-backends
|
||||
.. [#sol003] https://www.etsi.org/deliver/etsi_gs/NFV-SOL/001_099/003/03.05.01_60/gs_NFV-SOL003v030501p.pdf
|
||||
.. [#tf_lock] https://developer.hashicorp.com/terraform/language/state/locking
|
||||
.. [#tf_os] https://registry.terraform.io/providers/terraform-provider-openstack/openstack/latest
|
||||
.. [#tf_k8s] https://registry.terraform.io/providers/hashicorp/kubernetes/latest
|
||||
.. [#tf_docker] https://registry.terraform.io/providers/kreuzwerker/docker/latest
|
||||
.. [#tf_local] https://registry.terraform.io/providers/hashicorp/local/latest
|
||||
.. [#tf_state_sec] https://developer.hashicorp.com/terraform/language/settings/backends/configuration#credentials-and-sensitive-data
|
||||
.. [#tf_sec] https://cycode.com/7-terraform-security-best-practices/
|
||||
.. [#localstack] https://localstack.cloud/
|
||||
Loading…
Reference in New Issue
Block a user