Merge pull request #3813 from ewolinetz/role_decomposition_proposal

Creating initial proposal doc for review

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+# Scaffolding for decomposing large roles
+
+## Why?
+
+Currently we have roles that are very large and encompass a lot of different
+components. This makes for a lot of logic required within the role, can
+create complex conditionals, and increases the learning curve for the role.
+
+## How?
+
+Creating a guide on how to approach breaking up a large role into smaller,
+component based, roles. Also describe how to develop new roles, to avoid creating
+large roles.
+
+## Proposal
+
+Create a new guide or append to the current contributing guide a process for
+identifying large roles that can be split up, and how to compose smaller roles
+going forward.
+
+### Large roles
+
+A role should be considered for decomposition if it:
+
+1) Configures/installs more than one product.
+1) Can configure multiple variations of the same product that can live
+side by side.
+1) Has different entry points for upgrading and installing a product
+
+Large roles<sup>1</sup> should be responsible for:
+> 1 or composing playbooks
+
+1) Composing smaller roles to provide a full solution such as an Openshift Master
+1) Ensuring that smaller roles are called in the correct order if necessary
+1) Calling smaller roles with their required variables
+1) Performing prerequisite tasks that small roles may depend on being in place
+(openshift_logging certificate generation for example)
+
+### Small roles
+
+A small role should be able to:
+
+1) Be deployed independently of other products (this is different than requiring
+being installed after other base components such as OCP)
+1) Be self contained and able to determine facts that it requires to complete
+1) Fail fast when facts it requires are not available or are invalid
+1) "Make it so" based on provided variables and anything that may be required
+as part of doing such (this should include data migrations)
+1) Have a minimal set of dependencies in meta/main.yml, just enough to do its job
+
+### Example using decomposition of openshift_logging
+
+The `openshift_logging` role was created as a port from the deployer image for
+the `3.5` deliverable. It was a large role that created the service accounts,
+configmaps, secrets, routes, and deployment configs/daemonset required for each
+of its different components (Fluentd, Kibana, Curator, Elasticsearch).
+
+It was possible to configure any of the components independently of one another,
+up to a point. However, it was an all of nothing installation and there was a
+need from customers to be able to do things like just deploy Fluentd.
+
+Also being able to support multiple versions of configuration files would become
+increasingly messy with a large role. Especially if the components had changes
+at different intervals.
+
+#### Folding of responsibility
+
+There was a duplicate of work within the installation of three of the four logging
+components where there was a possibility to deploy both an 'operations' and
+'non-operations' cluster side-by-side. The first step was to collapse that
+duplicate work into a single path and allow a variable to be provided to
+configure such that either possibility could be created.
+
+#### Consolidation of responsibility
+
+The generation of OCP objects required for each component were being created in
+the same task file, all Service Accounts were created at the same time, all secrets,
+configmaps, etc. The only components that were not generated at the same time were
+the deployment configs and the daemonset. The second step was to make the small
+roles self contained and generate their own required objects.
+
+#### Consideration for prerequisites
+
+Currently the Aggregated Logging stack generates its own certificates as it has
+some requirements that prevent it from utilizing the OCP cert generation service.
+In order to make sure that all components were able to trust one another as they
+did previously, until the cert generation service can be used, the certificate
+generation is being handled within the top level `openshift_logging` role and
+providing the location of the generated certificates to the individual roles.
+
+#### Snippets
+
+[openshift_logging/tasks/install_logging.yaml](https://github.com/ewolinetz/openshift-ansible/blob/logging_component_subroles/roles/openshift_logging/tasks/install_logging.yaml)
+```yaml
+- name: Gather OpenShift Logging Facts
+  openshift_logging_facts:
+    oc_bin: "{{openshift.common.client_binary}}"
+    openshift_logging_namespace: "{{openshift_logging_namespace}}"
+
+- name: Set logging project
+  oc_project:
+    state: present
+    name: "{{ openshift_logging_namespace }}"
+
+- name: Create logging cert directory
+  file:
+    path: "{{ openshift.common.config_base }}/logging"
+    state: directory
+    mode: 0755
+  changed_when: False
+  check_mode: no
+
+- include: generate_certs.yaml
+  vars:
+    generated_certs_dir: "{{openshift.common.config_base}}/logging"
+
+## Elasticsearch
+- include_role:
+    name: openshift_logging_elasticsearch
+  vars:
+    generated_certs_dir: "{{openshift.common.config_base}}/logging"
+
+- include_role:
+    name: openshift_logging_elasticsearch
+  vars:
+    generated_certs_dir: "{{openshift.common.config_base}}/logging"
+    openshift_logging_es_ops_deployment: true
+  when:
+  - openshift_logging_use_ops | bool
+
+
+## Kibana
+- include_role:
+    name: openshift_logging_kibana
+  vars:
+    generated_certs_dir: "{{openshift.common.config_base}}/logging"
+    openshift_logging_kibana_namespace: "{{ openshift_logging_namespace }}"
+    openshift_logging_kibana_master_url: "{{ openshift_logging_master_url }}"
+    openshift_logging_kibana_master_public_url: "{{ openshift_logging_master_public_url }}"
+    openshift_logging_kibana_image_prefix: "{{ openshift_logging_image_prefix }}"
+    openshift_logging_kibana_image_version: "{{ openshift_logging_image_version }}"
+    openshift_logging_kibana_replicas: "{{ openshift_logging_kibana_replica_count }}"
+    openshift_logging_kibana_es_host: "{{ openshift_logging_es_host }}"
+    openshift_logging_kibana_es_port: "{{ openshift_logging_es_port }}"
+    openshift_logging_kibana_image_pull_secret: "{{ openshift_logging_image_pull_secret }}"
+
+- include_role:
+    name: openshift_logging_kibana
+  vars:
+    generated_certs_dir: "{{openshift.common.config_base}}/logging"
+    openshift_logging_kibana_ops_deployment: true
+    openshift_logging_kibana_namespace: "{{ openshift_logging_namespace }}"
+    openshift_logging_kibana_master_url: "{{ openshift_logging_master_url }}"
+    openshift_logging_kibana_master_public_url: "{{ openshift_logging_master_public_url }}"
+    openshift_logging_kibana_image_prefix: "{{ openshift_logging_image_prefix }}"
+    openshift_logging_kibana_image_version: "{{ openshift_logging_image_version }}"
+    openshift_logging_kibana_image_pull_secret: "{{ openshift_logging_image_pull_secret }}"
+    openshift_logging_kibana_es_host: "{{ openshift_logging_es_ops_host }}"
+    openshift_logging_kibana_es_port: "{{ openshift_logging_es_ops_port }}"
+    openshift_logging_kibana_nodeselector: "{{ openshift_logging_kibana_ops_nodeselector }}"
+    openshift_logging_kibana_cpu_limit: "{{ openshift_logging_kibana_ops_cpu_limit }}"
+    openshift_logging_kibana_memory_limit: "{{ openshift_logging_kibana_ops_memory_limit }}"
+    openshift_logging_kibana_hostname: "{{ openshift_logging_kibana_ops_hostname }}"
+    openshift_logging_kibana_replicas: "{{ openshift_logging_kibana_ops_replica_count }}"
+    openshift_logging_kibana_proxy_debug: "{{ openshift_logging_kibana_ops_proxy_debug }}"
+    openshift_logging_kibana_proxy_cpu_limit: "{{ openshift_logging_kibana_ops_proxy_cpu_limit }}"
+    openshift_logging_kibana_proxy_memory_limit: "{{ openshift_logging_kibana_ops_proxy_memory_limit }}"
+    openshift_logging_kibana_cert: "{{ openshift_logging_kibana_ops_cert }}"
+    openshift_logging_kibana_key: "{{ openshift_logging_kibana_ops_key }}"
+    openshift_logging_kibana_ca: "{{ openshift_logging_kibana_ops_ca}}"
+  when:
+  - openshift_logging_use_ops | bool
+
+
+## Curator
+- include_role:
+    name: openshift_logging_curator
+  vars:
+    generated_certs_dir: "{{openshift.common.config_base}}/logging"
+    openshift_logging_curator_namespace: "{{ openshift_logging_namespace }}"
+    openshift_logging_curator_master_url: "{{ openshift_logging_master_url }}"
+    openshift_logging_curator_image_prefix: "{{ openshift_logging_image_prefix }}"
+    openshift_logging_curator_image_version: "{{ openshift_logging_image_version }}"
+    openshift_logging_curator_image_pull_secret: "{{ openshift_logging_image_pull_secret }}"
+
+- include_role:
+    name: openshift_logging_curator
+  vars:
+    generated_certs_dir: "{{openshift.common.config_base}}/logging"
+    openshift_logging_curator_ops_deployment: true
+    openshift_logging_curator_namespace: "{{ openshift_logging_namespace }}"
+    openshift_logging_curator_master_url: "{{ openshift_logging_master_url }}"
+    openshift_logging_curator_image_prefix: "{{ openshift_logging_image_prefix }}"
+    openshift_logging_curator_image_version: "{{ openshift_logging_image_version }}"
+    openshift_logging_curator_image_pull_secret: "{{ openshift_logging_image_pull_secret }}"
+    openshift_logging_curator_cpu_limit: "{{ openshift_logging_curator_ops_cpu_limit }}"
+    openshift_logging_curator_memory_limit: "{{ openshift_logging_curator_ops_memory_limit }}"
+    openshift_logging_curator_nodeselector: "{{ openshift_logging_curator_ops_nodeselector }}"
+  when:
+  - openshift_logging_use_ops | bool
+
+
+## Fluentd
+- include_role:
+    name: openshift_logging_fluentd
+  vars:
+    generated_certs_dir: "{{openshift.common.config_base}}/logging"
+
+- include: update_master_config.yaml
+```
+
+[openshift_logging_elasticsearch/meta/main.yaml](https://github.com/ewolinetz/openshift-ansible/blob/logging_component_subroles/roles/openshift_logging_elasticsearch/meta/main.yaml)
+```yaml
+---
+galaxy_info:
+  author: OpenShift Red Hat
+  description: OpenShift Aggregated Logging Elasticsearch Component
+  company: Red Hat, Inc.
+  license: Apache License, Version 2.0
+  min_ansible_version: 2.2
+  platforms:
+  - name: EL
+    versions:
+    - 7
+  categories:
+  - cloud
+dependencies:
+- role: lib_openshift
+```
+
+[openshift_logging/meta/main.yaml](https://github.com/ewolinetz/openshift-ansible/blob/logging_component_subroles/roles/openshift_logging/meta/main.yaml)
+```yaml
+---
+galaxy_info:
+  author: OpenShift Red Hat
+  description: OpenShift Aggregated Logging
+  company: Red Hat, Inc.
+  license: Apache License, Version 2.0
+  min_ansible_version: 2.2
+  platforms:
+  - name: EL
+    versions:
+    - 7
+  categories:
+  - cloud
+dependencies:
+- role: lib_openshift
+- role: openshift_facts
+```
+
+[openshift_logging/tasks/install_support.yaml - old](https://github.com/openshift/openshift-ansible/blob/master/roles/openshift_logging/tasks/install_support.yaml)
+```yaml
+---
+# This is the base configuration for installing the other components
+- name: Check for logging project already exists
+  command: >
+    {{ openshift.common.client_binary }} --config={{ mktemp.stdout }}/admin.kubeconfig get project {{openshift_logging_namespace}} --no-headers
+  register: logging_project_result
+  ignore_errors: yes
+  when: not ansible_check_mode
+  changed_when: no
+
+- name: "Create logging project"
+  command: >
+    {{ openshift.common.admin_binary }} --config={{ mktemp.stdout }}/admin.kubeconfig new-project {{openshift_logging_namespace}}
+  when: not ansible_check_mode and "not found" in logging_project_result.stderr
+
+- name: Create logging cert directory
+  file: path={{openshift.common.config_base}}/logging state=directory mode=0755
+  changed_when: False
+  check_mode: no
+
+- include: generate_certs.yaml
+  vars:
+    generated_certs_dir: "{{openshift.common.config_base}}/logging"
+
+- name: Create temp directory for all our templates
+  file: path={{mktemp.stdout}}/templates state=directory mode=0755
+  changed_when: False
+  check_mode: no
+
+- include: generate_secrets.yaml
+  vars:
+    generated_certs_dir: "{{openshift.common.config_base}}/logging"
+
+- include: generate_configmaps.yaml
+
+- include: generate_services.yaml
+
+- name: Generate kibana-proxy oauth client
+  template: src=oauth-client.j2 dest={{mktemp.stdout}}/templates/oauth-client.yaml
+  vars:
+    secret: "{{oauth_secret}}"
+  when: oauth_secret is defined
+  check_mode: no
+  changed_when: no
+
+- include: generate_clusterroles.yaml
+
+- include: generate_rolebindings.yaml
+
+- include: generate_clusterrolebindings.yaml
+
+- include: generate_serviceaccounts.yaml
+
+- include: generate_routes.yaml
+```
+
+# Limitations
+
+There will always be exceptions for some of these rules, however the majority of
+roles should be able to fall within these guidelines.
+
+# Additional considerations
+
+## Playbooks including playbooks
+In some circumstances it does not make sense to have a composing role but instead
+a playbook would be best for orchestrating the role flow. Decisions made regarding
+playbooks including playbooks will need to be taken into consideration as part of
+defining this process.
+Ref: (link to rteague's presentation?)
+
+## Role dependencies
+We want to make sure that our roles do not have any extra or unnecessary dependencies
+in meta/main.yml without:
+
+1. Proposing the inclusion in a team meeting or as part of the PR review and getting agreement
+1. Documenting in meta/main.yml why it is there and when it was agreed to (date)
+
+## Avoiding overly verbose roles
+When we are splitting our roles up into smaller components we want to ensure we
+avoid creating roles that are, for a lack of a better term, overly verbose. What
+do we mean by that? If we have `openshift_master` as an example, and we were to
+split it up, we would have a component for `etcd`, `docker`, and possibly for
+its rpms/configs. We would want to avoid creating a role that would just create
+certificates as those would make sense to be contained with the rpms and configs.
+Likewise, when it comes to being able to restart the master, we wouldn't have a
+role where that was its sole purpose.
+
+The same would apply for the `etcd` and `docker` roles. Anything that is required
+as part of installing `etcd` such as generating certificates, installing rpms,
+and upgrading data between versions should all be contained within the single
+`etcd` role.
+
+## Enforcing standards
+Certain naming standards like variable names could be verified as part of a Travis
+test. If we were going to also enforce that a role either has tasks or includes
+(for example) then we could create tests for that as well.
+
+## CI tests for individual roles
+If we are able to correctly split up roles, it should be possible to test role
+installations/upgrades like unit tests (assuming they would be able to be installed
+independently of other components).