Add readiness init container docs

Signed-off-by: Mykola Morhun <[email protected]>

modules/administration-guide/nav.adoc

@@ -34,6 +34,8 @@
 
 * xref:migration-from-postgresql-9-to-postgresql-13.adoc[]
 
+* xref:enabling-readiness-init-containers.adoc[]
+
 * xref:caching-images-for-faster-workspace-start.adoc[]
 ** xref:defining-the-list-of-images-to-pull.adoc[]
 ** xref:defining-the-memory-parameters-for-the-image-puller.adoc[]

modules/administration-guide/pages/enabling-readiness-init-containers.adoc

@@ -0,0 +1,6 @@
+[id="enabling-readiness-init-containers"]
+:navtitle: Enabling readiness init containers
+:keywords: init-container, startup
+:page-aliases: .:enabling-readiness-init-containers
+
+include::partial$assembly_enabling-readiness-init-containers.adoc[]

modules/administration-guide/partials/assembly_enabling-readiness-init-containers.adoc

@@ -0,0 +1,20 @@
+:parent-context-of-assembly_enabling-readiness-init-containers: {context}
+
+[id="assembly_enabling-readiness-init-containers_{context}"]
+= Enabling readiness init containers
+
+:context: assembly_enabling-startup-init-containers
+
+Normally, {prod-short} Operator installs {prod} and starts its containers in the right order.
+However, if a node with {prod-short} gets restarted, than all {prod-short} containers start simultaneously and some might fail as dependent component might not be ready yet.
+To handle such a case, one should enable readiness init containers for {prod-short} components.
+
+Choose the procedure depending on installer type:
+
+* xref:enabling-readiness-init-containers.adoc#enabling-readiness-init-containers-for-operator-installer_{context}[]
+* xref:enabling-readiness-init-containers.adoc#enabling-readiness-init-containers-for-olm-installer_{context}[]
+
+include::partial$proc_enabling-readiness-init-containers-for-operator-installer.adoc[leveloffset=+1]
+include::partial$proc_enabling-readiness-init-containers-for-olm-installer.adoc[leveloffset=+1]
+
+:context: {arent-context-of-assembly_enabling-startup-init-containers}

modules/administration-guide/partials/proc_enabling-readiness-init-containers-for-olm-installer.adoc

@@ -0,0 +1,42 @@
+:_module-type: PROCEDURE
+
+[id="enabling-readiness-init-containers-for-olm-installer_{context}"]
+= Enabling readiness init containers for OLM installer
+
+This section describes how to enable (disable) components readiness init containers for {prod-short} in case of OLM installer.
+
+.Prerequisites
+
+. {prod} installed with OLM installer.
+
+.Procedure
+
+. Find {prod-short} Operator subscription name:
++
+```sh
+$ {orch-cli} get subscriptions -n {prod-namespace}
+```
+
+. Find CSV name in {prod-short} Operator subscription:
++
+```sh
+$ {orch-cli} get subscription <subscription-name> -n {prod-namespace} -o yaml | grep installedCSV
+```
+
+. Edit the CSV
++
+```sh
+$ {orch-cli} edit csv <csv-name> -n {prod-namespace}
+```
++
+by adding (removing) the following:
++
+```yaml
+ - name: ADD_COMPONENT_READINESS_INIT_CONTAINERS
+   value: "true"
+```
+
+. Wait while {prod-short} Operator restarts some components.
+
+[NOTE]
+When {prod} version is updated, OLM will create a new CSV and the procedure above should be repeated.

modules/administration-guide/partials/proc_enabling-readiness-init-containers-for-operator-installer.adoc

@@ -0,0 +1,24 @@
+:_module-type: PROCEDURE
+
+[id="enabling-readiness-init-containers-for-operator-installer_{context}"]
+= Enabling readiness init containers for Operator installer
+
+This section describes how to enable (disable) components readiness init containers for {prod-short} in case of Operator installer.
+
+.Prerequisites
+
+. {prod} installed with Operator installer.
+
+.Procedure
+
+. Find {prod-short} Operator deployment name.
+
+. Edit the deployment by adding `ADD_COMPONENT_READINESS_INIT_CONTAINERS` environment variable.
+Insert (remove) the following under `spec.template.spec.containers[0].env` section of the Operator deployment:
++
+```yaml
+ - name: ADD_COMPONENT_READINESS_INIT_CONTAINERS
+   value: "true"
+```
+
+. Wait while {prod-short} Operator restarts some components.