From 7ab448cc4d4103456842bedd3e321679a8847a13 Mon Sep 17 00:00:00 2001
From: "David A. Symons" <david_ext@algo1.ai>
Date: Thu, 23 Apr 2026 11:43:14 +0100
Subject: [PATCH] =?UTF-8?q?=F0=9F=9A=80=20feat:=20add=20wait-for-db=20init?=
 =?UTF-8?q?=20container=20for=20bundled=20PostgreSQL?=
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When deploying with the bundled PostgreSQL subchart, Sequin starts
before PostgreSQL accepts connections, causing crash-loop restarts
on every fresh install. The startup script (start_commands.sh) runs
Ecto migrations immediately with no retry logic.

Adds a built-in init container that polls pg_isready until the
database is reachable. Uses the PostgreSQL subchart image which
provides pg_isready. Gated on postgresql.enabled so it does not
run when using an external database.

New value: waitForDB.enabled (default: true)

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>
---
 templates/_helpers.tpl    |  8 ++++++++
 templates/deployment.yaml | 24 +++++++++++++++++++++++-
 values.yaml               | 12 ++++++++++++
 3 files changed, 43 insertions(+), 1 deletion(-)

diff --git a/templates/_helpers.tpl b/templates/_helpers.tpl
index 279cf7b..d49df1d 100644
--- a/templates/_helpers.tpl
+++ b/templates/_helpers.tpl
@@ -124,6 +124,14 @@ Return the Database Secret Name
 {{- end -}}
 {{- end -}}
 
+{{/*
+Return the image for the wait-for-db init container.
+Defaults to the PostgreSQL subchart image.
+*/}}
+{{- define "sequin.waitForDB.image" -}}
+{{- include "common.images.image" (dict "imageRoot" .Values.postgresql.image "global" .Values.global) -}}
+{{- end -}}
+
 {{/*
 Get the Redis&reg; fullname
 */}}
diff --git a/templates/deployment.yaml b/templates/deployment.yaml
index a0b9da1..84b812e 100644
--- a/templates/deployment.yaml
+++ b/templates/deployment.yaml
@@ -55,9 +55,31 @@ spec:
       {{- if .Values.podSecurityContext.enabled }}
       securityContext: {{- include "common.compatibility.renderSecurityContext" (dict "secContext" .Values.podSecurityContext "context" $) | nindent 8 }}
       {{- end }}
-      {{- if .Values.initContainers }}
+      {{- if or (and .Values.waitForDB.enabled .Values.postgresql.enabled) .Values.initContainers }}
       initContainers:
+        {{- if and .Values.waitForDB.enabled .Values.postgresql.enabled }}
+        - name: wait-for-db
+          image: {{ include "sequin.waitForDB.image" . }}
+          imagePullPolicy: {{ .Values.image.pullPolicy }}
+          {{- if .Values.containerSecurityContext.enabled }}
+          securityContext: {{- include "common.compatibility.renderSecurityContext" (dict "secContext" .Values.containerSecurityContext "context" $) | nindent 12 }}
+          {{- end }}
+          command:
+            - /bin/bash
+            - -ec
+            - |
+              host={{ include "sequin.database.host" . | quote }}
+              port={{ include "sequin.database.port" . | quote }}
+              user={{ include "sequin.database.username" . | quote }}
+              echo "Waiting for PostgreSQL at ${host}:${port}..."
+              until pg_isready -h "$host" -p "$port" -U "$user" -q; do
+                sleep 2
+              done
+              echo "PostgreSQL is accepting connections"
+        {{- end }}
+        {{- if .Values.initContainers }}
         {{- include "common.tplvalues.render" (dict "value" .Values.initContainers "context" $) | nindent 8 }}
+        {{- end }}
       {{- end }}
       containers:
         - name: sequin
diff --git a/values.yaml b/values.yaml
index 56abaef..a30c0a9 100644
--- a/values.yaml
+++ b/values.yaml
@@ -378,6 +378,18 @@ sidecars: []
 ##    command: ['sh', '-c', 'echo "hello world"']
 ##
 initContainers: []
+## @section Database readiness parameters
+##
+
+## Wait for database init container
+## Adds an init container that waits for PostgreSQL to accept connections
+## before starting Sequin. Prevents crash-loops on fresh installs when
+## deploying with the bundled PostgreSQL subchart.
+## Only takes effect when postgresql.enabled=true.
+## @param waitForDB.enabled Enable the wait-for-db init container
+##
+waitForDB:
+  enabled: true
 ## @section Traffic Exposure Parameters
 ##