Add sticky sessions support to terraform module

Enable sticky sessions for MCP session affinity in multi-replica deployments.
MCP sessions are stored in-memory, so requests must be routed to the same
replica. Uses Azure Container Apps ARRAffinity cookies for session routing.

- Add enable_sticky_sessions variable (default: true)
- Add null_resource to configure sticky sessions via az cli
- Add outputs for sticky sessions status and verification command

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

Author: surinderunitone

terraform/main.tf

@@ -435,7 +435,33 @@ resource "null_resource" "configure_github_auth" {
 }
 
 # ==============================================================================
-# 10. ACR Task for CI/CD (Optional)
+# 10. Sticky Sessions for MCP Session Affinity
+# ==============================================================================
+# MCP sessions are stored in-memory. When running multiple replicas, requests
+# must be routed to the same replica to maintain session state. Sticky sessions
+# use HTTP cookies (ARRAffinity) to ensure session affinity.
+resource "null_resource" "sticky_sessions" {
+  count = var.enable_sticky_sessions ? 1 : 0
+
+  triggers = {
+    container_app_id = azurerm_container_app.app.id
+    sticky_sessions  = var.enable_sticky_sessions
+  }
+
+  provisioner "local-exec" {
+    command = <<-EOT
+      az containerapp ingress sticky-sessions set \
+        --name ${local.container_app_name} \
+        --resource-group ${var.resource_group_name} \
+        --affinity sticky
+    EOT
+  }
+
+  depends_on = [azurerm_container_app.app]
+}
+
+# ==============================================================================
+# 11. ACR Task for CI/CD (Optional)
 # ==============================================================================
 resource "azurerm_container_registry_task" "build" {
   count = var.github_repo_url != "" && var.github_pat != "" ? 1 : 0

terraform/outputs.tf

@@ -127,3 +127,17 @@ output "github_callback_url" {
   description = "GitHub OAuth callback URL"
   value       = "https://${azurerm_container_app.app.ingress[0].fqdn}/.auth/login/github/callback"
 }
+
+# ------------------------------------------------------------------------------
+# Session Affinity
+# ------------------------------------------------------------------------------
+
+output "sticky_sessions_enabled" {
+  description = "Whether sticky sessions are enabled for MCP session affinity"
+  value       = var.enable_sticky_sessions
+}
+
+output "sticky_sessions_verify_command" {
+  description = "Command to verify sticky sessions configuration"
+  value       = "az containerapp show --name ${azurerm_container_app.app.name} --resource-group ${var.resource_group_name} --query \"properties.configuration.ingress.stickySessions\""
+}

terraform/variables.tf

@@ -164,3 +164,13 @@ variable "github_pat" {
   default     = ""
   sensitive   = true
 }
+
+# ------------------------------------------------------------------------------
+# Session Affinity Variables
+# ------------------------------------------------------------------------------
+
+variable "enable_sticky_sessions" {
+  description = "Enable sticky sessions for MCP session affinity. Required for multi-replica deployments with stateful MCP sessions."
+  type        = bool
+  default     = true
+}