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Deploying App Service Collection with Elastic Cloud Full Text PaaS Search Solution

v0.1 - 12/4/2019

Introduction

Some of Cobalt’s enterprise customers have a small number of microservices they'd like to deploy and host with Azure managed PaaS app services. Geospatial documents are indexed in Elastic Search to accomodate bounding box and radius distance querying scenarios. This template provisions an instance of an fully managed PaaS Elasticsearch hosted in EC.

This document outlines how Cobalt can be extended to meet the use cases of these customers. The intended audience of this document is the development and product teams working on Cobalt and related projects.

In Scope

  • Identify deployment topology needed by the customer
  • Identify key Terraform templates needed for deployment
  • Identify key Terraform modules needed for deployment
  • Identify gaps in Terraform provider templates

Out of scope

  • External customer sign-off
  • Template (Terraform, ARM) implementation
  • VNET Integration
  • Service Containerization
  • How existing storage services like Elastic Cloud and Cosmos can be imported to reduce azure subscription incurred costs

Key Terms

  • RG: Abbreviation for “Resource Group”
  • Sub: Abbreviation for “Subscription”
  • Persona: An archetype of a Cobalt customer
  • Stage: An application deployment stage (dev, qa, pre-prod, prod, etc...)
  • Region: A location in which an application is deployed

Customers

  • Admin: This persona represents an administrator of Azure. This persona does not implement the line of business applications but will help other teams deliver them.
  • App Developer Team: This persona is responsible for creating and maintaining the line of business applications

Open Questions

These open questions may impact the implementation plan and overall scope of the deployment described below

  • What are the azure monitoring rules for this template?
  • How can we shard a single instance of APIM so that it can be shared by many azure environments?
  • How can we shard a single instance of Elastic Seach so that it can be shared by many azure environments?

Deployment Topology

This graphic shows the targeted deployment topology needed by our enterprise customers. The deployment is deployed to a single tenant and subscription. The resources are partitioned to align with the different personas within the customer.

Deployment Topology

Template Topology

The graphic below outlines the topology of the terraform templates that will deploy the topology called out above.

Template Topology

Module and Template Deep Dive

Template Inputs

General Configuration

name type default description
resource_group_location string The Azure region where all resources in this template should be created
prefix string It serves as an identifier used to construct the names of all resources in this template
randomization_level number Number of additional random characters to include in resource names to insulate against unexpected resource name collisions

Service Plan Configuration

name type default description
monitoring_dimension_values ["*"] Dimensions used to determine service plan scaling
service_plan_size string S1 The size of the service plan instance. Valid values are I1, I2, I3
service_plan_tier string Standard The size of the service plan instance. Valid values are I1, I2, I3
scaling_rules list(obj) The scaling rules for the app service plan.

App Service Configuration

name type default description
app_services list(obj) Metadata about apps to deploy that also require authentication
vnet_subnet_id string The vnet integration subnet gateway identifier

Azure Function Configuration

name type default description
function_apps list(obj) Metadata about functions to deploy, such as repository location, docker file metadata and image names

Azure Container Registry Configuration

name type default description
container_registry_sku list(obj) Standard The container registry SKU. ie. 'Standard' 'Premium'.

App Service Authentication Configuration

name type default description
auth_suffix string easy-auth A name to be appended to all azure ad applications

Cosmos Configuration

name type default description
primary_replica_location string The name of the Azure region to host replicated data
cosmosdb_automatic_failover boolean false Determines if automatic failover is enabled for the created CosmosDB
consistency_level string Session The Consistency Level to use for this CosmosDB Account. Can be either 'BoundedStaleness', 'Eventual', 'Session', 'Strong' or 'ConsistentPrefix'

ServiceBus Configuration

name type default description
service_bus_namespace_name string The name of service bus namespace
service_bus_topics list(object({topic_name=string subscriptions=list(string)})) 0 The configuration of service bus topic and subscriptions mapping

Elastic Configuration

name type default description
high_availability_environment_count number 0 The number of high availability clusters that should be created
data_node_size_gb number 4 The size(in GB) of each data node
master_node_size_gb number 4 The size(in GB) of each master node

Storage Account Configuration

name type default description
storage_containers list(string) The list of storage container names to create.

Notes

  • The above list may change as we track down requirements for Cosmos
  • rule is a type defined here
  • MetricsConfig is a complex map type that adheres to this schema:
list(map(object({
	action_group_name           = string
	action_group_email_receiver = string
	metrics = list(map(object({
		metric_alert_name                 = string
		metric_alert_frequency            = string
		metric_alert_period               = string
		metric_alert_criteria_namespace   = string
		metric_alert_criteria_name        = string
		metric_alert_criteria_aggregation = string
		metric_alert_criteria_operator    = string
		metric_alert_criteria_threshold   = string
	})))
})))

Template Outputs

name type description
app_service_config map(string) Map of app service name with their respective slot apps
app_service_fqdns map(string) Map of app service name to VNET accessible domain name
app_service_names list(string) List of provisioned app service names
app_service_ids list(string) The IDs of the app services provisioned
azuread_app_ids list(string) The AAD application object ids used for app service easy auth
app_service_msi_object_ids list(string) The app service System Assiged MSI object ids
service_plan_name string Service Plan Name
service_plan_id string Service Plan Resource ID
resource_group string Resource group name for the application specific resource group
service_principal_application_id string Service principal application ID
key_vault_endpoint string Key Vault endpont
blob_storage_endpoint string Blob Storage endpoint
storage_account string Name of Storage Account
storage_account_id string Resource Identifier of the storage account
storage_account_containers string Map of storage account containers
function_app_properties map(string) Map of function app id and fqdn
container_registry_id string The resource identifier of the container registry.
container_registry_name string The name of the container registry.
redis_endpoint string REDIS instance endpoint
elastic_endpoint string Elasticsearch endpoint
elastic_user_kv_secret_name string Keyvault secret name storing the username for the Elasticsearch cluster
elastic_pwd_kv_secret_name string Keyvault secret name storing the password for the Elasticsearch cluster
cosmosdb_conn_string_kv_secret_name string Keyvault secret name storing the primary connection string for Cosmos
cosmosdb_properties map(string) Properties of the deployed CosmosDB account. endpoint, connection strings, primary master key and resource id
cosmosdb_account_name string Name of the CosmosDB account
service_bus_endpoint string Service Bus namespace endpoint
contributor_service_principal_id string ID of the service principal with contributor access to provisioned resources

Credential Management

Managed Identities (MI, or MSI) will be used to manage access to credentials when possible. This table identifies MSI support for each resource leveraged by the template (full compatability breakdown here):

Azure Service Supports MSI Mitigation Strategy
App Service Yes N/A
Key Vault Yes N/A
Azure Functions Yes N/A
Blob Storage Yes N/A
REDIS No Credentials stored in Key Vault
Cosmos No Credentials stored in Key Vault
Service Bus Yes N/A
Elastic No Credentials stored in Key Vault

Risks

  • Ingress / Egress for app services, functions and storage endpoints are not restricted to virtual network(s) by default. In summary, by default these services are exposed to the public internet.
    • Mitigation strategy: App Service VNET access restriction can be enabled by setting the vnet_subnet_id setting. We still need to support VNET restrictions for the functions module.

Security

Here is an overview of the security for the deployment strategy and templates discussed above:

  • Role Assignments: The service principal running the deployment will have to be an owner in the target subscription and granted admin consent to the Application.ReadWrite.OwnedBy role in Microsoft Graph. This template creates a new service principal that will be available for application developer team(s) to administer the provisioned Azure resources. The following role assignments will be made to that service principal:
    • Contributor access to App Service & App Insights in the first Resource Group
    • Contributor access to the second and third Resource Groups. If needed, we can lock this down further by granting role access to individual resources in this RG.
  • Service to Service communication: For services owned by the application development team persona we will leverage Managed Service Identity (MSI) for authenticating to cloud services wherever possible. Where this is not possible, MSI will be used to pull credentials from Key Vault. This connection is done via MSI and therefore it keeps all secrets out of the codebase. This limits the attack vector of the infrastructure. List of services that support MSI

License

Copyright © Microsoft Corporation

Licensed under the Apache License, Version 2.0 (the "License"); you may not use this file except in compliance with the License. You may obtain a copy of the License at

http://www.apache.org/licenses/LICENSE-2.0

Unless required by applicable law or agreed to in writing, software distributed under the License is distributed on an "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the License for the specific language governing permissions and limitations under the License.