Section 4 - App Engine

Overview

Simple way to deploy and scale your applications in GCP. Provides end-to-end application management.

Supports:

• Go, Java, .NET, Node.js, PHP, Python, Ruby using pre-configured runtimes.
• Use custom run-time and write code in any language.
• Connect to variety of Google Cloud storage products (Cloud SQL etc).

No usage charges - Pay for resources provisioned

Features:

• Automatic load balancing & Auto scaling.
• Managed platform updates & Application health monitoring.
• Application versioning.
• Traffic splitting.

App Engine Environments

Standard - Applications run in language specific sandboxes

• Complete isolation from OS/Disk/Other Apps.
• V1: Java, Python, PHP, Go (OLD Versions).
• ONLY for Python and PHP runtimes: Restricted network Access, Only white-listed extensions and libraries are allowed.
• No Restrictions for Java and Go runtimes.
• V2: Java, Python, PHP, Node.js, Ruby, Go (NEWER Versions).
• Full Network Access and No restrictions on Language Extensions.

Flexible - Application instances run within Docker containers

• Makes use of Compute Engine virtual machines.
• Support ANY runtime (with built-in support for Python, Java, Node.js, Go, Ruby, PHP, or .NET) so long as it can be made into a container.
• Provides access to background processes and local disks.

Application Hierarchy

Application (one per project).

Contains one or more:

Services (previously called modules. Each service can have different settings).

Contain one or more:

Versions (multiple versions of a service can be deployed with options to rollback and divide traffic).

Contain one or more:

Instances (multiple instances of each service version can be deployed).

Standard vs Flexible Environments

Feature	Standard	Flexible
Pricing Factors	Instance hours	vCPU, Memory & Persistent Disks
Scaling	Manual, Basic, Automatic	Manual, Automatic
Scaling to zero	Yes	No. Minimum one instance
Instance startup time	Seconds	Minutes
Rapid Scaling	Yes	No
Maximum request timeout	1 to 10 minutes	60 minutes
Local disk	Yes (except for Python, PHP). Can write to /tmp.	Yes. Ephemeral. New Disk on startup.
SSH (for debugging)	No	Yes

Scaling Instances

3 types of scaling:

Automatic Scaling

Recommended for Continuously Running Workloads.

• Auto scale based on:
• Target CPU Utilization - Configure a CPU usage threshold.
• Target Throughput Utilization - Configure a throughput threshold.
• Max Concurrent Requests - Configure max concurrent requests an instance can receive.
• Configure Max Instances and Min Instances.

Basic Scaling

• Instances are created as and when requests are received: Recommended for Adhoc Workloads.
• Instances are shutdown if ZERO requests (to keep costs low - high latency is possible).
• Configure Max Instances and Idle Timeout.

(NOT supported by App Engine Flexible Environment).

Manual Scaling

Configure specific number of instances to run. Adjust number of instances manually over time.