Architecting for Microservices Part 2

Denver Code Club Meetup Bill Schwanitz, Technical ArchitectDecember 15, 2016 Craig Martin, Vice President of Engineering

Agenda

•Microservices (isn’t that what we are here for?)

• What is a microservice?•NETFLIX OSS

• Zuul• Eureka• Hystrix• Archaius

•Million Song Library code walkthrough•Build Million Song Library

An overview of Microservices

• N number of modular components joined together via the network.

• Decomposed by units of business or functionality• Combined makes up an entire backend system• Single Responsibility Principle (SRP)

• Code with a singleness of purpose• Interface Segregation Principle (ISP)

• No client should be forced to depend on methods it does not use

• Service grouped by business domain area or capability

• Many standalone “vertical” stack focused on a single domain

• Netflix OSS• “Gatekeeper”

RoutingMonitoringSecurity

• Makes endpoints available• Main use cases

Auth-N (not Auth-z)DDOSTransformation

• Groovy and JavaFilters in Groovy

Zuul

Challenges• Performance• Forgetting to open endpoints• Logging

• “Pre” filter - First line of defence Check URL (Sitemap)Auth-NStructure Data Transformation

• “routing” filtersEndpoint Mapping Service Discovery

• “post” filtersData transformationlogging

• “static” filtersHealthcheck

References:

MSL server/msl-zuul:github.com/kenzanlabs/msl-

zuul/tree/master/src/main/groovy/filters

Zuul - How does it work?

Lessons Learned• Keep it

lightweight• Can be used for

soaking

Other Options• NginX• ELBs• API

Gateway

• Netflix OSS Service Registry

• Used for “discovery”• Heartbeat of the

application• Why not use ELBs?

Fewer IPsCompromise Security

GroupsStateless

• Replicated across regions• Load balancing• “Push” heartbeat

monitoring

Eureka

Challenges• Only works with

AWS• Performance• Scalability

Other Options• Containerizatio

n (Kubernetes)• Consul• ELBs

What is it?

• Eureka ClientRegisters with Eureka ServerPart of the bootstrap processRoutinely updates

• Eureka ServerMaintains mapping of VIPs to

IPsRedundancyRound Robin Load BalancingNetflix OSS Service Registry

• Typically abstract discovery via Ribbon Client

Best Practices• Discovery shouldn’t be a dev

responsibility• Single point of failure • Scale “correctly”

Eureka How it works.

Hystrix - What is it?Controls the interactions between distributed services, by:

• Adding latency tolerance logic

• Adding fault tolerance logic

• Isolating points of access between the services

• Stopping cascading failures across them

• Providing fallback options

Hystrix - Why?Compared to Monolithic applications, Microservices strongly rely upon networks.

So failure detection and manipulation logic is essential.

Normal function (Closed)

When a system is functioning smoothly

Failure state (Open)

At this juncture, every call to the dependency is short-circuited with a HystrixRuntimeException, giving clear indication of its cause.

Half-open state

Once the sleep Interval passes, Hystrix checks system availability, letting other requests fail-fast until the response is obtained. If the call is successful, go to Closed; in case of failure, go back to Open

Hystrix - How?● Wrapping all external calls in a HystrixCommand or HystrixObservableCommand ● Timing-out calls when needed.● Maintaining a small thread-pool for each dependency (monitor load)● Measuring successes, failures , timeouts, and thread rejections.● Tripping a circuit-breaker to stop all requests to a particular service for a period of time● Performing fallback logic when a request fails, is rejected, times-out, or short-circuits.● Monitoring metrics and configuration changes in near real-time.

For Additional information: https://github.com/Netflix/Hystrix/wiki/How-it-Works

ArchaiusJava library that provides APIs to access and utilize properties that can change dynamically at runtime. It includes the following features:

● Dynamic, Typed Properties

● High throughput and Thread Safe Configuration operations

● A polling framework that allows users to obtain property changes to a Configuration Source

● Allows retrieval of properties from local properties files or a properties server

○ Darchaius.configurationSource.additionalUrls=file:///apps/myapp/application.properties

○ Darchaius.configurationSource.additionalUrls=http://myserver/properties

● Automatically updates to all servers

Million Song Library

• Java 8• Netflix OSS (Eureka, Hystrix,

Zuul, Archaius)• Datastax (Cassandra)• Swagger

Backend Tech

Platform Tech• Maven • Docker• Spinnaker

Documentation Tech• Swagger• Ascii Docs

Time to Look at Some Code

Netflix OSS• Zuul• Eureka• Hystrix• Archaius

Zuul - Example of Zuul Configuration - pom.xml• In MSL, we configure Zuul

via the pom.xml and Archaius properties

• So here you see the pom.xml:

Zuul runs in jettyWe can supply

additional configuration via Archaius

Zuul will listen on port 9000

Example:<plugin> <groupId>org.eclipse.jetty</groupId> <artifactId>jetty-maven-plugin</artifactId> <version>${jetty-version}</version> <configuration> <systemProperties> <systemProperty> <name>archaius.deployment.applicationId</name> <value>zuul</value> </systemProperty> </systemProperties> . . . <httpConnector> <port>9000</port> </httpConnector> </configuration></plugin>

References:github.com/kenzanlabs/msl-zuul

Zuul - Example of Zuul Configuration - properties• In MSL, we configure Zuul

via the pom.xml and Archaius properties:

Locations of the pre, routing and post filters

Allowable and default clients

Configuration for one of those clients

• And an example of a URLNotice it goes to port

9000Has the client name

loginedgeThen the rest of the URL

is the URI to the client

• So Zuul redirects this request to login-edge:9001

Properties:zuul.filter.pre.path=src/main/groovy/filters/prezuul.filter.routing.path=src/main/groovy/filters/routezuul.filter.post.path=src/main/groovy/filters/post

zuul.niws.clientlist=loginedge|accountedge|catalogedge|ratingsedge

loginedge.zuul.client.DeploymentContextBasedVipAddresses=msl.login.edgeloginedge.zuul.client.Port=9001

Example URL:https://msl.kenzanlabs.com:9000/loginedge/login

References:github.com/kenzanlabs/msl-zuul/tree/master/src/main/resources

Eureka Example• Registration

Tell Eureka Server that a new instance of a microservice has started

Needs eureka properties

Needs Karyon to be instantiated

Handles routine heartbeat from client to server

• HealthcheckAllows Eureka Server

to check if instance is still up and running

Eureka Server will remove any down instance

Properties:eureka.name=loginedgeeureka.vipAddress=msl.login.edgeeureka.port=9001eureka.serviceUrl.default=http://localhost:8080/eureka/v2/eureka.region=defaulteureka.preferSameZone=trueeureka.registration.enabled=true

Karyon Startup:KaryonServer server = new KaryonServer();server.start();

Healthcheck ReST Endpoint:@Path("/healthcheck") public class HealthCheckResource { @GET @Produces(MediaType.APPLICATION_JSON) public Response healthcheck() { return Response.status(Response.Status.OK).build(); } }

Hystrix example

Setup• Create a subclass of

HystrixCommand• The command group key

groups commands for configuration, thread pooling, etc.

• Override the run() method• Optionally override the

getFallback() method

Calling• Instantiate your command

class• Call its execute() method

Code:class ValidateAccountCommand extends HystrixCommand<Boolean>{ private Account account;

protected ValidateAccountCommand(Account account) { super(Setter.withGroupKey(HystrixCommandGroupKey.Factory .asKey("validateAccount"))); this.account = account; }

@Override protected Boolean run() throws Exception { return AccountValidator.isValid(account); }

@Override protected Boolean getFallback() { return false; }}

public Boolean save(Account account) throws Exception { return (new ValidateAccountCommand(account).execute());}

Archaius Example• Configuration

Declare the properties source(s)

Can be a local file or a properties server

• UseProperties are typed

BooleanIntLongStringetc.

Only need to declare the DynamicXProperty once

Then just use x.get() whenever you need to use the value

Calling x.get() once and storing the result is an anti-pattern - doesn’t allow for dynamic reconfiguration

Properties:archaius.configurationSource.additionalUrls= file://msl-login-edge-config/edge-config.propertiesorarchaius.configurationSource.additionalUrls=http://myserver/properties

Code:static final DynamicLongProperty timeToWait = DynamicPropertyFactory .getInstance().getLongProperty("msl.sleep", 100);

void foo() { long t = timeToWait.get(); sleep(t)}

Anti-pattern:static final long t = DynamicPropertyFactory .getInstance().getLongProperty("msl.sleep", 100).get();

void foo() { sleep(t)}

Why?• The API is described in one place,

a yaml formatted file (can also be described using annotations in an existing Java file)

• From the yaml file, swagger tools generate client and server code stubs, and documentation

• Since code and documentation are created from the same yaml file, the code and the documentation will never diverge

Swagger - What?A specification and associated tools for describing, producing, consuming, and visualizing a ReST API

YAML File:

.

.

./catalog-edge/browse/album: x-swagger-router-controller: catalog_controller get: description: "Get browsing data for albums in the catalog" tags: - Catalog operationId: browse_albums parameters: - $ref: "#/parameters/PagingState" - $ref: "#/parameters/Items" - $ref: "#/parameters/Facets" responses: "200": description: Success schema: $ref: "#/definitions/AlbumList" "400": description: “Invalid pagingState or facet”...

Yaml Details• First line defines the URI path to

the endpoint• tags: grouping endpoints for docs• x-swagger-router-controller: the

name of the Node controller file• operationId: name of the function

in server stub• parameters: optional path and

query parameters

Swagger - Generated Server Stub

CatalogEdgeApi.java@Path("/catalog-edge")@Consumes({ "application/json" })@Produces({ "application/json" })public class CatalogEdgeApi {

private final CatalogEdgeApiService delegate = CatalogEdgeApiServiceFactory.getCatalogEdgeApi();

@GET @Path("/browse/album") @Consumes({ "application/json" }) @Produces({ "application/json" }) public Response browseAlbums( @QueryParam("items") Integer items, @QueryParam("pagingState") String pagingState, @QueryParam("facets") String facets) ) throws NotFoundException { return delegate.browseAlbums(items,pagingState,facets); } ...}

CatalogEdgeApiService.javapublic abstract class CatalogEdgeApiService { public abstract Response browseAlbums(Integer items,String pagingState,String facets) throws NotFoundException;}

MSL Local Installation

Prerequisites● git installed● personal git account created

CD to where you want to install itcd ~

Retrieve the main MSL repository from githubgit clone https://github.com/kenzanmedia/million-song-library

CD into the new directorycd million-song-library/bin

Be sure the setup script is executablechmod +x setup.sh

Run the setup script./setup.sh

Want to learn more?Follow us!

@kenzanmedia

www.linkedin.com/company/kenzan-media

techblog.kenzan.com

www.facebook.com/kenzanmedia/