Learn about event-driven data management for microservices in the fifth article in our series on microservices app development. We'll explore the problem of distributed data management, event-driven architecture, and atomicity.
The idea is to look at the shape of your data and use that to decide where you feel is the right threshold. One of the best ways to do that is to plot the quantiles.
Trying to set up a Single Sign-on Tomcat 7 server? Here's how to do so, complete with a look at what SPNEGO is, authentication vs. authorization, and Single Sign-on basics.
Here's a quick overview of building apps using microservices. Specifically, an exploration of service discovery, including why to use service discovery, client-side, and server-side info.
On the heels of the Kinesis Firehose announcement, more people are going to be looking to integrate Kinesis with logging systems. Here is one take on solving that problem that integrates syslog-ng with Kinesis.
Different techniques can be used to handle multi-tenant data in Solr. This article discusses routing techniques you can use depending on the size and number of shards.
An innovative approach that helps with an effective index and a dynamic config management system for massive multi-tenant search infrastructure in SolrCloud.
Webpack is the best module bundler I’ve ever used. Just this week I used it to reduce the JS footprint of an app from 906KB to 87KB for mobile visitors. An 800KB difference! Webpack‘s core premise is that you can require('./foo') your JavaScripts. That sea of
Continuing my Spring-Cloud learning journey, earlier I had covered how to write the infrastructure components of a typical Spring-Cloud and Netflix OSS based micro-services environment - in this specific instance two critical components, Eureka to register and discover services and Spring Cloud Configuration to maintain a centralized repository of configuration for a service. Here I will be showing how I developed two dummy micro-services, one a simple "pong" service and a "ping" service which uses the "pong" service. Sample-Pong microservice The endpoint handling the "ping" requests is a typical Spring MVC based endpoint: @RestController public class PongController { @Value("${reply.message}") private String message; @RequestMapping(value = "/message", method = RequestMethod.POST) public Resource pongMessage(@RequestBody Message input) { return new Resource<>( new MessageAcknowledgement(input.getId(), input.getPayload(), message)); } } It gets a message and responds with an acknowledgement. Here the service utilizes the Configuration server in sourcing the "reply.message" property. So how does the "pong" service find the configuration server, there are potentially two ways - directly by specifying the location of the configuration server, or by finding the Configuration server via Eureka. I am used to an approach where Eureka is considered a source of truth, so in this spirit I am using Eureka to find the Configuration server. Spring Cloud makes this entire flow very simple, all it requires is a "bootstrap.yml" property file with entries along these lines: --- spring: application: name: sample-pong cloud: config: discovery: enabled: true serviceId: SAMPLE-CONFIG eureka: instance: nonSecurePort: ${server.port:8082} client: serviceUrl: defaultZone: http://${eureka.host:localhost}:${eureka.port:8761}/eureka/ The location of Eureka is specified through the "eureka.client.serviceUrl" property and the "spring.cloud.config.discovery.enabled" is set to "true" to specify that the configuration server is discovered via the specified Eureka server. Just a note, this means that the Eureka and the Configuration server have to be completely up before trying to bring up the actual services, they are the pre-requisites and the underlying assumption is that the Infrastructure components are available at the application boot time. The Configuration server has the properties for the "sample-pong" service, this can be validated by using the Config-servers endpoint - http://localhost:8888/sample-pong/default, 8888 is the port where I had specified for the server endpoint, and should respond with a content along these lines: "name": "sample-pong", "profiles": [ "default" ], "label": "master", "propertySources": [ { "name": "classpath:/config/sample-pong.yml", "source": { "reply.message": "Pong" } } ] } As can be seen the "reply.message" property from this central configuration server will be used by the pong service as the acknowledgement message Now to set up this endpoint as a service, all that is required is a Spring-boot based entry point along these lines: @SpringBootApplication @EnableDiscoveryClient public class PongApplication { public static void main(String[] args) { SpringApplication.run(PongApplication.class, args); } } and that completes the code for the "pong" service. Sample-ping micro-service So now onto a consumer of the "pong" micro-service, very imaginatively named the "ping" micro-service. Spring-Cloud and Netflix OSS offer a lot of options to invoke endpoints on Eureka registered services, to summarize the options that I had: 1. Use raw Eureka DiscoveryClient to find the instances hosting a service and make calls using Spring's RestTemplate. 2. Use Ribbon, a client side load balancing solution which can use Eureka to find service instances 3. Use Feign, which provides a declarative way to invoke a service call. It internally uses Ribbon. I went with Feign. All that is required is an interface which shows the contract to invoke the service: package org.bk.consumer.feign; import org.bk.consumer.domain.Message; import org.bk.consumer.domain.MessageAcknowledgement; import org.springframework.cloud.netflix.feign.FeignClient; import org.springframework.http.MediaType; import org.springframework.web.bind.annotation.RequestBody; import org.springframework.web.bind.annotation.RequestMapping; import org.springframework.web.bind.annotation.RequestMethod; import org.springframework.web.bind.annotation.ResponseBody; @FeignClient("samplepong") public interface PongClient { @RequestMapping(method = RequestMethod.POST, value = "/message", produces = MediaType.APPLICATION_JSON_VALUE, consumes = MediaType.APPLICATION_JSON_VALUE) @ResponseBody MessageAcknowledgement sendMessage(@RequestBody Message message); } The annotation @FeignClient("samplepong") internally points to a Ribbon "named" client called "samplepong". This means that there has to be an entry in the property files for this named client, in my case I have these entries in my application.yml file: samplepong: ribbon: DeploymentContextBasedVipAddresses: sample-pong NIWSServerListClassName: com.netflix.niws.loadbalancer.DiscoveryEnabledNIWSServerList ReadTimeout: 5000 MaxAutoRetries: 2 The most important entry here is the "samplepong.ribbon.DeploymentContextBasedVipAddresses" which points to the "pong" services Eureka registration address using which the service instance will be discovered by Ribbon. The rest of the application is a routine Spring Boot application. I have exposed this service call behind Hystrix which guards against service call failures and essentially wraps around this FeignClient: package org.bk.consumer.service; import com.netflix.hystrix.contrib.javanica.annotation.HystrixCommand; import org.bk.consumer.domain.Message; import org.bk.consumer.domain.MessageAcknowledgement; import org.bk.consumer.feign.PongClient; import org.springframework.beans.factory.annotation.Autowired; import org.springframework.beans.factory.annotation.Qualifier; import org.springframework.stereotype.Service; @Service("hystrixPongClient") public class HystrixWrappedPongClient implements PongClient { @Autowired @Qualifier("pongClient") private PongClient feignPongClient; @Override @HystrixCommand(fallbackMethod = "fallBackCall") public MessageAcknowledgement sendMessage(Message message) { return this.feignPongClient.sendMessage(message); } public MessageAcknowledgement fallBackCall(Message message) { MessageAcknowledgement fallback = new MessageAcknowledgement(message.getId(), message.getPayload(), "FAILED SERVICE CALL! - FALLING BACK"); return fallback; } } Boot"ing up I have dockerized my entire set-up, so the simplest way to start up the set of applications is to first build the docker images for all of the artifacts this way: mvn clean package docker:build -DskipTests and bring all of them up using the following command, the assumption being that both docker and docker-compose are available locally: docker-compose up Assuming everything comes up cleanly, Eureka should show all the registered services, at http://dockerhost:8761 url - The UI of the ping application should be available at http://dockerhost:8080 url - Additionally a Hystrix dashboard should be available to monitor the requests to the "pong" app at this url http://dockerhost:8989/hystrix/monitor?stream=http%3A%2F%2Fsampleping%3A8080%2Fhystrix.stream: References 1. The code is available at my github location - https://github.com/bijukunjummen/spring-cloud-ping-pong-sample 2. Most of the code is heavily borrowed from the spring-cloud-samples repository - https://github.com/spring-cloud-samples
You are working on a big project, developing rules, events and processes at your enterprise for mission critical business needs. Part of the requirements state that a certain business unit will be providing their data model for you to leverage. This data model will not be designed in the JBoss BPM Suite Data Modeler but you need to have access to it while working on your rules, events and processes from the business central dashboard. For this article we will be using the JBoss BPM Travel Agency demo project as a reference, with it's current data model built externally to the JBoss BPM Suite business central. The external data model is called the acme-data-model and is found in the project directory: This data model is built during installation and provides you with an object data model as a Java Archive (JAR) file which is installed into the JBoss BPM Suite business central component by placing it into the following location: jboss-eap-6.4/standalone/deployments/business-central.war/WEB_INF/lib/acmeDataModel-1.0.jar Authoring --> Artifact repository. This way of deploying the data model means that it is available to all projects you work on in JBoss BPM Suite business central, something that might not always be preferable. What we need is a way to deploy external data models into JBoss BPM Suite and then selectively add them to projects as needed. Within JBoss BPM Suite there is an Artifact Repository that is made just for this purpose. We can upload through the business central dashboard UI all our models and then pick and choose from the repository artifacts (your data model is one artifact) on a per project basis. This gives you absolute control over the models that a project can access. Choose external data model file. There are a few steps involved that we will take you through here to change the current installation of JBoss BPM Travel Agency where the acmeDataModel-1.0.jar file will be removed from the previously mentioned business central component and uploaded into the Artifact Repository and added to the Special Trips Agency project. Here is how you can do it yourself: obtain and install JBoss BPM Travel Agency demo project remove current data model from global business central application: $ rm ./target/jboss-eap-6.4/standalone/deployments/business-central.war/WEB_INF/lib/acmeDataModel-1.0.jar Upload external model jar file. start JBoss BPM Suite server after installation as stated in the installation instructions login to JBoss BPM Suite at http://localhost:8080/business-centralwith: u: erics p: bpmsuite1! go to AUTHORING --> ARTIFACT REPOSITORY go to UPLOAD --> CHOOSE FILE... --> projects/acme-data-model/target/acmeDataModel-1.0.jar --> click button to UPLOAD this puts the external data model into the JBoss BPM Suite artifact repository Select dependencies to add to project. got to AUTHORING --> PROJECT AUTHORING --> OPEN PROJECT EDITOR in project editor select GENERAL PROJECT SETTINGS --> DEPENDENCIES in dependencies select ADD FROM REPOSITORY -> in pop-upSELECT entry acmeDataModel-1.0.jar This will result in the external data model being added only to the Special Trips Agency project and not available to other projects unless they add this same dependency from the JBoss BPM Suite artifact repository. If you build & deploy the project, run it as described in the project instructions you will find that the external data model is available and used by the various rules and process components that are the JBoss BPM Travel Agency. As a closing note, this works exactly the same for JBoss BRMS projects.
Haskell advocates are fond of saying that a Haskell function cannot launch missiles without you knowing it. Pure functions have no side effects, so they can only do what they purport to do. In a language that does not enforce functional purity, calling a function could have arbitrary side effects, including launching missiles. But this cannot happen in Haskell. The difference between pure functional languages and traditional imperative languages is not quite that simple in practice. Programming with pure functions is conceptually easy but can be awkward in practice. You could just pass each function the state of the world before the call, and it returns the state of the world after the call. It’s unrealistic to pass a program’s entire state as an argument each time, so you’d like to pass just that state that you need to, and have a convenient way of doing so. You’d also like the compiler to verify that you’re only passing around a limited slice of the world. That’s where monads come in. Suppose you want a function to compute square roots and log its calls. Your square root function would have to take two arguments: the number to find the root of, and the state of the log before the function call. It would also return two arguments: the square root, and the updated log. This is a pain, and it makes function composition difficult. Monads provide a sort of side-band for passing state around, things like our function call log. You’re still passing around the log, but you can do it implicitly using monads. This makes it easier to call and compose two functions that do logging. It also lets the compiler check that you’re passing around a log but not arbitrary state. A function that updates a log, for example, can effect the state of the log, but it can’t do anything else. It can’t launch missiles. Once monads get large and complicated, it’s hard to know what side effects they hide. Maybe they can launch missiles after all. You can only be sure by studying the source code. Now how do you know that calling a C function, for example, doesn’t launch missiles? You study the source code. In that sense Haskell and C aren’t entirely different. The Haskell compiler does give you assurances that a C compiler does not. But ultimately you have to study source code to know what a function does and does not do.
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