HousePricePrediction-ServingAPI

Main idea

• Load the trained model into memory when it starts.
• Encapsulate the loaded model as a bean (Singleton pattern compliant).
• Controller injects the bean by @Autowired and provide serving service outwards.

Before deploy you should

• Prepare a local spark environment or remote spark URL.
• Specify the location of the model file. (e.g. Local disk/ hdfs/ S3)
• Declare above two variables inside the yml.

After deploy you can

• View the API at online API page.
• Fill in the parameters one by one into the double array, then you can get the predicted value.
• Switch to other machine learning models that we train before. Then deploy again.

Implementation roadmap

1. Have to solve the dependent confict between Spark and SpringBoot because of the Logging Factory.

   • 1.1. Exlude the slf4j-log4j12.jar and log4j.jar out of spark.

     <dependency>
         <groupId>org.apache.spark</groupId>
         <artifactId>spark-mllib_2.11</artifactId>
         <version>2.4.7</version>
         <scope>provided</scope>
         <exclusions>  
             <exclusion>   
                 <groupId>org.slf4j</groupId>  
                 <artifactId>slf4j-log4j12</artifactId>  
             </exclusion>  
             <exclusion>   
                 <groupId>log4j</groupId>  
                 <artifactId>log4j</artifactId>  
             </exclusion>  
         </exclusions> 
     </dependency>
     

   • 1.2. Exlude the logging.jar out of spring-boot-starter-web.

     <dependency>
     	<groupId>org.springframework.boot</groupId>
     	<artifactId>spring-boot-starter-web</artifactId>
         <exclusions>
                <exclusion>
                    <groupId>org.springframework.boot</groupId>
                    <artifactId>spring-boot-starter-logging</artifactId>
                </exclusion>
         </exclusions>
     </dependency>
     

   • 1.3. Import the needed logging relevant jar.

     <dependency>
         <groupId>org.slf4j</groupId>
         <artifactId>log4j-over-slf4j</artifactId>
         <version>1.7.25</version>
     </dependency>
     <dependency>
         <groupId>org.slf4j</groupId>
         <artifactId>slf4j-api</artifactId>
         <version>1.7.5</version>
     </dependency>
     <dependency>
         <groupId>org.slf4j</groupId>
         <artifactId>slf4j-simple</artifactId>
         <version>1.6.4</version>
     </dependency>
     

2. Define two Java Beans inside the configuration: one for SparkContext, another for specific model.

   @Configuration
   public class ModelConfiguration {
   	@Bean(value = "sparkContext")
   	public SparkContextBean sparkContext() {
   		...
   	}
   	@Bean("decisionTreeModel")
   	@ConditionalOnBean(SparkContextBean.class)
   	public DecisionTreeModel decisionTreeModel(SparkContextBean bean) {
   		...
   	}
   }
   

3. Implement the initiate and destroy function for the SparkContextBean due to I/O connection issue with spark.

   public class SparkContextBean implements InitializingBean, DisposableBean {
   	@PostConstruct
   	public void init() {
   		...
   	}
   	@Override
   	public void destroy() throws Exception {
   		...
   	}
   	@Override
   	public void afterPropertiesSet() throws Exception {
   		...
   	}
   }