METRON-1853: Add shutdown hook to Stellar BaseFunctionResolver

[mmiklavc]

Contributor Comments

https://issues.apache.org/jira/browse/METRON-1853

Noodling on a method to add shutdown hooks to Stellar. Modified the StellarFunction interface to include a teardown method. Added a no-op to BaseStellarFunction to make it easy for implementations that don't need a teardown.

Rationale - some functions may have long-lived activities that include closeable resources. Adding the teardown method enables function implementers to close any resources opened during init gracefully.

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[ottobackwards]

Comments

[ottobackwards]

Should the resolver throw if there is a call after it is closed?
or just return nothing? Do we have a test for that? Either way we should.

[mmiklavc]

Should the resolver throw if there is a call after it is closed?
or just return nothing? Do we have a test for that? Either way we should.

What do you think of a no-op on multiple invocations of close? This would be consistent with the Closeable interface.

/**
 * Closes this stream and releases any system resources associated
 * with it. If the stream is already closed then invoking this
 * method has no effect.
...
 */
public void close() throws IOException;

[ottobackwards]

That is great

[mmiklavc]

@ottobackwards Ok, pushed out an update for that change along with accompanying unit test.

[mmiklavc]

Testing

Note - this test script can be used in conjunction with #1250 because this PR exposes the close() capability, but it does NOT add it to the parser/enrichment bolts or Stellar shell executor. i.e. you won't see the messages until that implementation is exposed. 1250 exposes the close() invocations.

Create a custom Stellar function

See the following for reference - https://github.com/apache/metron/blob/master/metron-stellar/stellar-common/3rdPartyStellar.md

1. Setup project dirs

   mkdir custom-stellar && cd custom-stellar
   mkdir -p src/main/java/com/thirdparty/stellar
   

2. Create a pom.xml

   <project xmlns="http://maven.apache.org/POM/4.0.0"
     xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
     xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">
     <modelVersion>4.0.0</modelVersion>
   
     <groupId>com.thirdparty</groupId>
     <artifactId>stellar-funcs</artifactId>
     <version>1.0-SNAPSHOT</version>
     <packaging>jar</packaging>
   
     <name>Stellar Functions</name>
   
     <properties>
       <project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
     </properties>
   
     <dependencies>
       <dependency>
         <groupId>org.apache.metron</groupId>
         <artifactId>stellar-common</artifactId>
         <version>0.6.1</version>
         <!-- NOTE: We will want to depend on the deployed common on the classpath. -->
         <scope>provided</scope>
       </dependency>
     </dependencies>
     <build>
       <plugins>
         <plugin>
           <groupId>org.apache.maven.plugins</groupId>
           <artifactId>maven-compiler-plugin</artifactId>
           <version>3.1</version>
           <configuration>
             <source>1.8</source>
             <target>1.8</target>
           </configuration>
         </plugin>
       </plugins>
     </build>
   </project>
   

3. Create a custom Stellar function

   package com.thirdparty.stellar;
   
   import org.apache.metron.stellar.common.utils.ConversionUtils;
   import org.apache.metron.stellar.dsl.Context;
   import org.apache.metron.stellar.dsl.ParseException;
   import org.apache.metron.stellar.dsl.Stellar;
   import org.apache.metron.stellar.dsl.StellarFunction;
   
   import java.io.IOException;
   import java.util.List;
   import org.jboss.netty.util.internal.ConversionUtil;
   
   public class StellarCustom {
   
     @Stellar(name = "NOW",
         description = "Simple now time",
         params = {
         "throwException - whether we should throw an exception on close()"
         },
         returns = "Time in millis"
     )
     public static class Now implements StellarFunction {
   
       private boolean isInitialized = false;
       private boolean throwException = false;
   
       public Object apply(List<Object> args, Context context) throws ParseException {
         if (args.size() == 1) {
           throwException = ConversionUtils.convert(args.get(0), Boolean.class);
         }
         return System.currentTimeMillis();
       }
   
       public void initialize(Context context) {
         try {
           System.out.println("Initializing function.");
         } finally {
           isInitialized = true;
         }
       }
   
       public boolean isInitialized() {
         return isInitialized;
       }
   
       public void close() throws IOException {
         System.out.println("Test function called close()!");
         if (throwException) {
           NullPointerException cause = new NullPointerException("Don't point at me!");
           throw new IOException("Something icky happened.", cause);
         }
       }
     }
   
   }
   

4. Build it

   mvn clean install

5. Ship it

   scp custom-stellar/target/stellar-funcs-1.0-SNAPSHOT.jar root@node1:/tmp/

6. Setup HDFS stellar

   sudo -u hdfs hdfs dfs -mkdir /apps/metron/stellar
   sudo -u hdfs hdfs dfs -put /tmp/stellar-funcs-1.0-SNAPSHOT.jar /apps/metron/stellar
   sudo -u hdfs hdfs dfs -chown -R metron:metron /apps/metron/stellar
   

7. Setup global config for Stellar HDFS location

   $METRON_HOME/bin/zk_load_configs.sh -m PULL -o $METRON_HOME/config/zookeeper -z $ZOOKEEPER -f
   vim $METRON_HOME/config/zookeeper/global.json
   # add this -> "stellar.function.paths" : "hdfs://node1:8020/apps/metron/stellar/.*.jar"
   # update global.json in ZK
   $METRON_HOME/bin/zk_load_configs.sh -m PUSH -i $METRON_HOME/config/zookeeper -z $ZOOKEEPER
   

8. Setup a parser or enrichment with the new function. (more specific details to come)

   Don't want an exception thrown
   NOW(false)
   Restart parser or enrichment using this function
   Should get data still
   Stop the topology - should see a notice about shutdown in the logs.

9. Same as before but throw exception on shutdown. (more specific details to come)

   WANT an exception thrown
   NOW(true)
   Restart parser or enrichment using this function
   Should get data still
   Stop the topology - should see our exception in the logs.

[merrimanr]

+1

[mmiklavc]

@ottobackwards Any other feedback on this?

[ottobackwards]

+1