Issue #450. First commit. Queue Based Load Leveling #521

Amarnath510 · 2016-11-20T11:05:54Z

I have completed coding, design (UML), README.md. jUnit tests.
This is my first code submission for open source.
Please review and let me know the issues.

I have one question,
In the README.md file we have to generate the "pumlid". I don't know how to generate the same.
As of now I have left it blank. Let me know how to generate the same.

iluwatar · 2016-11-20T14:50:58Z

@Amarnath510 the Travis CI build is failing and needs to be fixed first. Looks like there's wrong artifactId in queue-load-leveling/pom.xml.

Amarnath510 · 2016-11-20T16:31:42Z

@iluwatar
I have made changes in queue-load-leveling/pom.xml file and pushed.
Should I again do a pull request or my changes are visible to you?

iluwatar · 2016-11-20T17:33:23Z

@Amarnath510 thanks for the quick fix. The changes are applied automatically as you push. Unfortunately now there's a new (Checkstyle) error in the build - see https://travis-ci.org/iluwatar/java-design-patterns/builds/177451598

Amarnath510 · 2016-11-20T18:11:32Z

@iluwatar
I have updated all the checkstyle issues by looking at the error log.
Out of curiosity, how to get the issues produced in my development environment locally, that is in my Eclipse IDE? If these issues are coming in my environment I can fix them there itself.
FYI, I have given checkstyle.xml as the default one. Just the way it was mentioned here.

iluwatar · 2016-11-21T05:49:56Z

You can reproduce the Checkstyle issues in Eclipse IDE by selecting the project(s) in package/project explorer, right-clicking the project and choosing Checkstyle - Check Code with Checkstyle. I'll add that to the instructions.

Amarnath510 · 2016-11-21T07:22:32Z

@iluwatar
Thanks for the update.
But the issue now is different.

For more details see: /home/travis/build/iluwatar/java-design-patterns/queue-load-leveling/target/pmd.xml -> [Help 1]
org.apache.maven.lifecycle.LifecycleExecutionException: Failed to execute goal org.apache.maven.plugins:maven-pmd-plugin:3.6:check (default) on project queue-load-leveling: You have 1 PMD violation.

Just to make clear what steps I have done,

Forked the project and cloned it.
Installed Maven in Eclipse (Neon.1a Release (4.6.1)) and Java Verison 1.8.
Imported Existing Maven project by pointing to the root folder.
Done all the Checkstyle related stuff.
Right click on java-design-pattern in the project explorer - new - other - maven (in filer) - Maven Module
Create new module, queue-load-leveling
Created required Java files and UML files and README.md file.
Updated pom.xml file with builder/pom.xml file contents and update artifactid to queu-load-leveling

Please let me know if I have missed something here.
I am not able to figure out the issue.

iluwatar · 2016-11-21T19:55:50Z

There is maven-pmd-plugin configured in the build and it has detected an error in the project. Scan the build output for more details about the PMD error and fix that.

Amarnath510 · 2016-11-22T06:11:25Z

@iluwatar
How can I check this file,
For more details see: /home/travis/build/iluwatar/java-design-patterns/queue-load-leveling/target/pmd.xml

Also can you tell me how to compile the whole project locally. I want to check locally before committing my changes.

Added dependency "maven-pmd-plugin" to the pom file.

iluwatar · 2016-11-22T17:42:47Z

If you scroll the build output a bit upwards you will find this line: PMD Failure: org.queue.load.leveling.Task:29 Rule:UnusedModifier Priority:3 Avoid modifiers which are implied by the context.

To build locally you just need to do mvn clean install on the project root.

Amarnath510 · 2016-11-23T08:07:14Z

@iluwatar
Thanks for pointing out the error. After solving all the issues I understood the project flow.
Please review my code and let me know if I need to make any changes.

iluwatar

I suggest some improvements to the code. In general the pattern looks good already 👍

iluwatar · 2016-11-26T12:49:26Z

queue-load-leveling/README.md

+
+## Credits
+
+* [Design Pattern: Queue-Based Load Leveling Pattern](https://msdn.microsoft.com/en-us/library/dn589783.aspx)


I would formulate this Microsoft Cloud Design Patterns: Queue-Based Load Leveling Pattern

iluwatar · 2016-11-26T12:58:33Z

queue-load-leveling/src/main/java/org/queue/load/leveling/App.java

+      srvExec.start();
+    } catch (Exception e) {
+      LOGGER.error(e.getMessage());
+    }


Instead of working directly with Threads it is recommended practise to use ExecutorService instead. For example take a look at this tutorial.

iluwatar · 2016-11-26T13:02:20Z

queue-load-leveling/src/main/java/org/queue/load/leveling/Message.java

+  public String toString() {
+    return msg;
+  }
+}


I would refactor to make this class immutable. Remove no-args constructor and setter and make msg final.

iluwatar · 2016-11-26T13:02:36Z

queue-load-leveling/src/main/java/org/queue/load/leveling/MessageQueue.java

+
+  private static final Logger LOGGER = LoggerFactory.getLogger(App.class);
+
+  private BlockingQueue<Message> blkQueue;


iluwatar · 2016-11-26T13:03:39Z

queue-load-leveling/src/main/java/org/queue/load/leveling/ServiceExecutor.java

+
+  private static final Logger LOGGER = LoggerFactory.getLogger(App.class);
+
+  private MessageQueue msgQueue;


iluwatar · 2016-11-26T13:05:10Z

queue-load-leveling/src/main/java/org/queue/load/leveling/TaskGenerator.java

+  private MessageQueue msgQueue;
+
+  // Total message count that a TaskGenerator will submit.
+  private int msgCount;


Make attributes final

I am using msgCount to create particular number of messages which I am submitting to MessageQueue. For each message I am reducing the the msgCount value. If I make this value final then I can't keep count of message that I am creating.
Should I use a local variable and copy the value of the msgCount and then use it? Is this the way to do?

Apart from this I have made all the remaining changes.

It's ok then. Can you resolve the merge conflict, please?

iluwatar · 2016-11-26T13:06:05Z

queue-load-leveling/src/main/java/org/queue/load/leveling/TaskGenerator.java

+      while (this.msgCount > 0) {
+        String statusMsg = "Message-" + this.msgCount + " submitted by " + Thread.currentThread().getName();
+        Message newMessage = new Message(statusMsg);
+        this.submit(newMessage);


Message could be created and submitted on one line

iluwatar · 2016-11-26T13:06:47Z

queue-load-leveling/src/test/java/org/queue/load/leveling/AppTest.java

+import org.junit.Test;
+
+/**
+ * Tests that Caching example runs without errors.


Fix comment

iluwatar · 2016-11-26T13:07:22Z

queue-load-leveling/src/test/java/org/queue/load/leveling/MessageQueueTest.java

+    Message msg = new Message("MessageQueue Test");
+
+    // submit message
+    msgQueue.submitMsg(msg);


Message can be created and submitted on one line

Amarnath510 · 2016-11-27T18:46:51Z

@iluwatar
May be this questions seems to be too silly. Normally when I use TortoiseSVN, if there is a conflict I usually do code update and resolve the conflicts.
But in Git I don't have any knowledge on how to fix the below conflict. I am worried that I might screw up the code base. Could you please help me with steps about how to resolve this?

iluwatar · 2016-11-27T20:12:36Z

The conflict should be easy to resolve. See this guide for instructions how to solve this using the command line only.

Amarnath510 · 2016-11-28T15:25:29Z

@iluwatar
I have fixed the conflict. Thanks for the info.
I have made all the necessary changes after review. Please have a look.

iluwatar · 2016-11-28T17:06:41Z

Good job @Amarnath510 👍 I'm happy to accept your contribution.

Amarnath510 · 2016-11-29T06:08:40Z

@iluwatar
👍 👍 👍
Thanks a lot. This is my first contribution to open source and I am really excited.
Grateful for your help at every stage. Also will write the required blog.
Excited to pick up the new pattern. Will do that after few days.

iluwatar · 2016-11-29T18:26:44Z

Excellent, I'm looking forward to hearing from you again 😄

Issue iluwatar#450. First commit. Queue Based Load Leveling

12b70cb

iluwatar added the status: under review label Nov 20, 2016

iluwatar self-assigned this Nov 20, 2016

Issue iluwatar#450. Updated pom.xml

52a81eb

Updated checkstyle errors.

d6b5456

Amarnath510 added 2 commits November 22, 2016 12:06

Updated pom.xml with maven-pmd-plugin

e8f7187

Added dependency "maven-pmd-plugin" to the pom file.

Reverted pom.xml changes that are done previously.

5e7887d

Chandana Amarnath added 2 commits November 23, 2016 00:10

Fixed PMD issue.

b9ac0dc

Removed unused imports in tests

1a75ab8

iluwatar requested changes Nov 26, 2016

View reviewed changes

Chandana Amarnath added 2 commits November 28, 2016 20:13

Fixed all the code changes after review

1387e2b

pom.xml Fixed Conflict

1d6d0c5

iluwatar merged commit efc2c88 into iluwatar:master Nov 28, 2016

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Issue #450. First commit. Queue Based Load Leveling #521

Issue #450. First commit. Queue Based Load Leveling #521

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iluwatar commented Nov 29, 2016


		## Credits

		* [Design Pattern: Queue-Based Load Leveling Pattern](https://msdn.microsoft.com/en-us/library/dn589783.aspx)


		private static final Logger LOGGER = LoggerFactory.getLogger(App.class);

		private BlockingQueue<Message> blkQueue;


		private static final Logger LOGGER = LoggerFactory.getLogger(App.class);

		private MessageQueue msgQueue;

Issue #450. First commit. Queue Based Load Leveling #521

Issue #450. First commit. Queue Based Load Leveling #521

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