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Build flow in HDF/Nifi to push tweets to HDP

In this tutorial, we will learn how to use HDF to create a simple event processing flow by:

  • Install HDF/Nifi on sandbox using the Ambari service
  • Setup Solr/Banana/Hive table
  • Import/Instantiate a prebuilt Nifi template
  • Verify tweets got pushed to HDFS, Hive using Ambari views
  • Visualize tweets in Solr using Banana dashboard
  • Explore provenance features of Nifi

Change log

  • 9/30: Automation script to deploy HDP clusters (on any cloud) with this demo already setup, is available here
  • 9/15: Updated: Demo Ambari service for Nifi updated to support HDP 2.5 sandbox and Nifi 1.0. Steps to manually install demo artifacts remains unchanged (but below Nifi screenshots need to be updated)

References

For a primer on HDF, you can refer to the materials here to get a basic background

Thanks to @bbende@hortonworks.com for his earlier blog post that helped make this tutorial possible

Pre-Requisites

  • The lab is designed for the HDP Sandbox VM. To run on Azure sandbox, Azure specific pre-req steps provided here
  • Download the HDP Sandbox here, import into VMWare Fusion and start the VM
  • If running on VirtualBox you will need to forward port 9090. See here for detailed steps
  • After it boots up, find the IP address of the VM and add an entry into your machines hosts file e.g.
192.168.191.241 sandbox.hortonworks.com sandbox    

Connect to the VM via SSH (root/hadoop), correct the /etc/hosts entry

ssh root@sandbox.hortonworks.com
  • If using HDP 2.5 sandbox, you will also need to SSH into the docker based sandbox container:
ssh root@127.0.0.1 -p 2222
  • Deploy/update Nifi Ambari service on sandbox by running below
    • Note: on HDP 2.5 sandbox, the Nifi service definition is already installed, so you can skip this and proceed to installing Nifi via 'Install Wizard'
VERSION=`hdp-select status hadoop-client | sed 's/hadoop-client - \([0-9]\.[0-9]\).*/\1/'`
rm -rf /var/lib/ambari-server/resources/stacks/HDP/$VERSION/services/NIFI
sudo git clone https://github.com/abajwa-hw/ambari-nifi-service.git   /var/lib/ambari-server/resources/stacks/HDP/$VERSION/services/NIFI   
#sandbox
service ambari restart
#non sandbox
service ambari-server restart
  • To install Nifi, start the 'Install Wizard': Open Ambari (http://sandbox.hortonworks.com:8080) then:
    • On bottom left -> Actions -> Add service -> check NiFi server -> Next -> Next -> Change any config you like (e.g. install dir, port, setup_prebuilt or values in nifi.properties) -> Next -> Deploy. This will kick off the install which will run for 5-10min.

Steps

  • Import a simple flow to read Tweets into HDFS/Solr and visualize using Banana dashboard
    • HDP sandbox comes LW HDP search. Follow the steps below to use it to setup Banana, start SolrCloud and create a collection
      • On HDP 2.5 sandbox, HDPsearch can be installed via Ambari. Just use the same 'Install Wizard' used above and select all defaults
      • To install HDP search on non-sandbox, you can either:
    yum install -y lucidworks-hdpsearch
    sudo -u hdfs hadoop fs -mkdir /user/solr
    sudo -u hdfs hadoop fs -chown solr /user/solr
    
    • Ensure no log files owned by root (current sandbox version has files owned by root in log dir which causes problems when starting solr)
    chown -R solr:solr /opt/lucidworks-hdpsearch/solr  
    
    • Run solr setup steps as solr user
    su solr
    
    • Setup the Banana dashboard by copying default.json to dashboard dir
    cd /opt/lucidworks-hdpsearch/solr/server/solr-webapp/webapp/banana/app/dashboards/
    mv default.json default.json.orig
    wget https://raw.githubusercontent.com/abajwa-hw/ambari-nifi-service/master/demofiles/default.json
    
    • Edit solrconfig.xml by adding <str>EEE MMM d HH:mm:ss Z yyyy</str> underParseDateFieldUpdateProcessorFactory so it looks like below. This is done to allow Solr to recognize the timestamp format of tweets.
    vi /opt/lucidworks-hdpsearch/solr/server/solr/configsets/data_driven_schema_configs/conf/solrconfig.xml
    
      <processor>
        <arr name="format">
          <str>EEE MMM d HH:mm:ss Z yyyy</str>
    
    • Start/Restart Solr in cloud mode
      • If you installed Solr via Ambari, just use the 'Service Actions' dropdown to restart it
      • Otherwise, if you installed manually, start Solr as below after setting JAVA_HOME to the right location:
    export JAVA_HOME=/usr/lib/jvm/java-1.7.0-openjdk.x86_64 
    /opt/lucidworks-hdpsearch/solr/bin/solr start -c -z localhost:2181
    • create a collection called tweets
    /opt/lucidworks-hdpsearch/solr/bin/solr create -c tweets    -d data_driven_schema_configs    -s 1    -rf 1 
    
    • Solr setup is complete. Return to root user
    exit
    • Ensure the time on your sandbox is accurate or you will get errors using the GetTwitter processor. In case the time is not correct, run the below to fix it:
    yum install -y ntp
    service ntpd stop
    ntpdate pool.ntp.org
    service ntpd start
  • Now open Nifi webui (http://sandbox.hortonworks.com:9090/nifi) and run the remaining steps there:
    • Download prebuilt Twitter_Dashboard.xml template to your laptop from here
    • Import flow template info Nifi:
      • Import template by clicking on Templates (third icon from right) which will launch the 'Nifi Flow templates' popup Image
      • Browse and navigate to where ever you downloaded Twitter_Dashboard.xml on your local machine
      • Click Import. Now the template should appear: Image
      • Close the popup
    • Instantiate the Twitter dashboard template:
      • Drag/drop the Template icon (7th icon form left) onto the canvas so that a picklist popup appears Image
      • Select 'Twitter dashboard' and click Add
      • This should create a box (i.e processor group) named 'Twitter Dashboard'. Double click it to drill into the actual flow
    • Configure GetTwitter processor
      • Right click on 'GetTwitter' processor (near top) and click Configure
        • Under Properties:
          • Enter your Twitter key/secrets
          • ensure the 'Twitter Endpoint' is set to 'Filter Endpoint'
          • enter the search terms (e.g. AAPL,GOOG,MSFT,ORCL) under 'Terms to Filter on'Image
    • Configure PutContentSolrStream processor
      • Writes the selected attributes to Solr. In this case, assuming Solr is running in cloud mode with a collection 'tweets'
      • Confirm the Solr Location property is updated to reflect your Zookeeper configuration (for SolrCloud) or Solr standalone instance
      • If you installed Solr via Ambari, you will need to append /solr to the ZK string in the 'Solr Location':
      • 9166-9080-screen-shot-2016-11-02-at-115048-am.png

    • Review the other processors and modify properties as needed:
      • EvaluateJsonPath: Pulls out attributes of tweets
      • RouteonAttribute: Ensures only tweets with non-empty messages are processed
      • ReplaceText: Formats each tweet as pipe (|) delimited line entry e.g. tweet_id|unixtime|humantime|user_handle|message|full_tweet
      • MergeContent: Merges tweets into a single file (either 20 tweets or 120s, whichever comes first) to avoid having a large number of small files in HDFS. These values can be configured.
      • PutFile: writes tweets to local disk under /tmp/tweets/
      • PutHDFS: writes tweets to HDFS under /tmp/tweets_staging
    • If setup correctly, the top left hand of each processor on the canvas will show a red square (indicating the flow is stopped)
    • Click the Start button (green triangle near top of screen) to start the flow
    • After few seconds you will see tweets flowing Image
    • Create Hive table to be able to run queries on the tweets in HDFS
    sudo -u hdfs hadoop fs -chmod -R 777 /tmp/tweets_staging
    
    hive> create table if not exists tweets_text_partition(
      tweet_id bigint, 
      created_unixtime bigint, 
      created_time string, 
      displayname string, 
      msg string,
      fulltext string
    )
    row format delimited fields terminated by "|"
    location "/tmp/tweets_staging";

Viewing results

  • Other Nifi features
    • Flow statistics/graphs:
      • Right click on one of the processors (e.g. PutHDFS) and select click 'Stats' to see a number of charts/metrics: Image
      • You should also see Nifi metrics in Ambari (assuming you started Ambari metrics earlier)Image
    • Data provenance in Nifi:
      • In Nifi home screen, click Provenance icon (5th icon from top right corner) to open Provenance page: Image
      • Click Show lineage icon (2nd icon from right) on any row Image
      • Right click Send > View details > Content Image
      • From here you can view the tweet itself by
        • Clicking Content > View > formatted Image
      • You can also replay the event by
        • Replay > Submit
      • Close the provenance window using x icon on the inner window
      • Notice the event was replayed Image
      • Re-open the the provenance window on the row you you had originally selected Image
      • Notice that by viewing and replaying the tweet, you changed the provenance graph of this event: Send and replay events were added to the lineage graph
      • Also notice the time slider on the bottom left of the page which allows users to 'rewind' time and 'replay' the provenance events as they happened.404-screen-shot-2015-11-05-at-51631-pm.png
      • Right click on the Send event near the bottom of the flow and select Details Image
      • Notice that the details of request to view the tweet are captured here (who requested it, at what time etc)
      • Exit the Provenance window but clicking the x icon on the outer window
  • You have successfully created a basic Nifi flow that perfoms simple event processing to ingest tweets into HDP. Why was the processing 'simple'? There were no complex features like alerting users based on time windows (e.g. if a particular topic was tweeted about more than x times in 30s) etc which requires a higher fidelity form of transportation. For such functionality the recommendation would be to use Kafka/Storm. To see how you would use these technologies of the HDP stack to perform complex processing, take a look at the Twitter Storm demo at the Hortonworks Gallery under 'Sample Apps'

    Other things to try:

    Learn more about Nifi expression language and how to get started building a custom Nifi processor: http://community.hortonworks.com/articles/4356/getting-started-with-nifi-expression-language-and.htm...

    28,634 Views
    Comments

    Awesome tutorial, Thanks for sharing :)

    Rising Star

    Great Tutorial/Article @Ali Bajwa. Great way to start get familiar with Nifi.

    On question: Did you try and get working the Nifi Twitter Template so that the PutSolrContentStream connected to Solr Cloud instance as opposed to a standard/standalone solr instance.?

    He did use the SolrCloud mode for the PutSolrContentStream. I used SolrStandalone, so it should work either way :)

    From the HDF/NiFi standpoint, the only difference would be in a configuration switch for PutSolrContentStream:

    • Standalone connects to a Solr node directly (e.g. port 9893)
    • SolrCloud goes through a Zookeeper quorum (e.g. port 2181) and can talk to multiple nodes

    Thanks @George Vetticaden! As @Jonas Straub and @Andrew Grande mentioned, in this example I used cloud mode (notice that Solr was started with -c -z arguments) but you can easily change the Solr processor to point to Solr standalone instance too

    Rising Star

    Yup. got it working..my zookeeper connect string needed to have zhroot location which was solr in my case.

    Cloudera Employee

    376-screen-shot-2015-10-30-at-23530-pm.pngCheers.. This Works.! Good Stuff Ali.. Keep it Coming..!

    This demo will also work on VirtualBox but you will need to add port forwarding for port 9090. https://nsrc.org/workshops/2014/btnog/raw-attachment/wiki/Track2Agenda/ex-virtualbox-portforward-ssh...

    Mentor

    @Ali Bajwa big props for updating Nifi to 0.4.1, can you update the step where you say to navigate to http://sandbox.hortonworks.com:9090/ to http://sandbox.hortonworks.com:9090/nifi?

    Thanks @Artem Ervits! Updated it

    Thanks @Scott Shaw...updated

    One caveat: In case you reboot (reset) your VM/Sandbox, you should enable 'ntpd' daemon to start on bootup. I had trouble with GetTwitter as mentioned in the post above, even after following the steps to add ntpd and enable it. However, in the meantime, I had to reboot, which turned it off. To enable it on system bootup, run this command:

    chkconfig ntpd on
    

    To make sure it was effective, you can run this command to make sure 'ntpd' is enabled in the run modes (2,3,4,5):

    chkconfig --list | grep ntpd
    Guru

    @Ali Bajwa I am getting below error when I tried to replicate same case in my sandbox VM Fusion.

    5498-screen-shot-2016-07-05-at-124331-pm.png

    Guru

    @Ali Bajwa I have resolved it by adding proxy setting for nifi user.

    hadoop.proxyuser.nifi.groups=*

    hadoop.proxyuser.nifi.hosts=*

    Guru

    Anybody seen the following error when trying to create the tweet shard? And is there a known solution?

    	Unable to create core [tweets_shard1_replica1] Caused by: XML document structures must start and end within the same entity.
    
    
    New Contributor

    Thank you @Ali Bajwa for good tutoral.

    I am trying this example with a difference, My nifi is local and I try to put tweets in a remote Solr. Solr is in a VM that contains Hortonworks sandbox. Unfortunately I am getting this error on PutSolrContentStream processor:

    PutSolrContentStream[id=f6327477-fb7d-4af0-ec32-afcdb184e545] Failed to send StandardFlowFileRecord[uuid=9bc39142-c02c-4fa2-a911-9a9572e885d0,claim=StandardContentClaim [resourceClaim=StandardResourceClaim[id=1487148463852-14, container=default, section=14], offset=696096, length=2589],offset=0,name=103056151325300.json,size=2589] to Solr due to org.apache.solr.client.solrj.SolrServerException: IOException occured when talking to server at: http://172.17.0.2:8983/solr/tweets_shard1_replica1; routing to connection_failure: org.apache.solr.client.solrj.SolrServerException: IOException occured when talking to server at: http://172.17.0.2:8983/solr/tweets_shard1_replica1;

    Could you help me?

    thanks,

    Shanghoosh

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    Last update:
    ‎08-17-2019 02:05 PM
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