emiliosetiadarma commented on code in PR #5947:
URL: https://github.com/apache/nifi/pull/5947#discussion_r848770776


##########
nifi-nar-bundles/nifi-social-media-bundle/nifi-twitter-processors/src/main/java/org/apache/nifi/processors/twitter/ConsumeTwitter.java:
##########
@@ -0,0 +1,318 @@
+/*
+ * Licensed to the Apache Software Foundation (ASF) under one or more
+ * contributor license agreements.  See the NOTICE file distributed with
+ * this work for additional information regarding copyright ownership.
+ * The ASF licenses this file to You under the Apache License, Version 2.0
+ * (the "License"); you may not use this file except in compliance with
+ * the License.  You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+package org.apache.nifi.processors.twitter;
+
+import org.apache.nifi.annotation.behavior.InputRequirement;
+import org.apache.nifi.annotation.behavior.InputRequirement.Requirement;
+import org.apache.nifi.annotation.behavior.PrimaryNodeOnly;
+import org.apache.nifi.annotation.behavior.SupportsBatching;
+import org.apache.nifi.annotation.behavior.WritesAttribute;
+import org.apache.nifi.annotation.documentation.CapabilityDescription;
+import org.apache.nifi.annotation.documentation.Tags;
+import org.apache.nifi.annotation.lifecycle.OnScheduled;
+import org.apache.nifi.annotation.lifecycle.OnStopped;
+import org.apache.nifi.components.AllowableValue;
+import org.apache.nifi.components.PropertyDescriptor;
+import org.apache.nifi.flowfile.FlowFile;
+import org.apache.nifi.flowfile.attributes.CoreAttributes;
+import org.apache.nifi.processor.AbstractProcessor;
+import org.apache.nifi.processor.ProcessContext;
+import org.apache.nifi.processor.ProcessSession;
+import org.apache.nifi.processor.ProcessorInitializationContext;
+import org.apache.nifi.processor.Relationship;
+import org.apache.nifi.processor.exception.ProcessException;
+import org.apache.nifi.processor.io.OutputStreamCallback;
+import org.apache.nifi.processor.util.StandardValidators;
+
+import java.io.IOException;
+import java.io.OutputStream;
+import java.nio.charset.StandardCharsets;
+import java.util.Set;
+import java.util.List;
+import java.util.HashSet;
+import java.util.ArrayList;
+import java.util.Collections;
+import java.util.Map;
+import java.util.HashMap;
+import java.util.concurrent.BlockingQueue;
+import java.util.concurrent.LinkedBlockingQueue;
+
+@PrimaryNodeOnly
+@SupportsBatching
+@InputRequirement(Requirement.INPUT_FORBIDDEN)
+@Tags({"twitter", "tweets", "social media", "status", "json"})
+@CapabilityDescription("Streams tweets from Twitter's streaming API v2. The 
stream provides a sample stream or a search "
+    + "stream based on previously uploaded rules. This processor also provides 
a pass through for certain fields of the "
+    + "tweet to be returned as part of the response. See "
+    + 
"https://developer.twitter.com/en/docs/twitter-api/data-dictionary/introduction 
for more information regarding the "
+    + "Tweet object model. \n\n"
+    + "Warning: the underlying Java SDK used is still in beta as of the 
publishing of this processor feature.")
+@WritesAttribute(attribute = "mime.type", description = "Sets mime type to 
application/json")
+public class ConsumeTwitter extends AbstractProcessor {
+
+    static final AllowableValue ENDPOINT_SAMPLE = new AllowableValue("Sample 
Endpoint",
+            "Sample Endpoint",
+            "The endpoint that provides a stream of about 1% of tweets in 
real-time");
+    static final AllowableValue ENDPOINT_SEARCH = new AllowableValue("Search 
Endpoint",
+            "Search Endpoint",
+            "The endpoint that provides a stream of tweets that matches the 
rules you added to the stream. " +
+                    "If rules are not configured, then the stream will be 
empty");
+
+    public static final PropertyDescriptor ENDPOINT = new 
PropertyDescriptor.Builder()
+            .name("consume-twitter-endpoint")
+            .displayName("Twitter Endpoint")
+            .description("Specifies which endpoint tweets should be pulled 
from. " +
+                    "Usage of search endpoint requires that rules be uploaded 
beforehand. See " +
+                    
"https://developer.twitter.com/en/docs/twitter-api/tweets/filtered-stream/api-reference/";
 +
+                    "post-tweets-search-stream-rules")
+            .required(true)
+            .allowableValues(ENDPOINT_SAMPLE, ENDPOINT_SEARCH)
+            .defaultValue(ENDPOINT_SAMPLE.getValue())
+            .build();
+    public static final PropertyDescriptor BASE_PATH = new 
PropertyDescriptor.Builder()
+            .name("base-path")
+            .displayName("Base Path")
+            .description("Specifies which base path the API client will use 
for HTTP requests. " +
+                    "Generally should not be changed from the default 
https://api.twitter.com except for testing")
+            .required(true)
+            .addValidator(StandardValidators.NON_EMPTY_VALIDATOR)
+            .defaultValue("https://api.twitter.com";)
+            .build();
+    public static final PropertyDescriptor BEARER_TOKEN = new 
PropertyDescriptor.Builder()
+            .name("bearer-token")
+            .displayName("Bearer Token")
+            .description("The Bearer Token provided by Twitter.")
+            .required(true)
+            .sensitive(true)
+            .addValidator(StandardValidators.NON_EMPTY_VALIDATOR)
+            .build();
+    public static final PropertyDescriptor QUEUE_SIZE = new 
PropertyDescriptor.Builder()
+            .name("queue-size")
+            .displayName("Queue Size")
+            .description("The size of the queue used to queue tweets")
+            .required(true)
+            .addValidator(StandardValidators.POSITIVE_INTEGER_VALIDATOR)
+            .defaultValue("10000")
+            .build();
+    public static final PropertyDescriptor BATCH_SIZE = new 
PropertyDescriptor.Builder()
+            .name("batch-size")
+            .displayName("Batch Size")
+            .description("The maximum size of the number of tweets to be 
written to a single FlowFile." +
+                    "Will write less tweets if it there are not any tweets 
left in queue")
+            .required(true)
+            .addValidator(StandardValidators.POSITIVE_INTEGER_VALIDATOR)
+            .defaultValue("10")
+            .build();
+    public static final PropertyDescriptor TWEET_FIELDS = new 
PropertyDescriptor.Builder()
+            .name("tweet-fields")
+            .displayName("Tweet Fields")
+            .description("A comma-separated list of tweet fields to be 
returned as part of the tweet. Refer to " +
+                    
"https://developer.twitter.com/en/docs/twitter-api/data-dictionary/object-model/tweet
 " +
+                    "for proper usage. Possible field values are: " +
+                    "attachments, author_id, context_annotations, 
conversation_id, created_at, entities, geo, id, " +
+                    "in_reply_to_user_id, lang, non_public_metrics, 
organic_metrics, possibly_sensitive, promoted_metrics, " +
+                    "public_metrics, referenced_tweets, reply_settings, 
source, text, withheld")
+            .required(false)
+            .addValidator(StandardValidators.NON_EMPTY_VALIDATOR)
+            .build();
+    public static final PropertyDescriptor USER_FIELDS = new 
PropertyDescriptor.Builder()
+            .name("user-fields")
+            .displayName("User Fields")
+            .description("A comma-separated list of user fields to be returned 
as part of the tweet. Refer to " +
+                    
"https://developer.twitter.com/en/docs/twitter-api/data-dictionary/object-model/user
 " +
+                    "for proper usage. Possible field values are: " +
+                    "created_at, description, entities, id, location, name, 
pinned_tweet_id, profile_image_url, " +
+                    "protected, public_metrics, url, username, verified, 
withheld")
+            .required(false)
+            .addValidator(StandardValidators.NON_EMPTY_VALIDATOR)
+            .build();
+    public static final PropertyDescriptor MEDIA_FIELDS = new 
PropertyDescriptor.Builder()
+            .name("media-fields")
+            .displayName("Media Fields")
+            .description("A comma-separated list of media fields to be 
returned as part of the tweet. Refer to " +
+                    
"https://developer.twitter.com/en/docs/twitter-api/data-dictionary/object-model/media
 " +
+                    "for proper usage. Possible field values are: " +
+                    "alt_text, duration_ms, height, media_key, 
non_public_metrics, organic_metrics, preview_image_url, " +
+                    "promoted_metrics, public_metrics, type, url, width")
+            .required(false)
+            .addValidator(StandardValidators.NON_EMPTY_VALIDATOR)
+            .build();
+    public static final PropertyDescriptor POLL_FIELDS = new 
PropertyDescriptor.Builder()
+            .name("poll-fields")
+            .displayName("Poll Fields")
+            .description("A comma-separated list of poll fields to be returned 
as part of the tweet. Refer to " +
+                    
"https://developer.twitter.com/en/docs/twitter-api/data-dictionary/object-model/poll
 " +
+                    "for proper usage. Possible field values are: " +
+                    "duration_minutes, end_datetime, id, options, 
voting_status")
+            .required(false)
+            .addValidator(StandardValidators.NON_EMPTY_VALIDATOR)
+            .build();
+    public static final PropertyDescriptor PLACE_FIELDS = new 
PropertyDescriptor.Builder()
+            .name("place-fields")
+            .displayName("Place Fields")
+            .description("A comma-separated list of place fields to be 
returned as part of the tweet. Refer to " +
+                    
"https://developer.twitter.com/en/docs/twitter-api/data-dictionary/object-model/place
 " +
+                    "for proper usage. Possible field values are: " +
+                    "contained_within, country, country_code, full_name, geo, 
id, name, place_type")
+            .required(false)
+            .addValidator(StandardValidators.NON_EMPTY_VALIDATOR)
+            .build();
+    public static final PropertyDescriptor EXPANSIONS = new 
PropertyDescriptor.Builder()
+            .name("expansions")
+            .displayName("Expansions")
+            .description("A comma-separated list of expansions for objects in 
the returned tweet. See " +
+                    
"https://developer.twitter.com/en/docs/twitter-api/expansions " +
+                    "for proper usage. Possible field values are: " +
+                    "author_id, referenced_tweets.id, 
referenced_tweets.id.author_id, entities.mentions.username, " +
+                    "attachments.poll_ids, attachments.media_keys 
,in_reply_to_user_id, geo.place_id")
+            .required(false)
+            .addValidator(StandardValidators.NON_EMPTY_VALIDATOR)
+            .build();
+    public static final PropertyDescriptor BACKFILL_MINUTES = new 
PropertyDescriptor.Builder()
+            .name("backfill-minutes")
+            .displayName("Backfill Minutes")
+            .description("The number of minutes (up to 5 minutes) of streaming 
data to be requested after a " +
+                    "disconnect. Only available for project with academic 
research access. See " +
+                    
"https://developer.twitter.com/en/docs/twitter-api/tweets/filtered-stream/integrate/";
 +
+                    "recovery-and-redundancy-features")
+            .required(true)
+            .defaultValue("0")
+            .addValidator(StandardValidators.NON_NEGATIVE_INTEGER_VALIDATOR)
+            .build();
+
+    public static final Relationship REL_SUCCESS = new Relationship.Builder()
+            .name("success")
+            .description("All tweets will be routed to this relationship.")
+            .build();
+
+    private List<PropertyDescriptor> descriptors;
+    private Set<Relationship> relationships;
+
+    private TwitterStreamAPI api;
+
+    private volatile BlockingQueue<String> messageQueue;
+
+    private void emptyQueue() {
+        while (!messageQueue.isEmpty()) {
+            messageQueue.poll();
+        }
+    }
+
+    @Override
+    protected void init(ProcessorInitializationContext context) {
+        final List<PropertyDescriptor> descriptors = new ArrayList<>();
+        descriptors.add(ENDPOINT);
+        descriptors.add(BASE_PATH);
+        descriptors.add(BEARER_TOKEN);
+        descriptors.add(QUEUE_SIZE);
+        descriptors.add(BATCH_SIZE);
+        descriptors.add(TWEET_FIELDS);
+        descriptors.add(USER_FIELDS);
+        descriptors.add(MEDIA_FIELDS);
+        descriptors.add(POLL_FIELDS);
+        descriptors.add(PLACE_FIELDS);
+        descriptors.add(EXPANSIONS);
+        descriptors.add(BACKFILL_MINUTES);
+
+        this.descriptors = Collections.unmodifiableList(descriptors);
+
+        final Set<Relationship> relationships = new HashSet<>();
+        relationships.add(REL_SUCCESS);
+        this.relationships = Collections.unmodifiableSet(relationships);
+    }
+
+    @Override
+    public Set<Relationship> getRelationships() {
+        return this.relationships;
+    }
+
+    @Override
+    public final List<PropertyDescriptor> getSupportedPropertyDescriptors() {
+        return this.descriptors;
+    }
+
+
+    @OnScheduled
+    public void onScheduled(final ProcessContext context) {
+        messageQueue = new 
LinkedBlockingQueue<>(context.getProperty(QUEUE_SIZE).asInteger());
+
+        api = new TwitterStreamAPI(context, messageQueue, getLogger());
+        api.setBasePath(context.getProperty(BASE_PATH).getValue());
+        final String endpointName = context.getProperty(ENDPOINT).getValue();
+        if (ENDPOINT_SAMPLE.getValue().equals(endpointName)) {
+            api.start(TwitterStreamAPI.SAMPLE_ENDPOINT);
+        } else if (ENDPOINT_SEARCH.getValue().equals(endpointName)) {
+            api.start(TwitterStreamAPI.SEARCH_ENDPOINT);
+        } else {
+            throw new ProcessException("Endpoint was invalid value: " + 
endpointName);
+        }
+    }
+
+    @Override
+    public void onTrigger(ProcessContext context, ProcessSession session) 
throws ProcessException {
+        if (messageQueue.isEmpty()) {
+            context.yield();
+            return;
+        }
+
+        FlowFile flowFile = session.create();
+        flowFile = session.write(flowFile, new OutputStreamCallback() {
+            @Override
+            public void process(OutputStream out) throws IOException {
+                out.write("[".getBytes(StandardCharsets.UTF_8));
+                final int batchSize = 
context.getProperty(BATCH_SIZE).asInteger();
+                String tweet = messageQueue.poll();
+                out.write(tweet.getBytes(StandardCharsets.UTF_8));
+                int tweetCount = 1;
+                while (tweetCount < batchSize && !messageQueue.isEmpty()) {
+                    out.write(",".getBytes(StandardCharsets.UTF_8));
+                    tweet = messageQueue.poll();

Review Comment:
   I can implement that if I change the `isEmpty` condition to `(tweet = 
messageQueue.poll()) != null`. Making those changes!



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