Github user trixpan commented on a diff in the pull request:
https://github.com/apache/nifi/pull/1521#discussion_r101916202
--- Diff:
nifi-nar-bundles/nifi-aws-bundle/nifi-aws-processors/src/main/java/org/apache/nifi/processors/aws/iot/GetAWSIoTShadow.java
---
@@ -0,0 +1,114 @@
+/*
+ * 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.aws.iot;
+
+import com.amazonaws.services.iotdata.AWSIotDataClient;
+import com.amazonaws.services.iotdata.model.GetThingShadowRequest;
+import com.amazonaws.services.iotdata.model.GetThingShadowResult;
+import org.apache.nifi.annotation.behavior.*;
+import org.apache.nifi.annotation.documentation.CapabilityDescription;
+import org.apache.nifi.annotation.documentation.SeeAlso;
+import org.apache.nifi.annotation.documentation.Tags;
+import org.apache.nifi.components.PropertyDescriptor;
+import org.apache.nifi.flowfile.FlowFile;
+import org.apache.nifi.processor.ProcessContext;
+import org.apache.nifi.processor.ProcessSession;
+import org.apache.nifi.processor.Relationship;
+import org.apache.nifi.processor.exception.ProcessException;
+import org.apache.nifi.processor.io.OutputStreamCallback;
+
+import java.io.IOException;
+import java.io.OutputStream;
+import java.util.Arrays;
+import java.util.Collections;
+import java.util.List;
+import java.util.Set;
+import java.util.HashMap;
+import java.util.Map;
+
+@EventDriven
+@Tags({"Amazon", "AWS", "IOT", "Shadow", "Get"})
+@InputRequirement(InputRequirement.Requirement.INPUT_ALLOWED)
+@CapabilityDescription("Gets last persisted state of a thing in AWS IoT by
reading out the shadow. " +
+ "A shadow might change more often than you get triggered. In order
to get every message send " +
+ "out by a thing you better use ConsumeAWSIoTMqtt processor. You
can dynamically set a thing-name " +
+ "when overriding the processor-configuration with a
message-attribute \"aws.iot.thing.override\".")
+@SeeAlso({ ConsumeAWSIoTMqtt.class })
+@ReadsAttributes({
+ @ReadsAttribute(attribute = "aws.iot.thing.override", description
= "Overrides the processor configuration for topic."),
+})
+@WritesAttributes({
+ @WritesAttribute(attribute = "aws.iot.thing", description = "Thing
name in AWS IoT"),
+})
+public class GetAWSIoTShadow extends AbstractAWSIoTShadowProcessor {
+ public static final List<PropertyDescriptor> properties =
Collections.unmodifiableList(
+ Arrays.asList(
+ PROP_THING,
+ AWS_CREDENTIALS_PROVIDER_SERVICE,
+ TIMEOUT,
+ PROXY_HOST,
+ PROXY_HOST_PORT,
+ REGION));
+
+ private final static String ATTR_NAME_THING = PROP_NAME_THING +
".override";
+
+ @Override
+ protected List<PropertyDescriptor> getSupportedPropertyDescriptors() {
+ return properties;
+ }
+
+ @Override
+ public Set<Relationship> getRelationships() {
+ return Collections.singleton(REL_SUCCESS);
+ }
+
+ @Override
+ public void onTrigger(final ProcessContext context, final
ProcessSession session) throws ProcessException {
+ final AWSIotDataClient iotClient = this.getClient();
--- End diff --
**JPercivall**
This onTrigger potentially gets a FlowFile and creates a new one. In this
instance where the processor can act as a source processor but also accepts
input the logic to cover all use-cases gets a little tricky. For an example,
check out the InvokeHTTP processor[1], specifically the check to see if there
is a non-loop connection when the flowfile is null.
In addition to checking to see if the processor should run, you must handle
both FlowFiles (transfer or remove). In this case you should probably have
three relationships one for the original when it fails, one for the original
when it succeeds and one for the created shadow when it succeeds.
[1]
https://github.com/apache/nifi/blob/eb6f9f0fec3042350864afee17a67ea62ef5f37a/nifi-nar-bundles/nifi-standard-bundle/nifi-standard-processors/src/main/java/org/apache/nifi/processors/standard/InvokeHTTP.java#L527-L527
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