mosermw commented on code in PR #9476:
URL: https://github.com/apache/nifi/pull/9476#discussion_r1904578246


##########
nifi-extension-bundles/nifi-standard-bundle/nifi-standard-rules/pom.xml:
##########
@@ -23,7 +23,20 @@
     <artifactId>nifi-standard-rules</artifactId>
     <packaging>jar</packaging>
 
-    <dependencies>
-
-    </dependencies>
+    <dependencies />
+    
+    <build>
+        <plugins>
+            <plugin>
+                <groupId>org.apache.rat</groupId>
+                <artifactId>apache-rat-plugin</artifactId>
+                <configuration>
+                    <excludes combine.children="append">
+                        
<exclude>src/test/resources/RestrictBackpressureSettings/RestrictBackpressureSettings_noViolation.json</exclude>
+                        
<exclude>src/test/resources/RestrictBackpressureSettings/RestrictBackpressureSettings.json</exclude>
+                    </excludes>
+                </configuration>
+            </plugin>
+        </plugins>
+    </build>

Review Comment:
   Let's add a newline at the end of this pom.xml



##########
nifi-extension-bundles/nifi-standard-bundle/nifi-standard-rules/src/main/java/org/apache/nifi/flowanalysis/rules/RestrictBackpressureSettings.java:
##########
@@ -0,0 +1,242 @@
+/*
+ * 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.flowanalysis.rules;
+
+import org.apache.nifi.annotation.documentation.CapabilityDescription;
+import org.apache.nifi.annotation.documentation.Tags;
+import org.apache.nifi.components.PropertyDescriptor;
+import org.apache.nifi.components.ValidationContext;
+import org.apache.nifi.components.ValidationResult;
+import org.apache.nifi.flow.VersionedComponent;
+import org.apache.nifi.flow.VersionedConnection;
+import org.apache.nifi.flow.VersionedProcessGroup;
+import org.apache.nifi.flow.VersionedProcessor;
+import org.apache.nifi.flowanalysis.AbstractFlowAnalysisRule;
+import org.apache.nifi.flowanalysis.FlowAnalysisRuleContext;
+import org.apache.nifi.flowanalysis.GroupAnalysisResult;
+import org.apache.nifi.processor.DataUnit;
+import org.apache.nifi.processor.util.StandardValidators;
+
+import java.util.ArrayList;
+import java.util.Collection;
+import java.util.HashSet;
+import java.util.List;
+import java.util.Map;
+import java.util.function.Function;
+import java.util.stream.Collectors;
+import java.util.stream.Stream;
+
+@Tags({"connection", "backpressure"})
+@CapabilityDescription("This rule will generate a violation if backpressure 
settings of a connection exceed configured thresholds. "
+        + "Improper configuration of backpressure settings can lead to 
decreased performances because of excessive swapping as well as "
+        + "to filled up content repository with too much in-flight data in 
NiFi.")
+public class RestrictBackpressureSettings extends AbstractFlowAnalysisRule {
+
+    public static final PropertyDescriptor COUNT_MIN = new 
PropertyDescriptor.Builder()
+            .name("Minimum Backpressure Object Count Threshold")
+            .description("This is the minimum value that should be set for the 
Object Count backpressure setting on connections. "
+                    + "This can be used to prevent a user from setting a value 
of 0 which disables backpressure based on count.")
+            .required(true)
+            .addValidator(StandardValidators.POSITIVE_LONG_VALIDATOR)
+            .defaultValue("1")
+            .build();
+
+    public static final PropertyDescriptor COUNT_MAX = new 
PropertyDescriptor.Builder()
+            .name("Maximum Backpressure Object Count Threshold")
+            .description("This is the maximum value that should be set for the 
Object Count backpressure setting on connections. "
+                    + "This can be used to prevent a user from setting a very 
high value that may be leading to a lot of swapping.")
+            .required(true)
+            .addValidator(StandardValidators.POSITIVE_LONG_VALIDATOR)
+            .defaultValue("10000")
+            .build();
+
+    public static final PropertyDescriptor SIZE_MIN = new 
PropertyDescriptor.Builder()
+            .name("Minimum Backpressure Data Size Threshold")
+            .description("This is the minimum value that should be set for the 
Data Size backpressure setting on connections. "
+                    + "This can be used to prevent a user from setting a value 
of 0 which disables backpressure based on size.")
+            .required(true)
+            .addValidator(StandardValidators.DATA_SIZE_VALIDATOR)
+            .defaultValue("1 MB")
+            .build();
+
+    public static final PropertyDescriptor SIZE_MAX = new 
PropertyDescriptor.Builder()
+            .name("Maximum Backpressure Data Size Threshold")
+            .description("This is the maximum value that should be set for the 
Data Size backpressure setting on connections. "
+                    + "This can be used to prevent a user from setting a very 
high value that may be filling up the content repo.")
+            .required(true)
+            .addValidator(StandardValidators.DATA_SIZE_VALIDATOR)
+            .defaultValue("1 GB")
+            .build();
+
+    private static final List<PropertyDescriptor> PROPERTIES = List.of(
+            COUNT_MIN,
+            COUNT_MAX,
+            SIZE_MIN,
+            SIZE_MAX
+    );
+
+    @Override
+    protected Collection<ValidationResult> customValidate(ValidationContext 
validationContext) {
+        final List<ValidationResult> results = new 
ArrayList<ValidationResult>();

Review Comment:
   Correct new PMD violation by using diamond operator here.



##########
nifi-extension-bundles/nifi-standard-bundle/nifi-standard-rules/src/main/java/org/apache/nifi/flowanalysis/rules/RestrictBackpressureSettings.java:
##########
@@ -0,0 +1,242 @@
+/*
+ * 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.flowanalysis.rules;
+
+import org.apache.nifi.annotation.documentation.CapabilityDescription;
+import org.apache.nifi.annotation.documentation.Tags;
+import org.apache.nifi.components.PropertyDescriptor;
+import org.apache.nifi.components.ValidationContext;
+import org.apache.nifi.components.ValidationResult;
+import org.apache.nifi.flow.VersionedComponent;
+import org.apache.nifi.flow.VersionedConnection;
+import org.apache.nifi.flow.VersionedProcessGroup;
+import org.apache.nifi.flow.VersionedProcessor;
+import org.apache.nifi.flowanalysis.AbstractFlowAnalysisRule;
+import org.apache.nifi.flowanalysis.FlowAnalysisRuleContext;
+import org.apache.nifi.flowanalysis.GroupAnalysisResult;
+import org.apache.nifi.processor.DataUnit;
+import org.apache.nifi.processor.util.StandardValidators;
+
+import java.util.ArrayList;
+import java.util.Collection;
+import java.util.HashSet;
+import java.util.List;
+import java.util.Map;
+import java.util.function.Function;
+import java.util.stream.Collectors;
+import java.util.stream.Stream;
+
+@Tags({"connection", "backpressure"})
+@CapabilityDescription("This rule will generate a violation if backpressure 
settings of a connection exceed configured thresholds. "
+        + "Improper configuration of backpressure settings can lead to 
decreased performances because of excessive swapping as well as "
+        + "to filled up content repository with too much in-flight data in 
NiFi.")
+public class RestrictBackpressureSettings extends AbstractFlowAnalysisRule {
+
+    public static final PropertyDescriptor COUNT_MIN = new 
PropertyDescriptor.Builder()
+            .name("Minimum Backpressure Object Count Threshold")
+            .description("This is the minimum value that should be set for the 
Object Count backpressure setting on connections. "
+                    + "This can be used to prevent a user from setting a value 
of 0 which disables backpressure based on count.")
+            .required(true)
+            .addValidator(StandardValidators.POSITIVE_LONG_VALIDATOR)
+            .defaultValue("1")
+            .build();
+
+    public static final PropertyDescriptor COUNT_MAX = new 
PropertyDescriptor.Builder()
+            .name("Maximum Backpressure Object Count Threshold")
+            .description("This is the maximum value that should be set for the 
Object Count backpressure setting on connections. "
+                    + "This can be used to prevent a user from setting a very 
high value that may be leading to a lot of swapping.")
+            .required(true)
+            .addValidator(StandardValidators.POSITIVE_LONG_VALIDATOR)
+            .defaultValue("10000")
+            .build();
+
+    public static final PropertyDescriptor SIZE_MIN = new 
PropertyDescriptor.Builder()
+            .name("Minimum Backpressure Data Size Threshold")
+            .description("This is the minimum value that should be set for the 
Data Size backpressure setting on connections. "
+                    + "This can be used to prevent a user from setting a value 
of 0 which disables backpressure based on size.")
+            .required(true)
+            .addValidator(StandardValidators.DATA_SIZE_VALIDATOR)
+            .defaultValue("1 MB")
+            .build();
+
+    public static final PropertyDescriptor SIZE_MAX = new 
PropertyDescriptor.Builder()
+            .name("Maximum Backpressure Data Size Threshold")
+            .description("This is the maximum value that should be set for the 
Data Size backpressure setting on connections. "
+                    + "This can be used to prevent a user from setting a very 
high value that may be filling up the content repo.")
+            .required(true)
+            .addValidator(StandardValidators.DATA_SIZE_VALIDATOR)
+            .defaultValue("1 GB")
+            .build();
+
+    private static final List<PropertyDescriptor> PROPERTIES = List.of(
+            COUNT_MIN,
+            COUNT_MAX,
+            SIZE_MIN,
+            SIZE_MAX
+    );
+
+    @Override
+    protected Collection<ValidationResult> customValidate(ValidationContext 
validationContext) {
+        final List<ValidationResult> results = new 
ArrayList<ValidationResult>();
+
+        final long minCount = 
validationContext.getProperty(COUNT_MIN).asLong();
+        final long maxCount = 
validationContext.getProperty(COUNT_MAX).asLong();
+        final double minSize = 
validationContext.getProperty(SIZE_MIN).asDataSize(DataUnit.B);
+        final double maxSize = 
validationContext.getProperty(SIZE_MAX).asDataSize(DataUnit.B);
+
+        if (minCount > maxCount) {
+            results.add(
+                    new ValidationResult.Builder()
+                    .subject(COUNT_MIN.getName())
+                    .valid(false)
+                    .explanation("Value of '" + COUNT_MIN.getName() + "' 
cannot be strictly greater than '" + COUNT_MAX.getName() + "'")
+                    .build());
+        }
+        if (Double.compare(minSize, maxSize) > 0) {
+            results.add(
+                    new ValidationResult.Builder()
+                    .subject(SIZE_MIN.getName())
+                    .valid(false)
+                    .explanation("Value of '" + SIZE_MIN.getName() + "' cannot 
be strictly greater than '" + SIZE_MAX.getName() + "'")
+                    .build());
+        }
+
+        return results;
+    }
+
+    @Override
+    protected List<PropertyDescriptor> getSupportedPropertyDescriptors() {
+        return PROPERTIES;
+    }
+
+    @Override
+    public Collection<GroupAnalysisResult> 
analyzeProcessGroup(VersionedProcessGroup pg, FlowAnalysisRuleContext context) {
+        final Collection<GroupAnalysisResult> results = new 
HashSet<GroupAnalysisResult>();

Review Comment:
   Correct new PMD violation by using diamond operator here



##########
nifi-extension-bundles/nifi-standard-bundle/nifi-standard-rules/src/main/resources/META-INF/services/org.apache.nifi.flowanalysis.FlowAnalysisRule:
##########
@@ -13,4 +13,5 @@
 # See the License for the specific language governing permissions and
 # limitations under the License.
 
-org.apache.nifi.flowanalysis.rules.DisallowComponentType
\ No newline at end of file
+org.apache.nifi.flowanalysis.rules.DisallowComponentType
+org.apache.nifi.flowanalysis.rules.RestrictBackpressureSettings

Review Comment:
   Let's add a newline at the end of this file.



##########
nifi-extension-bundles/nifi-standard-bundle/nifi-standard-rules/src/main/java/org/apache/nifi/flowanalysis/rules/RestrictBackpressureSettings.java:
##########
@@ -0,0 +1,242 @@
+/*
+ * 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.flowanalysis.rules;
+
+import org.apache.nifi.annotation.documentation.CapabilityDescription;
+import org.apache.nifi.annotation.documentation.Tags;
+import org.apache.nifi.components.PropertyDescriptor;
+import org.apache.nifi.components.ValidationContext;
+import org.apache.nifi.components.ValidationResult;
+import org.apache.nifi.flow.VersionedComponent;
+import org.apache.nifi.flow.VersionedConnection;
+import org.apache.nifi.flow.VersionedProcessGroup;
+import org.apache.nifi.flow.VersionedProcessor;
+import org.apache.nifi.flowanalysis.AbstractFlowAnalysisRule;
+import org.apache.nifi.flowanalysis.FlowAnalysisRuleContext;
+import org.apache.nifi.flowanalysis.GroupAnalysisResult;
+import org.apache.nifi.processor.DataUnit;
+import org.apache.nifi.processor.util.StandardValidators;
+
+import java.util.ArrayList;
+import java.util.Collection;
+import java.util.HashSet;
+import java.util.List;
+import java.util.Map;
+import java.util.function.Function;
+import java.util.stream.Collectors;
+import java.util.stream.Stream;
+
+@Tags({"connection", "backpressure"})
+@CapabilityDescription("This rule will generate a violation if backpressure 
settings of a connection exceed configured thresholds. "
+        + "Improper configuration of backpressure settings can lead to 
decreased performances because of excessive swapping as well as "
+        + "to filled up content repository with too much in-flight data in 
NiFi.")
+public class RestrictBackpressureSettings extends AbstractFlowAnalysisRule {
+
+    public static final PropertyDescriptor COUNT_MIN = new 
PropertyDescriptor.Builder()
+            .name("Minimum Backpressure Object Count Threshold")
+            .description("This is the minimum value that should be set for the 
Object Count backpressure setting on connections. "
+                    + "This can be used to prevent a user from setting a value 
of 0 which disables backpressure based on count.")
+            .required(true)
+            .addValidator(StandardValidators.POSITIVE_LONG_VALIDATOR)
+            .defaultValue("1")
+            .build();
+
+    public static final PropertyDescriptor COUNT_MAX = new 
PropertyDescriptor.Builder()
+            .name("Maximum Backpressure Object Count Threshold")
+            .description("This is the maximum value that should be set for the 
Object Count backpressure setting on connections. "
+                    + "This can be used to prevent a user from setting a very 
high value that may be leading to a lot of swapping.")
+            .required(true)
+            .addValidator(StandardValidators.POSITIVE_LONG_VALIDATOR)
+            .defaultValue("10000")
+            .build();
+
+    public static final PropertyDescriptor SIZE_MIN = new 
PropertyDescriptor.Builder()
+            .name("Minimum Backpressure Data Size Threshold")
+            .description("This is the minimum value that should be set for the 
Data Size backpressure setting on connections. "
+                    + "This can be used to prevent a user from setting a value 
of 0 which disables backpressure based on size.")
+            .required(true)
+            .addValidator(StandardValidators.DATA_SIZE_VALIDATOR)
+            .defaultValue("1 MB")
+            .build();
+
+    public static final PropertyDescriptor SIZE_MAX = new 
PropertyDescriptor.Builder()
+            .name("Maximum Backpressure Data Size Threshold")
+            .description("This is the maximum value that should be set for the 
Data Size backpressure setting on connections. "
+                    + "This can be used to prevent a user from setting a very 
high value that may be filling up the content repo.")
+            .required(true)
+            .addValidator(StandardValidators.DATA_SIZE_VALIDATOR)
+            .defaultValue("1 GB")
+            .build();
+
+    private static final List<PropertyDescriptor> PROPERTIES = List.of(
+            COUNT_MIN,
+            COUNT_MAX,
+            SIZE_MIN,
+            SIZE_MAX
+    );
+
+    @Override
+    protected Collection<ValidationResult> customValidate(ValidationContext 
validationContext) {
+        final List<ValidationResult> results = new 
ArrayList<ValidationResult>();
+
+        final long minCount = 
validationContext.getProperty(COUNT_MIN).asLong();
+        final long maxCount = 
validationContext.getProperty(COUNT_MAX).asLong();
+        final double minSize = 
validationContext.getProperty(SIZE_MIN).asDataSize(DataUnit.B);
+        final double maxSize = 
validationContext.getProperty(SIZE_MAX).asDataSize(DataUnit.B);
+
+        if (minCount > maxCount) {
+            results.add(
+                    new ValidationResult.Builder()
+                    .subject(COUNT_MIN.getName())
+                    .valid(false)
+                    .explanation("Value of '" + COUNT_MIN.getName() + "' 
cannot be strictly greater than '" + COUNT_MAX.getName() + "'")
+                    .build());
+        }
+        if (Double.compare(minSize, maxSize) > 0) {
+            results.add(
+                    new ValidationResult.Builder()
+                    .subject(SIZE_MIN.getName())
+                    .valid(false)
+                    .explanation("Value of '" + SIZE_MIN.getName() + "' cannot 
be strictly greater than '" + SIZE_MAX.getName() + "'")
+                    .build());
+        }
+
+        return results;
+    }
+
+    @Override
+    protected List<PropertyDescriptor> getSupportedPropertyDescriptors() {
+        return PROPERTIES;
+    }
+
+    @Override
+    public Collection<GroupAnalysisResult> 
analyzeProcessGroup(VersionedProcessGroup pg, FlowAnalysisRuleContext context) {
+        final Collection<GroupAnalysisResult> results = new 
HashSet<GroupAnalysisResult>();
+
+        final long minCount = context.getProperty(COUNT_MIN).asLong();
+        final long maxCount = context.getProperty(COUNT_MAX).asLong();
+        final double minSize = 
context.getProperty(SIZE_MIN).asDataSize(DataUnit.B);
+        final double maxSize = 
context.getProperty(SIZE_MAX).asDataSize(DataUnit.B);
+
+        // Map of all id/components to generate more human readable violations
+        final Map<String, VersionedComponent> idComponent = Stream.of(
+                    pg.getFunnels().stream(),
+                    pg.getProcessors().stream(),
+                    pg.getInputPorts().stream(),
+                    pg.getOutputPorts().stream()
+                ).flatMap(c -> c)
+                .collect(Collectors.toMap(c -> c.getIdentifier(), 
Function.identity()));
+
+        pg.getConnections().stream().forEach(
+                connection -> {
+                    if (connection.getBackPressureObjectThreshold() < 
minCount) {
+                        results.add(buildViolation(connection,
+                                
idComponent.get(connection.getSource().getId()),
+                                
idComponent.get(connection.getDestination().getId()),
+                                
BackpressureViolationType.BP_COUNT_THRESHOLD_BELOW_LIMIT,
+                                
getViolationMessage(BackpressureViolationType.BP_COUNT_THRESHOLD_BELOW_LIMIT, 
connection.getBackPressureObjectThreshold().toString(), 
Long.toString(minCount))));
+                    }
+                    if (connection.getBackPressureObjectThreshold() > 
maxCount) {
+                        results.add(buildViolation(connection,
+                                
idComponent.get(connection.getSource().getId()),
+                                
idComponent.get(connection.getDestination().getId()),
+                                
BackpressureViolationType.BP_COUNT_THRESHOLD_ABOVE_LIMIT,
+                                
getViolationMessage(BackpressureViolationType.BP_COUNT_THRESHOLD_ABOVE_LIMIT, 
connection.getBackPressureObjectThreshold().toString(), 
Long.toString(maxCount))));
+                    }
+                    final double sizeThreshold = 
DataUnit.parseDataSize(connection.getBackPressureDataSizeThreshold(), 
DataUnit.B);
+                    if (Double.compare(sizeThreshold, minSize) < 0) {
+                        results.add(buildViolation(connection,
+                                
idComponent.get(connection.getSource().getId()),
+                                
idComponent.get(connection.getDestination().getId()),
+                                
BackpressureViolationType.BP_SIZE_THRESHOLD_BELOW_LIMIT,
+                                
getViolationMessage(BackpressureViolationType.BP_SIZE_THRESHOLD_BELOW_LIMIT, 
connection.getBackPressureDataSizeThreshold(), 
context.getProperty(SIZE_MIN).getValue())));
+                    }
+                    if (Double.compare(sizeThreshold, maxSize) > 0) {
+                        results.add(buildViolation(connection,
+                                
idComponent.get(connection.getSource().getId()),
+                                
idComponent.get(connection.getDestination().getId()),
+                                
BackpressureViolationType.BP_SIZE_THRESHOLD_ABOVE_LIMIT,
+                                
getViolationMessage(BackpressureViolationType.BP_SIZE_THRESHOLD_ABOVE_LIMIT, 
connection.getBackPressureDataSizeThreshold(), 
context.getProperty(SIZE_MAX).getValue())));
+                    }
+                }
+            );
+
+        return results;
+    }
+
+    private GroupAnalysisResult buildViolation(final VersionedConnection 
connection, final VersionedComponent source,

Review Comment:
   This method chooses whether to assign the violation to the connection or 
nearest real Processor.  Ideally, backpressure violations would always be 
assigned to the connection.  Was this done as a workaround for NIFI-13953 
because the UI does not showing a "Go To" link for connection violations?
   
   I'm not sure we should keep a workaround like this.  If you feel that we 
need the workaround, then a comment in the code to that effect should be here, 
stating why it works like this and when it should be replaced.



##########
nifi-extension-bundles/nifi-standard-bundle/nifi-standard-rules/src/main/java/org/apache/nifi/flowanalysis/rules/RestrictBackpressureSettings.java:
##########
@@ -0,0 +1,242 @@
+/*
+ * 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.flowanalysis.rules;
+
+import org.apache.nifi.annotation.documentation.CapabilityDescription;
+import org.apache.nifi.annotation.documentation.Tags;
+import org.apache.nifi.components.PropertyDescriptor;
+import org.apache.nifi.components.ValidationContext;
+import org.apache.nifi.components.ValidationResult;
+import org.apache.nifi.flow.VersionedComponent;
+import org.apache.nifi.flow.VersionedConnection;
+import org.apache.nifi.flow.VersionedProcessGroup;
+import org.apache.nifi.flow.VersionedProcessor;
+import org.apache.nifi.flowanalysis.AbstractFlowAnalysisRule;
+import org.apache.nifi.flowanalysis.FlowAnalysisRuleContext;
+import org.apache.nifi.flowanalysis.GroupAnalysisResult;
+import org.apache.nifi.processor.DataUnit;
+import org.apache.nifi.processor.util.StandardValidators;
+
+import java.util.ArrayList;
+import java.util.Collection;
+import java.util.HashSet;
+import java.util.List;
+import java.util.Map;
+import java.util.function.Function;
+import java.util.stream.Collectors;
+import java.util.stream.Stream;
+
+@Tags({"connection", "backpressure"})
+@CapabilityDescription("This rule will generate a violation if backpressure 
settings of a connection exceed configured thresholds. "
+        + "Improper configuration of backpressure settings can lead to 
decreased performances because of excessive swapping as well as "
+        + "to filled up content repository with too much in-flight data in 
NiFi.")
+public class RestrictBackpressureSettings extends AbstractFlowAnalysisRule {
+
+    public static final PropertyDescriptor COUNT_MIN = new 
PropertyDescriptor.Builder()
+            .name("Minimum Backpressure Object Count Threshold")
+            .description("This is the minimum value that should be set for the 
Object Count backpressure setting on connections. "
+                    + "This can be used to prevent a user from setting a value 
of 0 which disables backpressure based on count.")
+            .required(true)
+            .addValidator(StandardValidators.POSITIVE_LONG_VALIDATOR)
+            .defaultValue("1")
+            .build();
+
+    public static final PropertyDescriptor COUNT_MAX = new 
PropertyDescriptor.Builder()
+            .name("Maximum Backpressure Object Count Threshold")
+            .description("This is the maximum value that should be set for the 
Object Count backpressure setting on connections. "
+                    + "This can be used to prevent a user from setting a very 
high value that may be leading to a lot of swapping.")
+            .required(true)
+            .addValidator(StandardValidators.POSITIVE_LONG_VALIDATOR)
+            .defaultValue("10000")
+            .build();
+
+    public static final PropertyDescriptor SIZE_MIN = new 
PropertyDescriptor.Builder()
+            .name("Minimum Backpressure Data Size Threshold")
+            .description("This is the minimum value that should be set for the 
Data Size backpressure setting on connections. "
+                    + "This can be used to prevent a user from setting a value 
of 0 which disables backpressure based on size.")
+            .required(true)
+            .addValidator(StandardValidators.DATA_SIZE_VALIDATOR)
+            .defaultValue("1 MB")
+            .build();
+
+    public static final PropertyDescriptor SIZE_MAX = new 
PropertyDescriptor.Builder()
+            .name("Maximum Backpressure Data Size Threshold")
+            .description("This is the maximum value that should be set for the 
Data Size backpressure setting on connections. "
+                    + "This can be used to prevent a user from setting a very 
high value that may be filling up the content repo.")
+            .required(true)
+            .addValidator(StandardValidators.DATA_SIZE_VALIDATOR)
+            .defaultValue("1 GB")
+            .build();
+
+    private static final List<PropertyDescriptor> PROPERTIES = List.of(
+            COUNT_MIN,
+            COUNT_MAX,
+            SIZE_MIN,
+            SIZE_MAX
+    );
+
+    @Override
+    protected Collection<ValidationResult> customValidate(ValidationContext 
validationContext) {
+        final List<ValidationResult> results = new 
ArrayList<ValidationResult>();
+
+        final long minCount = 
validationContext.getProperty(COUNT_MIN).asLong();
+        final long maxCount = 
validationContext.getProperty(COUNT_MAX).asLong();
+        final double minSize = 
validationContext.getProperty(SIZE_MIN).asDataSize(DataUnit.B);
+        final double maxSize = 
validationContext.getProperty(SIZE_MAX).asDataSize(DataUnit.B);
+
+        if (minCount > maxCount) {
+            results.add(
+                    new ValidationResult.Builder()
+                    .subject(COUNT_MIN.getName())
+                    .valid(false)
+                    .explanation("Value of '" + COUNT_MIN.getName() + "' 
cannot be strictly greater than '" + COUNT_MAX.getName() + "'")
+                    .build());
+        }
+        if (Double.compare(minSize, maxSize) > 0) {
+            results.add(
+                    new ValidationResult.Builder()
+                    .subject(SIZE_MIN.getName())
+                    .valid(false)
+                    .explanation("Value of '" + SIZE_MIN.getName() + "' cannot 
be strictly greater than '" + SIZE_MAX.getName() + "'")
+                    .build());
+        }
+
+        return results;
+    }
+
+    @Override
+    protected List<PropertyDescriptor> getSupportedPropertyDescriptors() {
+        return PROPERTIES;
+    }
+
+    @Override
+    public Collection<GroupAnalysisResult> 
analyzeProcessGroup(VersionedProcessGroup pg, FlowAnalysisRuleContext context) {
+        final Collection<GroupAnalysisResult> results = new 
HashSet<GroupAnalysisResult>();
+
+        final long minCount = context.getProperty(COUNT_MIN).asLong();
+        final long maxCount = context.getProperty(COUNT_MAX).asLong();
+        final double minSize = 
context.getProperty(SIZE_MIN).asDataSize(DataUnit.B);
+        final double maxSize = 
context.getProperty(SIZE_MAX).asDataSize(DataUnit.B);
+
+        // Map of all id/components to generate more human readable violations
+        final Map<String, VersionedComponent> idComponent = Stream.of(
+                    pg.getFunnels().stream(),
+                    pg.getProcessors().stream(),
+                    pg.getInputPorts().stream(),
+                    pg.getOutputPorts().stream()
+                ).flatMap(c -> c)
+                .collect(Collectors.toMap(c -> c.getIdentifier(), 
Function.identity()));
+
+        pg.getConnections().stream().forEach(
+                connection -> {
+                    if (connection.getBackPressureObjectThreshold() < 
minCount) {
+                        results.add(buildViolation(connection,
+                                
idComponent.get(connection.getSource().getId()),
+                                
idComponent.get(connection.getDestination().getId()),
+                                
BackpressureViolationType.BP_COUNT_THRESHOLD_BELOW_LIMIT,
+                                
getViolationMessage(BackpressureViolationType.BP_COUNT_THRESHOLD_BELOW_LIMIT, 
connection.getBackPressureObjectThreshold().toString(), 
Long.toString(minCount))));
+                    }
+                    if (connection.getBackPressureObjectThreshold() > 
maxCount) {
+                        results.add(buildViolation(connection,
+                                
idComponent.get(connection.getSource().getId()),
+                                
idComponent.get(connection.getDestination().getId()),
+                                
BackpressureViolationType.BP_COUNT_THRESHOLD_ABOVE_LIMIT,
+                                
getViolationMessage(BackpressureViolationType.BP_COUNT_THRESHOLD_ABOVE_LIMIT, 
connection.getBackPressureObjectThreshold().toString(), 
Long.toString(maxCount))));
+                    }
+                    final double sizeThreshold = 
DataUnit.parseDataSize(connection.getBackPressureDataSizeThreshold(), 
DataUnit.B);
+                    if (Double.compare(sizeThreshold, minSize) < 0) {
+                        results.add(buildViolation(connection,
+                                
idComponent.get(connection.getSource().getId()),
+                                
idComponent.get(connection.getDestination().getId()),
+                                
BackpressureViolationType.BP_SIZE_THRESHOLD_BELOW_LIMIT,
+                                
getViolationMessage(BackpressureViolationType.BP_SIZE_THRESHOLD_BELOW_LIMIT, 
connection.getBackPressureDataSizeThreshold(), 
context.getProperty(SIZE_MIN).getValue())));
+                    }
+                    if (Double.compare(sizeThreshold, maxSize) > 0) {
+                        results.add(buildViolation(connection,
+                                
idComponent.get(connection.getSource().getId()),
+                                
idComponent.get(connection.getDestination().getId()),
+                                
BackpressureViolationType.BP_SIZE_THRESHOLD_ABOVE_LIMIT,
+                                
getViolationMessage(BackpressureViolationType.BP_SIZE_THRESHOLD_ABOVE_LIMIT, 
connection.getBackPressureDataSizeThreshold(), 
context.getProperty(SIZE_MAX).getValue())));
+                    }
+                }
+            );
+
+        return results;
+    }
+
+    private GroupAnalysisResult buildViolation(final VersionedConnection 
connection, final VersionedComponent source,
+            final VersionedComponent destination, final 
BackpressureViolationType backpressureViolationType, final String 
violationMessage) {
+        if (!(source instanceof VersionedProcessor) && !(destination 
instanceof VersionedProcessor)) {
+            // connection between two components that are not processors and 
cannot be invalid, setting violation on connection
+            return GroupAnalysisResult.forComponent(connection,
+                    connection.getIdentifier() + "_" + 
backpressureViolationType.getId(),
+                    getLocationMessage(connection, source, destination) + 
violationMessage).build();
+        } else if (source instanceof VersionedProcessor) {
+            // defining violation on source processor
+            return GroupAnalysisResult.forComponent(source,
+                    connection.getIdentifier() + "_" + 
backpressureViolationType.getId(),
+                    getLocationMessage(connection, source, destination) + 
violationMessage).build();
+        } else {
+            // defining violation on destination processor
+            return GroupAnalysisResult.forComponent(destination,
+                    connection.getIdentifier() + "_" + 
backpressureViolationType.getId(),
+                    getLocationMessage(connection, source, destination) + 
violationMessage).build();
+        }
+    }
+
+    private String getLocationMessage(final VersionedConnection connection, 
final VersionedComponent source, final VersionedComponent destination) {
+        if (source == null || destination == null) {
+            return "The connection [" + connection.getIdentifier() + "] is 
violating the rule for backpressure settings. ";
+        }
+        return "The connection [" + connection.getIdentifier() + "] connecting 
" + source.getName() + " [" + source.getIdentifier() + "] to "
+                + destination.getName() + " [" + destination.getIdentifier() + 
"] is violating the rule for backpressure settings. ";
+    }
+
+    private String getViolationMessage(final BackpressureViolationType 
backpressureViolationType, final String configured, final String limit) {
+        switch (backpressureViolationType) {
+            case BP_COUNT_THRESHOLD_ABOVE_LIMIT:
+                return "The connection is configured with a Backpressure Count 
Threshold of " + configured + " and it should be lesser or equal than " + limit 
+ ".";
+            case BP_COUNT_THRESHOLD_BELOW_LIMIT:
+                return "The connection is configured with a Backpressure Count 
Threshold of " + configured + " and it should be greater or equal than " + 
limit + ".";
+            case BP_SIZE_THRESHOLD_ABOVE_LIMIT:
+                return "The connection is configured with a Backpressure Data 
Size Threshold of " + configured + " and it should be lesser or equal than " + 
limit + ".";
+            case BP_SIZE_THRESHOLD_BELOW_LIMIT:
+                return "The connection is configured with a Backpressure Data 
Size Threshold of " + configured + " and it should be greater or equal than " + 
limit + ".";
+            default:
+                return null;
+        }
+    }
+
+    private enum BackpressureViolationType {
+
+        BP_COUNT_THRESHOLD_BELOW_LIMIT("BackpressureCountThresholdTooLow"),
+        BP_COUNT_THRESHOLD_ABOVE_LIMIT("BackpressureCountThresholdTooHigh"),
+        BP_SIZE_THRESHOLD_BELOW_LIMIT("BackpressureSizeThresholdTooLow"),
+        BP_SIZE_THRESHOLD_ABOVE_LIMIT("BackpressureSizeThresholdTooHigh");
+
+        private String id;

Review Comment:
   Recommend making this variable final.



##########
nifi-extension-bundles/nifi-standard-bundle/nifi-standard-rules/src/main/java/org/apache/nifi/flowanalysis/rules/RestrictBackpressureSettings.java:
##########
@@ -0,0 +1,242 @@
+/*
+ * 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.flowanalysis.rules;
+
+import org.apache.nifi.annotation.documentation.CapabilityDescription;
+import org.apache.nifi.annotation.documentation.Tags;
+import org.apache.nifi.components.PropertyDescriptor;
+import org.apache.nifi.components.ValidationContext;
+import org.apache.nifi.components.ValidationResult;
+import org.apache.nifi.flow.VersionedComponent;
+import org.apache.nifi.flow.VersionedConnection;
+import org.apache.nifi.flow.VersionedProcessGroup;
+import org.apache.nifi.flow.VersionedProcessor;
+import org.apache.nifi.flowanalysis.AbstractFlowAnalysisRule;
+import org.apache.nifi.flowanalysis.FlowAnalysisRuleContext;
+import org.apache.nifi.flowanalysis.GroupAnalysisResult;
+import org.apache.nifi.processor.DataUnit;
+import org.apache.nifi.processor.util.StandardValidators;
+
+import java.util.ArrayList;
+import java.util.Collection;
+import java.util.HashSet;
+import java.util.List;
+import java.util.Map;
+import java.util.function.Function;
+import java.util.stream.Collectors;
+import java.util.stream.Stream;
+
+@Tags({"connection", "backpressure"})
+@CapabilityDescription("This rule will generate a violation if backpressure 
settings of a connection exceed configured thresholds. "
+        + "Improper configuration of backpressure settings can lead to 
decreased performances because of excessive swapping as well as "
+        + "to filled up content repository with too much in-flight data in 
NiFi.")

Review Comment:
   Looks like a grammar typo here.  Recommend the second sentence read
   "Improper configuration of backpressure settings can lead to decreased 
performance because of excessive swapping and can fill up the content 
repository with too much in-flight data."



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