Hi Enrico, Why can't you create multiple independent Consumers ? > They will share the same resources (memory pools, thread pools)
You can do that but it means the user has to manage the consumption from each of the consumer instances manually. This is already solved in the existing multi topic consumer. This change adds user convenience - to continue consuming from multiple topics in a single consumer instance, but allowing them to customise the configuration. - Dave On Fri, Jul 8, 2022 at 4:26 PM Enrico Olivelli <eolive...@gmail.com> wrote: > Dave, > Why can't you create multiple independent Consumers ? > They will share the same resources (memory pools, thread pools) > > > > > Enrico > > Il giorno ven 8 lug 2022 alle ore 15:00 Dave Maughan > <dave.maug...@streamnative.io.invalid> ha scritto: > > > > Hi Pulsar community, > > > > I've opened a PIP to discuss a new Java client option to allow setting > > topic specific consumer priorityLevel. > > > > Proposal Link: https://github.com/apache/pulsar/issues/16481 > > > > --- > > > > ## Motivation > > > > The Pulsar Java consumer supports setting a priority level for priority > > message > > dispatch in shared subscription consumers and priority assignment in > > failover > > subscription consumers. See the [ConsumerBuilder.html#priorityLevel(int) > > Javadoc]( > > > https://javadoc.io/static/org.apache.pulsar/pulsar-client-api/2.10.1/org/apache/pulsar/client/api/ConsumerBuilder.html#priorityLevel(int) > > ) > > for a detailed functional description. The Pulsar Java consumer also > > supports > > consuming from multiple topics. However, it is not possible to set a > > different > > priority level for different topics in the same Consumer instance. > > > > This behaviour is desirable in some use cases. For example, a consumer > > processing region specific topics might wish to configure region > stickiness > > - A > > multi-region application might be consuming from topics events-us-east-1 > and > > events-eu-west-1. Consumers in all regions should be configured to > consume > > all > > topics to ensure data completeness. However, to ensure low latency, the > > us-east-1 consumer would need to set a higher priority level for the > > us-east-1 > > topic. Similarly, the eu-west-1 consumer would need to set a higher > priority > > level for the eu-west-1 topic. > > > > ## Goal > > > > Update the Java client API to allow the configuration of different > priority > > levels for different topics. > > > > Do so in such a way that supports the addition of other topic specific > > configuration options or overrides in the future. > > > > Issues will be created to track feature parity in the other client > > implementations for this PIP. > > > > ## API Changes > > > > In pulsar-client-api, update `ConsumerBuilder` to include two new > methods: > > > > ```java > > public interface ConsumerBuilder<T> extends Cloneable { > > ... > > > > TopicConsumerBuilder<T> topicConfiguration(String > topicNameOrPattern); > > > > ConsumerBuilder<T> topicConfiguration(String topicNameOrPattern, > > java.util.function.Consumer<TopicConsumerBuilder<T>> > > builderConsumer); > > } > > ``` > > > > Create a new interface: > > > > ```java > > public interface TopicConsumerBuilder<T> { > > TopicConsumerBuilder<T> priorityLevel(int priorityLevel); > > > > ConsumerBuilder<T> build(); > > } > > ``` > > > > In pulsar-client-original, update `ConsumerConfigurationData` to include > a > > new field: > > > > ```java > > @Data > > public class ConsumerConfigurationData<T> implements Serializable, > > Cloneable { > > ... > > > > private List<TopicConsumerConfigurationData> topicConfigurations = > new > > ArrayList<>(); > > } > > ``` > > > > Create a topic configuration class: > > > > ```java > > @Data > > public class TopicConsumerConfigurationData implements Serializable { > > private static final long serialVersionUID = 1L; > > > > private String topicNameOrPattern; > > private int priorityLevel; > > > > public boolean matchesTopicName(String topicName) { > > return > > Pattern.compile(topicNameOrPattern).matcher(topicName).matches(); > > } > > > > public static TopicConsumerConfigurationData of(String > > topicNameOrPattern, > > ConsumerConfigurationData<?> conf) { > > return new TopicConsumerConfigurationData(topicNameOrPattern, > > conf.getPriorityLevel()); > > } > > } > > ``` > > > > Then, in `ConsumerImpl` the appropriate topic configuration can be > selected > > based on the topic being subscribed to. Since the topic configuration is > > effectively keyed by a topic name or pattern, it’s possible for the user > to > > be > > able configure multiple topic configurations that match the same concrete > > topic > > name. In this case the first topic name match should be selected. > > > > ```java > > TopicConsumerConfigurationData getMatchingTopicConfiguration(String > > topicName, > > ConsumerConfigurationData conf) { > > return topicConfigurations.stream() > > .filter(topicConf -> topicConf.matchesTopicName(topicName)) > > .findFirst() > > .orElseGet(() -> TopicConsumerConfigurationData.of(topicName, > > conf)); > > } > > ``` > > > > Example Usage: > > > > ```java > > pulsarClient.newConsumer() > > .topicsPattern("events.*") > > .priorityLevel(1) > > .topicConfiguration(".*us-east-1", b -> b.priorityLevel(0)) > > .subscribe(); > > ``` > > > > or > > > > ```java > > pulsarClient.newConsumer() > > .topicsPattern("events.*") > > .priorityLevel(1) > > .topicConfiguration(".*us-east-1") > > .priorityLevel(0) > > .build() > > .subscribe(); > > ``` > > > > ## Rejected Alternatives > > > > * Extend the existing `ConsumerBuilder` rather than introducing a nested, > > topic specific builder class. > > > > Rejection reason: Does not provide a clear API to discover and extend > other > > topic specific configuration options and overrides. > > > > ```java > > public interface ConsumerBuilder<T> extends Cloneable { > > ... > > > > ConsumerBuilder<T> topicPriorityLevel(String topicNameOrPattern, int > > priorityLevel); > > } > > ``` > > > > Example usage: > > > > ```java > > pulsarClient.newConsumer() > > .topicsPattern("events.*") > > .priorityLevel(1) > > .topicPriorityLevel(".*us-east-1", 0) > > .subscribe(); > > ``` > > > > * Provide a configurator interface to configure options and overrides at > > runtime > > > > Rejection reason: Not compatible with `ConsumerBuilder.loadConf`. > > > > ```java > > @Data > > class TopicConsumerConfigurationData { > > private int priorityLevel; > > } > > ``` > > > > ```java > > interface TopicConsumerConfigurator extends Serializable { > > void configure(String topicName, TopicConsumerConfigurationData > > topicConf); > > } > > ``` > > > > ```java > > public interface ConsumerBuilder<T> extends Cloneable { > > ... > > > > ConsumerBuilder<T> topicConfigurator(TopicConsumerConfigurator > > configurator); > > } > > ``` > > > > Example usage: > > > > ```java > > pulsarClient.newConsumer() > > .topicsPattern("events.*") > > .priorityLevel(1) > > .topicConfigurator((topicName, topicConf) -> { > > if (topicName.endsWith("us-east-1") { > > topicConf.setPriorityLevel(0); > > } > > }) > > .subscribe(); > > ``` >
