Java Kafka adminClient topic configuration. Configuration values are overwritten

Question

While trying to configure a newly created kafka topic, using java kafka adminClient, values are overwritten.

I have tried to set the same topic configuration using console commands and it works. Unfortunately when I try through Java code some values collide and are overwritten.

ConfigResource resource = new ConfigResource(ConfigResource.Type.TOPIC, topicName);
Map<ConfigResource, Config> updateConfig = new HashMap<>();

// update retention Bytes for this topic
ConfigEntry retentionBytesEntry = new ConfigEntry(TopicConfig.RETENTION_BYTES_CONFIG, String.valueOf(retentionBytes));
updateConfig.put(resource, new Config(Collections.singleton(retentionBytesEntry)));

// update retention ms for this topic
ConfigEntry retentionMsEntry = new ConfigEntry(TopicConfig.RETENTION_MS_CONFIG, String.valueOf(retentionMs));
updateConfig.put(resource, new Config(Collections.singleton(retentionMsEntry)));

// update segment Bytes for this topic
ConfigEntry segmentBytesEntry = new ConfigEntry(TopicConfig.SEGMENT_BYTES_CONFIG, String.valueOf(segmentbytes));
updateConfig.put(resource, new Config(Collections.singleton(segmentBytesEntry)));

// update segment ms for this topic
ConfigEntry segmentMsEntry = new ConfigEntry(TopicConfig.SEGMENT_MS_CONFIG, String.valueOf(segmentMs));
updateConfig.put(resource, new Config(Collections.singleton(segmentMsEntry)));

// Update the configuration
client.alterConfigs(updateConfig);

I expect the topic to have all given configuration values correctly.

Answer 1

Your logic is not working correctly because you call Map.put() several times with the same key. Hence only the last entry is kept.

The correct way to specify multiple topic configurations is to add them in the ConfigEntry object. Only after add the ConfigEntry to the Map .

For example:

// Your Topic Resource
ConfigResource cr = new ConfigResource(Type.TOPIC, "mytopic");

// Create all your configurations
Collection<ConfigEntry> entries = new ArrayList<>();
entries.add(new ConfigEntry(TopicConfig.SEGMENT_BYTES_CONFIG, String.valueOf(segmentbytes)));
entries.add(new ConfigEntry(TopicConfig.RETENTION_BYTES_CONFIG, String.valueOf(retentionBytes)));
...

// Create the Map
Config config = new Config(entries);
Map<ConfigResource, Config> configs = new HashMap<>();
configs.put(cr, config);

// Call alterConfigs()
admin.alterConfigs(configs);