Pushkar,
You are not wrong. Indeed whatever deserialization errors that happens
during the poll() method will cause your code to be interrupted without
much information about which offset failed. A workaround would be trying
to parse the message contained in the exception SerializationException
and try to recover. But this is too pushy.
Taking a more closer look in the stack trace that you shared, it seems
that the real problem might be connectivity with Schema Registry. Hence
why the last mile of your exception says that there is a 'Connection
Refused' in place.
```
Caused by: java.net.ConnectException: Connection refused (Connection
refused)
at java.base/java.net.PlainSocketImpl.socketConnect(Native Method)
at java.base/java.net.AbstractPlainSocketImpl.doConnect(Unknown Source)
at java.base/java.net.AbstractPlainSocketImpl.connectToAddress(Unknown
Source)
at java.base/java.net.AbstractPlainSocketImpl.connect(Unknown Source)
at java.base/java.net.Socket.connect(Unknown Source)
at java.base/sun.net.NetworkClient.doConnect(Unknown Source)
at java.base/sun.net.www.http.HttpClient.openServer(Unknown Source)
at java.base/sun.net.www.http.HttpClient.openServer(Unknown Source)
at java.base/sun.net.www.http.HttpClient.<init>(Unknown Source)
at java.base/sun.net.www.http.HttpClient.New(Unknown Source)
at java.base/sun.net.www.http.HttpClient.New(Unknown Source)
at
java.base/sun.net.www.protocol.http.HttpURLConnection.getNewHttpClient(Unknown
Source)
at
java.base/sun.net.www.protocol.http.HttpURLConnection.plainConnect0(Unknown
Source)
at
java.base/sun.net.www.protocol.http.HttpURLConnection.plainConnect(Unknown
Source)
at java.base/sun.net.www.protocol.http.HttpURLConnection.connect(Unknown
Source)
at
java.base/sun.net.www.protocol.http.HttpURLConnection.getInputStream0(Unknown
Source)
at
java.base/sun.net.www.protocol.http.HttpURLConnection.getInputStream(Unknown
Source)
at java.base/java.net.HttpURLConnection.getResponseCode(Unknown Source)
at
io.confluent.kafka.schemaregistry.client.rest.RestService.sendHttpRequest(RestService.java:208)
*<------------- [5] Here, way after everything it tries to connect to
the service but fails.*
at
io.confluent.kafka.schemaregistry.client.rest.RestService.httpRequest(RestService.java:252)
at
io.confluent.kafka.schemaregistry.client.rest.RestService.getId(RestService.java:482)
at
io.confluent.kafka.schemaregistry.client.rest.RestService.getId(RestService.java:475)
at
io.confluent.kafka.schemaregistry.client.CachedSchemaRegistryClient.getSchemaByIdFromRegistry(CachedSchemaRegistryClient.java:153)
at
io.confluent.kafka.schemaregistry.client.CachedSchemaRegistryClient.getBySubjectAndId(CachedSchemaRegistryClient.java:232)
at
io.confluent.kafka.schemaregistry.client.CachedSchemaRegistryClient.getById(CachedSchemaRegistryClient.java:211)
*<------------- [4] This is the part where the AvroDeserializer tries to
contact Schema Registry to fetch the Schema*
at
io.confluent.kafka.serializers.AbstractKafkaAvroDeserializer.deserialize(AbstractKafkaAvroDeserializer.java:116)
at
io.confluent.kafka.serializers.AbstractKafkaAvroDeserializer.deserialize(AbstractKafkaAvroDeserializer.java:88)
*<------------- [3] So far so good. No major deserialization errors*
at
io.confluent.kafka.serializers.KafkaAvroDeserializer.deserialize(KafkaAvroDeserializer.java:55)
at
org.apache.kafka.common.serialization.Deserializer.deserialize(Deserializer.java:60)
at
org.apache.kafka.clients.consumer.internals.Fetcher.parseRecord(Fetcher.java:1268)
*<------------- [2] Up to this point the record is read*
at
org.apache.kafka.clients.consumer.internals.Fetcher.access$3600(Fetcher.java:124)
at
org.apache.kafka.clients.consumer.internals.Fetcher$PartitionRecords.fetchRecords(Fetcher.java:1492)
at
org.apache.kafka.clients.consumer.internals.Fetcher$PartitionRecords.access$1600(Fetcher.java:1332)
at
org.apache.kafka.clients.consumer.internals.Fetcher.fetchRecords(Fetcher.java:645)
at
org.apache.kafka.clients.consumer.internals.Fetcher.fetchedRecords(Fetcher.java:606)
at
org.apache.kafka.clients.consumer.KafkaConsumer.pollForFetches(KafkaConsumer.java:1294)
at
org.apache.kafka.clients.consumer.KafkaConsumer.poll(KafkaConsumer.java:1225)
at
org.apache.kafka.clients.consumer.KafkaConsumer.poll(KafkaConsumer.java:1201)
*<------------- [1] Things start here*
```
Thanks,
-- Ricardo
On 6/18/20 10:08 AM, Pushkar Deole wrote:
Hi Ricardo,
Probably this is more complicated than that since the exception has
occurred during Consumer.poll itself, so there is no ConsumerRecord
for the application to process and hence the application doesn't know
the offset of record where the poll has failed.
On Thu, Jun 18, 2020 at 7:03 PM Ricardo Ferreira
<rifer...@riferrei.com <mailto:rifer...@riferrei.com>> wrote:
Pushkar,
Kafka uses the concept of offsets to identify the order of each
record within the log. But this concept is more powerful than it
looks like. Committed offsets are also used to keep track of which
records has been successfully read and which ones are not. When
you commit a offset in the consumer; a message is sent to Kafka
that in turn register this commit into a internal topic called
`__committed_offsets`.
Point being: you can elegantly solve this problem by handling
properly the exception in your code but only committing the offset
if the record was deemed fully read -- which means being able to
deserialize the record with no exceptions thrown. In order to do
this, you will need to disable auto commit and manually commit the
offsets either in a per-batch basis or in a per-record basis.
Non-committed offsets will be picked up by the same or another
thread from the consumer group. This is the part where
*Gerbrand's* suggestion might take place. You might want to have
another stream processor specifically handling those outliers and
sending them out to a DLQ topic for manual reprocessing purposes.
Thanks,
-- Ricardo
On 6/18/20 7:45 AM, Pushkar Deole wrote:
Hi Gerbrand,
thanks for the update, however if i dig more into it, the issue is because
of schema registry issue and the schema registry not accessible. So the
error is coming during poll operation itself:
So this is a not a bad event really but the event can't be deserialized
itself due to schema not available. Even if this record is skipped, the
next record will meet the same error.
Exception in thread "Thread-9"
org.apache.kafka.common.errors.SerializationException: Error deserializing
key/value for partition tenant.avro-2 at offset 1. If needed, please seek
past the record to continue consumption.
Caused by: org.apache.kafka.common.errors.SerializationException: Error
deserializing Avro message for id 93
Caused by: java.net.ConnectException: Connection refused (Connection
refused)
at java.base/java.net.PlainSocketImpl.socketConnect(Native Method)
at java.base/java.net.AbstractPlainSocketImpl.doConnect(Unknown Source)
at java.base/java.net.AbstractPlainSocketImpl.connectToAddress(Unknown
Source)
at java.base/java.net.AbstractPlainSocketImpl.connect(Unknown Source)
at java.base/java.net.Socket.connect(Unknown Source)
at java.base/sun.net.NetworkClient.doConnect(Unknown Source)
at java.base/sun.net.www.http.HttpClient.openServer(Unknown Source)
at java.base/sun.net.www.http.HttpClient.openServer(Unknown Source)
at java.base/sun.net.www.http.HttpClient.<init>(Unknown Source)
at java.base/sun.net.www.http.HttpClient.New(Unknown Source)
at java.base/sun.net.www.http.HttpClient.New(Unknown Source)
at
java.base/sun.net.www.protocol.http.HttpURLConnection.getNewHttpClient(Unknown
Source)
at
java.base/sun.net.www.protocol.http.HttpURLConnection.plainConnect0(Unknown
Source)
at
java.base/sun.net.www.protocol.http.HttpURLConnection.plainConnect(Unknown
Source)
at java.base/sun.net.www.protocol.http.HttpURLConnection.connect(Unknown
Source)
at
java.base/sun.net.www.protocol.http.HttpURLConnection.getInputStream0(Unknown
Source)
at
java.base/sun.net.www.protocol.http.HttpURLConnection.getInputStream(Unknown
Source)
at java.base/java.net.HttpURLConnection.getResponseCode(Unknown Source)
at
io.confluent.kafka.schemaregistry.client.rest.RestService.sendHttpRequest(RestService.java:208)
at
io.confluent.kafka.schemaregistry.client.rest.RestService.httpRequest(RestService.java:252)
at
io.confluent.kafka.schemaregistry.client.rest.RestService.getId(RestService.java:482)
at
io.confluent.kafka.schemaregistry.client.rest.RestService.getId(RestService.java:475)
at
io.confluent.kafka.schemaregistry.client.CachedSchemaRegistryClient.getSchemaByIdFromRegistry(CachedSchemaRegistryClient.java:153)
at
io.confluent.kafka.schemaregistry.client.CachedSchemaRegistryClient.getBySubjectAndId(CachedSchemaRegistryClient.java:232)
at
io.confluent.kafka.schemaregistry.client.CachedSchemaRegistryClient.getById(CachedSchemaRegistryClient.java:211)
at
io.confluent.kafka.serializers.AbstractKafkaAvroDeserializer.deserialize(AbstractKafkaAvroDeserializer.java:116)
at
io.confluent.kafka.serializers.AbstractKafkaAvroDeserializer.deserialize(AbstractKafkaAvroDeserializer.java:88)
at
io.confluent.kafka.serializers.KafkaAvroDeserializer.deserialize(KafkaAvroDeserializer.java:55)
at
org.apache.kafka.common.serialization.Deserializer.deserialize(Deserializer.java:60)
at
org.apache.kafka.clients.consumer.internals.Fetcher.parseRecord(Fetcher.java:1268)
at
org.apache.kafka.clients.consumer.internals.Fetcher.access$3600(Fetcher.java:124)
at
org.apache.kafka.clients.consumer.internals.Fetcher$PartitionRecords.fetchRecords(Fetcher.java:1492)
at
org.apache.kafka.clients.consumer.internals.Fetcher$PartitionRecords.access$1600(Fetcher.java:1332)
at
org.apache.kafka.clients.consumer.internals.Fetcher.fetchRecords(Fetcher.java:645)
at
org.apache.kafka.clients.consumer.internals.Fetcher.fetchedRecords(Fetcher.java:606)
at
org.apache.kafka.clients.consumer.KafkaConsumer.pollForFetches(KafkaConsumer.java:1294)
at
org.apache.kafka.clients.consumer.KafkaConsumer.poll(KafkaConsumer.java:1225)
at
org.apache.kafka.clients.consumer.KafkaConsumer.poll(KafkaConsumer.java:1201)
at
com.avaya.analytics.dsi.DsiConsumer.runAdminConsumer(DsiConsumer.java:797)
at java.base/java.lang.Thread.run(Unknown Source)
On Thu, Jun 18, 2020 at 3:17 PM Gerbrand van Dieijen<gerbr...@vandieijen.nl>
<mailto:gerbr...@vandieijen.nl>
wrote:
Hello Pushkar,
I'd split records/events in categories based on the error:
- Events that can be parsed or otherwise handled correctly, e.g. good
events
- Fatal error, like parsing error, empty or incorrect values, etc., e.g.
bad events
- Non-fatal, like database-connection failure, io-failure, out of memory,
and others
that could be retried
Best to avoid doing something blocking while handling the error, so create
a separate stream for each. That way 'good' events don't have to wait for
the handling of 'bad' events.
Any fatal can events you could store in a separate topic, or send to some
monitoring/logging system. As a simple start you could sent the erroneous
events to a separate topic named something like 'errorevents'.
Any non-fatal errors could be retried. Last time I used Akka for that (
https://doc.akka.io/docs/alpakka-kafka/current/errorhandling.html) but
afaik KStreams has mechanism for that as well. You could also store
records that you want to retry into a separate topic 'retry'.
Do not store records that that you want to retry back into the original
topic! If you do that you're have a great risk that overload you're whole
kafka-cluster.
Op 18-06-2020 09:55 heeft Pushkar Deole<pdeole2...@gmail.com>
<mailto:pdeole2...@gmail.com>
geschreven:
Hi All,
This is what I am observing: we have a consumer which polls data from
topic, does the processing, again polls data which keeps happening
continuously.
At one time, there was some bad data on the topic which could not be
consumed by consumer, probably because it couldn't deserialize the
event
due to incompatible avro schema or something similar,
and consumer got error deserializing event. Since the exception wasn't
handled, it crashed the consumer thread which then stopped consuming
data.
The question here is how these kind of scenarios can be handled:
1. Even if I catch the exception and log it, the consumer will i think
process the next event. So the bad event will be lost
2. When consumer goes for another poll, it would commit offsets of
previous
poll which includes bad event, So the event will be lost
How can this scenario be handled in best possible way?
