title: Confluent kafka Python client Avro producer.producer() executes without error but no data in topic
body: <p>My producer isnt throwing any errors but data is not being sent to the destination topic. Can you recommend any techniques to debug this situation.</p>
  
  <p>I have call to a Confluent Python Avro Producer inside a synchronous loop to send data to a topic like so:</p>
  
  <pre><code>self.producer.produce(topic=test2, value=msg_dict)
  </code></pre>
  
  <p>After this call I have a piece of code like so to flush the queue:</p>
  
  <pre><code>num_messages_in_queue = self.producer.flush(timeout = 2.0)
  print(f"flushed {num_messages_in_queue} messages from producer queue in iteration {num_iterations} ")
  </code></pre>
  
  <p>this executes without any error. But also there is no callback fired after this code executes. My producer is initiated as follows:</p>
  
  <pre><code> def __init__(self,broker_url=None,topic=None,schema_registry_url=None,schema_path=None):
    try:
      with open(schema_path, 'r') as content_file:
        schema = avro.loads(content_file.read())
    except Exception as e:
      print(f"Error when trying to read avro schema file : {schema_path}")
  
    self.conf = {
      'bootstrap.servers': broker_url,
      'on_delivery': self.delivery_report,
      'schema.registry.url': schema_registry_url,
      'acks': -1, #This guarantees that the record will not be lost as long as at least one in-sync replica remains alive. 
      'enable.idempotence': False, #
      "error_cb":self.error_cb
    }
    self.topic = topic
    self.schema_path = schema_path
    self.producer = AvroProducer(self.conf,default_key_schema=schema, default_value_schema=schema) 
  </code></pre>
  
  <p>My callback method is as follows:</p>
  
  <pre><code>def delivery_report(self, err, msg):
      print(f"began delivery_report")
      if err is None:
          print(f"delivery_report --&gt; Delivered msg.value = {msg.value()} to topic= {msg.topic()} offset = {msg.offset} without err.")
      else:
          print(f"conf_worker AvroProducer failed to deliver message {msg.value()} to topic {self.topic}. got error= {err}") 
  </code></pre>
  
  <p>After this code is executed, I look at my topic on the schema registry container like so:</p>
  
  <pre><code>docker exec schema_registry_container kafka-avro-console-consumer --bootstrap-server kafka:29092 --topic test2 --from-beginning
  </code></pre>
  
  <p>I see this output:</p>
  
  <blockquote>
    <blockquote>
      <p>[2020-04-03 15:48:38,064] INFO Registered kafka:type=kafka.Log4jController MBean 
      (kafka.utils.Log4jControllerRegistration$)
      [2020-04-03 15:48:38,742] 
      INFO ConsumerConfig values: 
            auto.commit.interval.ms = 5000
            auto.offset.reset = earliest
            bootstrap.servers = [kafka:29092]
            check.crcs = true
            client.dns.lookup = default
            client.id = 
            connections.max.idle.ms = 540000
            default.api.timeout.ms = 60000
            enable.auto.commit = false
            exclude.internal.topics = true
            fetch.max.bytes = 52428800
            fetch.max.wait.ms = 500
            fetch.min.bytes = 1
            group.id = console-consumer-49056
            heartbeat.interval.ms = 3000
            interceptor.classes = []
            internal.leave.group.on.close = true
            isolation.level = read_uncommitted
            key.deserializer = class >> org.apache.kafka.common.serialization.ByteArrayDeserializer
             max.partition.fetch.bytes = 1048576
             max.poll.interval.ms = 300000
             max.poll.records = 500
             metadata.max.age.ms = 300000
             metric.reporters = []
             metrics.num.samples = 2
             metrics.recording.level = INFO
             metrics.sample.window.ms = 30000
             partition.assignment.strategy = [class org.apache.kafka.clients.consumer.RangeAssignor]
             receive.buffer.bytes = 65536
             reconnect.backoff.max.ms = 1000
            reconnect.backoff.ms = 50
             request.timeout.ms = 30000
             retry.backoff.ms = 100
             sasl.client.callback.handler.class = null
             sasl.jaas.config = null
             sasl.kerberos.kinit.cmd = /usr/bin/kinit
             sasl.kerberos.min.time.before.relogin = 60000
             sasl.kerberos.service.name = null
             sasl.kerberos.ticket.renew.jitter = 0.05
             sasl.kerberos.ticket.renew.window.factor = 0.8
             sasl.login.callback.handler.class = null
             sasl.login.class = null
             sasl.login.refresh.buffer.seconds = 300
             sasl.login.refresh.min.period.seconds = 60
             sasl.login.refresh.window.factor = 0.8
             sasl.login.refresh.window.jitter = 0.05
             sasl.mechanism = GSSAPI
             security.protocol = PLAINTEXT
             send.buffer.bytes = 131072
             session.timeout.ms = 10000
             ssl.cipher.suites = null
             ssl.enabled.protocols = [TLSv1.2, TLSv1.1, TLSv1]
             ssl.endpoint.identification.algorithm = https
             ssl.key.password = null
             ssl.keymanager.algorithm = SunX509
             ssl.keystore.location = null
             ssl.keystore.password = null
             ssl.keystore.type = JKS
             ssl.protocol = TLS
             ssl.provider = null
             ssl.secure.random.implementation = null
             ssl.trustmanager.algorithm = PKIX
             ssl.truststore.location = null
             ssl.truststore.password = null
             ssl.truststore.type = JKS
             value.deserializer = class >>org.apache.kafka.common.serialization.ByteArrayDeserializer
       (org.apache.kafka.clients.consumer.ConsumerConfig)
      [2020-04-03 15:48:38,887] INFO Kafka version : 2.1.0-cp1 (org.apache.kafka.common.utils.AppInfoParser)
      [2020-04-03 15:48:38,887] INFO Kafka commitId : bda8715f42a1a3db (org.apache.kafka.common.utils.AppInfoParser)
      [2020-04-03 15:48:39,221] INFO Cluster ID: KHKziPBvRKiozobbwvP1Fw (org.apache.kafka.clients.Metadata)
      [2020-04-03 15:48:39,224] INFO [Consumer clientId=consumer-1, groupId=console-consumer-49056] Discovered group coordinator kafka:29092 (id: 2147483646 rack: null) (org.apache.kafka.clients.consumer.internals.AbstractCoordinator)
      [2020-04-03 15:48:39,231] INFO [Consumer clientId=consumer-1, groupId=console-consumer-49056] Revoking previously assigned partitions [] 
      (org.apache.kafka.clients.consumer.internals.ConsumerCoordinator)
      [2020-04-03 15:48:39,231] INFO [Consumer clientId=consumer-1, groupId=console-consumer-49056] (Re-)joining group >(org.apache.kafka.clients.consumer.internals.AbstractCoordinator)
      [2020-04-03 15:48:42,264] INFO [Consumer clientId=consumer-1, groupId=console-consumer-49056] Successfully joined group with generation 1 
      (org.apache.kafka.clients.consumer.internals.AbstractCoordinator)
      [2020-04-03 15:48:42,267] INFO [Consumer clientId=consumer-1, groupId=console-consumer-49056] Setting newly assigned partitions [test2-0] >(org.apache.kafka.clients.consumer.internals.ConsumerCoordinator)
      [2020-04-03 15:48:42,293] INFO [Consumer clientId=consumer-1, groupId=console-consumer-49056] Resetting offset for partition test2-0 to offset 0. >(org.apache.kafka.clients.consumer.internals.Fetcher)</p>
    </blockquote>
  </blockquote>