// this method shows an example of how EventData.Body can be deserialized into multiple records.
protected override IEnumerable <EventHubRecord> DeserializeEventData(EventDataFromCapture eventData)
{
// assumes EventData.Body is a gzipped line separated records.
using (var stream = new MemoryStream(eventData.Body))
{
try
{
// deserialize body from a single eventdata completely. Skip eventData message body with invalid format.
using (var unzippedStream = new GZipStream(stream, CompressionMode.Decompress))
{
return(this.contentDeserializer
.Deserialize(unzippedStream)
.Select(
payload => new EventHubRecord()
{
Offset = eventData.Offset,
Payload = payload
})
.ToArray());
}
}
catch (Exception e)
{
var shortErrorMessage = $"Error deserializing eventhub message with offset: {eventData.Offset} SequenceNumber:{eventData.SequenceNumber}";
this.diagnostics.WriteError(
shortErrorMessage,
$"{shortErrorMessage} Exception: {e}");
return(Enumerable.Empty <EventHubRecord>());
}
}
}
public override IEnumerable <T> Deserialize(Stream stream)
{
IFileReader <GenericRecord> reader = null;
try
{
reader = DataFileReader <GenericRecord> .OpenReader(stream);
}
catch (Exception e)
{
this.diagnostics.WriteError(
briefMessage: "Unable to open stream as avro. Please check if the stream is from eventhub capture. https://docs.microsoft.com/en-us/azure/event-hubs/event-hubs-capture-overview ",
detailedMessage: e.Message);
throw;
}
foreach (GenericRecord genericRecord in reader.NextEntries)
{
EventDataFromCapture eventData = this.ConvertToEventDataFromCapture(genericRecord);
// deserialize records from eventdata body.
foreach (T record in this.DeserializeEventData(eventData))
{
yield return(record);
}
}
reader.Dispose();
}
private EventDataFromCapture ConvertToEventDataFromCapture(GenericRecord genericRecord)
{
try
{
var eventData = new EventDataFromCapture()
{
EnqueuedTimeUtc = (string)genericRecord["EnqueuedTimeUtc"],
Offset = (string)genericRecord["Offset"],
SequenceNumber = (long)genericRecord["SequenceNumber"],
Body = (byte[])genericRecord["Body"],
};
return(eventData);
}
catch (Exception e)
{
this.diagnostics.WriteError(
briefMessage: $"Unable to get fields required to create captured event data. Error: {e.Message}",
detailedMessage: e.ToString());
throw;
}
}
protected abstract IEnumerable <T> DeserializeEventData(EventDataFromCapture eventData);
