Tracked that error down .. now getting this one:


08 Jan 2017 05:00:21,789 ERROR [pool-8-thread-1] (org.apache.flume.source.SpoolDirectorySource$SpoolDirectoryRunnable.run:256)  - FATAL: Spool Directory source persistence-dev-source: { spoolDir: /home/flume/ready }: Uncaught exception in SpoolDirectorySource thread. Restart or reconfigure Flume to continue processing.
org.apache.flume.FlumeException: Unable to instantiate Builder from org.apache.flume.serialization.FlumeEventAvroEventDeserializer: does not appear to implement org.apache.flume.serialization.EventDeserializer$Builder
        at org.apache.flume.serialization.EventDeserializerFactory.getInstance(EventDeserializerFactory.java:65)
        at org.apache.flume.client.avro.ReliableSpoolingFileEventReader.openFile(ReliableSpoolingFileEventReader.java:520)
        at org.apache.flume.client.avro.ReliableSpoolingFileEventReader.getNextFile(ReliableSpoolingFileEventReader.java:484)
        at org.apache.flume.client.avro.ReliableSpoolingFileEventReader.readEvents(ReliableSpoolingFileEventReader.java:243)
        at org.apache.flume.source.SpoolDirectorySource$SpoolDirectoryRunnable.run(SpoolDirectorySource.java:228)



Thoughts ?


Jim


From: Jim Langston <jlangston@resolutebi.com>
Sent: Saturday, January 7, 2017 11:14:02 PM
To: user@flume.apache.org
Subject: Re: Avro configuration
 

Hi Laxman - gave it a shot, but I'm getting this exception:


org.apache.flume.FlumeException: Unable to instantiate Builder from org.apache.flume.serialization.FlumeEventAvroEventDeserializer: does not appear to implement org.apache.flume.serialization.EventDeserializer$Builder
        at org.apache.flume.serialization.EventDeserializerFactory.getInstance(EventDeserializerFactory.java:65)

Jim


From: Laxman Ch <laxman.lux@gmail.com>
Sent: Thursday, January 5, 2017 4:49:31 PM
To: user@flume.apache.org
Subject: Re: Avro configuration
 
I noticed in the Jira that you pointed me at that there has been some activity on the deserializer - will that do what I'm looking for now ? without writing one ? 

Yes Jim. I think patch in that jira will be helpful for you. Please give a try.

On 6 January 2017 at 00:45, Jim Langston <jlangston@resolutebi.com> wrote:

Hi Laxman - I noticed in the Jira that you pointed me at that there has been some activity on the deserializer - will that do what I'm looking for now ? without writing one ? If so, can I get ahold of it to implement ? I'm on apache-flume-1.6.0-bin



I have tried to use this: agent.sinks.persistence-sink.sink.serializer = com.adaltas.flume.serialization.HeaderAndBodyTextEventSerializer$Builder


and it does put the files out to disk with the header and the body , tried with spooldir , but nothing on the other end. So, I take it that I'm not paired

correctly. 



Thanks,


Jim


From: Jim Langston <jlangston@resolutebi.com>
Sent: Tuesday, January 3, 2017 1:59:15 PM

To: user@flume.apache.org
Subject: Re: Avro configuration
 

Hi - yes - got the gist from your initial response, went off on the track to find examples of writing and deploying a serializer before starting to do so when I realized what file_roll was really doing, that's why I got confused on your next response. I still haven't found anything that gives guidance on doing so. 


What I want to do is relatively simple (or so I thought), that is, a production stream is providing the initial avro data, the data needs to be used in a staging and a development environment, the problem is if staging is down or development is down, it affects the production flumes. I want to stop that, I was going to do so by saving the data to disk (it is not important to be real time), and scoop it out and move it on. file_roll loses the data integrity by wrapping it, and spooldir picks up the arvo headers of the wrapping , not of the original source.


I will look into writing a serializer that file_roll can use that will place the events to disk without wrapping the event.


Jim


From: Laxman Ch <laxman.lux@gmail.com>
Sent: Friday, December 30, 2016 11:19:35 PM
To: user@flume.apache.org
Subject: Re: Avro configuration
 
Apologies for any confusion Jim.

You need to make serializer and deserializer in sync. That's the gist of my first response.

hdfs.AvroEventSerializer is expecting some headers. We may need to pass some headers in the event at source.
Can you please post your sample code & config for end-to-end flow in git?

On 31 December 2016 at 04:51, Jim Langston <jlangston@resolutebi.com> wrote:

Ok - after messing with this for quite awhile, I am getting this error


FlumeException: Could not find schema for event


I added a schema and placed in in hdfs


agent.sinks.persistence-sink.type = file_roll
agent.sinks.persistence-sink.sink.directory = /home/flume/persistence
agent.sinks.persistence-sink.sink.serializer = org.apache.flume.sink.hdfs.AvroEventSerializer$Builder
agent.sinks.persistence-sink.sink.serializer.schemaURL = hdfs://namenode/persistence/persistence.avsc
# Holders , can be used for tuning, defaults are the values
agent.sinks.persistence-sink.batchSize = 1000
agent.sinks.persistence-sink.sink.rollInterval = 300


Looking at the configurations syntax for file_roll , can it traverse  serializer.schemaURL ? I see where
HDFS has serializer and serializer.* , but file_roll does not

Also, looking at the source code, it looks like the only way this error message can be generated
is is the schemaURL is null 

private void initialize(Event event) throws IOException {
Schema schema = null;
String schemaUrl = event.getHeaders().get(AVRO_SCHEMA_URL_HEADER);
if (schemaUrl != null) {
schema = schemaCache.get(schemaUrl);
if (schema == null) {
schema = loadFromUrl(schemaUrl);
schemaCache.put(schemaUrl, schema);
}
}
if (schema == null) {
String schemaString = event.getHeaders().get(AVRO_SCHEMA_LITERAL_HEADER);
if (schemaString == null) {
throw new FlumeException("Could not find schema for event " + event);
}
schema = new Schema.Parser().parse(schemaString);
}




From: Jim Langston <jlangston@resolutebi.com>
Sent: Friday, December 30, 2016 8:34:42 AM

To: user@flume.apache.org
Subject: Re: Avro configuration
 

thanks - I was following your initial response


- Use a custom AvroEventSerializer to directly serialize the avro event and use it with file_roll sink.
Reference implementation is available in hdfs sink (org.apache.flume.sink.hdfs.AvroEventSerializer)
You may strip of hdfs dependencies from it achieve what you want.

This seems to indicate that I need to do a custom serializer following the constructs of the hdfs sink, what
I couldn't find were some good examples of creating custom serializers and then deploying them. I was tempted to
post to the developers group, but chose to just keep the context within this thread ..

Your new response has me confused, this seems to indicate that all I need to do is use the hdfs serializer


Jim


From: Laxman Ch <laxman.lux@gmail.com>
Sent: Thursday, December 29, 2016 3:22:04 PM
To: user@flume.apache.org
Subject: Re: Avro configuration
 
Directly configure this serializer to file_roll sink in your configuration.
>> agent.sinks.persistence-sink.sink.serializer = org.apache.flume.sink.hdfs.AvroEventSerializer

Please go through the documentation before you proceed.


On 29 December 2016 at 23:29, Jim Langston <jlangston@resolutebi.com> wrote:

Thanks - I have pulled the flume source, are there any good step-by-step examples of creating a custom Serializer and deploying it for flume to use ? 


Jim


From: Laxman Ch <laxman.lux@gmail.com>
Sent: Wednesday, December 28, 2016 12:05:08 AM
To: user@flume.apache.org
Subject: Re: Avro configuration
 
Jim,

In one-liner, FlumeEventAvroEventSerializer and AvroEventDeserializer are not in sync and they can't be used as a serde pair.

Flume's built-in avro serializer FlumeEventAvroEventSerializer which serializes Flume events with shell. It's important to note that, here actual raw event is wrapped inside the flume shell object and this raw object is treated as binary (which can be thrift, avro, or just a byte array, etc). 
Flume's built-in avro deserializer AvroEventDeserializer which deserializes any generic event serialized and it wraps the deserialized event into another flume shell object.

This means as per your configuration, spool directory source (persistence-dev-source) will get an double wrapped flume event (FlumeEvent -> FlumeEvent -> raw event body)

To solve this problem, we need to have serializer and deserializer to be in sync. We can achieve it in either of the following approaches.
- Use a custom FluemEventAvroEventDeserializer to extract directly FlumeEvent without double wrapper and use it with spool directory source.

Similar attempt has already been made by Sebastian here.

I personally recommend to write a FlumeEventAvroEventDeserializethan to modify the existing one.

- Use a custom AvroEventSerializer to directly serialize the avro event and use it with file_roll sink.
Reference implementation is available in hdfs sink (org.apache.flume.sink.hdfs.AvroEventSerializer)
You may strip of hdfs dependencies from it achieve what you want.


On 28 December 2016 at 01:17, Jim Langston <jlangston@resolutebi.com> wrote:

Hi all,


I'm looking for some guidance , I have been trying to get a flow working that involves the following:


Source Avro --> mem channel --> file_roll 


File Roll config


agent.sinks.persistence-sink.type = file_roll
agent.sinks.persistence-sink.sink.directory = /home/flume/persistence
agent.sinks.persistence-sink.sink.serializer = avro_event
agent.sinks.persistence-sink.batchSize = 1000
agent.sinks.persistence-sink.sink.rollInterval = 300


Once the data is on local disk, I want to flume the data to another flume server

Source spooldir --> mem channel -- Avro Sink (to another flume server)

agent.sources.persistence-dev-source.type = spooldir
agent.sources.persistence-dev-source.spoolDir = /home/flume/ready
agent.sources.persistence-dev-source.deserializer = avro
agent.sources.persistence-dev-source.deserializer.schemaType = LITERAL
agent.sources.persistence-dev-source.batchSize = 1000



The problem is that file_roll will put the incoming Avro data into a Avro container before storing the data on the local file system. Then when the data is picked up by the spooldir source , and sent to the flume server, it will have the file_roll headers when being read by the interceptor.

Is there a recommended way to save the Avro data coming in, that will maintain its integrity when sending on to another flume server, which is waiting on Avro data to multiplex and send to its channels.

I have tried many different variations, with the result of the above configurations getting the Avro to the other server with the Avro data that was received, but the problem is that the applications will see the container headers from the file_roll , and not the headers from the records from the initial Avro data.


Thanks,

Jim

schema that gets set by file_roll on its writes to disk:

{
  "type" : "record",
  "name" : "Event",
  "fields" : [ {
    "name" : "headers",
    "type" : {
      "type" : "map",
      "values" : "string"
    }
  }, {
    "name" : "body",
    "type" : "bytes"
  } ]
}








--
Thanks,
Laxman



--
Thanks,
Laxman



--
Thanks,
Laxman



--
Thanks,
Laxman