embed avro data in an envelop

[Wai Yip Tung]

I am looking for some avro usage advice. We have created various schema 
for different applications, say to represent, item id, name, metric, 
etc. On the other hand our infrastructure group want to include some 
meta data on all messages. This should include things like timestamp, 
hostname, etc. This meta data is the same for all application messages.

One way to do it is to have a meta data schema that has timestamp, 
hostname and a binary content field for the application data. This way 
each message need to be decoded twice using two schema.

Another way is to somehow have a composite schema that include both the 
meta data and the application specific data. So each message is just 
decoded once and it automatically include the needed meta data. I wonder 
if this can be done and if it is a good idea. Have other people 
considered  similar usage?

Wai Yip