GH-558: Serialization/deserialization of WorkflowInstance
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Key: OOZIE-346
URL: https://issues.apache.org/jira/browse/OOZIE-346
Project: Oozie
Issue Type: Bug
Reporter: Hadoop QA
Oozie team at yahoo has recently experienced multiple production issues when a
new oozie version is upgraded attributed to the modifications of Workflow
tables' structure.
More specifically, we added a new field into workflow table. Hence, for
example, if a user submits a WF job in earlier oozie version and if the job is
still active after the upgrade, oozie fails to de-serialize the WFInstance
object. In other words, the object was originally serialized using the old
structure whereas oozie tries to deserailize using the new structures after the
upgrade. Therefore it throws exception.
Some observations that came up from our internal discussion:
1. Is it required to store the blob into table? Can't we create the the object
from the other fields of the table? I know it might not be that straight
forward. However, other options might be worse than this.
2. If we want to keep the blob, the new field(s) should be added at the end
during serialization. However if some fields are removed, how could we handle
that? Might not be a flexible idea.
3. During serialization, we could use some type of version at the beginning,
that would help to de-serailize the object. This might make the coding very
ugly depending on how many old versions we would like to support.
4. Since it is a very well-known problem, there should be some standard
procedure. However they might not be easy too.
Anyway these are just the initial thoughts. We didn't come up in any conclusion
yet.
Please feel free to make comment?
Thanks,
Mohammad
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