Make HostAndPort implement Serializable

[mjtieman]

Currently we use a single Redis instance as the primary data store for each of our Storm topologies and are making the transition to Redis cluster. We want to set a list of HostAndPort objects (one for each cluster nodes) as a property on some of the bolts, which requires them to be HostAndPort to be serializable.

[marcosnils]

@mjtieman HostAndPort should be serializable. Why do you say it is not?

[mjtieman]

HostAndPort currently does not implement Serializable. Perhaps I should rename the issue to change HostAndPort to implement Serializable.

[marcosnils]

@mjtieman why do you need it to explicitly implement serializable?. A class can be serialized even though it does not implement the Serializable marker interface. Storm needs it?. @HeartSaVioR has some experience with Storm so he might provide more information about this.

[mjtieman]

When storm distributes it components it first serializes them, requiring all properties of the class to be either Serializable or declared as transient and later instantiated during the prepare method. Our requirements are such that setting the bolt's HostAndPort before serialization would be easier than after.

[HeartSaVioR]

@marcosnils @mjtieman
https://github.com/apache/storm/blob/master/storm-core/src/jvm/backtype/storm/utils/Utils.java#L83

While Storm uses Kryo to serialize/deserialize Tuples, Storm still uses Java ObjectOutputStream to serialize/deserialize Spout / Bolt class.
And HostAndPort is not serializable in point of ObjectOutputStream's view.

So it makes sense to make HostAndPort Serializable.

[HeartSaVioR]

@marcosnils I also think HostAndPort should be serializable cause it only contains serializable fields, but unfortunately seems like Java doesn't support it.

[marcosnils]

Fixed in #1127