[GitHub] [knox] pzampino commented on pull request #326: KNOX-2357 - Descriptor handler should not default discovery type to A…

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pzampino commented on pull request #326:
URL: https://github.com/apache/knox/pull/326#issuecomment-620003022


   > My two cents:
   > 
   > * checking the `username` and `passwordAlias` here is not enough because in CM discovery Knox defaults to `cm.discovery.user` and `cm.discovery.password` if they are not defined -> following the new logic, performing the emptyness check here does not mean the user does not want service discovery
   > * checking the `address` here is not enough because in Ambari discovery Knox defaults to the value of `gateway.discovery.default.address` Gateway configuration
   > 
   And in this case, the discovery type must be set in the descriptor to trigger discovery (which it will be because CM is not the default type).
   
   > What if we simply rely on the discovery type. If none is selected -> no discovery will be performed. Discovery type is still optional (that is, the end-user does not need to select one) and makes the code easier to read and understand:
   > 
   My only concern is that existing descriptors that depend on the default type determination may be broken. Perhaps, that is not a significant concern though.
   
   > * `performDiscovery` should only be invoked if discovery type is not `null` [here](https://github.com/apache/knox/blob/v1.4.0/gateway-topology-simple/src/main/java/org/apache/knox/gateway/topology/simple/SimpleDescriptorHandler.java#L109)
   > * the [default discovery type](https://github.com/apache/knox/blob/v1.4.0/gateway-topology-simple/src/main/java/org/apache/knox/gateway/topology/simple/SimpleDescriptorHandler.java#L71) should be removed
   > * we may want to add some `WARN` level messages in the log in case discovery type is not selected but any of the other discovery related configuration is present. This check should be implemented in `SimpleDescriptorImpl` instead of in `SimpleDescriptorHandler` where only the log should be placed.
   > 
   I may be misunderstanding, but I think I disagree about the placement of this logic. The handler is interpreting the descriptor state to make the decision to perform discovery or not; I don't think that is an implementation-specific decision, and I don't think the descriptor should be responsible for discovery logic since it's really just a representation of a config file.
   
   


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