Catch the exception of no database connection

[senwu]

There is no exception catch for database connection error, and the program runs forever...

[rionda]

This happens often more generally, i.e., that an exception is thrown but DD keeps running without really doing anything. What shall we do about it?

[rionda]

@zifeishan : does your most recent pull request fix this?

[zifeishan]

It fixes non-termination errors in case of:

• parsing config file
• invalid inference rule

I am not sure where this no-database-connection error may occur. In fact, I realized that this fix does not guarantee fixing all non-termination errors, since we has multiple Akka actors (InferenceManager, ExtractionManager, etc), and simply catching errors in DeepDive class may not handle all cases. But it do fix a portion of them.

[rionda]

I guess it may occur at any point where the JDBC connection is opened? Or if the database "disappears" from the network or something? @senwu can you give us more info, please?