#972: Strategy for generating nodeId and nodePrivateKey

[lucassaldanha]

Fixes #972

[coveralls]

Coverage increased (+0.04%) to 55.956% when pulling e524fdb on lucassaldanha:issue-972 into aa6e7d8 on ethereum:develop.

[zilm13]

@lucassaldanha I'd prefer direct way to set fallback strategy in GenerateNodeIdFromPropsFile and change its name to GetNodeIdFromPropsFile. You will need to pass databaseDir 2 times in SystemProperties on init but it will not look like a hidden magic. Everything else looks great!
@mkalinin what do you think?

[zilm13]

So it will look this way in SystemProperties:

this.generateNodeIdStrategy = new GetNodeIdFromPropsFile(databaseDir()).withFallback(new GenerateNodeIdRandomly(databaseDir()));

[lucassaldanha]

I'd prefer direct way to set fallback strategy in GenerateNodeIdFromPropsFile

@zilm13 Sure! Do you want the fallback to be optional? e.g. If one doesn't specify the fallback, what should happen? Thrown an error?

[zilm13]

@lucassaldanha yeah I think exception is better than null, so we see that something is wrong immediately if we have bad initialization.

[lucassaldanha]

@zilm13 I've updated the PR. Let me know what you think. :)

[zilm13]

@lucassaldanha Looks good, thanks