Apache Spark 1.0 is to be released any day now; currently "release candidate 6 (rc6)" is being evaluated and will be voted upon imminently. But is it ready?
There are currently 16 issues marked as "unresolved blockers" in Jira for Spark, at least one of which is known to produce erroneous data results.
Then there is the state of the REPL, the interactive Spark Shell recently lauded for making Spark accessible to data scientists, as opposed to just hard-core software developers. Because the Spark Shell wraps every user-entered command and class to do its interactive magic, some basic Spark functions fail to operate, such as lookup() and anything requiring equals() on a compound key (i.e. custom Scala class as opposed to just using String or Int for a key) for groupByKey() and other combineByKey() derivatives. It even affects map(), the most fundamental of all functional programming operations.
Even putting the REPL aside and considering just writing full-fledged Scala programs, the native language of Spark, simple combinations such as map() and lookup() throw exceptions.
Don't get me wrong. Spark is a great platform, and is where it should be after two years of open source development. It's the "1.0" badge that I object to. It feels more like a 0.9.2 release.