Github user JoshRosen commented on the pull request:
https://github.com/apache/spark/pull/2624#issuecomment-57722450
@davies:
> In the past, I remembered that we can have two different SparkEnv in the
same JVM, a different SparkEnv for executor to hold different TrackerClients.
Maybe it's not needed anymore.
`SparkEnv.create` is only called in two places, SparkContext and Executor's
constructors.
In Executor, we only create a new SparkContext if we're not running in
local mode:
```scala
// Initialize Spark environment (using system properties read above)
private val env = {
if (!isLocal) {
val _env = SparkEnv.create(conf, executorId, slaveHostname, 0,
isDriver = false, isLocal = false)
SparkEnv.set(_env)
_env.metricsSystem.registerSource(executorSource)
_env
} else {
SparkEnv.get
}
}
```
Since we only have one `Executor` instance per JVM, we only have one
SparkEnv per JVM (since we don't currently support concurrently-running
SparkContexts in the same JVM).
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