Github user srowen commented on a diff in the pull request:
https://github.com/apache/spark/pull/2623#discussion_r18334033
--- Diff: core/src/main/scala/org/apache/spark/util/Utils.scala ---
@@ -1437,7 +1437,13 @@ private[spark] object Utils extends Logging {
val serviceString = if (serviceName.isEmpty) "" else s" '$serviceName'"
for (offset <- 0 to maxRetries) {
// Do not increment port if startPort is 0, which is treated as a
special port
- val tryPort = if (startPort == 0) startPort else (startPort +
offset) % 65536
+ val _tryPort = if (startPort == 0) startPort else (startPort +
offset) % 65536
--- End diff --
The formulas differ at least whenever `startPort + offset >= 65536`. For
example, try port 65526 and offsets 10, 11, 12 ... We need it to return 1024,
1025, 1026, not 0, 1, 2.
I don't think the question here is whether ports under 1024 should be
usable in Spark. I think they should be, if that's what the caller wants. Yes,
it will fail if the user does not run with root privileges, but that's to be
expected.
(There's an argument here that failing to bind to a specified, privileged
port should just be an error. That is, if I ask for port 80, it's probably not
right to try 81, 82, ... because those can be canonical ports for other types
of service.)
The problem here is requesting a _non-privileged_ port like 65535, but then
finding that Spark starts trying _privileged_ ports. That doesn't seem OK. I
think just adding `- 1024` to your original patch makes it work.
Separately then, is there support for failing if a privileged port is
requested and is not available, rather than trying other ports?
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