From fc92d25f2a27e81ef2d5031dcf856af1cc1d8c31 Mon Sep 17 00:00:00 2001
From: Felix Cheung <felixcheung@apache.org>
Date: Wed, 28 Jun 2017 20:06:29 -0700
Subject: [PATCH] Revert "[SPARK-21094][R] Terminate R's worker processes in
the parent of R's daemon to prevent a leak"
This reverts commit 6b3d02285ee0debc73cbcab01b10398a498fbeb8.
---
R/pkg/inst/worker/daemon.R | 59 +++-----------------------------------
1 file changed, 4 insertions(+), 55 deletions(-)
diff --git a/R/pkg/inst/worker/daemon.R b/R/pkg/inst/worker/daemon.R
index 6e385b2a27..3a318b71ea 100644
--- a/R/pkg/inst/worker/daemon.R
+++ b/R/pkg/inst/worker/daemon.R
@@ -30,55 +30,8 @@ port <- as.integer(Sys.getenv("SPARKR_WORKER_PORT"))
inputCon <- socketConnection(
port = port, open = "rb", blocking = TRUE, timeout = connectionTimeout)
-# Waits indefinitely for a socket connecion by default.
-selectTimeout <- NULL
-
-# Exit code that children send to the parent to indicate they exited.
-exitCode <- 1
-
while (TRUE) {
- ready <- socketSelect(list(inputCon), timeout = selectTimeout)
-
- # Note that the children should be terminated in the parent. If each child terminates
- # itself, it appears that the resource is not released properly, that causes an unexpected
- # termination of this daemon due to, for example, running out of file descriptors
- # (see SPARK-21093). Therefore, the current implementation tries to retrieve children
- # that are exited (but not terminated) and then sends a kill signal to terminate them properly
- # in the parent.
- #
- # There are two paths that it attempts to send a signal to terminate the children in the parent.
- #
- # 1. Every second if any socket connection is not available and if there are child workers
- # running.
- # 2. Right after a socket connection is available.
- #
- # In other words, the parent attempts to send the signal to the children every second if
- # any worker is running or right before launching other worker children from the following
- # new socket connection.
-
- # Only the process IDs of children sent data to the parent are returned below. The children
- # send a custom exit code to the parent after being exited and the parent tries
- # to terminate them only if they sent the exit code.
- children <- parallel:::selectChildren(timeout = 0)
-
- if (is.integer(children)) {
- lapply(children, function(child) {
- # This data should be raw bytes if any data was sent from this child.
- # Otherwise, this returns the PID.
- data <- parallel:::readChild(child)
- if (is.raw(data)) {
- # This checks if the data from this child is the exit code that indicates an exited child.
- if (unserialize(data) == exitCode) {
- # If so, we terminate this child.
- tools::pskill(child, tools::SIGUSR1)
- }
- }
- })
- } else if (is.null(children)) {
- # If it is NULL, there are no children. Waits indefinitely for a socket connecion.
- selectTimeout <- NULL
- }
-
+ ready <- socketSelect(list(inputCon))
if (ready) {
port <- SparkR:::readInt(inputCon)
# There is a small chance that it could be interrupted by signal, retry one time
@@ -91,16 +44,12 @@ while (TRUE) {
}
p <- parallel:::mcfork()
if (inherits(p, "masterProcess")) {
- # Reach here because this is a child process.
close(inputCon)
Sys.setenv(SPARKR_WORKER_PORT = port)
try(source(script))
- # Note that this mcexit does not fully terminate this child. So, this writes back
- # a custom exit code so that the parent can read and terminate this child.
- parallel:::mcexit(0L, send = exitCode)
- } else {
- # Forking succeeded and we need to check if they finished their jobs every second.
- selectTimeout <- 1
+ # Set SIGUSR1 so that child can exit
+ tools::pskill(Sys.getpid(), tools::SIGUSR1)
+ parallel:::mcexit(0L)
}
}
}
--
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