Github user HyukjinKwon commented on a diff in the pull request:
https://github.com/apache/spark/pull/18320#discussion_r122605188
--- Diff: R/pkg/inst/worker/daemon.R ---
@@ -31,7 +31,15 @@ inputCon <- socketConnection(
port = port, open = "rb", blocking = TRUE, timeout = connectionTimeout)
while (TRUE) {
- ready <- socketSelect(list(inputCon))
+ ready <- socketSelect(list(inputCon), timeout = 1)
--- End diff --
The logic here can be tested as below:
With a terminal (terminal A) running the command as below:
```bash
nc -l 7777
```
with another terminal (terminal B) running the codes below in R shell.
```R
inputCon <- socketConnection(port = "7777", open = "rb", blocking = TRUE)
print(socketSelect(list(inputCon), timeout = 1))
```
This prints `FALSE` as it does not have any data first.
In terminal A, if any character is typed first, this returns `TRUE` in
terminal B with another execution.
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