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https://issues.apache.org/jira/browse/MESOS-3035?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
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Marco Massenzio updated MESOS-3035:
-----------------------------------
Comment: was deleted
(was: When reviewing the code in [r/36425|https://reviews.apache.org/r/36425/]
[~benjaminhindman] noticed that there is a better abstraction that is possible
to introduce for {{os::shell()}} that will simplify the caller's life.
Instead of having to handle all possible outcomes, we propose to refactor
{{os::shell()}} as follows:
{code}
/**
* Returns the output from running the specified command with the shell.
*/
Try<std::string> shell(const string& command)
{
// Actually handle the WIFEXITED, WIFSIGNALED here!
}
{code}
where the returned string is {{stdout}} and, should the program be signaled, or
exit with a non-zero exit code, we will simply return a {{Failure}} with an
error message that will encapsulate both the returned/signaled state, and,
possibly {{stderr}}.
And some test driven development:
{code}
EXPECT_ERROR(os::shell("false"));
EXPECT_SOME(os::shell("true"));
EXPECT_SOME_EQ("hello world", os::shell("echo hello world"));
{code}
Alternatively, the caller can ask to have {{stderr}} conflated with {{stdout}}:
{code}
Try<string> outAndErr = os::shell("myCmd --foo 2>&1");
{code}
However, {{stderr}} will be ignored by default:
{code}
// We don't read standard error by default.
EXPECT_SOME_EQ("", os::shell("echo hello world 1>&2"));
// We don't even read stderr if something fails (to return in Try::error).
Try<string> output = os::shell("echo hello world 1>&2 && false");
EXPECT_ERROR(output);
EXPECT_FALSE(strings::contains(output.error(), "hello world"));
{code}
An analysis of existing usage shows that in almost all cases, the caller only
cares {{if not error}}; in fact, the actual exit code is read only once, and
even then, in a test case.
We believe this will simplify the API to the caller, and will significantly
reduce the length and complexity at the calling sites (<6 LOC against the
current 20+).)
> As a Developer I would like a standard way to run a Subprocess in libprocess
> ----------------------------------------------------------------------------
>
> Key: MESOS-3035
> URL: https://issues.apache.org/jira/browse/MESOS-3035
> Project: Mesos
> Issue Type: Story
> Components: libprocess
> Reporter: Marco Massenzio
> Assignee: Marco Massenzio
>
> As part of MESOS-2830 and MESOS-2902 I have been researching the ability to
> run a {{Subprocess}} and capture the {{stdout / stderr}} along with the exit
> status code.
> {{process::subprocess()}} offers much of the functionality, but in a way that
> still requires a lot of handiwork on the developer's part; we would like to
> further abstract away the ability to just pass a string, an optional set of
> command-line arguments and then collect the output of the command (bonus:
> without blocking).
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