Kill using -g instead of -s (#68)

* Kill using -g instead of -s

* Add integration test for kill-process!

* feedback from dpo

* feedback from shams

waiter/integration/waiter/shell_scheduler_integration_test.clj

@@ -0,0 +1,30 @@
+(ns waiter.shell-scheduler-integration-test
+  (:require [clojure.java.shell :as sh]
+            [clojure.string :as str]
+            [clojure.test :refer :all]
+            [waiter.shell-scheduler :refer :all]
+            [waiter.test-helpers :refer :all]
+            [waiter.utils :as utils])
+  (:import (java.nio.file Files
+                          Paths)
+           java.nio.file.attribute.FileAttribute))
+
+(deftest ^:parallel ^:integration-fast test-kill-process
+  (let [working-dir (Files/createTempDirectory nil
+                                               (make-array FileAttribute 0))
+        test-cmd (-> (Paths/get "test-files/test-command.sh" (make-array String 0))
+                     .toAbsolutePath
+                     .toString)
+        port->reservation-atom (atom {})
+        {:keys [shell-scheduler/pid] :as instance} (launch-instance "abc" working-dir test-cmd "http" {} 1
+                                                                    port->reservation-atom [40000 50000])]
+    ; There are 4 processes spawned by the instance:
+    ; 1. The wrapper process launched by the scheduler
+    ; 2. The `test-command.sh` script
+    ; 3/4 sleep commands forked by `test-command.sh`
+    (is (wait-for #(= 4 (count (str/split (:out (sh/sh "pgrep" "-g" (str pid)))
+                                          #"\n")))
+                  :interval 1 :timeout 10))
+    (kill-process! instance port->reservation-atom 100)
+    (is (wait-for #(= "" (:out (sh/sh "pgrep" "-g" (str pid))))
+                  :interval 1 :timeout 10))))

waiter/src/waiter/shell_scheduler.clj

@@ -97,7 +97,7 @@
   (try
     (log/info "killing process:" instance)
     (.destroyForcibly process)
-    (sh/sh "pkill" "-9" "-s" (str pid))
+    (sh/sh "pkill" "-9" "-g" (str pid))
     (release-port! port->reservation-atom port port-grace-period-ms)
     (doseq [port extra-ports]
       (release-port! port->reservation-atom port port-grace-period-ms))

waiter/test-files/test-command.sh

@@ -0,0 +1,3 @@
+sleep 120 &
+sleep 120 &
+wait