KAFKA-8746: Kibosh must handle an empty JSON string from Trogdor (#7155)

When Trogdor wants to clear all the faults injected to Kibosh, it sends the empty JSON object {}. However, Kibosh expects {"faults":[]} instead.  Kibosh should handle the empty JSON object, since that's consistent with how Trogdor handles empty JSON fields in general (if they're empty, they can be omitted). We should also have a test for this.

Reviewers: David Arthur <mumrah@gmail.com>, Stanislav Kozlovski <stanislav_kozlovski@outlook.com>

tests/docker/Dockerfile

@@ -71,8 +71,8 @@ RUN curl -s "$KAFKA_MIRROR/kafka-streams-2.2.1-test.jar" -o /opt/kafka-2.2.1/lib
 RUN curl -s "$KAFKA_MIRROR/kafka-streams-2.3.0-test.jar" -o /opt/kafka-2.3.0/libs/kafka-streams-2.3.0-test.jar
 
 # The version of Kibosh to use for testing.
-# If you update this, also update vagrant/base.sy
-ARG KIBOSH_VERSION="d85ac3ec44be0700efe605c16289fd901cfdaa13"
+# If you update this, also update vagrant/base.sh
+ARG KIBOSH_VERSION="8841dd392e6fbf02986e2fb1f1ebf04df344b65a"
 
 # Install Kibosh
 RUN apt-get install fuse

tests/kafkatest/services/trogdor/kibosh.py

@@ -133,9 +133,12 @@ class KiboshService(Service):
         :param node:        The node.
         :param spec:        An array of FaultSpec objects describing the faults.
         """
-        fault_array = [spec.kibosh_message for spec in specs]
-        obj = { 'faults': fault_array }
-        obj_json = json.dumps(obj)
+        if len(specs) == 0:
+            obj_json = "{}"
+        else:
+            fault_array = [spec.kibosh_message for spec in specs]
+            obj = { 'faults': fault_array }
+            obj_json = json.dumps(obj)
         node.account.create_file(self.control_path, obj_json)
 
     def get_fault_json(self, node):

tests/kafkatest/tests/tools/kibosh_test.py

@@ -70,12 +70,16 @@ class KiboshTest(Test):
                 [self.nodes[0].name], KiboshTest.TARGET, "/foo", 12)
         node = self.nodes[0]
 
-        def check(self, node):
+        def check(self, node, expected_json):
             fault_json = self.kibosh.get_fault_json(node)
-            expected_json = json.dumps({"faults": [spec.kibosh_message]})
             self.logger.info("Read back: [%s].  Expected: [%s]." % (fault_json, expected_json))
             return fault_json == expected_json
 
+        wait_until(lambda: check(self, node, '{"faults":[]}'),
+                   timeout_sec=10, backoff_sec=.2, err_msg="Failed to read back initial empty fault array.")
         self.kibosh.set_faults(node, [spec])
-        wait_until(lambda: check(self, node),
+        wait_until(lambda: check(self, node, json.dumps({"faults": [spec.kibosh_message]})),
                    timeout_sec=10, backoff_sec=.2, err_msg="Failed to read back fault array.")
+        self.kibosh.set_faults(node, [])
+        wait_until(lambda: check(self, node, "{}"),
+                   timeout_sec=10, backoff_sec=.2, err_msg="Failed to read back final empty fault array.")

vagrant/base.sh

@@ -18,7 +18,7 @@ set -ex
 
 # The version of Kibosh to use for testing.
 # If you update this, also update tests/docker/Dockerfile
-export KIBOSH_VERSION=d85ac3ec44be0700efe605c16289fd901cfdaa13
+export KIBOSH_VERSION=8841dd392e6fbf02986e2fb1f1ebf04df344b65a
 
 path_to_jdk_cache() {
   jdk_version=$1