add workaround for a multi thread issue of ruamel.yaml (ansible#200)

* use safe ruamel.yaml instance

Signed-off-by: hirokuni-kitahara <[email protected]>

* add retrying to yaml.dump

Signed-off-by: hirokuni-kitahara <[email protected]>

---------

Signed-off-by: hirokuni-kitahara <[email protected]>

ansible_risk_insight/yaml.py

@@ -17,14 +17,15 @@
 import io
 from contextvars import ContextVar
 from ruamel.yaml import YAML
+from ruamel.yaml.emitter import EmitterError
 
 
 _yaml: ContextVar[YAML] = ContextVar("yaml")
 
 
-def _set_yaml():
-    if not _yaml.get(None):
-        yaml = YAML(typ="rt", pure=True)
+def _set_yaml(force=False):
+    if not _yaml.get(None) or force:
+        yaml = YAML(typ="safe", pure=True)
         yaml.default_flow_style = False
         yaml.preserve_quotes = True
         yaml.allow_duplicate_keys = True
@@ -53,9 +54,30 @@ def load(stream: any):
     return yaml.load(stream)
 
 
+# `ruamel.yaml` has a bug around multi-threading, and its YAML() instance could be broken
+# while concurrent dump() operation. So we try retrying if the specific error occurs.
+# Bug details: https://sourceforge.net/p/ruamel-yaml/tickets/367/
 def dump(data: any):
     _set_yaml()
-    yaml = _yaml.get()
-    output = io.StringIO()
-    yaml.dump(data, output)
-    return output.getvalue()
+    retry = 2
+    err = None
+    result = None
+    for i in range(retry):
+        try:
+            yaml = _yaml.get()
+            output = io.StringIO()
+            yaml.dump(data, output)
+            result = output.getvalue()
+        except EmitterError as exc:
+            err = exc
+        except Exception:
+            raise
+        if err:
+            if i < retry - 1:
+                _set_yaml(force=True)
+                err = None
+            else:
+                raise err
+        else:
+            break
+    return result