fix: failsafe for non-valid json and failed LLM calls

haystack/components/evaluators/context_relevance.py

@@ -70,6 +70,7 @@ def __init__(
         progress_bar: bool = True,
         api: str = "openai",
         api_key: Secret = Secret.from_env_var("OPENAI_API_KEY"),
+        raise_on_failure: bool = True,
     ):
         """
         Creates an instance of ContextRelevanceEvaluator.
@@ -97,6 +98,9 @@ def __init__(
             Supported APIs: "openai".
         :param api_key:
             The API key.
+        :param raise_on_failure:
+            Whether to raise an exception if the API call fails.
+
         """
         self.instructions = (
             "Your task is to judge how relevant the provided context is for answering a question. "
@@ -117,6 +121,7 @@ def __init__(
             examples=self.examples,
             api=self.api,
             api_key=self.api_key,
+            raise_on_failure=raise_on_failure,
             progress_bar=progress_bar,
         )
 
@@ -138,7 +143,10 @@ def run(self, questions: List[str], contexts: List[List[str]]) -> Dict[str, Any]
         result = super().run(questions=questions, contexts=contexts)
 
         # calculate average statement relevance score per query
-        for res in result["results"]:
+        for idx, res in enumerate(result["results"]):
+            if res is None:
+                result["results"][idx] = {"statements": [], "statement_scores": [], "score": float("nan")}
+                continue
             if not res["statements"]:
                 res["score"] = 0
             else:

haystack/components/evaluators/faithfulness.py

@@ -84,6 +84,7 @@ def __init__(
         progress_bar: bool = True,
         api: str = "openai",
         api_key: Secret = Secret.from_env_var("OPENAI_API_KEY"),
+        raise_on_failure: bool = True,
     ):
         """
         Creates an instance of FaithfulnessEvaluator.
@@ -112,6 +113,8 @@ def __init__(
             Supported APIs: "openai".
         :param api_key:
             The API key.
+        :param raise_on_failure:
+            Whether to raise an exception if the API call fails.
 
         """
         self.instructions = (
@@ -134,6 +137,7 @@ def __init__(
             examples=self.examples,
             api=self.api,
             api_key=self.api_key,
+            raise_on_failure=raise_on_failure,
             progress_bar=progress_bar,
         )
 
@@ -157,7 +161,10 @@ def run(self, questions: List[str], contexts: List[List[str]], predicted_answers
         result = super().run(questions=questions, contexts=contexts, predicted_answers=predicted_answers)
 
         # calculate average statement faithfulness score per query
-        for res in result["results"]:
+        for idx, res in enumerate(result["results"]):
+            if res is None:
+                result["results"][idx] = {"statements": [], "statement_scores": [], "score": float("nan")}
+                continue
             if not res["statements"]:
                 res["score"] = 0
             else:

haystack/components/evaluators/llm_evaluator.py

@@ -3,7 +3,8 @@
 # SPDX-License-Identifier: Apache-2.0
 
 import json
-from typing import Any, Dict, List, Tuple, Type
+from typing import Any, Dict, List, Optional, Tuple, Type
+from warnings import warn
 
 from tqdm import tqdm
 
@@ -54,6 +55,7 @@ def __init__(
         examples: List[Dict[str, Any]],
         progress_bar: bool = True,
         *,
+        raise_on_failure: bool = True,
         api: str = "openai",
         api_key: Secret = Secret.from_env_var("OPENAI_API_KEY"),
     ):
@@ -73,6 +75,8 @@ def __init__(
              `outputs` parameters.
             Each example is a dictionary with keys "inputs" and "outputs"
             They contain the input and output as dictionaries respectively.
+        :param raise_on_failure:
+            If True, the component will raise an exception on an unsuccessful API call.
         :param progress_bar:
             Whether to show a progress bar during the evaluation.
         :param api:
@@ -83,6 +87,7 @@ def __init__(
 
         """
         self.validate_init_parameters(inputs, outputs, examples)
+        self.raise_on_failure = raise_on_failure
         self.instructions = instructions
         self.inputs = inputs
         self.outputs = outputs
@@ -168,7 +173,8 @@ def run(self, **inputs) -> Dict[str, Any]:
         :returns:
             A dictionary with a single `results` entry that contains a list of results.
             Each result is a dictionary containing the keys as defined in the `outputs` parameter of the LLMEvaluator
-            and the evaluation results as the values.
+            and the evaluation results as the values. If an exception occurs for a particular input value, the result
+            will be `None` for that entry.
         """
         self.validate_input_parameters(dict(self.inputs), inputs)
 
@@ -177,14 +183,31 @@ def run(self, **inputs) -> Dict[str, Any]:
         input_names, values = inputs.keys(), list(zip(*inputs.values()))
         list_of_input_names_to_values = [dict(zip(input_names, v)) for v in values]
 
-        results = []
+        results: List[Optional[Dict[str, Any]]] = []
+        errors = 0
         for input_names_to_values in tqdm(list_of_input_names_to_values, disable=not self.progress_bar):
             prompt = self.builder.run(**input_names_to_values)
-            result = self.generator.run(prompt=prompt["prompt"])
-
-            self.validate_outputs(expected=self.outputs, received=result["replies"][0])
-            parsed_result = json.loads(result["replies"][0])
-            results.append(parsed_result)
+            try:
+                result = self.generator.run(prompt=prompt["prompt"])
+            except Exception as e:
+                msg = f"Error while generating response for prompt: {prompt}. Error: {e}"
+                if self.raise_on_failure:
+                    raise ValueError(msg)
+                warn(msg)
+                results.append(None)
+                errors += 1
+                continue
+
+            if self.is_valid_json_and_has_expected_keys(expected=self.outputs, received=result["replies"][0]):
+                parsed_result = json.loads(result["replies"][0])
+                results.append(parsed_result)
+            else:
+                results.append(None)
+                errors += 1
+
+        if errors > 0:
+            msg = f"LLM evaluator failed for {errors} out of {len(list_of_input_names_to_values)} inputs."
+            warn(msg)
 
         return {"results": results}
 
@@ -299,20 +322,37 @@ def validate_input_parameters(expected: Dict[str, Any], received: Dict[str, Any]
             )
             raise ValueError(msg)
 
-    @staticmethod
-    def validate_outputs(expected: List[str], received: str) -> None:
+    def is_valid_json_and_has_expected_keys(self, expected: List[str], received: str) -> bool:
         """
-        Validate the output.
+        Output must be a valid JSON with the expected keys.
 
         :param expected:
             Names of expected outputs
         :param received:
             Names of received outputs
 
         :raises ValueError:
-            If not all expected outputs are present in the received outputs
+            If the output is not a valid JSON with the expected keys:
+            - with `raise_on_failure` set to True a ValueError is raised.
+            - with `raise_on_failure` set to False a warning is issued and False is returned.
+
+        :returns:
+            True if the received output is a valid JSON with the expected keys, False otherwise.
         """
-        parsed_output = json.loads(received)
+        try:
+            parsed_output = json.loads(received)
+        except json.JSONDecodeError:
+            msg = "Response from LLM evaluator is not a valid JSON."
+            if self.raise_on_failure:
+                raise ValueError(msg)
+            warn(msg)
+            return False
+
         if not all(output in parsed_output for output in expected):
             msg = f"Expected response from LLM evaluator to be JSON with keys {expected}, got {received}."
-            raise ValueError(msg)
+            if self.raise_on_failure:
+                raise ValueError(msg)
+            warn(msg)
+            return False
+
+        return True

releasenotes/notes/add-failsafe-for-LLM-based-evaluators-34cdc183ab545315.yaml

@@ -0,0 +1,5 @@
+---
+enhancements:
+  - |
+    If an LLM-based evaluator (e.g., `Faithfulness` or `ContextRelevance`) is initialised with `raise_on_failure=False`, and if a call to an LLM fails or an LLM outputs an invalid JSON, the score of the sample is set to `NaN` instead of raising an exception.
+    The user is notified with a warning indicating the number of requests that failed.

test/components/evaluators/test_context_relevance_evaluator.py

@@ -4,6 +4,8 @@
 import os
 from typing import List
 
+import math
+
 import pytest
 
 from haystack.components.evaluators import ContextRelevanceEvaluator
@@ -159,6 +161,45 @@ def test_run_missing_parameters(self, monkeypatch):
         with pytest.raises(TypeError, match="missing 2 required positional arguments"):
             component.run()
 
+    def test_run_handles_nan(self, monkeypatch):
+        monkeypatch.setenv("OPENAI_API_KEY", "test-api-key")
+        component = ContextRelevanceEvaluator(raise_on_failure=False)
+
+        def generator_run(self, *args, **kwargs):
+            if "Python" in kwargs["prompt"]:
+                raise Exception("OpenAI API request failed.")
+            else:
+                return {"replies": ['{"statements": ["c", "d"], "statement_scores": [1, 1]}']}
+
+        monkeypatch.setattr("haystack.components.generators.openai.OpenAIGenerator.run", generator_run)
+
+        questions = ["Which is the most popular global sport?", "Who created the Python language?"]
+        contexts = [
+            [
+                "The popularity of sports can be measured in various ways, including TV viewership, social media "
+                "presence, number of participants, and economic impact. Football is undoubtedly the world's most "
+                "popular sport with major events like the FIFA World Cup and sports personalities like Ronaldo and "
+                "Messi, drawing a followership of more than 4 billion people."
+            ],
+            [
+                "Python, created by Guido van Rossum in the late 1980s, is a high-level general-purpose programming "
+                "language. Its design philosophy emphasizes code readability, and its language constructs aim to help "
+                "programmers write clear, logical code for both small and large-scale software projects."
+            ],
+        ]
+        results = component.run(questions=questions, contexts=contexts)
+
+        assert math.isnan(results["score"])
+
+        assert results["individual_scores"][0] == 1.0
+        assert math.isnan(results["individual_scores"][1])
+
+        assert results["results"][0] == {"statements": ["c", "d"], "statement_scores": [1, 1], "score": 1.0}
+
+        assert results["results"][1]["statements"] == []
+        assert results["results"][1]["statement_scores"] == []
+        assert math.isnan(results["results"][1]["score"])
+
     @pytest.mark.skipif(
         not os.environ.get("OPENAI_API_KEY", None),
         reason="Export an env var called OPENAI_API_KEY containing the OpenAI API key to run this test.",

test/components/evaluators/test_faithfulness_evaluator.py

@@ -2,8 +2,10 @@
 #
 # SPDX-License-Identifier: Apache-2.0
 import os
+import math
 from typing import List
 
+import numpy as np
 import pytest
 
 from haystack.components.evaluators import FaithfulnessEvaluator
@@ -191,6 +193,49 @@ def test_run_missing_parameters(self, monkeypatch):
         with pytest.raises(TypeError, match="missing 3 required positional arguments"):
             component.run()
 
+    def test_run_handles_nan(self, monkeypatch):
+        monkeypatch.setenv("OPENAI_API_KEY", "test-api-key")
+        component = FaithfulnessEvaluator(raise_on_failure=False)
+
+        def generator_run(self, *args, **kwargs):
+            if "Python" in kwargs["prompt"]:
+                raise Exception("OpenAI API request failed.")
+            else:
+                return {"replies": ['{"statements": ["c", "d"], "statement_scores": [1, 1]}']}
+
+        monkeypatch.setattr("haystack.components.generators.openai.OpenAIGenerator.run", generator_run)
+
+        questions = ["Which is the most popular global sport?", "Who created the Python language?"]
+        contexts = [
+            [
+                "The popularity of sports can be measured in various ways, including TV viewership, social media "
+                "presence, number of participants, and economic impact. Football is undoubtedly the world's most "
+                "popular sport with major events like the FIFA World Cup and sports personalities like Ronaldo and "
+                "Messi, drawing a followership of more than 4 billion people."
+            ],
+            [
+                "Python, created by Guido van Rossum in the late 1980s, is a high-level general-purpose programming "
+                "language. Its design philosophy emphasizes code readability, and its language constructs aim to help "
+                "programmers write clear, logical code for both small and large-scale software projects."
+            ],
+        ]
+        predicted_answers = [
+            "Football is the most popular sport with around 4 billion followers worldwide.",
+            "Guido van Rossum.",
+        ]
+        results = component.run(questions=questions, contexts=contexts, predicted_answers=predicted_answers)
+
+        assert math.isnan(results["score"])
+
+        assert results["individual_scores"][0] == 1.0
+        assert math.isnan(results["individual_scores"][1])
+
+        assert results["results"][0] == {"statements": ["c", "d"], "statement_scores": [1, 1], "score": 1.0}
+
+        assert results["results"][1]["statements"] == []
+        assert results["results"][1]["statement_scores"] == []
+        assert math.isnan(results["results"][1]["score"])
+
     @pytest.mark.skipif(
         not os.environ.get("OPENAI_API_KEY", None),
         reason="Export an env var called OPENAI_API_KEY containing the OpenAI API key to run this test.",

test/components/evaluators/test_llm_evaluator.py

@@ -3,6 +3,7 @@
 # SPDX-License-Identifier: Apache-2.0
 from typing import List
 
+import numpy as np
 import pytest
 
 from haystack.components.evaluators import LLMEvaluator
@@ -379,10 +380,41 @@ def test_invalid_outputs(self, monkeypatch):
             ],
         )
         with pytest.raises(ValueError):
-            component.validate_outputs(expected=["score", "another_expected_output"], received='{"score": 1.0}')
+            component.is_valid_json_and_has_expected_keys(
+                expected=["score", "another_expected_output"], received='{"score": 1.0}'
+            )
+
+        with pytest.raises(ValueError):
+            component.is_valid_json_and_has_expected_keys(expected=["score"], received='{"wrong_name": 1.0}')
+
+    def test_output_invalid_json_raise_on_failure_false(self, monkeypatch):
+        monkeypatch.setenv("OPENAI_API_KEY", "test-api-key")
+        component = LLMEvaluator(
+            instructions="test-instruction",
+            inputs=[("predicted_answers", List[str])],
+            outputs=["score"],
+            examples=[
+                {"inputs": {"predicted_answers": "Football is the most popular sport."}, "outputs": {"score": 0}}
+            ],
+            raise_on_failure=False,
+        )
+        assert (
+            component.is_valid_json_and_has_expected_keys(expected=["score"], received="some_invalid_json_output")
+            is False
+        )
 
+    def test_output_invalid_json_raise_on_failure_true(self, monkeypatch):
+        monkeypatch.setenv("OPENAI_API_KEY", "test-api-key")
+        component = LLMEvaluator(
+            instructions="test-instruction",
+            inputs=[("predicted_answers", List[str])],
+            outputs=["score"],
+            examples=[
+                {"inputs": {"predicted_answers": "Football is the most popular sport."}, "outputs": {"score": 0}}
+            ],
+        )
         with pytest.raises(ValueError):
-            component.validate_outputs(expected=["score"], received='{"wrong_name": 1.0}')
+            component.is_valid_json_and_has_expected_keys(expected=["score"], received="some_invalid_json_output")
 
     def test_unsupported_api(self):
         with pytest.raises(ValueError):