Add pytest with some example events

The lambda now has some local tests we can use to confirm we're handling
events correctly.

We also have a new env var supported that allows us to enable incoming
event logging for all events.  Even if this is off, failure to handle an
event should still result in the event message being logged.

.gitignore

@@ -3,3 +3,4 @@ terraform.tfstate
 *.tfstate*
 terraform.tfvars
 functions/*.zip
+functions/pytest.ini

functions/notify_slack.py

@@ -1,4 +1,5 @@
 from __future__ import print_function
+from urllib.error import HTTPError
 import os, boto3, json, base64
 import urllib.request, urllib.parse
 import logging
@@ -59,6 +60,11 @@ def notify_slack(message, region):
         "icon_emoji": slack_emoji,
         "attachments": []
     }
+
+    if isinstance(message, str):
+        logging.warning("message is a string, assuming it's JSON and decoding")
+        message = json.loads(message)
+
     if "AlarmName" in message:
         notification = cloudwatch_notification(message, region)
         payload['text'] = "AWS CloudWatch notification - " + message["AlarmName"]
@@ -69,14 +75,25 @@ def notify_slack(message, region):
 
     data = urllib.parse.urlencode({"payload": json.dumps(payload)}).encode("utf-8")
     req = urllib.request.Request(slack_url)
-    urllib.request.urlopen(req, data)
+
+    try:
+        result = urllib.request.urlopen(req, data)
+        return result.getcode(), result.info()
+
+    except HTTPError as e:
+        logging.error("{}: result".format(e))
+        return e.getcode(), e.info()
 
 
 def lambda_handler(event, context):
+    if 'LOG_EVENTS' in os.environ and os.environ['LOG_EVENTS'] == 'True':
+        logging.warning('Event logging enabled: `{}`'.format(event))
+
     message = event['Records'][0]['Sns']['Message']
     region = event['Records'][0]['Sns']['TopicArn'].split(":")[3]
-    notify_slack(message, region)
+    code, info = notify_slack(message, region)
 
-    return message
+    if code is not None and code != 200:
+        logging.error("Error: received status `{}` using event `{}` and context `{}`".format(info, event, context))
 
-#notify_slack({"AlarmName":"Example","AlarmDescription":"Example alarm description.","AWSAccountId":"000000000000","NewStateValue":"ALARM","NewStateReason":"Threshold Crossed","StateChangeTime":"2017-01-12T16:30:42.236+0000","Region":"EU - Ireland","OldStateValue":"OK"}, "eu-west-1")
+    return code, info

functions/notify_slack_test.py

@@ -0,0 +1,67 @@
+#!/usr/bin/env pytest
+
+import notify_slack
+import pytest
+from os import environ
+
+events = (
+    (
+        {
+            "Records": [
+                {
+                    "EventSource": "aws:sns",
+                    "EventVersion": "1.0",
+                    "EventSubscriptionArn": "arn:aws:sns:eu-west-2:735598076380:service-updates:d29b4e2c-6840-9c4e-ceac-17128efcc337",
+                    "Sns": {
+                        "Type": "Notification",
+                        "MessageId": "f86e3c5b-cd17-1ab8-80e9-c0776d4f1e7a",
+                        "TopicArn": "arn:aws:sns:eu-west-2:735598076380:service-updates",
+                        "Subject": "OK: \"DBMigrationRequired\" in EU (London)",
+                        "Message": "{\"AlarmName\":\"DBMigrationRequired\",\"AlarmDescription\":\"App is reporting \\\"A JPA error occurred (Unable to build EntityManagerFactory)\\\"\",\"AWSAccountId\":\"735598076380\",\"NewStateValue\":\"OK\",\"NewStateReason\":\"Threshold Crossed: 1 datapoint [1.0 (12/02/19 15:44:00)] was not less than the threshold (1.0).\",\"StateChangeTime\":\"2019-02-12T15:45:24.006+0000\",\"Region\":\"EU (London)\",\"OldStateValue\":\"ALARM\",\"Trigger\":{\"MetricName\":\"DBMigrationRequired\",\"Namespace\":\"LogMetrics\",\"StatisticType\":\"Statistic\",\"Statistic\":\"SUM\",\"Unit\":null,\"Dimensions\":[],\"Period\":60,\"EvaluationPeriods\":1,\"ComparisonOperator\":\"LessThanThreshold\",\"Threshold\":1.0,\"TreatMissingData\":\"- TreatMissingData:                    NonBreaching\",\"EvaluateLowSampleCountPercentile\":\"\"}}",
+                        "Timestamp": "2019-02-12T15:45:24.091Z",
+                        "SignatureVersion": "1",
+                        "Signature": "WMYdVRN7ECNXMWZ0faRDD4fSfALW5MISB6O//LMd/LeSQYNQ/1eKYEE0PM1SHcH+73T/f/eVHbID/F203VZaGECQTD4LVA4B0DGAEY39LVbWdPTCHIDC6QCBV5ScGFZcROBXMe3UBWWMQAVTSWTE0eP526BFUTecaDFM4b9HMT4NEHWa4A2TA7d888JaVKKdSVNTd4bGS6Q2XFG1MOb652BRAHdARO7A6//2/47JZ5COM6LR0/V7TcOYCBZ20CRF6L5XLU46YYL3I1PNGKbEC1PIeVDVJVPcA17NfUbFXWYBX8LHfM4O7ZbGAPaGffDYLFWM6TX1Y6fQ01OSMc21OdUGV6HQR01e%==",
+                        "SigningCertUrl": "https://sns.eu-west-2.amazonaws.com/SimpleNotificationService-7dd85a2b76adaa8dd603b7a0c9150589.pem",
+                        "UnsubscribeUrl": "https://sns.eu-west-2.amazonaws.com/?Action=Unsubscribe&SubscriptionArn=arn:aws:sns:eu-west-2:735598076380:service-updates:d29b4e2c-6840-9c4e-ceac-17128efcc337",
+                        "MessageAttributes": {}
+                    }
+                }
+            ]
+        }
+    ),
+    (
+        {
+            "AlarmName": "Example",
+            "AlarmDescription": "Example alarm description.",
+            "AWSAccountId": "000000000000",
+            "NewStateValue": "ALARM",
+            "NewStateReason": "Threshold Crossed",
+            "StateChangeTime": "2017-01-12T16:30:42.236+0000",
+            "Region": "EU - Ireland",
+            "OldStateValue": "OK"
+        }
+    )
+)
+
+
+@pytest.fixture(scope='module', autouse=True)
+def check_environment_variables():
+    required_environment_variables = ("SLACK_CHANNEL", "SLACK_EMOJI", "SLACK_USERNAME", "SLACK_WEBHOOK_URL")
+    missing_environment_variables = []
+    for k in required_environment_variables:
+        if k not in environ:
+            missing_environment_variables.append(k)
+
+    if len(missing_environment_variables) > 0:
+        pytest.exit('Missing environment variables: {}'.format(", ".join(missing_environment_variables)))
+
+
+@pytest.mark.parametrize("event", events)
+def test_lambda_handler(event):
+    if 'Records' in event:
+        (code, info) = notify_slack.lambda_handler(event, 'self-context')
+
+    else:
+        (code, info) = notify_slack.notify_slack(event, 'eu-west-1')
+
+    assert code == 200

functions/pytest.ini.sample

@@ -0,0 +1,8 @@
+[pytest]
+addopts = --disable-pytest-warnings
+env =
+  SLACK_CHANNEL=slack_testing_sandbox
+  SLACK_EMOJI=:aws:
+  SLACK_USERNAME=notify_slack_test
+  SLACK_WEBHOOK_URL=https://hooks.slack.com/services/YOUR/WEBOOK/URL
+

functions/requirements.txt

@@ -0,0 +1,4 @@
+boto3
+
+pytest
+pytest-env