Set up logging

Set up a logger and configure logging on AWS.

For:
#11

.ebextensions/logs.config

@@ -0,0 +1,6 @@
+# This should stream our logs to AWS CloudWatch.
+option_settings:
+  aws:elasticbeanstalk:cloudwatch:logs:
+    StreamLogs: true
+    DeleteOnTerminate: false
+    RetentionInDays: 60

doc/logs.md

@@ -0,0 +1,7 @@
+# Logs
+
+When running locally, logs are written to stdout. When running on AWS,
+logs can be viewed in CloudWatch. To view the logs, navigate to the
+CloudWatch web console, then in the side bar click the link to the log
+groups page. Then look for the `web.stdout.log` log group. Then click
+the appropriate log stream (probably the most recent one).

src/app.py

@@ -4,24 +4,31 @@
 """
 
 # Built-in libraries:
+import logging
 import os
 import subprocess
 
 # Third-party dependencies:
 from flask import Flask
 
+# Configure logger.
+logging.basicConfig(level=logging.INFO)
+logger = logging.getLogger(__name__)
+
 app = Flask(__name__)
 
 
 @app.route("/")
 def hello_world():
     """A cheeky hello world route."""
+    logger.info("User accessed /")
     return "<p>Look on my Affiliations Service, ye Mighty, and despair!</p>"
 
 
 @app.route("/sha")
 def current_git_sha():
     """Displays current Git SHA."""
+    logger.info("User accessed /sha")
     command = ["git", "rev-parse", "HEAD"]
     output = subprocess.run(command, check=False, capture_output=True).stdout.decode(
         "utf-8"
@@ -34,4 +41,5 @@ def current_git_sha():
 @app.route("/env")
 def display_env_var():
     """Displays environment variable for testing purposes."""
+    logger.info("User accessed /env")
     return os.environ.get("SOME_VAR")