Add a version check for Frontend

Author: jaimebuelta

ch11/microservices/frontend/docker/app/Dockerfile

@@ -39,6 +39,7 @@ RUN apk add --update python3 curl libffi postgresql-libs
 RUN mkdir -p /opt/uwsgi
 ADD docker/app/uwsgi.ini /opt/uwsgi/
 ADD docker/app/start_server.sh /opt/uwsgi/
+ADD docker/app/check_dependencies_services.py /opt/uwsgi/
 
 # Create a user to run the service
 RUN addgroup -S uwsgi

ch11/microservices/frontend/docker/app/check_dependencies_services.py

@@ -0,0 +1,36 @@
+import os
+import requests
+from natsort import natsorted
+
+
+VERSIONS = {
+    'thoughts_backend': (f'{os.environ["USER_BACKEND_URL"]}/admin/version/',
+                         'v2.4'),
+}
+
+
+def check_version(min_version, version):
+    versions = natsorted([min_version, version])
+    # Return the lower is the minimum version
+    return versions[0] == min_version
+
+
+def main():
+    for service, (url, min_version) in VERSIONS.items():
+        print(f'Checking minimum version for {service}')
+        resp = requests.get(url)
+        if resp.status_code != 200:
+            print(f'Error connecting to {url}: {resp}')
+            exit(-1)
+
+        result = resp.json()
+        version = result['version']
+        print(f'Minimum {min_version}, found {version}')
+        if not check_version(min_version, version):
+            msg = f'Version {version} is incorrect (min {min_version})'
+            print(msg)
+            exit(-1)
+
+
+if __name__ == '__main__':
+    main()

ch11/microservices/frontend/docker/app/start_server.sh

@@ -1,4 +1,5 @@
 #!/bin/sh
+set -e
 
 _term() {
   echo "Caught SIGTERM signal! Sending graceful stop to uWSGI through the master-fifo"
@@ -10,6 +11,8 @@ _term() {
 
 trap _term SIGTERM
 
+python3 /opt/uwsgi/check_dependencies_services.py
+
 uwsgi --ini /opt/uwsgi/uwsgi.ini &
 
 # We need to wait to properly catch the signal, that's why uWSGI is started

ch11/microservices/frontend/environment.env

@@ -1,2 +1,4 @@
+# Remember to tweak this parameters to point to your IP, as 
+# describred in Chapter 6: Implementing multiple services
 THOUGHTS_BACKEND_URL=http://10.0.10.5:8000
 USER_BACKEND_URL=http://10.0.10.5:8001

ch11/microservices/frontend/requirements.txt

@@ -5,3 +5,4 @@ requests==2.22.0
 bcrypt==3.1.7
 cryptography==2.6.1
 django-prometheus==1.0.15
+natsort==6.0.0