Switch out requests_version for docker_base_extra_python_requirements

README.md

@@ -18,6 +18,16 @@ This role expects the following variables:
  - `docker_rotate_version` defines the version of the Docker Rotate library to install, default 3.0
  - `docker_compose_version` defines the version of Docker Compose to install, may be "latest",
    default 1.8.0. To skip installation of docker_compose, specify `null` or `""`
+ - `docker_base_extra_python_requirements`: defines a list of extra python requirements you may need
+   in the event of a version conflict. Each item of the list is a extra entry in the generated requirements.txt
+   Latest docker-py and docker-compose needed different versions of `requests` so we added this.
+   See Also: `pip requirements sub dependency resolution`
+
+   Example:
+
+     docker_base_extra_python_requirements:
+       - "requests==2.7.0"
+
  - `docker_rotate_images_arguments`: arguments to pass to "docker-rotate images" when cleanup cron
    job runs. If blank, job will not be run. Default is "--keep 3 --name ~busybox --tag ~latest".
    For documentation, see the
@@ -37,9 +47,6 @@ This role expects the following variables:
  - `docker_registries_to_login`: list of maps, each map containing login credentials for a Docker
    registry. Expected keys are `username`, `password`, `email`, and `url`. The role will attempt to
    log into each registry described in the list. Default is empty.
- - `requests_version`: if you want to explicitly install a specific version of requests library. 
-    Latest docker-py and docker-compose need different versions of requests so we have to 
-    explicitly install a specific version of requests library.  
 
 Example for `docker_registries_to_login`:
 
@@ -63,3 +70,15 @@ In order to run this role:
  - python and pip must be installed.
  - docker engine must be installed. For a role that installs docker engine, see
    [here](https://github.com/locationlabs/ansible-role_docker)
+
+## pip requirements sub dependency resolution
+There are times when we will need to be explicit about versions of sub dependencies
+installed so that we ensure that the versions installed are compatible with both
+docker_py and docker_compose as well as any other requirements. We do this since
+pip doesn't have proper sub dependency resolution:
+    https://github.com/pypa/pip/issues/988
+
+We should update `docker_base_extra_python_requirements` as needed when changing
+what we install with pip. Especially if we change default versions of
+`docker_py_version` or `docker_compose_version` since the version of `requests`
+compatible with both could change when this happens.

defaults/main.yml

@@ -16,6 +16,13 @@ docker_py_version: "1.9.0"
 # 'latest' to install the newest version, null or empty string to install nothing.
 docker_compose_version: "1.8.0"
 
+# Extra python requirements.
+# There are times when we will need to be explicit about versions of other libraries
+# See README.md for detals.
+# Empty list means don't specify any additional versions
+docker_base_extra_python_requirements:
+  - "requests==2.7.0"
+
 # Version of docker-rotate to use. Versions lower than 3.0 are not supported due
 # to API changes.
 #

templates/requirements.txt.j2

@@ -1,8 +1,8 @@
-{% if requests_version is defined %}
-requests{{ '' if requests_version == 'latest' else ('==' + requests_version) }}
-{% endif%}
 docker-py{{ '' if docker_py_version == 'latest' else ('==' + docker_py_version) }}
 dockerrotate=={{ docker_rotate_version }}
 {% if docker_compose_version is not none and docker_compose_version != '' %}
 docker-compose{{ '' if docker_compose_version == 'latest' else ('==' + docker_compose_version) }}
 {% endif %}
+{% for item in docker_base_extra_python_requirements %}
+{{ item }}
+{% endfor %}