introduce epicast development guide

- includes detailed instructions for local development, checking code 
into the `dev` branch, and cherry-picking code over to the `prod` branch
- the guide lives in the `master` branch since it is about the 
development process in general, and is not specific to the the `dev` 
branch

Author: dfarrow0

README.md

@@ -38,3 +38,8 @@ Friday through Monday), except in case of a critical bugfix.
 In any case, all code commits to `prod` should only consist of merges from
 `dev`, rather than direct commits. (An exception to this is configuration,
 which differs between environments.)
+
+# Development
+
+For developing the website, see the
+[epicast development guide](docs/epicast_development.md).

docs/epicast_development.md

@@ -0,0 +1,260 @@
+# Epicast Website Development Guide
+
+**Prerequisite:** this guide assumes that you have read the
+[frontend development guide](https://github.com/cmu-delphi/operations/blob/master/docs/frontend_development.md).
+
+This guide describes how run a local development instance of the Epicast
+website. For preliminary steps,
+[install docker and create a virtual network](https://github.com/cmu-delphi/operations/blob/master/docs/frontend_development.md#setup).
+
+# setup
+
+For working on the Epicast website, you'll need the following two Delphi
+repositories:
+
+- [operations](https://github.com/cmu-delphi/operations)
+- [www-epicast](https://github.com/cmu-delphi/www-epicast)
+
+You likely won't need to modify the `operations` repo, so cloning directly from
+`cmu-delphi` is usually sufficient. However, since you _are_ going to be
+modifying `www-epicast` sources, you'll first need to fork the repository
+and then clone your personal fork. For more details, see the Delphi-specific
+[discussion on forking and branching](https://github.com/cmu-delphi/operations/blob/master/docs/backend_development.md#everyone).
+
+Here's an example of how to setup your local workspace. Note that you will need
+to use your own GitHub username where indicated.
+
+```bash
+# collect everything in a directory called "repos"
+mkdir repos && cd repos
+
+# delphi python (sub)packages
+mkdir delphi && cd delphi
+git clone https://github.com/cmu-delphi/operations
+git clone https://github.com/Your-GitHub-Username/www-epicast
+cd ..
+
+# go back up to the workspace root
+cd ..
+```
+
+Your workspace should now look like this:
+
+```bash
+tree -L 3 .
+```
+
+```
+.
+└── repos
+    └── delphi
+        ├── operations
+        └── www-epicast
+```
+
+# branches and deployment
+
+Note that Epicast follows a weekly release cadence whereby select changes in
+the `dev` branch are
+[cherry-picked](https://www.atlassian.com/git/tutorials/cherry-pick)
+into the `prod` branch. The `prod` branch should never be committed to
+directly, and changes shouldn't be merged in from `dev` during active
+forecasting, which is nominally Friday through Monday each week.
+
+The `HEAD` of the `dev` branch is continuously deployed to a staging server
+which, with credentials, you can access at
+https://app-mono-dev-01.delphi.cmu.edu/cc-test. Similarly, the `HEAD` of the
+`prod` branch is continuously deployed to the production server which is
+publicly accessible at https://delphi.cmu.edu/crowdcast/.
+
+For additional details about the various branches, and the intended use-cases
+of each, see [the top-level readme](../README.md). Notably, the `master` branch
+has only documentation and not code. This is because documentation (e.g. this
+guide) is generally not specific to any particular branch, whereas the master
+branch has intentionally undefined deployment semantics and should not contain
+any code.
+
+# build images
+
+For the purposes of this guide, which is broadly focused on the typical Epicast
+development workflow, go ahead and checkout the `dev` branch which is where the
+development version of the code lives. We will return to the `prod` branch
+later in this guide.
+
+```bash
+git \
+--git-dir repos/delphi/www-epicast/.git \
+--work-tree repos/delphi/www-epicast \
+checkout dev
+```
+
+We now need images for the Epicast web server and database. These are both
+based on core Delphi images which are defined in the
+[`operations` repo](https://github.com/cmu-delphi/operations) which you cloned
+above. The base images are built first, followed by the derived
+`epicast`-specific images.
+
+- The [`delphi_web_epicast` image](../dev/docker/web/epicast/README.md) adds
+  the Epicast website to the `delphi_web` image.
+- The
+  [`delphi_database_epicast` image](../dev/docker/database/epicast/README.md)
+  adds the `epi` user account, `epicast2` (legacy name) database, and relevant
+  tables to the `delphi_database` image.
+
+From the root of your workspace, all of the images can be built as follows.
+**Be sure to have checked out an appropriate branch as described above, as
+branch `master` doesn't contain the requisite files.**
+
+```bash
+docker build -t delphi_web \
+  -f repos/delphi/operations/dev/docker/web/Dockerfile .
+
+docker build -t delphi_web_epicast \
+  -f repos/delphi/www-epicast/dev/docker/web/epicast/Dockerfile .
+
+docker build -t delphi_database \
+  -f repos/delphi/operations/dev/docker/database/Dockerfile .
+
+docker build -t delphi_database_epicast \
+  -f repos/delphi/www-epicast/dev/docker/database/epicast/Dockerfile .
+```
+
+# develop
+
+At this point you're ready to bring the stack online. To do that, just start
+containers for the Epicast-specific web and database images. As an aside, the
+output from these commands (especially the web server) can be very helpful for
+debugging. For example, in separate terminals:
+
+```bash
+# launch the database
+docker run --rm -p 13306:3306 \
+  --network delphi-net --name delphi_database_epicast \
+  delphi_database_epicast
+
+# launch the web server
+docker run --rm -p 10080:80 \
+  --network delphi-net --name delphi_web_epicast \
+  delphi_web_epicast
+```
+
+You should now be able to visit your own personal instance of the website,
+backed by your own personal instance of the database, by visiting
+http://localhost:10080/ in a web browser. Note that your user ID for login is
+"00000000", as defined in `src/ddl/development_data.sql` (see the line like
+`INSERT INTO ``ec_fluv_users`` ... `).
+
+After making website changes, bring the `delphi_web_epicast` container down
+(e.g. `docker stop delphi_web_epicast`), rebuild the image, and relaunch the
+container. This stop-build-start cycle is necessary to pick up modifications to
+your local source files. This is good for the sake of bundling and running a
+self-contained and isolated unit of code, but it's suboptimal in terms of rapid
+iteration and developer experience.
+
+It's possible to [bind-mount](https://docs.docker.com/storage/bind-mounts/) a
+local directory (say `repos/delphi/www-epicast/site/`) to a directory in a
+container. This opens up your local filesystem to the container, which is not
+normally granted such visibility. By doing it this way, local changes to source
+files are immediately visible (subject to page refresh and caching, etc) in
+your local instance of the website. The huge benefit of doing it this way is
+that you don't have to stop, rebuild, and restart every time you want to test
+out a code change. However, there are some drawbacks to keep in mind:
+
+- your local filesystem is now exposed to code running in the container (this
+isn't much of a practical concern in this case since we generally trust the
+code written by fellow Delphi developers, but still something to be aware of)
+- this is very tedious to specify on the command line, and changes to directory
+structure can cause the mount flag to no longer work
+- several mount flags, each of which is tedious, may be needed, depending on
+how the code in the repo maps to code on the server (i.e. must replicate the
+mapping defined in `deploy.json`)
+
+Here's an example of how to bind-mount the website source files in your local
+`www-epicast` repository into a `delphi_web_epicast` container:
+
+```bash
+# launch the web server, serving website files from your actual filesystem
+# rather than from the image
+docker run --rm -p 10080:80 \
+  --mount type=bind,source="$(pwd)"/repos/delphi/www-epicast/site,target=/var/www/html,readonly \
+  --mount type=bind,source="$(pwd)"/repos/delphi/www-epicast/dev/docker/web/epicast/assets/settings.php,target=/var/www/html/common/settings.php,readonly \
+  --network delphi-net --name delphi_web_epicast \
+  delphi_web_epicast
+```
+
+When development is finished, it's a good idea to test things out one final
+time _without_ bind-mounting. This helps to ensure that all the code is working
+as intended without depending on changes to other bind-mounted local files
+which haven't captured by the image.
+
+# updating `prod`
+
+[Cherry-picking](https://www.atlassian.com/git/tutorials/cherry-pick) is the
+process by which specific commits are taken from the `dev` branch and copied
+over to the `prod` branch. Aside from production-specific configuration
+changes, this is the only way by which code changes should be introduced to the
+`prod` branch.
+
+To begin, suppose there has been some sequence of commits made to the `dev`
+branch, one of which we now want to port over to the `prod` branch. This can be
+done from the root of your workspace, but for simplicity, change directory into
+the `www-epicast` repo. Then, identify the commit by its hash, which can
+determined by `git log`, for example:
+
+```bash
+# move into the repo to simplify subsequent git commands
+cd repos/delphi/www-epicast
+
+# checkout the dev branch
+git checkout dev
+
+# show recent commits
+git log --oneline | head -5
+```
+
+```
+965682a database ddl and local docker development
+be9867e grant access during local docker development
+6f3f719 remove unused css-as-php files
+b61eb03 update advanced preferences, fixes #12
+a27efc0 get latest issue from epidata api
+```
+
+Let's assume that we want to bring over the changes from "update advanced
+preferences, fixes #12", with commit hash `b61eb03`.
+
+Switch over to the `prod` branch, and make the cherry-pick:
+
+```bash
+# checkout the prod branch
+git checkout prod
+
+# cherry-pick the bugfix
+git cherry-pick b61eb03
+```
+
+```
+[prod f64268b] update advanced preferences, fixes #12
+ Date: Tue Apr 28 15:05:18 2020 -0500
+ 1 file changed, 4 insertions(+), 4 deletions(-)
+```
+
+You can confirm that the commit was cherry-picked into `prod` by `git log`.
+
+In case of merge conflicts, you will see a message similar to the following:
+
+```
+error: could not apply d43ef45... remove the caching service worker
+hint: after resolving the conflicts, mark the corrected paths
+hint: with 'git add <paths>' or 'git rm <paths>'
+hint: and commit the result with 'git commit'
+```
+
+In this case, you'll have to manually resolve the merge conflict (use `git
+status` to find the modified but unstaged file), add the resolved file(s), and
+then finish up with `git commit`.
+
+Finally, submit a pull request against the `prod` branch of the `www-epicast`
+repo, where after quick sanity check review, the changes can be merged into the
+`prod` branch and subsequently automatically deployed to the production
+environment.