Add Skaffold configuration and readme (pangeo-data#207)

* Add Skaffold configuration and readme

* Move skaffold-skaffolding to skaffold subfolder

Co-authored-by: Alex <[email protected]>

[ci skip]

skaffold.yaml

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+apiVersion: skaffold/v2alpha3
+kind: Config
+
+build:
+  local:
+    push: false
+    useBuildkit: true
+  tagPolicy:
+    envTemplate:
+      template: "dask-gateway-server:latest"
+  artifacts:
+  - image: dask-gateway-server
+    docker:
+      dockerfile: skaffold/Dockerfile
+
+deploy:
+  helm:
+    releases:
+    - name: dask-gateway
+      chartPath: resources/helm/dask-gateway/
+      namespace: default
+      valuesFiles:
+        - resources/helm/dask-gateway/values.yaml
+      setValues:
+        gateway.image.name: dask-gateway-server
+        gateway.image.pullPolicy: IfNotPresent
+        gateway.cookieSecret: <key>
+        gateway.proxyToken: <key>
+        local: true
+      recreatePods: true

skaffold/Dockerfile

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+FROM daskgateway/dask-gateway-server:latest
+
+COPY --chown=dask:dask skaffold/condarc /opt/conda/condarc
+
+RUN conda install -c conda-forge \
+go=1.12.5 \ 
+cryptography \
+# Leaving tornado for backwards compatibility. 
+tornado \
+traitlets \
+sqlalchemy \
+python-kubernetes \
+aiohttp \
+colorlog \
+-y
+
+COPY --chown=dask:dask . /dask
+WORKDIR /dask/dask-gateway-server/
+# Perform an editable install to avoid packaging a wheel.
+RUN pip install -e .
+# TODO: Add kubernetes extras once the kubernetes backend is ready.
+# RUN pip install -e .[kubernetes]
+WORKDIR /srv/dask-gateway
+USER root
+RUN chown dask:dask /srv/dask-gateway
+USER 1000:1000
+
+CMD ["dask-gateway-server", "--config", "/etc/dask-gateway/dask_gateway_config.py"]``

skaffold/SKAFFOLD.md

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+# Skaffold
+
+[Skaffold](https://skaffold.dev) is a CLI developed by Google that streamlines
+the local Kubernetes development cycle. We're going to use it to streamline
+development of Dask Gateway Server.
+
+Note, this workflow is compatible with release version 0.6.1. The current
+gateway server build succeeds but the container fails because the Kubernetes
+backend has not been implemented yet. Nevertheless, the Skaffold development
+cycle can be leveraged as work on the backend proceeds.
+
+## Installation
+
+Install [Skaffold](https://skaffold.dev/docs/install/).
+```bash
+brew install skaffold
+```
+
+[Activate](https://docs.conda.io/projects/conda/en/latest/user-guide/tasks/manage-environments.html#activating-an-environment)
+your conda environment.
+
+Enable [Docker
+Buildkit](https://docs.docker.com/develop/develop-images/build_enhancements/).
+```bash
+export DOCKER_BUILDKIT=1
+```
+
+## Configuration
+
+Generate a randomized key for the `cookieSecret` and `proxyToken` in
+[skaffold.yaml](skaffold.yaml).
+```bash
+sed -i "s|<key>|$(openssl rand -hex 32)|" skaffold.yaml
+```
+
+## Usage
+
+Run Skaffold in [dev mode](https://skaffold.dev/docs/). This ensures that any
+modifications to the source result in a rebuild and redeployment (via Helm) of
+the source code. The `--no-prune=false` and `--cache-artifacts=false` automate
+the image [clean-up](https://skaffold.dev/docs/pipeline-stages/cleanup/)
+process.
+```bash
+skaffold dev --no-prune=false --cache-artifacts=false
+```
+
+You may want to create an alias for the above command.
+```bash
+# bash
+echo 'alias skd="skaffold dev --no-prune=false --cache-artifacts=false"' >> ~/.bash_profile
+# zsh
+echo 'alias skd="skaffold dev --no-prune=false --cache-artifacts=false"' >> ~/.zshrc
+```
+
+Update one of the source files in `skaffold/dask-gateway/dask-gateway-server`
+and rejoice.
+
+The very first build will take about 90 seconds. After that, the Docker build
+process won't need to re-run `conda install`, so subsequent builds should take
+around 5.4s!
+
+If you're using an internal artifact store, open [condarc](condarc) and follow
+the instructions on the first two lines.

skaffold/condarc

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+# Note: If you're using an internal artifact store, uncomment lines 3 and 4
+# and populate the channel_alias field with a link to the store. 
+# channel_alias: 
+# allow_other_channels: false
+
+channels:
+  - conda-forge
+  - defaults