Add contribution guide for CPS flink connector (#370)

CONTRIBUTING.md

@@ -2,8 +2,7 @@ Want to contribute? Great! First, read this page (including the small print at t
 
 ### Before you contribute
 Before we can use your code, you must sign the
-[Google Individual Contributor License Agreement]
-(https://cla.developers.google.com/about/google-individual)
+[Google Individual Contributor License Agreement](https://cla.developers.google.com/about/google-individual)
 (CLA), which you can do online. The CLA is necessary mainly because you own the
 copyright to your changes, even after your contribution becomes part of our
 codebase, so we need your permission to use and distribute your code. We also
@@ -16,12 +15,15 @@ us first through the issue tracker with your idea so that we can help out and
 possibly guide you. Coordinating up front makes it much easier to avoid
 frustration later on.
 
+### Review Our Community Guidelines
+This project follows
+[Google's Open Source Community Guidelines](https://opensource.google/conduct/).
+
 ### Code reviews
 All submissions, including submissions by project members, require review. We
 use Github pull requests for this purpose.
 
 ### The small print
 Contributions made by corporations are covered by a different agreement than
 the one above, the
-[Software Grant and Corporate Contributor License Agreement]
-(https://cla.developers.google.com/about/google-corporate).
+[Software Grant and Corporate Contributor License Agreement](https://cla.developers.google.com/about/google-corporate).

flink-connector/CONTRIBUTING.md

@@ -0,0 +1,101 @@
+# How to Contribute
+
+We'd love to accept your patches and contributions to this project. There are
+just a few small guidelines you need to follow.
+
+## Before You Begin
+
+Please review the repo-level
+[CONTRIBUTING](https://github.com/GoogleCloudPlatform/pubsub/blob/master/CONTRIBUTING.md)
+for legal requirements and our community guidelines. The rest of this page
+describes the contribution process for the `flink-connector` project.
+
+## Contribution Process
+
+### Discuss Your Changes (optional)
+
+Before you start working on a contribution, consider getting in touch with us
+first by
+[creating an issue](https://github.com/GoogleCloudPlatform/pubsub/issues/new)
+with the label "flink connector" to discuss your idea. This is especially
+important for large, significant, or speculative changes. Starting a discussion
+and getting consensus up front can avoid a lot of frustration during code
+review.
+
+### Building and Running Tests
+
+Build, package, and run tests.
+
+```sh
+mvn clean verify
+
+# Skip integration tests.
+mvn clean verify -pl '!flink-connector-gcp-pubsub-e2e-tests'
+```
+
+Run integration and unit tests.
+
+```sh
+mvn clean test
+```
+
+Run only unit tests.
+
+```sh
+mvn clean test -pl '!flink-connector-gcp-pubsub-e2e-tests'
+```
+
+#### Running Integration Tests
+
+Integration tests connect to a local instance of the
+[Cloud Pub/Sub emulator](https://cloud.google.com/pubsub/docs/emulator). By
+default, integration tests start a test container that hosts the emulator. The
+container is cleaned up after the test finishes.
+
+In addition to connecting to test containers, integration tests can connect to
+emulators started outside of the test process. If the environment variable
+`PUBSUB_EMULATOR_HOST` is set, integration tests skip starting a test container
+and try to connect to the specified endpoint.
+
+Start a Cloud Pub/Sub emulator.
+
+```sh
+# The emulator listens on port 8085 by default.
+gcloud beta emulators pubsub start
+```
+
+Run integration tests against the local emulator.
+
+```sh
+PUBSUB_EMULATOR_HOST=localhost:8085 mvn test
+```
+
+### Code Reviews
+
+All submissions, including submissions by project members, require review. We
+use GitHub pull requests for this purpose. Consult
+[GitHub Help](https://help.github.com/articles/about-pull-requests/) for more
+information on using pull requests.
+
+These guidelines will help get your contributions merged smoothly and quickly.
+
+-   Create **small PRs** that are narrowly focused on **addressing a single
+    concern**. Create more PRs to address different concerns.
+
+-   Features and behavior changes should generally include builder options that
+    allow other connector users to disable them. These type of changes should be
+    disabled by default, unless there is a compelling reason to enable these by
+    default.
+
+-   Provide a good **PR description** as a record of **what** change is being
+    made and **why** it was made. Link to a GitHub issue if it exists.
+
+-   If you are adding a new file, make sure it has the copyright message
+    template at the top as a comment. You can copy over the message from an
+    existing file and update the year.
+
+-   Maintain **clean commit history** and use **meaningful commit messages**.
+    PRs with messy commit history are difficult to review. Push changes that
+    address PR review feedback as a separate or multiple commits (avoid vague
+    messages like `addressed pr feedback`). Commits will be squashed into one
+    when merging PRs.

flink-connector/README.md

@@ -36,7 +36,7 @@ Learn more about Flink at [https://flink.apache.org/](https://flink.apache.org/)
 
 ## Using the Connector
 
-We are in the process of uploading the connector to a public respository. In the
+We are in the process of uploading the connector to a public repository. In the
 meantime, you can build the connector JAR file from source to be packaged with
 your Flink deployment.
 
@@ -137,7 +137,7 @@ data flows through Pub/Sub and the example Flink job as expected.
     Flink job successfully used Pub/Sub as both a source and sink
 
 The following commands set variables for your GCP project name, Pub/Sub topic
-names, and Pub/Sub subcription names. These variables are referenced in this
+names, and Pub/Sub subscription names. These variables are referenced in this
 section's commands. The placeholder value for `PROJECT_NAME` must be updated to
 your GCP project name. The other placeholder values can be used as is or updated
 to your liking.
@@ -276,3 +276,17 @@ Stop the example Flink job.
 ```sh
 flink cancel {Flink JobID output when it started}
 ```
+
+## Contributing
+
+Contributions to this library are always welcome and highly encouraged.
+
+See
+[CONTRIBUTING](https://github.com/GoogleCloudPlatform/pubsub/blob/master/flink-connector/CONTRIBUTING.md)
+for more information on how to get started.
+
+## License
+
+Apache 2.0 - See
+[LICENSE](https://github.com/GoogleCloudPlatform/pubsub/blob/master/LICENSE) for
+more information.