GCS documentation (#4622)

* GCS documentation and review fixes.

docs/gateway/README.md

@@ -1,48 +1,9 @@
 # Minio Gateway [![Slack](https://slack.minio.io/slack?type=svg)](https://slack.minio.io)
-Minio Gateway adds Amazon S3 compatibility to third party cloud storage providers. Currently only Microsoft Azure Blob Storage is supported. 
+Minio Gateway adds Amazon S3 compatibility to third party cloud storage providers.
-
+- [Microsoft Azure Blob Storage](https://github.com/minio/minio/blob/master/docs/gateway/azure.md)
-## Run Minio Gateway for Microsoft Azure Blob Storage
+- [Google Cloud Storage](https://github.com/minio/minio/blob/master/docs/gateway/gcs.md) _Alpha release_
-### Using Docker
-```
-docker run -p 9000:9000 --name azure-s3 \
- -e "MINIO_ACCESS_KEY=azureaccountname" \
- -e "MINIO_SECRET_KEY=azureaccountkey" \
- minio/minio gateway azure
-```
-
-### Using Binary
-```
-export MINIO_ACCESS_KEY=azureaccountname
-export MINIO_SECRET_KEY=azureaccountkey
-minio gateway azure
-```
-## Test using Minio Browser
-Minio Gateway comes with an embedded web based object browser. Point your web browser to http://127.0.0.1:9000 ensure your server has started successfully.
-
-![Screenshot](https://github.com/minio/minio/blob/master/docs/screenshots/minio-browser-gateway.png?raw=true)
-## Test using Minio Client `mc`
-`mc` provides a modern alternative to UNIX commands such as ls, cat, cp, mirror, diff etc. It supports filesystems and Amazon S3 compatible cloud storage services.
-
-### Configure `mc`
-```
-mc config host add myazure http://gateway-ip:9000 azureaccountname azureaccountkey
-```
-
-### List containers on Microsoft Azure
-```
-mc ls myazure
-[2017-02-22 01:50:43 PST]     0B ferenginar/
-[2017-02-26 21:43:51 PST]     0B my-container/
-[2017-02-26 22:10:11 PST]     0B test-container1/
-```
 
 ## Roadmap
 * Minio & AWS S3
 * Edge Caching - Disk based proxy caching support
-* Google Cloud Storage 
 
-## Explore Further
-- [`mc` command-line interface](https://docs.minio.io/docs/minio-client-quickstart-guide)
-- [`aws` command-line interface](https://docs.minio.io/docs/aws-cli-with-minio)
-- [`minfs` filesystem interface](http://docs.minio.io/docs/minfs-quickstart-guide)
-- [`minio-go` Go SDK](https://docs.minio.io/docs/golang-client-quickstart-guide)

docs/gateway/azure.md

@@ -0,0 +1,46 @@
+# Minio Azure Gateway [![Slack](https://slack.minio.io/slack?type=svg)](https://slack.minio.io)
+Minio Gateway adds Amazon S3 compatibility to Microsoft Azure Blob Storage.
+
+## Run Minio Gateway for Microsoft Azure Blob Storage
+### Using Docker
+```
+docker run -p 9000:9000 --name azure-s3 \
+ -e "MINIO_ACCESS_KEY=azureaccountname" \
+ -e "MINIO_SECRET_KEY=azureaccountkey" \
+ minio/minio gateway azure
+```
+
+### Using Binary
+```
+export MINIO_ACCESS_KEY=azureaccountname
+export MINIO_SECRET_KEY=azureaccountkey
+minio gateway azure
+```
+## Test using Minio Browser
+Minio Gateway comes with an embedded web based object browser. Point your web browser to http://127.0.0.1:9000 ensure your server has started successfully.
+
+![Screenshot](https://github.com/minio/minio/blob/master/docs/screenshots/minio-browser-gateway.png?raw=true)
+## Test using Minio Client `mc`
+`mc` provides a modern alternative to UNIX commands such as ls, cat, cp, mirror, diff etc. It supports filesystems and Amazon S3 compatible cloud storage services.
+
+### Configure `mc`
+```
+mc config host add myazure http://gateway-ip:9000 azureaccountname azureaccountkey
+```
+
+### List containers on Microsoft Azure
+```
+mc ls myazure
+[2017-02-22 01:50:43 PST]     0B ferenginar/
+[2017-02-26 21:43:51 PST]     0B my-container/
+[2017-02-26 22:10:11 PST]     0B test-container1/
+```
+
+### Known limitations
+[Limitations](https://github.com/minio/minio/blob/master/docs/gateway/azure-limitations.md)
+
+## Explore Further
+- [`mc` command-line interface](https://docs.minio.io/docs/minio-client-quickstart-guide)
+- [`aws` command-line interface](https://docs.minio.io/docs/aws-cli-with-minio)
+- [`minfs` filesystem interface](http://docs.minio.io/docs/minfs-quickstart-guide)
+- [`minio-go` Go SDK](https://docs.minio.io/docs/golang-client-quickstart-guide)

docs/gateway/gcs-limitations.md

@@ -0,0 +1,9 @@
+## Minio GCS Gateway Limitations
+
+Gateway inherits the following GCS limitations:
+
+- Maximum number of parts per upload is 1024.
+- No support for bucket policies yet.
+- No support for bucket notifications yet.
+- _List Multipart Uploads_ and _List Object parts_ always returns empty list. i.e Client will need to remember all the parts that it has uploaded and use it for _Complete Multipart Upload_
+

docs/gateway/gcs.md

@@ -0,0 +1,63 @@
+# Minio GCS Gateway [![Slack](https://slack.minio.io/slack?type=svg)](https://slack.minio.io)
+Minio GCS Gateway adds Amazon S3 compatibility to Google Cloud Storage.
+
+## Run Minio Gateway for GCS
+### Create service account key for GCS and get the credentials file
+1. Go to the [API Console Credentials page](https://console.developers.google.com/project/_/apis/credentials).
+2. Select your project or create a new project. Note down your project ID.
+3. On the Credentials page, select the __Create credentials__ drop-down, then select __Service account key__.
+4. From the __Service account__ drop-down, select __New service account__
+5. Fill up __Service account name__ and __Service account ID__
+6. For the __Role__, click the selec dropdown to choose __Storage__ -> __Storage Admin__ _(Full control of GCS resources)_
+7. Click the __Create__ button. This will download a credentials file to your desktop. Let's call this credentials.json
+
+Note: Alternate ways to setup *Application Default Credentials* is explained [here](https://developers.google.com/identity/protocols/application-default-credentials)
+
+### Using Docker
+```
+docker run -p 9000:9000 --name gcs-s3 \
+ -v /path/to/credentials.json:/credentials.json \
+ -e "GOOGLE_APPLICATION_CREDENTIALS=/credentials.json" \
+ -e "MINIO_ACCESS_KEY=minioaccountname" \
+ -e "MINIO_SECRET_KEY=minioaccountkey" \
+ minio/minio gateway gcs yourprojectid
+```
+
+### Using Binary
+```
+export GOOGLE_APPLICATION_CREDENTIALS=/path/to/credentials.json
+export MINIO_ACCESS_KEY=minioaccesskey
+export MINIO_SECRET_KEY=miniosecretkey
+minio gateway gcs yourprojectid
+```
+
+## Test using Minio Browser
+Minio Gateway comes with an embedded web based object browser. Point your web browser to http://127.0.0.1:9000 ensure your server has started successfully.
+
+![Screenshot](https://github.com/minio/minio/blob/master/docs/screenshots/minio-browser-gateway.png?raw=true)
+
+## Test using Minio Client `mc`
+`mc` provides a modern alternative to UNIX commands such as ls, cat, cp, mirror, diff etc. It supports filesystems and Amazon S3 compatible cloud storage services.
+
+### Configure `mc`
+```
+mc config host add mygcs http://gateway-ip:9000 minioaccesskey miniosecretkey
+```
+
+### List containers on GCS
+```
+mc ls mygcs
+[2017-02-22 01:50:43 PST]     0B ferenginar/
+[2017-02-26 21:43:51 PST]     0B my-container/
+[2017-02-26 22:10:11 PST]     0B test-container1/
+```
+
+### Known limitations
+[Limitations](https://github.com/minio/minio/blob/master/docs/gateway/gcs-limitations.md)
+
+## Explore Further
+- [`mc` command-line interface](https://docs.minio.io/docs/minio-client-quickstart-guide)
+- [`aws` command-line interface](https://docs.minio.io/docs/aws-cli-with-minio)
+- [`minfs` filesystem interface](http://docs.minio.io/docs/minfs-quickstart-guide)
+- [`minio-go` Go SDK](https://docs.minio.io/docs/golang-client-quickstart-guide)
+