1. Moved simple extractor out of pyclowder as part of sample extractors.

2. Started adding README for simple extractor
3. Updated docker file for simple extractor

Author: sandeep-ps

docker.sh

@@ -10,6 +10,7 @@ export DEBUG=${DEBUG:-""}
 ${DEBUG} docker build --tag clowder/pyclowder:latest .
 ${DEBUG} docker build --tag clowder/pyclowder:onbuild --file Dockerfile.onbuild .
 ${DEBUG} docker build --tag clowder/extractors-binary-preview:onbuild sample-extractors/binary-preview
+${DEBUG} docker build --tag clowder/extractors-simple-extractor:latest sample-extractors/simple-extractor
 
 # build sample extractors
 ${DEBUG} docker build --tag clowder/extractors-wordcount:latest sample-extractors/wordcount

sample-extractors/simple-extractor/Dockerfile

@@ -0,0 +1,6 @@
+FROM clowder/pyclowder:onbuild
+
+ENV EXTRACTION_FUNC=""
+ENV EXTRACTION_MODULE=""
+
+CMD python -c "from simple_extractor import SimpleExtractor; from EXTRACTION_MODULE import *; SimpleExtractor(${EXTRACTION_FUNC}).start()"

sample-extractors/simple-extractor/README.md

@@ -0,0 +1,38 @@
+# Simple Extractor
+
+The goal of the simple extractor is to make writing of an extractor as easy as possible. It wraps almost all of the 
+complexities in itself and exposes only one environment variable called ```EXTRACTION_FUNC```. This environment 
+variable needs to contain the name of the method that needs to be called when this extractor receives a message from 
+the message broker.
+ 
+# When to Use This
+
+1. This simple extractor is meant to be used in those situations when there is already some Python code available that 
+needs to be wrapped as an extractor as quickly as possible.
+2. This extractor ONLY generates JSON format metadata or a list of preview files. If your extractor generates 
+any additional information like generated files, datasets, collections, thumbnails, etc., this method cannot be use and 
+you need to write your extractor the normal way using [PyClowder2](https://opensource.ncsa.illinois.edu/bitbucket/projects/CATS/repos/pyclowder2/browse)
+3. [Docker](https://www.docker.com/) is the recommended way of developing / wrapping your code using the Simple Extractor.
+
+## Steps for Writing an Extractor Using the Simple Extractor
+
+To write an extractor using the Simple Extractor, you need to have your Python program available. The main function of 
+this Python program needs to accept an input file path as its parameter. It needs to return a Python dictionary that 
+can contain either metadata information ("metadata"), details about file previews ("previews") or both. For example:
+
+``` json
+{   
+    "metadata": dict(),
+    "previews": array() 
+}
+```
+
+1. Let's call your main Python program file ```your_python_program.py``` and the main function ```your_main_function```.
+
+2. Let's create a Dockerfile for your extractor. Its contents need to be:
+
+        FROM clowder/extractors-simple-extractor:latest
+        ENV EXTRACTION_FUNC="your_python_program.your_main_function"
+
+TODO: Complete this.
+

sample-extractors/simple-extractor/__init__.py

@@ -0,0 +1 @@
+

pyclowder/simpleextractor.py …ors/simple-extractor/simple_extractor.pypyclowder/simpleextractor.py renamed to sample-extractors/simple-extractor/simple_extractor.py pyclowder/simpleextractor.py renamed to sample-extractors/simple-extractor/simple_extractor.py

@@ -0,0 +1,3 @@
+FROM clowder/extractors-simple-extractor:latest
+
+ENV EXTRACTION_FUNC="wordcount"