Update readme.md

Author: sylwesterdec

data-platform/open-source-data-platforms/oci-data-flow/code-examples/Streaming_from_ObjectStorage/readme.md

@@ -1,11 +1,52 @@
-OCI Data Flow Reading files from Object Storage in Streaming mode
+# OCI Data Flow Reading files from Object Storage in Streaming mode
 
-When to use this asset?
+Sometimes you would like to continously monitor a Object Storage (S3 compatible) location and incrementally process new incoming data.</br>
+With Spark we can create a StreamingQuery using ObjectStorage source and process data from files in streaming mode .... without streaming platform.
+All we need is to use spark.readStream with a location - object storage or S3 compatible. 
+It looks like this:
 
-When you need continously monitor a Object Storage (S3 location) and incrementally process new incoming data
+## START 
 
-How to use this asset?
+### Define source and target locations
+namespace = 'objstr_namespace' </br>
+source_bucket = 'src_bucket'</br>
+inc_folder = 'inc_folder'</br>
+target_bucket = 'trg_bucket'</br>
+target_folder = 'trg_folder'</br>
+checkpoint_bucket = 'check_bucket'</br>
+checkpoint_folder = 'check_folder'</br>
+input_path = 'oci://'+source_bucket+'@'+namespace+'/'+inc_folder</br>
+archivelocation = 'oci://archivebucket+'@'+namespace+'/arch_folder'</br>
+
+### Infer schema from sample file
+example_file = 'oci://'+source_bucket+'@'+namespace+'/'+inc_folder+'/example_file.parquet'</br>
+example = spark.read.option("basePath", input_path).option("inferSchema", "true").parquet(example_file)</br>
+schema = example.schema</br>
+
+### Read files in streaming mode - streaming query
+kafka = spark.readStream.schema(schema).parquet(input_path)</br>
+stream_path = 'oci://'+target_bucket+'@'+namespace+'/'+target_folder</br>
+
+wr = kafka.writeStream.queryName('StreamObjects').format("parquet").option("path", stream_path).option("checkpointLocation", 'oci://'+checkpoint_bucket+'@'+namespace+'/'+checkpoint_folder).option("cleanSource", "archive").option("sourceArchiveDir", archivelocation).start()
+
+### Stop streaming query
+wr.awaitTermination(60)</br>
+wr.stop()</br>
 
+### Check streamed data 
+nd = spark.read.option("inferSchema", "true").parquet(stream_path+'/*.parquet')</br>
+nd.count()
+
+## END of code
+
+## Additional comments:
+You may to provide :
+option("checkpointLocation") - to persist medatada about processed files
+Option("cleanSource") — It can archive or delete the source file after processing. Values can be archive, delete and default is off.
+Option("sourceArchiveDir")  — Archive directory if the cleanSource option is set to archive.
+
+
+How to use this asset?
 Review the code in the notebook and add the code to your personal OCI Data Flow application.
 
 License