Implement logging strategy (#444)

* Logging strategy and convert all prints() to logging invocations

trustgraph-ocr/trustgraph/decoding/ocr/pdf_decoder.py

@@ -6,12 +6,16 @@ PDF document as text as separate output objects.
 
 import tempfile
 import base64
+import logging
 import pytesseract
 from pdf2image import convert_from_bytes
 
 from ... schema import Document, TextDocument, Metadata
 from ... base import FlowProcessor, ConsumerSpec, ProducerSpec
 
+# Module logger
+logger = logging.getLogger(__name__)
+
 default_ident = "pdf-decoder"
 
 class Processor(FlowProcessor):
@@ -41,15 +45,15 @@ class Processor(FlowProcessor):
             )
         )
 
-        print("PDF OCR inited")
+        logger.info("PDF OCR processor initialized")
 
     async def on_message(self, msg, consumer, flow):
 
-        print("PDF message received", flush=True)
+        logger.info("PDF message received")
 
         v = msg.value()
 
-        print(f"Decoding {v.metadata.id}...", flush=True)
+        logger.info(f"Decoding {v.metadata.id}...")
 
         blob = base64.b64decode(v.data)
 
@@ -60,7 +64,7 @@ class Processor(FlowProcessor):
             try:
                 text = pytesseract.image_to_string(page, lang='eng')
             except Exception as e:
-                print(f"Page did not OCR: {e}")
+                logger.warning(f"Page did not OCR: {e}")
                 continue
 
             r = TextDocument(
@@ -70,7 +74,7 @@ class Processor(FlowProcessor):
 
             await flow("output").send(r)
 
-        print("Done.", flush=True)
+        logger.info("PDF decoding complete")
 
     @staticmethod
     def add_args(parser):