Print all output as raw bytes

Printing all output as raw bytes allows MaxScale to control the formatting
process. This also removes the need to convert the bytes to Python strings
and the need to parse the JSON.

server/modules/protocol/examples/cdc.py

@@ -12,52 +12,32 @@
 # Public License.
 
 import time
-import json
-import re
 import sys
 import socket
 import hashlib
 import argparse
-import subprocess
 import selectors
 import binascii
 import os
 
-# Read data as JSON
-def read_json():
-    decoder = json.JSONDecoder()
-    rbuf = bytes()
-    ep = selectors.EpollSelector()
-    ep.register(sock, selectors.EVENT_READ)
+def read_data():
+    sel = selectors.DefaultSelector()
+    sel.register(sock, selectors.EVENT_READ)
 
     while True:
-        pollrc = ep.select(timeout=int(opts.read_timeout) if int(opts.read_timeout) > 0 else None)
-        try:
-            buf = sock.recv(4096, socket.MSG_DONTWAIT)
-            rbuf += buf
-            while True:
-                rbuf = rbuf.lstrip()
-                data = decoder.raw_decode(rbuf.decode('ascii'))
-                rbuf = rbuf[data[1]:]
-                print(json.dumps(data[0]))
-        except ValueError as err:
-            sys.stdout.flush()
-            pass
-        except Exception:
-            break
-
-# Read data as Avro
-def read_avro():
-    ep = selectors.EpollSelector()
-    ep.register(sock, selectors.EVENT_READ)
-
-    while True:
-        pollrc = ep.select(timeout=int(opts.read_timeout) if int(opts.read_timeout) > 0 else None)
         try:
+            events = sel.select(timeout=int(opts.read_timeout) if int(opts.read_timeout) > 0 else None)
             buf = sock.recv(4096, socket.MSG_DONTWAIT)
+            if len(buf) > 0:
                 os.write(sys.stdout.fileno(), buf)
                 sys.stdout.flush()
-        except Exception:
+            else:
+                raise Exception('Socket was closed')
+
+        except BlockingIOError:
+            break
+        except Exception as ex:
+            print(ex, file=sys.stderr)
             break
 
 parser = argparse.ArgumentParser(description = "CDC Binary consumer", conflict_handler="resolve")
@@ -91,7 +71,4 @@ response = str(sock.recv(1024)).encode('utf_8')
 # Request a data stream
 sock.send(bytes(("REQUEST-DATA " + opts.FILE + (" " + opts.GTID if opts.GTID else "")).encode()))
 
-if opts.format == "JSON":
-    read_json()
-elif opts.format == "AVRO":
-    read_avro()
+read_data()