Make "unexpected EOF" messages DEBUG1 unless in an open transaction

"Unexpected EOF on client connection" without an open transaction
is mostly noise, so turn it into DEBUG1. With an open transaction it's
still indicating a problem, so keep those as ERROR, and change the message
to indicate that it happened in a transaction.

src/backend/commands/copy.c

@@ -547,7 +547,7 @@ CopyGetData(CopyState cstate, void *databuf, int minread, int maxread)
 				/* Only a \. terminator is legal EOF in old protocol */
 				ereport(ERROR,
 						(errcode(ERRCODE_CONNECTION_FAILURE),
-						 errmsg("unexpected EOF on client connection")));
+						 errmsg("unexpected EOF on client connection with an open transaction")));
 			}
 			bytesread = minread;
 			break;
@@ -566,11 +566,11 @@ CopyGetData(CopyState cstate, void *databuf, int minread, int maxread)
 					if (mtype == EOF)
 						ereport(ERROR,
 								(errcode(ERRCODE_CONNECTION_FAILURE),
-							 errmsg("unexpected EOF on client connection")));
+							 errmsg("unexpected EOF on client connection with an open transaction")));
 					if (pq_getmessage(cstate->fe_msgbuf, 0))
 						ereport(ERROR,
 								(errcode(ERRCODE_CONNECTION_FAILURE),
-							 errmsg("unexpected EOF on client connection")));
+							 errmsg("unexpected EOF on client connection with an open transaction")));
 					switch (mtype)
 					{
 						case 'd':		/* CopyData */

src/backend/tcop/fastpath.c

@@ -285,9 +285,22 @@ HandleFunctionRequest(StringInfo msgBuf)
 	{
 		if (GetOldFunctionMessage(msgBuf))
 		{
-			ereport(COMMERROR,
-					(errcode(ERRCODE_PROTOCOL_VIOLATION),
-					 errmsg("unexpected EOF on client connection")));
+			if (IsTransactionState())
+				ereport(COMMERROR,
+						(errcode(ERRCODE_CONNECTION_FAILURE),
+						 errmsg("unexpected EOF on client connection with an open transaction")));
+			else
+			{
+				/*
+				 * Can't send DEBUG log messages to client at this point.
+				 * Since we're disconnecting right away, we don't need to
+				 * restore whereToSendOutput.
+				 */
+				whereToSendOutput = DestNone;
+				ereport(DEBUG1,
+						(errcode(ERRCODE_CONNECTION_DOES_NOT_EXIST),
+						 errmsg("unexpected EOF on client connection")));
+			}
 			return EOF;
 		}
 	}

src/backend/tcop/postgres.c

@@ -343,9 +343,22 @@ SocketBackend(StringInfo inBuf)
 
 	if (qtype == EOF)			/* frontend disconnected */
 	{
-		ereport(COMMERROR,
-				(errcode(ERRCODE_PROTOCOL_VIOLATION),
-				 errmsg("unexpected EOF on client connection")));
+		if (IsTransactionState())
+			ereport(COMMERROR,
+					(errcode(ERRCODE_CONNECTION_FAILURE),
+					 errmsg("unexpected EOF on client connection with an open transaction")));
+		else
+		{
+			/*
+			 * Can't send DEBUG log messages to client at this point.
+			 * Since we're disconnecting right away, we don't need to
+			 * restore whereToSendOutput.
+			 */
+			whereToSendOutput = DestNone;
+			ereport(DEBUG1,
+					(errcode(ERRCODE_CONNECTION_DOES_NOT_EXIST),
+					 errmsg("unexpected EOF on client connection")));
+		}
 		return qtype;
 	}
 
@@ -366,9 +379,22 @@ SocketBackend(StringInfo inBuf)
 				/* old style without length word; convert */
 				if (pq_getstring(inBuf))
 				{
-					ereport(COMMERROR,
-							(errcode(ERRCODE_PROTOCOL_VIOLATION),
-							 errmsg("unexpected EOF on client connection")));
+					if (IsTransactionState())
+						ereport(COMMERROR,
+								(errcode(ERRCODE_CONNECTION_FAILURE),
+								 errmsg("unexpected EOF on client connection with an open transaction")));
+					else
+					{
+						/*
+						 * Can't send DEBUG log messages to client at this
+						 * point.Since we're disconnecting right away, we
+						 * don't need to restore whereToSendOutput.
+						 */
+						whereToSendOutput = DestNone;
+						ereport(DEBUG1,
+								(errcode(ERRCODE_CONNECTION_DOES_NOT_EXIST),
+								 errmsg("unexpected EOF on client connection")));
+					}
 					return EOF;
 				}
 			}