[PLC4X-339] modbus connection causes memory leak

• Type: Bug
• Status: Open
• Priority: Major
• Resolution: Unresolved
• Affects Version/s: 0.9.0
• Component/s: Driver-Modbus
• Environment: Windows 10; jdk1.8 32bit

Language

Java

• Assignee: Unassigned
• Reporter: liangjian
• Created: 24/Apr/22 03:44
• Updated: 09/Nov/22 10:21

Description

Note: The version is 0.9.1.

1. The document (here)https://plc4x.apache.org/users/protocols/modbus.html seems wrong. It tells me the connection string format is: "modbus-tcp:tcp://127.0.0.1:502", but my test code throws exception saying no driver until I change it to "modbus://127.0.0.1".

2. My test code writes (or reads) some value via modbus tcp every 1 second, using short tcp connection (open and close every time). The memory increases every second until out-of-memory. In process monitor I find the thread count increases 1 every time the connection opens, but never releases, althought I consider the `try-block` shall closes it automatically. In fact, I see it calls `connection.close` after the `try-block`.

Test code:

        while (true) {
            String connectionString = "modbus://127.0.0.1";
            try (PlcConnection plcConnection = new PlcDriverManager().getConnection(connectionString)) {
                PlcWriteRequest.Builder builder = plcConnection.writeRequestBuilder();
                builder.addItem("value-1", "holding-register:1:DINT", 30000);
                builder.addItem("value-2", "holding-register:3:REAL", 3.14);
                PlcWriteRequest writeRequest = builder.build();
                PlcWriteResponse response = writeRequest.execute().get();
                
                for (String fieldName : response.getFieldNames()) {
                    if(response.getResponseCode(fieldName) == PlcResponseCode.OK) {
                        System.out.println("Value[" + fieldName + "]: updated");
                    }

                    // Something went wrong, to output an error message instead.
                    else {
                        System.out.println("Error[" + fieldName + "]: " + response.getResponseCode(fieldName).name());                     
					}
                }
                System.out.println("done");
            }
            Thread.sleep(1000);
        }

It shows the connection is not cleaned properly.

I see it's more efficient to do this using long tcp connection (reuse 1 connection or use a pool). But short tcp connection should also work.