Re: [HACKERS] pgjdbc logical replication client throwing exception

[Vladimir Sitnikov <sitnikov.vladimir@xxxxxxxxx>]

++pgjdbc dev list.

>I am facing unusual connection breakdown problem. Here is the simple code that I am using to read WAL file:

Does it always fails?

Can you create a test case? For instance, if you file a pull request with the test, it will get automatically tested across various PG versions, so it would be easier to reson about

Have you tried "withStatusInterval(20, TimeUnit.SECONDS)" instead of 20 millis? I don't think it matter much, however 20ms seems to be an overkill.

Vladimir

пт, 15 сент. 2017 г. в 19:57, Dipesh Dangol <ddipeshdan@xxxxxxxxx>:

hi,

I am trying to implement logical replication stream API of postgresql.

I am facing unusual connection breakdown problem. Here is the simple code that I am

using to read WAL file:

String url = "">            Properties props = new Properties();
            PGProperty.USER.set(props, "benchmarksql");
            PGProperty.PASSWORD.set(props, "benchmarksql");
            PGProperty.ASSUME_MIN_SERVER_VERSION.set(props, "9.4");
            PGProperty.REPLICATION.set(props, "database");
            PGProperty.PREFER_QUERY_MODE.set(props, "simple");

            Connection conn = DriverManager.getConnection(url, props);
            PGConnection replConnection = conn.unwrap(PGConnection.class);

            PGReplicationStream stream = replConnection.getReplicationAPI()
                    .replicationStream().logical()
                    .withSlotName("replication_slot3")
                    .withSlotOption("include-xids", true)
                    .withSlotOption("include-timestamp", "on")
                    .withSlotOption("skip-empty-xacts", true)
                    .withStatusInterval(20, TimeUnit.MILLISECONDS).start();
            while (true) {

                ByteBuffer msg = stream.read();

                if (msg == null) {
                    TimeUnit.MILLISECONDS.sleep(10L);
                    continue;
                }

                int offset = msg.arrayOffset();
                byte[] source = msg.array();
                int length = source.length - offset;
                String data = "" String(source, offset, length);
                System.out.println(data);

                stream.setAppliedLSN(stream.getLastReceiveLSN());
                stream.setFlushedLSN(stream.getLastReceiveLSN());

            }

Even the slightest modification in the code like commenting System.out.println(data);

which is just printing the data in the console, causes connection breakdown problem with

following error msg

org.postgresql.util.PSQLException: Database connection failed when reading from copy
    at org.postgresql.core.v3.QueryExecutorImpl.readFromCopy(QueryExecutorImpl.java:1028)
    at org.postgresql.core.v3.CopyDualImpl.readFromCopy(CopyDualImpl.java:41)
    at org.postgresql.core.v3.replication.V3PGReplicationStream.receiveNextData(V3PGReplicationStream.java:155)
    at org.postgresql.core.v3.replication.V3PGReplicationStream.readInternal(V3PGReplicationStream.java:124)
    at org.postgresql.core.v3.replication.V3PGReplicationStream.read(V3PGReplicationStream.java:70)
    at Server.main(Server.java:52)
Caused by: java.net.SocketException: Socket closed
    at java.net.SocketInputStream.socketRead0(Native Method)
    at java.net.SocketInputStream.socketRead(SocketInputStream.java:116)
    at java.net.SocketInputStream.read(SocketInputStream.java:171)
    at java.net.SocketInputStream.read(SocketInputStream.java:141)
    at org.postgresql.core.VisibleBufferedInputStream.readMore(VisibleBufferedInputStream.java:140)
    at org.postgresql.core.VisibleBufferedInputStream.ensureBytes(VisibleBufferedInputStream.java:109)
    at org.postgresql.core.VisibleBufferedInputStream.read(VisibleBufferedInputStream.java:191)
    at org.postgresql.core.PGStream.receive(PGStream.java:495)
    at org.postgresql.core.PGStream.receive(PGStream.java:479)
    at org.postgresql.core.v3.QueryExecutorImpl.processCopyResults(QueryExecutorImpl.java:1161)
    at org.postgresql.core.v3.QueryExecutorImpl.readFromCopy(QueryExecutorImpl.java:1026)
    ... 5 more

I am trying to implement some logic like filtering out the unrelated table after reading log.

But due to this unusual behavior I couldn't implement properly.

Can somebody give me some hint how to solve this problem.

Thank you.