From: | Dipesh Dangol <ddipeshdan(at)gmail(dot)com> |
---|---|
To: | pgsql-general(at)postgresql(dot)org |
Subject: | logical replication API to read WAL file through replication slot |
Date: | 2017-09-06 18:55:58 |
Message-ID: | CA+=-RVY0anrEoHn+u-4235AWE-ckDzmdhmWLC-BPC3r5mgSXsQ@mail.gmail.com |
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Thread: | |
Lists: | pgsql-general |
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 = "jdbc:postgresql://pcnode2:5432/benchmarksql";
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 = new 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.
Dipesh Dangol
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