o Initial import of postgresql LISTEN/NOTIFY code.HEADmaster

19 files changed, 1052 insertions, 0 deletions

diff --git a/.gitignore b/.gitignore
new file mode 100644
index 0000000..f83e8cf
--- /dev/null
+++ b/.gitignore
@@ -0,0 +1,3 @@
+.idea
+target
+*.iml
diff --git a/LICENSE.txt b/LICENSE.txt
new file mode 100644
index 0000000..4dc9c3c
--- /dev/null
+++ b/LICENSE.txt
@@ -0,0 +1,21 @@
+The MIT License (MIT)
+
+Copyright (c) <2014> Trygve Laugstøl <trygvis@inamo.no>
+
+Permission is hereby granted, free of charge, to any person obtaining a copy
+of this software and associated documentation files (the "Software"), to deal
+in the Software without restriction, including without limitation the rights
+to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+copies of the Software, and to permit persons to whom the Software is
+furnished to do so, subject to the following conditions:
+
+The above copyright notice and this permission notice shall be included in
+all copies or substantial portions of the Software.
+
+THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
+THE SOFTWARE.
diff --git a/init.sql b/init.sql
new file mode 100644
index 0000000..0ec0477
--- /dev/null
+++ b/init.sql
@@ -0,0 +1,37 @@
+-- Create a table for incoming mail
+
+CREATE TABLE mail_raw (
+  id  SERIAL PRIMARY KEY,
+  raw TEXT
+);
+
+-- Insert a row into the table;
+
+INSERT INTO mail_raw (raw) VALUES ('my mail');
+NOTIFY mail_raw;
+
+--
+-- Alternate technique with implicit notifies through triggers
+--
+
+CREATE TABLE mail_raw_t (
+  id  SERIAL PRIMARY KEY,
+  raw TEXT
+);
+
+-- This trigger function does the notification
+CREATE FUNCTION notify_trigger()
+  RETURNS TRIGGER AS $$
+BEGIN
+  PERFORM pg_notify(TG_TABLE_NAME, NEW.id :: TEXT);
+  RETURN NULL;
+END;
+$$ LANGUAGE plpgsql;
+
+-- Create a trigger on the mail_raw_t table and make it run on each new row
+CREATE TRIGGER mail_raw_t_notify
+AFTER INSERT ON mail_raw_t
+FOR EACH ROW
+EXECUTE PROCEDURE notify_trigger();
+
+INSERT INTO mail_raw_t (raw) VALUES ('my mail');
diff --git a/pom.xml b/pom.xml
new file mode 100644
index 0000000..c0a5ad5
--- /dev/null
+++ b/pom.xml
@@ -0,0 +1,55 @@
+<project>
+  <modelVersion>4.0.0</modelVersion>
+  <parent>
+    <groupId>io.trygvis</groupId>
+    <artifactId>trygvis-parent</artifactId>
+    <version>1</version>
+  </parent>
+  <groupId>io.trygvis.javazone-2014</groupId>
+  <artifactId>javazone-2014</artifactId>
+  <version>1.0-SNAPSHOT</version>
+
+  <properties>
+    <maven.compiler.source>1.8</maven.compiler.source>
+    <maven.compiler.target>1.8</maven.compiler.target>
+    <project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
+  </properties>
+
+  <dependencies>
+    <dependency>
+      <groupId>org.postgresql</groupId>
+      <artifactId>postgresql</artifactId>
+      <version>9.3-1102-jdbc41</version>
+    </dependency>
+
+    <dependency>
+      <groupId>com.impossibl.pgjdbc-ng</groupId>
+      <artifactId>pgjdbc-ng</artifactId>
+      <version>0.4</version>
+    </dependency>
+
+    <dependency>
+      <groupId>org.slf4j</groupId>
+      <artifactId>slf4j-api</artifactId>
+      <version>1.7.7</version>
+    </dependency>
+
+    <dependency>
+      <groupId>ch.qos.logback</groupId>
+      <artifactId>logback-classic</artifactId>
+      <version>1.1.2</version>
+    </dependency>
+  </dependencies>
+
+  <build>
+    <plugins>
+      <plugin>
+        <artifactId>maven-compiler-plugin</artifactId>
+        <configuration>
+          <source>${maven.compiler.source}</source>
+          <target>${maven.compiler.target}</target>
+        </configuration>
+      </plugin>
+    </plugins>
+  </build>
+</project>
diff --git a/src/main/java/io/trygvis/jz14/db/DbListener.java b/src/main/java/io/trygvis/jz14/db/DbListener.java
new file mode 100644
index 0000000..f16f391
--- /dev/null
+++ b/src/main/java/io/trygvis/jz14/db/DbListener.java
@@ -0,0 +1,223 @@
+package io.trygvis.jz14.db;
+
+import org.slf4j.Logger;
+
+import java.io.Closeable;
+import java.io.IOException;
+import java.sql.Connection;
+import java.sql.SQLException;
+import java.util.Collections;
+import java.util.Timer;
+import java.util.concurrent.Callable;
+import java.util.concurrent.TimeUnit;
+import java.util.function.Supplier;
+
+import static io.trygvis.jz14.db.RobustTimerTask.robustTimerTask;
+import static java.util.concurrent.TimeUnit.HOURS;
+import static java.util.concurrent.TimeUnit.MILLISECONDS;
+import static java.util.concurrent.TimeUnit.MINUTES;
+import static org.slf4j.LoggerFactory.getLogger;
+
+public class DbListener implements Closeable {
+    private final Logger log = getLogger(getClass());
+
+    private final DbListenerConfig config;
+    private final Timer timer;
+
+    private final Listener listener;
+
+    @FunctionalInterface
+    public static interface NewItemCallback {
+        void newItem(boolean wasNotified, Iterable<String> parameters) throws Exception;
+    }
+
+    public static final class PostgresConnection<T> implements Closeable {
+        public final Connection sqlConnection;
+        public final T underlying;
+
+        public PostgresConnection(Connection sqlConnection, T underlying) {
+            this.sqlConnection = sqlConnection;
+            this.underlying = underlying;
+        }
+
+        @Override
+        public final void close() {
+            try {
+                sqlConnection.close();
+            } catch (SQLException e) {
+                throw new RuntimeException(e);
+            }
+        }
+    }
+
+    public abstract static class DbListenerConfig {
+
+        /**
+         * Default scanner delay; 1 minute;
+         */
+        public static final long DEFAULT_SCANNER_DELAY = ms(1, MINUTES);
+
+        /**
+         * Default scanner period; 1 hour.
+         */
+        public static final long DEFAULT_SCANNER_PERIOD = ms(1, HOURS);
+
+        /**
+         * Default connection life check interval; 1 hour;
+         */
+        public static final long DEFAULT_LISTENER_CONNECTION_LIVE_CHECK_INTERVAL = ms(1, HOURS);
+
+        /**
+         * Default sleep time after failure; 1 second;
+         */
+        public static final long DEFAULT_LISTENER_SLEEP_INTERVAL = ms(200, MILLISECONDS);
+
+        /**
+         * Default sleep time after failure; 1 minute;
+         */
+        public static final long DEFAULT_LISTENER_FAILURE_SLEEP_INTERVAL = ms(1, MINUTES);
+
+        /**
+         * The name of the channel to listen on.
+         */
+        public final String name;
+
+        /**
+         * Should the scanner thread be started?
+         */
+        public final boolean runScanner;
+
+        /**
+         * Should the listener thread be started?
+         */
+        public final boolean runListener;
+
+        /**
+         * How long should the scanner wait after start before starting to scan.
+         */
+        public final long scannerDelay;
+
+        /**
+         * How often should the scanner wait between scans.
+         */
+        public long scannerPeriod;
+
+        /**
+         * How long should the listener sleep after each poll.
+         */
+        public long listenerSleepInterval;
+
+        /**
+         * How often should the listener do a live check of the connection.
+         */
+        public long listenerConnectionLiveCheckInterval;
+
+        /**
+         * How long should the listener sleep after a failure.
+         */
+        public long listenerFailureSleepInterval;
+
+        /**
+         * Configures a listener with the default parameters,
+         */
+        public DbListenerConfig(String name) {
+            this(name, true, true, DEFAULT_SCANNER_DELAY, DEFAULT_SCANNER_PERIOD,
+                    DEFAULT_LISTENER_SLEEP_INTERVAL, DEFAULT_LISTENER_CONNECTION_LIVE_CHECK_INTERVAL, DEFAULT_LISTENER_FAILURE_SLEEP_INTERVAL);
+        }
+
+        public DbListenerConfig(String name, boolean runScanner, boolean runListener, long scannerDelay, long scannerPeriod,
+                                long listenerSleepInterval, long listenerConnectionLiveCheckInterval, long listenerFailureSleepInterval) {
+            this.name = name;
+            this.runScanner = runScanner;
+            this.runListener = runListener;
+            this.scannerDelay = scannerDelay;
+            this.scannerPeriod = scannerPeriod;
+            this.listenerSleepInterval = listenerSleepInterval;
+            this.listenerConnectionLiveCheckInterval = listenerConnectionLiveCheckInterval;
+            this.listenerFailureSleepInterval = listenerFailureSleepInterval;
+        }
+
+        public static long ms(long count, TimeUnit unit) {
+            return MILLISECONDS.convert(count, unit);
+        }
+    }
+
+    public static DbListener nativeDbListener(DbListenerConfig config, NewItemCallback callable,
+                                              Supplier<PostgresConnection<org.postgresql.PGConnection>> connectionSupplier) throws SQLException {
+        return new DbListener(config, callable, connectionSupplier, null);
+    }
+
+    public static DbListener ngDbListener(DbListenerConfig config, NewItemCallback callable,
+                                          Supplier<PostgresConnection<com.impossibl.postgres.api.jdbc.PGConnection>> connectionSupplier) throws SQLException {
+        return new DbListener(config, callable, null, connectionSupplier);
+    }
+
+    private DbListener(DbListenerConfig config, NewItemCallback callable,
+                       Supplier<PostgresConnection<org.postgresql.PGConnection>> nativeSup,
+                       Supplier<PostgresConnection<com.impossibl.postgres.api.jdbc.PGConnection>> ngSup) throws SQLException {
+        this.config = config;
+
+        log.info("DB Listener: {}", config.name);
+        log.info(" Run scanner: {}", config.runScanner);
+        log.info(" Run listener: {}", config.runListener);
+
+        if (config.runScanner) {
+            timer = new Timer("Timer \"" + config.name + "\"", true);
+
+            timer.schedule(robustTimerTask(new NewItemCallbackCallable<>(callable)), config.scannerDelay, config.scannerPeriod);
+        } else {
+            timer = null;
+        }
+
+        if (config.runListener) {
+            try (PostgresConnection<?> pg = (nativeSup != null ? nativeSup : ngSup).get()) {
+                Connection c = pg.sqlConnection;
+                if (c.getMetaData().getDatabaseProductName().toLowerCase().contains("postgresql")) {
+                    if (nativeSup != null) {
+                        listener = new NativeListener(config, nativeSup, callable);
+                    } else {
+                        listener = new NgListener(config, ngSup, callable);
+                    }
+                    Thread thread = new Thread(listener, "LISTEN \"" + config.name + "\"");
+                    thread.start();
+                } else {
+                    log.info("Mail listener is configured to run, but the database isn't a PostgreSQL database");
+                    listener = null;
+                }
+            }
+        } else {
+            listener = null;
+        }
+    }
+
+    public void close() {
+        log.info("Stopping DB listener {}", config.name);
+        if (timer != null) {
+            timer.cancel();
+        }
+
+        if (listener != null) {
+            try {
+                listener.close();
+            } catch (IOException e) {
+                log.warn("Exception while closing listener.", e);
+            }
+        }
+    }
+
+    private class NewItemCallbackCallable<A> implements Callable<A> {
+
+        private final NewItemCallback callback;
+
+        private NewItemCallbackCallable(NewItemCallback callback) {
+            this.callback = callback;
+        }
+
+        @Override
+        public A call() throws Exception {
+            callback.newItem(false, Collections.emptyList());
+
+            return null;
+        }
+    }
+}
diff --git a/src/main/java/io/trygvis/jz14/db/Listener.java b/src/main/java/io/trygvis/jz14/db/Listener.java
new file mode 100644
index 0000000..4e8c7c1
--- /dev/null
+++ b/src/main/java/io/trygvis/jz14/db/Listener.java
@@ -0,0 +1,6 @@
+package io.trygvis.jz14.db;
+
+import java.io.Closeable;
+
+public interface Listener extends Runnable, Closeable {
+}
diff --git a/src/main/java/io/trygvis/jz14/db/NativeConnectionSupplier.java b/src/main/java/io/trygvis/jz14/db/NativeConnectionSupplier.java
new file mode 100644
index 0000000..d9db909
--- /dev/null
+++ b/src/main/java/io/trygvis/jz14/db/NativeConnectionSupplier.java
@@ -0,0 +1,44 @@
+package io.trygvis.jz14.db;
+
+import io.trygvis.jz14.db.DbListener.PostgresConnection;
+import org.postgresql.PGConnection;
+
+import javax.sql.DataSource;
+import java.sql.Connection;
+import java.sql.SQLException;
+import java.util.function.Supplier;
+
+public class NativeConnectionSupplier implements Supplier<PostgresConnection<PGConnection>> {
+    private final DataSource dataSource;
+
+    public NativeConnectionSupplier(DataSource dataSource) {
+        this.dataSource = dataSource;
+    }
+
+    @Override
+    public PostgresConnection<PGConnection> get() {
+        try {
+            Connection sqlConnection = dataSource.getConnection();
+            PGConnection pgConnection = unwrap(sqlConnection);
+            return new PostgresConnection<>(sqlConnection, pgConnection);
+        } catch (SQLException e) {
+            throw new RuntimeException(e);
+        }
+    }
+
+    public static PGConnection unwrap(Connection c) {
+        if (c instanceof PGConnection) {
+            return (PGConnection) c;
+        }
+
+        /* If you're using Spring, you need to add these two to properly unwrap the underlying PGConnection.
+        if (c instanceof ConnectionHandle) {
+            return unwrap(((ConnectionHandle) c).getInternalConnection());
+        }
+        if (c instanceof ConnectionProxy) {
+            return unwrap(DataSourceUtils.getTargetConnection(c));
+        }
+        */
+        throw new RuntimeException("Could not unwrap connection to a PGConnection: " + c.getClass());
+    }
+}
diff --git a/src/main/java/io/trygvis/jz14/db/NativeListener.java b/src/main/java/io/trygvis/jz14/db/NativeListener.java
new file mode 100644
index 0000000..c44a7cc
--- /dev/null
+++ b/src/main/java/io/trygvis/jz14/db/NativeListener.java
@@ -0,0 +1,157 @@
+package io.trygvis.jz14.db;
+
+import io.trygvis.jz14.db.DbListener.PostgresConnection;
+import org.postgresql.PGConnection;
+import org.postgresql.PGNotification;
+import org.slf4j.Logger;
+
+import java.sql.PreparedStatement;
+import java.sql.SQLException;
+import java.util.ArrayList;
+import java.util.List;
+import java.util.concurrent.atomic.AtomicBoolean;
+import java.util.function.Supplier;
+
+import static io.trygvis.jz14.db.DbListener.DbListenerConfig;
+import static io.trygvis.jz14.db.DbListener.NewItemCallback;
+import static java.lang.System.currentTimeMillis;
+import static java.lang.Thread.sleep;
+import static org.slf4j.LoggerFactory.getLogger;
+
+class NativeListener implements Listener {
+    private final Logger log = getLogger(getClass());
+
+    private final AtomicBoolean shouldRun = new AtomicBoolean(true);
+    private final DbListenerConfig config;
+    private final Supplier<PostgresConnection<PGConnection>> connectionSupplier;
+    private final NewItemCallback callback;
+
+    private PostgresConnection<PGConnection> c;
+    private long lastLiveCheck;
+
+    public NativeListener(DbListenerConfig config, Supplier<PostgresConnection<PGConnection>> connectionSupplier, NewItemCallback callback) {
+        this.config = config;
+        this.connectionSupplier = connectionSupplier;
+        this.callback = callback;
+    }
+
+    public synchronized void close() {
+        shouldRun.set(false);
+        notifyAll();
+    }
+
+    @Override
+    public void run() {
+        while (shouldRun.get()) {
+            try {
+                doIt();
+            } catch (Throwable e) {
+                log.error("doIt failed", e);
+                try {
+                    sleep(config.listenerFailureSleepInterval);
+                } catch (InterruptedException ex2) {
+                    if (!shouldRun.get()) {
+                        log.error("Got interrupted.", ex2);
+                    }
+                }
+            }
+        }
+    }
+
+    private void doIt() throws Exception {
+
+        if (c == null) {
+            log.debug("Connecting to database");
+
+            try {
+                c = connectAndListen();
+            } catch (Throwable ex) {
+                onError("Unable to connect to database", ex);
+                return;
+            }
+        }
+
+        long now = currentTimeMillis();
+
+        if (now - lastLiveCheck > config.listenerConnectionLiveCheckInterval) {
+            log.debug("Doing live check");
+            try {
+                doLiveCheck();
+                lastLiveCheck = now;
+            } catch (Exception ex) {
+                onError("Live check failed", ex);
+                return;
+            }
+        }
+
+        PGNotification[] notifications;
+        try {
+            notifications = c.underlying.getNotifications();
+        } catch (SQLException e) {
+            onError("Error while checking for notifications on connection.", e);
+            return;
+        }
+
+        if (notifications != null) {
+            List<String> strings = new ArrayList<>();
+            for (PGNotification notification : notifications) {
+                String parameter = notification.getParameter();
+                if (parameter == null) {
+                    continue;
+                }
+
+                parameter = parameter.trim();
+
+                if (!parameter.isEmpty()) {
+                    strings.add(parameter);
+                }
+            }
+
+            log.debug("Got notification: parameters={}", strings);
+
+            try {
+                callback.newItem(true, strings);
+            } catch (Exception ex) {
+                onError("Notification handler failed", ex);
+                return;
+            }
+        }
+
+        sleep(config.listenerSleepInterval);
+    }
+
+    private void onError(String msg, Throwable ex) throws InterruptedException {
+        log.info(msg, ex);
+
+        // Do a last attempt at closing the connection, the connection pool might appreciate it.
+        if (c != null) {
+            try {
+                c.close();
+            } catch (Throwable e) {
+                log.info("Exception when closing connection after error", e);
+            }
+        }
+        c = null;
+        log.info("Sleeping for {} ms after failure", config.listenerFailureSleepInterval);
+        sleep(config.listenerFailureSleepInterval);
+        log.info("Resuming work after failure");
+    }
+
+    private PostgresConnection<PGConnection> connectAndListen() throws SQLException {
+        PostgresConnection<PGConnection> c = connectionSupplier.get();
+        c.sqlConnection.setAutoCommit(true);
+
+        lastLiveCheck = currentTimeMillis();
+
+        PreparedStatement s = c.sqlConnection.prepareStatement("LISTEN \"" + config.name + "\"");
+        s.execute();
+        s.close();
+        return c;
+    }
+
+    private void doLiveCheck() throws SQLException {
+        PreparedStatement s = c.sqlConnection.prepareStatement("SELECT 1");
+        s.executeQuery().close();
+        s.close();
+    }
+}
diff --git a/src/main/java/io/trygvis/jz14/db/NgConnectionSupplier.java b/src/main/java/io/trygvis/jz14/db/NgConnectionSupplier.java
new file mode 100644
index 0000000..4006f1d
--- /dev/null
+++ b/src/main/java/io/trygvis/jz14/db/NgConnectionSupplier.java
@@ -0,0 +1,52 @@
+package io.trygvis.jz14.db;
+
+import com.impossibl.postgres.api.jdbc.PGConnection;
+import io.trygvis.jz14.db.DbListener.PostgresConnection;
+
+import javax.sql.DataSource;
+import java.sql.Connection;
+import java.sql.SQLException;
+import java.util.function.Supplier;
+
+public class NgConnectionSupplier implements Supplier<PostgresConnection<PGConnection>> {
+    private final DataSource dataSource;
+
+    public NgConnectionSupplier(DataSource dataSource) {
+        this.dataSource = dataSource;
+    }
+
+    @Override
+    public PostgresConnection<PGConnection> get() {
+        try {
+            Connection sqlConnection = dataSource.getConnection();
+            PGConnection pgConnection = unwrap(sqlConnection);
+            return new PostgresConnection<>(sqlConnection, pgConnection);
+        } catch (SQLException e) {
+            throw new RuntimeException(e);
+        }
+    }
+
+    public static PGConnection unwrap(Connection c) {
+        if (c instanceof PGConnection) {
+            return (PGConnection) c;
+        }
+
+        /* If you're using Spring, you need to add these two to properly unwrap the underlying PGConnection.
+        if (c instanceof ConnectionHandle) {
+            return unwrap(((ConnectionHandle) c).getInternalConnection());
+        }
+        if (c instanceof ConnectionProxy) {
+            return unwrap(DataSourceUtils.getTargetConnection(c));
+        }
+        */
+        Class<? extends Connection> klass = c.getClass();
+
+        Class<?>[] interfaces = klass.getInterfaces();
+        System.out.println("interfaces.length = " + interfaces.length);
+        for (Class<?> anInterface : interfaces) {
+            System.out.println("anInterface = " + anInterface);
+        }
+
+        throw new RuntimeException("Could not unwrap connection to a PGConnection: " + c.getClass());
+    }
+}
diff --git a/src/main/java/io/trygvis/jz14/db/NgListener.java b/src/main/java/io/trygvis/jz14/db/NgListener.java
new file mode 100644
index 0000000..b875ea1
--- /dev/null
+++ b/src/main/java/io/trygvis/jz14/db/NgListener.java
@@ -0,0 +1,126 @@
+package io.trygvis.jz14.db;
+
+import com.impossibl.postgres.api.jdbc.PGConnection;
+import com.impossibl.postgres.api.jdbc.PGNotificationListener;
+import io.trygvis.jz14.db.DbListener.PostgresConnection;
+import org.slf4j.Logger;
+
+import java.sql.PreparedStatement;
+import java.sql.SQLException;
+import java.util.Collections;
+import java.util.concurrent.atomic.AtomicBoolean;
+import java.util.function.Supplier;
+
+import static io.trygvis.jz14.db.DbListener.DbListenerConfig;
+import static io.trygvis.jz14.db.DbListener.NewItemCallback;
+import static java.lang.Thread.sleep;
+import static org.slf4j.LoggerFactory.getLogger;
+
+class NgListener implements Listener, PGNotificationListener {
+    private final Logger log = getLogger(getClass());
+
+    private final AtomicBoolean shouldRun = new AtomicBoolean(true);
+    private final DbListenerConfig config;
+    private final Supplier<PostgresConnection<PGConnection>> connectionSupplier;
+    private final NewItemCallback callback;
+
+    private PostgresConnection<PGConnection> c;
+
+    public NgListener(DbListenerConfig config, Supplier<PostgresConnection<PGConnection>> connectionSupplier, NewItemCallback callback) {
+        this.config = config;
+        this.connectionSupplier = connectionSupplier;
+        this.callback = callback;
+    }
+
+    public synchronized void close() {
+        shouldRun.set(false);
+        notifyAll();
+    }
+
+    @Override
+    public void run() {
+        while (shouldRun.get()) {
+            try {
+                doIt();
+            } catch (Throwable e) {
+                log.error("doIt failed", e);
+                try {
+                    sleep(config.listenerFailureSleepInterval);
+                } catch (InterruptedException ex2) {
+                    if (!shouldRun.get()) {
+                        log.error("Got interrupted.", ex2);
+                    }
+                }
+            }
+        }
+    }
+
+    private void doIt() throws Exception {
+
+        if (c == null) {
+            log.debug("Connecting to database");
+
+            try {
+                c = connectAndListen();
+            } catch (Throwable ex) {
+                onError("Unable to connect to database", ex);
+                return;
+            }
+        }
+
+        log.debug("Doing live check");
+        try {
+            doLiveCheck();
+        } catch (Exception ex) {
+            onError("Live check failed", ex);
+            return;
+        }
+
+        sleep(config.listenerConnectionLiveCheckInterval);
+    }
+
+    private void onError(String msg, Throwable ex) throws InterruptedException {
+        log.info(msg, ex);
+
+        // Do a last attempt at closing the connection, the connection pool might appreciate it.
+        if (c != null) {
+            try {
+                c.close();
+            } catch (Throwable e) {
+                log.info("Exception when closing connection after error", e);
+            }
+        }
+        c = null;
+        log.info("Sleeping for {} ms after failure", config.listenerFailureSleepInterval);
+        sleep(config.listenerFailureSleepInterval);
+        log.info("Resuming work after failure");
+    }
+
+    private PostgresConnection<PGConnection> connectAndListen() throws SQLException {
+        PostgresConnection<PGConnection> c = connectionSupplier.get();
+        c.sqlConnection.setAutoCommit(true);
+
+        c.underlying.addNotificationListener(this);
+
+        PreparedStatement s = c.sqlConnection.prepareStatement("LISTEN \"" + config.name + "\"");
+        s.execute();
+        s.close();
+
+        return c;
+    }
+
+    private void doLiveCheck() throws SQLException {
+        PreparedStatement s = c.sqlConnection.prepareStatement("SELECT 1");
+        s.executeQuery().close();
+        s.close();
+    }
+
+    @Override
+    public void notification(int processId, String channelName, String payload) {
+        try {
+            callback.newItem(true, Collections.singletonList(payload));
+        } catch (Exception e) {
+            log.warn("Exception while processing callback, payload=" + payload, e);
+        }
+    }
+}
diff --git a/src/main/java/io/trygvis/jz14/db/RobustTimerTask.java b/src/main/java/io/trygvis/jz14/db/RobustTimerTask.java
new file mode 100644
index 0000000..af55aa7
--- /dev/null
+++ b/src/main/java/io/trygvis/jz14/db/RobustTimerTask.java
@@ -0,0 +1,47 @@
+package io.trygvis.jz14.db;
+
+import org.slf4j.Logger;
+import org.slf4j.LoggerFactory;
+
+import java.util.TimerTask;
+import java.util.concurrent.Callable;
+
+public abstract class RobustTimerTask extends TimerTask {
+    private static final Logger log = LoggerFactory.getLogger(RobustTimerTask.class);
+
+    private final Class<?> klass;
+
+    private RobustTimerTask(Class<?> klass) {
+        this.klass = klass;
+    }
+
+    protected RobustTimerTask() {
+        this.klass = getClass();
+    }
+
+    public static TimerTask robustTimerTask(final TimerTask timerTask) {
+        return new RobustTimerTask(timerTask.getClass()) {
+            public void timerRun() throws Exception {
+                timerTask.run();
+            }
+        };
+    }
+
+    public static <T> TimerTask robustTimerTask(final Callable<T> callable) {
+        return new RobustTimerTask(callable.getClass()) {
+            public void timerRun() throws Exception {
+                callable.call();
+            }
+        };
+    }
+
+    public void run() {
+        try {
+            timerRun();
+        } catch (Exception e) {
+            log.error("Timer task " + klass.getName() + " failed.", e);
+        }
+    }
+
+    public abstract void timerRun() throws Exception;
+}
diff --git a/src/main/java/io/trygvis/jz14/demo/Db.java b/src/main/java/io/trygvis/jz14/demo/Db.java
new file mode 100644
index 0000000..9de8d7d
--- /dev/null
+++ b/src/main/java/io/trygvis/jz14/demo/Db.java
@@ -0,0 +1,67 @@
+package io.trygvis.jz14.demo;
+
+import com.impossibl.postgres.jdbc.PGDataSource;
+import org.postgresql.ds.PGPoolingDataSource;
+
+import javax.sql.DataSource;
+import java.sql.Connection;
+import java.sql.DriverManager;
+import java.sql.SQLException;
+
+import static java.util.Optional.ofNullable;
+
+public class Db {
+
+    public final String applicationName;
+    public final boolean ng;
+
+    public Db(String applicationName) {
+        this.applicationName = applicationName;
+        ng = false;
+    }
+
+    public Db(String applicationName, boolean ng) {
+        this.applicationName = applicationName;
+        this.ng = ng;
+    }
+
+    public Connection getConnection() throws SQLException {
+        return DriverManager.getConnection(jdbcUrl(), jdbcUsername(), jdbcPassword());
+    }
+
+    private String jdbcPassword() {
+        return ofNullable(System.getenv("password")).orElseGet(() -> System.getProperty("user.name"));
+    }
+
+    private String jdbcUsername() {
+        return ofNullable(System.getenv("username")).orElseGet(() -> System.getProperty("user.name"));
+    }
+
+    private String jdbcDatabase() {
+        return ofNullable(System.getenv("database")).orElseGet(() -> System.getProperty("user.name"));
+    }
+
+    private String jdbcUrl() {
+        if (ng) {
+            return "jdbc:pgsql://localhost/" + System.getProperty("user.name") + "?ApplicationName=" + applicationName;
+        }
+        return "jdbc:postgresql://localhost/" + System.getProperty("user.name") + "?ApplicationName=" + applicationName;
+    }
+
+    public DataSource dataSource() throws SQLException {
+        if (!ng) {
+            PGPoolingDataSource ds = new PGPoolingDataSource();
+            ds.setUrl(jdbcUrl());
+            ds.setUser(jdbcUsername());
+            ds.setPassword(jdbcPassword());
+            return ds;
+        } else {
+            PGDataSource ds = new PGDataSource();
+            ds.setHost("localhost");
+            ds.setUser(jdbcUsername());
+            ds.setPassword(jdbcPassword());
+            ds.setDatabase(jdbcDatabase());
+            return ds;
+        }
+    }
+}
diff --git a/src/main/java/io/trygvis/jz14/demo/InserterMain.java b/src/main/java/io/trygvis/jz14/demo/InserterMain.java
new file mode 100644
index 0000000..1192a09
--- /dev/null
+++ b/src/main/java/io/trygvis/jz14/demo/InserterMain.java
@@ -0,0 +1,37 @@
+package io.trygvis.jz14.demo;
+
+import org.slf4j.Logger;
+
+import java.sql.Connection;
+import java.sql.PreparedStatement;
+import java.util.Random;
+
+import static org.slf4j.LoggerFactory.getLogger;
+
+public class InserterMain {
+    Logger log = getLogger(getClass());
+    Db db = new Db("inserter");
+    Random r = new Random();
+
+    public static void main(String[] args) throws Exception {
+        new InserterMain().main();
+    }
+
+    public void main() throws Exception {
+        Connection c = db.getConnection();
+        c.setAutoCommit(false);
+
+        PreparedStatement stmt = c.prepareStatement("INSERT INTO mail_raw_t(raw) VALUES(?)");
+        int count = 1 + r.nextInt(9);
+
+        for (int i = 0; i < count; i++) {
+            stmt.setString(1, "mail #" + i);
+            stmt.execute();
+        }
+        c.commit();
+
+        log.info("INSERT performed, count={}", count);
+
+        c.close();
+    }
+}
diff --git a/src/main/java/io/trygvis/jz14/demo/KillListenerMain.java b/src/main/java/io/trygvis/jz14/demo/KillListenerMain.java
new file mode 100644
index 0000000..6ea982a
--- /dev/null
+++ b/src/main/java/io/trygvis/jz14/demo/KillListenerMain.java
@@ -0,0 +1,58 @@
+package io.trygvis.jz14.demo;
+
+import io.trygvis.jz14.db.DbListener;
+import org.slf4j.Logger;
+
+import java.sql.Connection;
+import java.sql.ResultSet;
+import java.sql.Statement;
+import java.util.ArrayList;
+import java.util.List;
+
+import static org.slf4j.LoggerFactory.getLogger;
+
+/**
+ * Kills all connections from {@link io.trygvis.jz14.demo.ListenerMain}.
+ * <p/>
+ * Note that this is slightly different from a postgresql backend failing, as the client will be told that it was
+ * killed, but the effect in this code is the same.
+ */
+public class KillListenerMain implements DbListener.NewItemCallback {
+    Logger log = getLogger(getClass());
+    Db db = new Db("killer");
+
+    public static void main(String[] args) throws Exception {
+        new KillListenerMain().main();
+    }
+
+    private void main() throws Exception {
+        Connection c = db.getConnection();
+        Statement s = c.createStatement();
+
+        ResultSet rs = s.executeQuery("SELECT pid FROM pg_stat_activity WHERE usename=user AND application_name='listener'");
+        if (!rs.next()) {
+            System.out.println("Couldn't find any listener");
+        } else {
+            List<Integer> pids = new ArrayList<>();
+
+            do {
+                int pid = rs.getInt("pid");
+                pids.add(pid);
+            } while (rs.next());
+
+            for (Integer pid : pids) {
+                System.out.println("Killing " + pid);
+                ResultSet rs2 = s.executeQuery("select pg_terminate_backend(" + pid + ")");
+                rs2.next();
+                System.out.println("rs2.getBoolean(1) = " + rs2.getBoolean(1));
+            }
+        }
+
+        c.close();
+    }
+
+    @Override
+    public void newItem(boolean wasNotified, Iterable<String> parameters) throws Exception {
+        log.info("ListenerMain.newItem: wasNotified={}, parameters={}", wasNotified, parameters);
+    }
+}
diff --git a/src/main/java/io/trygvis/jz14/demo/ListenerMain.java b/src/main/java/io/trygvis/jz14/demo/ListenerMain.java
new file mode 100644
index 0000000..82f7c27
--- /dev/null
+++ b/src/main/java/io/trygvis/jz14/demo/ListenerMain.java
@@ -0,0 +1,55 @@
+package io.trygvis.jz14.demo;
+
+import io.trygvis.jz14.db.DbListener;
+import io.trygvis.jz14.db.DbListener.DbListenerConfig;
+import io.trygvis.jz14.db.NativeConnectionSupplier;
+import io.trygvis.jz14.db.NgConnectionSupplier;
+import org.slf4j.Logger;
+
+import static java.util.concurrent.TimeUnit.SECONDS;
+import static org.slf4j.LoggerFactory.getLogger;
+
+public class ListenerMain implements DbListener.NewItemCallback {
+    Logger log = getLogger(getClass());
+
+    public void main(boolean useNative) throws Exception {
+        DbListener listener;
+        if (useNative) {
+            Db db = new Db("listener");
+            listener = DbListener.nativeDbListener(
+                    new DbListenerConfigForListenerMain("mail_raw"),
+                    this, new NativeConnectionSupplier(db.dataSource())
+            );
+        } else {
+            Db db = new Db("listener", true);
+            listener = DbListener.ngDbListener(
+                    new DbListenerConfigForListenerMain("mail_raw"),
+                    this, new NgConnectionSupplier(db.dataSource())
+            );
+        }
+
+        Runtime.getRuntime().addShutdownHook(new Thread() {
+            @Override
+            public void run() {
+                listener.close();
+            }
+        });
+
+        while (true) {
+            Thread.sleep(Long.MAX_VALUE);
+        }
+    }
+
+    @Override
+    public void newItem(boolean wasNotified, Iterable<String> parameters) throws Exception {
+        log.info("ListenerMain.newItem: wasNotified={}, parameters={}", wasNotified, parameters);
+    }
+
+    private class DbListenerConfigForListenerMain extends DbListenerConfig {
+        public DbListenerConfigForListenerMain(String name) {
+            super(name);
+            listenerFailureSleepInterval = ms(5, SECONDS);
+            listenerConnectionLiveCheckInterval = ms(5, SECONDS);
+        }
+    }
+}
diff --git a/src/main/java/io/trygvis/jz14/demo/NativeListenerMain.java b/src/main/java/io/trygvis/jz14/demo/NativeListenerMain.java
new file mode 100644
index 0000000..03f1c51
--- /dev/null
+++ b/src/main/java/io/trygvis/jz14/demo/NativeListenerMain.java
@@ -0,0 +1,8 @@
+package io.trygvis.jz14.demo;
+
+public class NativeListenerMain {
+    public static void main(String[] args) throws Exception {
+        new ListenerMain().main(true);
+    }
+}
+
diff --git a/src/main/java/io/trygvis/jz14/demo/NgListenerMain.java b/src/main/java/io/trygvis/jz14/demo/NgListenerMain.java
new file mode 100644
index 0000000..0ea79df
--- /dev/null
+++ b/src/main/java/io/trygvis/jz14/demo/NgListenerMain.java
@@ -0,0 +1,7 @@
+package io.trygvis.jz14.demo;
+
+public class NgListenerMain {
+    public static void main(String[] args) throws Exception {
+        new ListenerMain().main(false);
+    }
+}
diff --git a/src/main/java/io/trygvis/jz14/demo/NotifierMain.java b/src/main/java/io/trygvis/jz14/demo/NotifierMain.java
new file mode 100644
index 0000000..12dad41
--- /dev/null
+++ b/src/main/java/io/trygvis/jz14/demo/NotifierMain.java
@@ -0,0 +1,34 @@
+package io.trygvis.jz14.demo;
+
+import org.slf4j.Logger;
+
+import java.sql.Connection;
+import java.util.Random;
+
+import static org.slf4j.LoggerFactory.getLogger;
+
+public class NotifierMain {
+    Logger log = getLogger(getClass());
+    Db db = new Db("notifier");
+    Random r = new Random();
+
+    public static void main(String[] args) throws Exception {
+        new NotifierMain().main();
+    }
+
+    public void main() throws Exception {
+        Connection c = db.getConnection();
+//        c.setAutoCommit(false);
+
+        int count = 1 + r.nextInt(9);
+
+        for (int i = 0; i < count; i++) {
+            c.createStatement().execute("NOTIFY mail_raw, '" + i + "';");
+        }
+//        c.commit();
+
+        log.info("NOTIFY performed, count={}", count);
+
+        c.close();
+    }
+}
diff --git a/src/main/resources/logback.xml b/src/main/resources/logback.xml
new file mode 100644
index 0000000..31e60d0
--- /dev/null
+++ b/src/main/resources/logback.xml
@@ -0,0 +1,15 @@
+<configuration debug="false" scan="true" scanPeriod="1 second">
+
+  <appender name="STDOUT" class="ch.qos.logback.core.ConsoleAppender">
+    <encoder>
+      <pattern>%d{HH:mm:ss.SSS} %-5level [%-17thread] %-20logger{0} - %msg%n</pattern>
+    </encoder>
+  </appender>
+
+  <logger name="com.googlecode.flyway.core.dbsupport.SqlScript" level="INFO"/>
+  <logger name="org.eclipse.jetty" level="INFO"/>
+
+  <root level="DEBUG">
+    <appender-ref ref="STDOUT"/>
+  </root>
+</configuration>