From d6989f1e54104d09b8af6d22cf46ea4f6fc5f4dc Mon Sep 17 00:00:00 2001
From: Trygve Laugstøl <trygvis@inamo.no>
Date: Wed, 10 Sep 2014 00:12:30 +0200
Subject: o Initial import of postgresql LISTEN/NOTIFY code.

---
 src/main/java/io/trygvis/jz14/db/NgListener.java | 126 +++++++++++++++++++++++
 1 file changed, 126 insertions(+)
 create mode 100644 src/main/java/io/trygvis/jz14/db/NgListener.java

(limited to 'src/main/java/io/trygvis/jz14/db/NgListener.java')

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);
+        }
+    }
+}
-- 
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