The MySQL plugin compare server and client timezone

embulk-input-jdbc/src/main/java/org/embulk/input/jdbc/AbstractJdbcInputPlugin.java

@@ -193,7 +193,7 @@ public ConfigDiff transaction(ConfigSource config,
         return buildNextConfigDiff(task, control.run(task.dump(), schema, 1));
     }
 
-    private Schema setupTask(JdbcInputConnection con, PluginTask task) throws SQLException
+    protected Schema setupTask(JdbcInputConnection con, PluginTask task) throws SQLException
     {
         if (task.getTable().isPresent()) {
             String actualTableName = normalizeTableNameCase(con, task.getTable().get());

embulk-input-mysql/src/main/java/org/embulk/input/MySQLInputPlugin.java

@@ -12,10 +12,12 @@
 import org.embulk.config.Config;
 import org.embulk.config.ConfigDefault;
 import org.embulk.input.jdbc.AbstractJdbcInputPlugin;
+import org.embulk.input.jdbc.JdbcInputConnection;
 import org.embulk.input.jdbc.getter.ColumnGetterFactory;
 import org.embulk.input.mysql.MySQLInputConnection;
 import org.embulk.input.mysql.getter.MySQLColumnGetterFactory;
 import org.embulk.spi.PageBuilder;
+import org.embulk.spi.Schema;
 import org.joda.time.DateTimeZone;
 
 public class MySQLInputPlugin
@@ -163,4 +165,13 @@ private void loadTimeZoneMappings()
             }
         }
     }
+
+    @Override
+    protected Schema setupTask(JdbcInputConnection con, PluginTask task) throws SQLException
+    {
+        MySQLInputConnection mySQLCon = (MySQLInputConnection)con;
+        mySQLCon.compareTimeZone();
+        return super.setupTask(con,task);
+    }
+
 }

embulk-input-mysql/src/main/java/org/embulk/input/MySQLTimeZoneComparison.java

@@ -0,0 +1,104 @@
+package org.embulk.input;
+
+import org.embulk.spi.Exec;
+import org.slf4j.Logger;
+
+import java.sql.Connection;
+import java.sql.ResultSet;
+import java.sql.SQLException;
+import java.sql.Statement;
+import java.util.Date;
+import java.util.Locale;
+import java.util.TimeZone;
+
+public class MySQLTimeZoneComparison
+{
+    private static final int ONE_HOUR_SEC = 3600;
+    private static final int ONE_MIN_SEC = 60;
+
+    private Connection connection;
+
+    private final Logger logger = Exec.getLogger(getClass());
+
+    public MySQLTimeZoneComparison(Connection connection)
+    {
+        this.connection = connection;
+    }
+
+    public void compareTimeZone()
+            throws SQLException
+    {
+        TimeZone serverTimeZone = null;
+        try {
+            serverTimeZone = getServerTimeZone();
+        }
+        catch (SQLException ex) {
+            logger.warn("Can't get server TimeZone.");
+            logger.warn(String.format(Locale.ENGLISH, "SQLException raised %s", ex.toString()));
+        }
+
+        TimeZone clientTimeZone = TimeZone.getDefault();
+        Date today = new Date();
+        int clientOffset = clientTimeZone.getRawOffset();
+
+        if (clientTimeZone.inDaylightTime(today)) {
+            clientOffset += clientTimeZone.getDSTSavings();
+        }
+
+        //
+        // Compare offset only. Although I expect to return true, the following code return false,
+        //
+        // TimeZone tz_jst   = TimeZone.getTimeZone("JST");
+        // TimeZone tz_gmt9  = TimeZone.getTimeZone("GMT+9");
+        // tz_jst.hasSameRules(tz_gmt9) // return false.
+        //
+        if (clientOffset != serverTimeZone.getRawOffset()) {
+            logger.warn(String.format(Locale.ENGLISH,
+                    "The client timezone(%s) is different from the server timezone(%s). The plugin will fetch wrong datetime values.",
+                    clientTimeZone.getID(), serverTimeZone.getID()));
+            logger.warn(String.format(Locale.ENGLISH,
+                    "You may need to set options `useLegacyDatetimeCode` and `serverTimezone`"));
+            logger.warn(String.format(Locale.ENGLISH,
+                    "Example. `options: { useLegacyDatetimeCode: false, serverTimezone: UTC }`"));
+        }
+        logger.warn(String.format(Locale.ENGLISH, "The plugin will set `useLegacyDatetimeCode=false` by default in future."));
+    }
+
+    private TimeZone getServerTimeZone()
+            throws SQLException
+    {
+        //
+        // First, I used `@@system_time_zone`. but It return non Time Zone Abbreviations name on a specific platform.
+        // So, This method calculate GMT offset with query.
+        //
+        String query = "select TIME_TO_SEC(timediff(now(),utc_timestamp()));";
+        Statement stmt = connection.createStatement();
+
+        try {
+            ResultSet rs = stmt.executeQuery(query);
+            if (rs.next()) {
+                int offsetSeconds = rs.getInt(1);
+                return fromGMTOffsetSeconds(offsetSeconds);
+            }
+            throw new SQLException(String.format(Locale.ENGLISH,
+                    "The timezone comparison query(%s) doesn't return the result.",query));
+        }
+        finally {
+            stmt.close();
+        }
+    }
+
+    private TimeZone fromGMTOffsetSeconds(int offsetSeconds)
+    {
+        if (offsetSeconds == 0) {
+            return TimeZone.getTimeZone("UTC");
+        }
+
+        String sign = offsetSeconds > 0 ? "+" : "-";
+        int absOffsetSec = Math.abs(offsetSeconds);
+        int tzHour = absOffsetSec / ONE_HOUR_SEC;
+        int tzMin = absOffsetSec % ONE_HOUR_SEC / ONE_MIN_SEC;
+        String tzName = String.format(Locale.ENGLISH, "GMT%s%02d:%02d", sign, tzHour, tzMin);
+        return TimeZone.getTimeZone(tzName);
+    }
+}

embulk-input-mysql/src/main/java/org/embulk/input/mysql/MySQLInputConnection.java

@@ -9,6 +9,7 @@
 
 import com.mysql.jdbc.ConnectionImpl;
 import com.mysql.jdbc.ConnectionProperties;
+import org.embulk.input.MySQLTimeZoneComparison;
 import org.embulk.input.jdbc.JdbcInputConnection;
 import org.embulk.input.jdbc.JdbcLiteral;
 import org.embulk.input.jdbc.getter.ColumnGetter;
@@ -59,4 +60,11 @@ public TimeZone getServerTimezoneTZ()
     {
         return ((ConnectionImpl) connection).getServerTimezoneTZ();
     }
+
+    public void compareTimeZone() throws SQLException
+    {
+        MySQLTimeZoneComparison timeZoneComparison = new MySQLTimeZoneComparison(connection);
+        timeZoneComparison.compareTimeZone();
+    }
+
 }