test: add java fast_write_example for 3.0

docs/examples/java/src/main/java/com/taos/example/highvolume/DataBaseMonitor.java

+package com.taos.example.highvolume;
+
+import java.sql.*;
+
+/**
+ * Prepare target database.
+ * Count total records in database periodically so that we can estimate the writing speed.
+ */
+public class DataBaseMonitor {
+    private Connection conn;
+    private Statement stmt;
+
+    public DataBaseMonitor init() throws SQLException {
+        if (conn == null) {
+            String jdbcURL = System.getenv("TDENGINE_JDBC_URL");
+            conn = DriverManager.getConnection(jdbcURL);
+            stmt = conn.createStatement();
+        }
+        return this;
+    }
+
+    public void close() {
+        try {
+            stmt.close();
+        } catch (SQLException e) {
+        }
+        try {
+            conn.close();
+        } catch (SQLException e) {
+        }
+    }
+
+    public void prepareDatabase() throws SQLException {
+        stmt.execute("DROP DATABASE IF EXISTS test");
+        stmt.execute("CREATE DATABASE test");
+        stmt.execute("CREATE STABLE test.meters (ts TIMESTAMP, current FLOAT, voltage INT, phase FLOAT) TAGS (location BINARY(64), groupId INT)");
+    }
+
+    public Long count() throws SQLException {
+        if (!stmt.isClosed()) {
+            ResultSet result = stmt.executeQuery("SELECT count(*) from test.meters");
+            result.next();
+            return result.getLong(1);
+        }
+        return null;
+    }
+
+    /**
+     * show test.stables;
+     *
+     *               name              |      created_time       | columns |  tags  |   tables    |
+     * ============================================================================================
+     *  meters                         | 2022-07-20 08:39:30.902 |       4 |      2 |      620000 |
+     */
+    public  Long getTableCount() throws SQLException {
+        if (!stmt.isClosed()) {
+            ResultSet result = stmt.executeQuery("show test.stables");
+            result.next();
+            return result.getLong(5);
+        }
+        return null;
+    }
+}
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docs/examples/java/src/main/java/com/taos/example/highvolume/FastWriteExample.java

+package com.taos.example.highvolume;
+
+import org.slf4j.Logger;
+import org.slf4j.LoggerFactory;
+
+import java.sql.*;
+import java.util.ArrayList;
+import java.util.List;
+import java.util.concurrent.ArrayBlockingQueue;
+import java.util.concurrent.BlockingQueue;
+
+
+public class FastWriteExample {
+    final static Logger logger = LoggerFactory.getLogger(FastWriteExample.class);
+
+    final static int taskQueueCapacity = 1000000;
+    final static List<BlockingQueue<String>> taskQueues = new ArrayList<>();
+    final static List<ReadTask> readTasks = new ArrayList<>();
+    final static List<WriteTask> writeTasks = new ArrayList<>();
+    final static DataBaseMonitor databaseMonitor = new DataBaseMonitor();
+
+    public static void stopAll() {
+        logger.info("shutting down");
+        readTasks.forEach(task -> task.stop());
+        writeTasks.forEach(task -> task.stop());
+        databaseMonitor.close();
+    }
+
+    public static void main(String[] args) throws InterruptedException, SQLException {
+        int readTaskCount = args.length > 0 ? Integer.parseInt(args[0]) : 1;
+        int writeTaskCount = args.length > 1 ? Integer.parseInt(args[1]) : 3;
+        int tableCount = args.length > 2 ? Integer.parseInt(args[2]) : 1000;
+        int maxBatchSize = args.length > 3 ? Integer.parseInt(args[3]) : 3000;
+
+        logger.info("readTaskCount={}, writeTaskCount={} tableCount={} maxBatchSize={}",
+                readTaskCount, writeTaskCount, tableCount, maxBatchSize);
+
+        databaseMonitor.init().prepareDatabase();
+
+        // Create task queues, whiting tasks and start writing threads.
+        for (int i = 0; i < writeTaskCount; ++i) {
+            BlockingQueue<String> queue = new ArrayBlockingQueue<>(taskQueueCapacity);
+            taskQueues.add(queue);
+            WriteTask task = new WriteTask(queue, maxBatchSize);
+            Thread t = new Thread(task);
+            t.setName("WriteThread-" + i);
+            t.start();
+        }
+
+        // create reading tasks and start reading threads
+        int tableCountPerTask = tableCount / readTaskCount;
+        for (int i = 0; i < readTaskCount; ++i) {
+            ReadTask task = new ReadTask(i, taskQueues, tableCountPerTask);
+            Thread t = new Thread(task);
+            t.setName("ReadThread-" + i);
+            t.start();
+        }
+
+        Runtime.getRuntime().addShutdownHook(new Thread(FastWriteExample::stopAll));
+
+        long lastCount = 0;
+        while (true) {
+            Thread.sleep(10000);
+            long numberOfTable = databaseMonitor.getTableCount();
+            long count = databaseMonitor.count();
+            logger.info("numberOfTable={} count={} speed={}", numberOfTable, count, (count - lastCount) / 10);
+            lastCount = count;
+        }
+    }
+}
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docs/examples/java/src/main/java/com/taos/example/highvolume/MockDataSource.java

+package com.taos.example.highvolume;
+
+import java.util.Iterator;
+
+/**
+ * Generate test data
+ */
+class MockDataSource implements Iterator {
+    private String tbNamePrefix;
+    private int tableCount;
+    private long maxRowsPerTable = 1000000000L;
+
+    // 100 milliseconds between two neighbouring rows.
+    long startMs = System.currentTimeMillis() - maxRowsPerTable * 100;
+    private int currentRow = 0;
+    private int currentTbId = -1;
+
+    // mock values
+    String[] location = {"LosAngeles", "SanDiego", "Hollywood", "Compton", "San Francisco"};
+    float[] current = {8.8f, 10.7f, 9.9f, 8.9f, 9.4f};
+    int[] voltage = {119, 116, 111, 113, 118};
+    float[] phase = {0.32f, 0.34f, 0.33f, 0.329f, 0.141f};
+
+    public MockDataSource(String tbNamePrefix, int tableCount) {
+        this.tbNamePrefix = tbNamePrefix;
+        this.tableCount = tableCount;
+    }
+
+    @Override
+    public boolean hasNext() {
+        currentTbId += 1;
+        if (currentTbId == tableCount) {
+            currentTbId = 0;
+            currentRow += 1;
+        }
+        return currentRow < maxRowsPerTable;
+    }
+
+    @Override
+    public String next() {
+        long ts = startMs + 100 * currentRow;
+        int groupId = currentTbId % 5 == 0 ? currentTbId / 5 : currentTbId / 5 + 1;
+        StringBuilder sb = new StringBuilder(tbNamePrefix + "_" + currentTbId + ","); // tbName
+        sb.append(ts).append(','); // ts
+        sb.append(current[currentRow % 5]).append(','); // current
+        sb.append(voltage[currentRow % 5]).append(','); // voltage
+        sb.append(phase[currentRow % 5]).append(','); // phase
+        sb.append(location[currentRow % 5]).append(','); // location
+        sb.append(groupId); // groupID
+
+        return sb.toString();
+    }
+}
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docs/examples/java/src/main/java/com/taos/example/highvolume/ReadTask.java

+package com.taos.example.highvolume;
+
+import org.slf4j.Logger;
+import org.slf4j.LoggerFactory;
+
+import java.util.Iterator;
+import java.util.List;
+import java.util.concurrent.BlockingQueue;
+
+class ReadTask implements Runnable {
+    private final static Logger logger = LoggerFactory.getLogger(ReadTask.class);
+    private final int taskId;
+    private final List<BlockingQueue<String>> taskQueues;
+    private final int queueCount;
+    private final int tableCount;
+    private boolean active = true;
+
+    public ReadTask(int readTaskId, List<BlockingQueue<String>> queues, int tableCount) {
+        this.taskId = readTaskId;
+        this.taskQueues = queues;
+        this.queueCount = queues.size();
+        this.tableCount = tableCount;
+    }
+
+    /**
+     * Assign data received to different queues.
+     * Here we use the suffix number in table name.
+     * You are expected to define your own rule in practice.
+     *
+     * @param line record received
+     * @return which queue to use
+     */
+    public int getQueueId(String line) {
+        String tbName = line.substring(0, line.indexOf(',')); // For example: tb1_101
+        String suffixNumber = tbName.split("_")[1];
+        return Integer.parseInt(suffixNumber) % this.queueCount;
+    }
+
+    @Override
+    public void run() {
+        logger.info("started");
+        Iterator<String> it = new MockDataSource("tb" + this.taskId, tableCount);
+        try {
+            while (it.hasNext() && active) {
+                String line = it.next();
+                int queueId = getQueueId(line);
+                taskQueues.get(queueId).put(line);
+            }
+        } catch (Exception e) {
+            logger.error("Read Task Error", e);
+        }
+    }
+
+    public void stop() {
+        logger.info("stop");
+        this.active = false;
+    }
+}
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docs/examples/java/src/main/java/com/taos/example/highvolume/SQLWriter.java

+package com.taos.example.highvolume;
+
+import org.slf4j.Logger;
+import org.slf4j.LoggerFactory;
+
+import java.sql.*;
+import java.util.HashMap;
+import java.util.Map;
+
+/**
+ * A helper class encapsulate the logic of writing using SQL.
+ * <p>
+ * The main interfaces are two methods:
+ * <ol>
+ *     <li>{@link SQLWriter#processLine}, which receive raw lines from WriteTask and group them by table names.</li>
+ *     <li>{@link  SQLWriter#flush}, which assemble INSERT statement and execute it.</li>
+ * </ol>
+ * <p>
+ * There is a technical skill worth mentioning: we create table as needed when "table does not exist" error occur instead of creating table automatically using syntax "INSET INTO tb USING stb".
+ * This ensure that checking table existence is a one-time-only operation.
+ * </p>
+ *
+ * </p>
+ */
+public class SQLWriter {
+    final static Logger logger = LoggerFactory.getLogger(SQLWriter.class);
+
+    private Connection conn;
+    private Statement stmt;
+
+    /**
+     * current number of buffered records
+     */
+    private int bufferedCount = 0;
+    /**
+     * Maximum number of buffered records.
+     * Flush action will be triggered if bufferedCount reached this value,
+     */
+    private int maxBatchSize;
+
+
+    /**
+     * Maximum SQL length.
+     */
+    private int maxSQLLength;
+
+    /**
+     * Map from table name to column values. For example:
+     * "tb001" -> "(1648432611249,2.1,114,0.09) (1648432611250,2.2,135,0.2)"
+     */
+    private Map<String, String> tbValues = new HashMap<>();
+
+    /**
+     * Map from table name to tag values in the same order as creating stable.
+     * Used for creating table.
+     */
+    private Map<String, String> tbTags = new HashMap<>();
+
+    public SQLWriter(int maxBatchSize) {
+        this.maxBatchSize = maxBatchSize;
+    }
+
+
+    /**
+     * Get Database Connection
+     *
+     * @return Connection
+     * @throws SQLException
+     */
+    private static Connection getConnection() throws SQLException {
+        String jdbcURL = System.getenv("TDENGINE_JDBC_URL");
+        return DriverManager.getConnection(jdbcURL);
+    }
+
+    /**
+     * Create Connection and Statement
+     *
+     * @throws SQLException
+     */
+    public void init() throws SQLException {
+        conn = getConnection();
+        stmt = conn.createStatement();
+        stmt.execute("use test");
+        ResultSet rs = stmt.executeQuery("show variables");
+        while (rs.next()) {
+            String configName = rs.getString(1);
+            if ("maxSQLLength".equals(configName)) {
+                maxSQLLength = Integer.parseInt(rs.getString(2));
+                logger.info("maxSQLLength={}", maxSQLLength);
+            }
+        }
+    }
+
+    /**
+     * Convert raw data to SQL fragments, group them by table name and cache them in a HashMap.
+     * Trigger writing when number of buffered records reached maxBachSize.
+     *
+     * @param line raw data get from task queue in format: tbName,ts,current,voltage,phase,location,groupId
+     */
+    public void processLine(String line) throws SQLException {
+        bufferedCount += 1;
+        int firstComma = line.indexOf(',');
+        String tbName = line.substring(0, firstComma);
+        int lastComma = line.lastIndexOf(',');
+        int secondLastComma = line.lastIndexOf(',', lastComma - 1);
+        String value = "(" + line.substring(firstComma + 1, secondLastComma) + ") ";
+        if (tbValues.containsKey(tbName)) {
+            tbValues.put(tbName, tbValues.get(tbName) + value);
+        } else {
+            tbValues.put(tbName, value);
+        }
+        if (!tbTags.containsKey(tbName)) {
+            String location = line.substring(secondLastComma + 1, lastComma);
+            String groupId = line.substring(lastComma + 1);
+            String tagValues = "('" + location + "'," + groupId + ')';
+            tbTags.put(tbName, tagValues);
+        }
+        if (bufferedCount == maxBatchSize) {
+            flush();
+        }
+    }
+
+
+    /**
+     * Assemble INSERT statement using buffered SQL fragments in Map {@link SQLWriter#tbValues} and execute it.
+     * In case of "Table does not exit" exception, create all tables in the sql and retry the sql.
+     */
+    public void flush() throws SQLException {
+        StringBuilder sb = new StringBuilder("INSERT INTO ");
+        for (Map.Entry<String, String> entry : tbValues.entrySet()) {
+            String tableName = entry.getKey();
+            String values = entry.getValue();
+            String q = tableName + " values " + values + " ";
+            if (sb.length() + q.length() > maxSQLLength) {
+                executeSQL(sb.toString());
+                logger.warn("increase maxSQLLength or decrease maxBatchSize to gain better performance");
+                sb = new StringBuilder("INSERT INTO ");
+            }
+            sb.append(q);
+        }
+        executeSQL(sb.toString());
+        tbValues.clear();
+        bufferedCount = 0;
+    }
+
+    private void executeSQL(String sql) throws SQLException {
+        try {
+            stmt.executeUpdate(sql);
+        } catch (SQLException e) {
+            // convert to error code defined in taoserror.h
+            int errorCode = e.getErrorCode() & 0xffff;
+            if (errorCode == 0x362 || errorCode == 0x218) {
+                // Table does not exist
+                createTables();
+                executeSQL(sql);
+            } else {
+                logger.error("Execute SQL: {}", sql);
+                throw e;
+            }
+        } catch (Throwable throwable) {
+            logger.error("Execute SQL: {}", sql);
+            throw throwable;
+        }
+    }
+
+    /**
+     * Create tables in batch using syntax:
+     * <p>
+     * CREATE TABLE [IF NOT EXISTS] tb_name1 USING stb_name TAGS (tag_value1, ...) [IF NOT EXISTS] tb_name2 USING stb_name TAGS (tag_value2, ...) ...;
+     * </p>
+     */
+    private void createTables() throws SQLException {
+        StringBuilder sb = new StringBuilder("CREATE TABLE ");
+        for (String tbName : tbValues.keySet()) {
+            String tagValues = tbTags.get(tbName);
+            sb.append("IF NOT EXISTS ").append(tbName).append(" USING meters TAGS ").append(tagValues).append(" ");
+        }
+        String sql = sb.toString();
+        try {
+            stmt.executeUpdate(sql);
+        } catch (Throwable throwable) {
+            logger.error("Execute SQL: {}", sql);
+            throw throwable;
+        }
+    }
+
+    public boolean hasBufferedValues() {
+        return bufferedCount > 0;
+    }
+
+    public int getBufferedCount() {
+        return bufferedCount;
+    }
+
+    public void close() {
+        try {
+            stmt.close();
+        } catch (SQLException e) {
+        }
+        try {
+            conn.close();
+        } catch (SQLException e) {
+        }
+    }
+}
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docs/examples/java/src/main/java/com/taos/example/highvolume/StmtWriter.java

+package com.taos.example.highvolume;
+
+public class StmtWriter {
+}

docs/examples/java/src/main/java/com/taos/example/highvolume/WriteTask.java

+package com.taos.example.highvolume;
+
+import org.slf4j.Logger;
+import org.slf4j.LoggerFactory;
+
+import java.util.concurrent.BlockingQueue;
+
+class WriteTask implements Runnable {
+    private final static Logger logger = LoggerFactory.getLogger(WriteTask.class);
+    private final int maxBatchSize;
+
+    // the queue from which this writing task get raw data.
+    private final BlockingQueue<String> queue;
+
+    // A flag indicate whether to continue.
+    private boolean active = true;
+
+    public WriteTask(BlockingQueue<String> taskQueue, int maxBatchSize) {
+        this.queue = taskQueue;
+        this.maxBatchSize = maxBatchSize;
+    }
+
+    @Override
+    public void run() {
+        logger.info("started");
+        String line = null; // data getting from the queue just now.
+        SQLWriter writer = new SQLWriter(maxBatchSize);
+        try {
+            writer.init();
+            while (active) {
+                line = queue.poll();
+                if (line != null) {
+                    // parse raw data and buffer the data.
+                    writer.processLine(line);
+                } else if (writer.hasBufferedValues()) {
+                    // write data immediately if no more data in the queue
+                    writer.flush();
+                } else {
+                    // sleep a while to avoid high CPU usage if no more data in the queue and no buffered records, .
+                    Thread.sleep(100);
+                }
+            }
+            if (writer.hasBufferedValues()) {
+                writer.flush();
+            }
+        } catch (Exception e) {
+            String msg = String.format("line=%s, bufferedCount=%s", line, writer.getBufferedCount());
+            logger.error(msg, e);
+        } finally {
+            writer.close();
+        }
+    }
+
+    public void stop() {
+        logger.info("stop");
+        this.active = false;
+    }
+}
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