1、从hive中拉数据
1.1 <b>入口</b>：在presto指定根目录下/etc/catalog/hive.properties
1.2 <b>读取配置文件</b>com.facebook.presto.connector.ConnectorManager：
private void loadCatalog(File file)
throws Exception
{
//读取catalog下面的文件，把后缀名给去掉
String catalogName = Files.getNameWithoutExtension(file.getName());
if (disabledCatalogs.contains(catalogName)) {
log.info("Skipping disabled catalog %s", catalogName);
return;
}
log.info("-- Loading catalog %s --", file);
//加载文件中的配置信息到map中
Map<String, String> properties = new HashMap<>(loadProperties(file));
//获取connector.name 这里一般是写hive不同版本（hive-hadoop2等）
String connectorName = properties.remove("connector.name");
checkState(connectorName != null, "Catalog configuration %s does not contain connector.name", file.getAbsoluteFile());
//创建连接
connectorManager.createConnection(catalogName, connectorName, ImmutableMap.copyOf(properties));
log.info("-- Added catalog %s using connector %s --", catalogName, connectorName);
}
<b>1.3 创建连接到hive</b>
//catalogName=hive connectorName=我使用的是hive-hadoop2 properties包含hive.metastore.uri连接
connectorManager.createConnection(catalogName, connectorName, ImmutableMap.copyOf(properties));
public synchronized ConnectorId createConnection(String catalogName, String connectorName, Map<String, String> properties)
{
requireNonNull(connectorName, "connectorName is null");
//这个connectorFactories怎么来的?
ConnectorFactory connectorFactory = connectorFactories.get(connectorName);
checkArgument(connectorFactory != null, "No factory for connector %s", connectorName);
return createConnection(catalogName, connectorFactory, properties);
}
疑问：上面的connectorFactories是怎么来的呢？
public synchronized void addConnectorFactory(ConnectorFactory connectorFactory)
{
ConnectorFactory existingConnectorFactory = connectorFactories.putIfAbsent(connectorFactory.getName(), connectorFactory);
}
谁调用了上面的这个函数呢？
<b>在PluginManager类中有这样的函数：
public void installPlugin(Plugin plugin)
{
......
for (com.facebook.presto.spi.ConnectorFactory connectorFactory : plugin.getLegacyConnectorFactories()) {
log.info("Registering legacy connector %s", connectorFactory.getName());
//会读取plugin的目录，然后加载插件，添加到factory中
connectorManager.addConnectorFactory(new LegacyTransactionConnectorFactory(connectorFactory));
}
public PluginManager(
参数省略)
{
......
//读取配置信息获取plugin所在的目录地址，即服务的plugin
installedPluginsDir = config.getInstalledPluginsDir();
if (config.getPlugins() == null) {
this.plugins = ImmutableList.of();
}
else {
this.plugins = ImmutableList.copyOf(config.getPlugins());
}
public void loadPlugins()
throws Exception
{
....
//读取plugin目录下的所有目录加载插件，并加载
for (File file : listFiles(installedPluginsDir)) {
if (file.isDirectory()) {
loadPlugin(file.getAbsolutePath());
}
}
for (String plugin : plugins) {
loadPlugin(plugin);
}
.......
}
<b>1.4 来看看具体的加载数据</b>
上面我们已经明确了创建连接的过程了，接下面要介绍如何读取hive中的数据。
我们回到上面createConnection的方法
private synchronized ConnectorId createConnection(String catalogName, ConnectorFactory connectorFactory, Map<String, String> properties)
{
//省略
//重点是这句话
addCatalogConnector(catalogName, connectorId, connectorFactory, properties);
//省略
}
private synchronized void addCatalogConnector(String catalogName, ConnectorId connectorId, ConnectorFactory factory, Map<String, String> properties)
{
//创建一个connector，由之前的factorys来获取HiveConnectorFactory（presto/spi/connector包下）
Connector connector = createConnector(connectorId, factory, properties);
//标准的表，也就是hive中的用户表信息
addConnectorInternal(ConnectorType.STANDARD, catalogName, connectorId, connector);
//hive的表结构信息
ConnectorId informationSchemaId = createInformationSchemaConnectorId(connectorId);
addConnectorInternal(ConnectorType.INFORMATION_SCHEMA, catalogName, informationSchemaId, new InformationSchemaConnector(catalogName, nodeManager, metadataManager));
//系统表信息
ConnectorId systemId = createSystemTablesConnectorId(connectorId);
addConnectorInternal(ConnectorType.SYSTEM, catalogName, systemId, new SystemConnector(
systemId,
nodeManager,
connector.getSystemTables(),
transactionId -> transactionManager.getConnectorTransaction(transactionId, connectorId)));
}
其中addConnectorInternal的动作：
1、将connector放入到map中
2、获取ConnectorSplitManager（spi具体connector实现）
3、获取PageSourceProvider
4、获取PageSinkProvider
5、获取IndexProvider
6、获取NodePartitioningProvider
7、获取AccessControl
8、把上面获取到的对象添加到presto自身的Manager中，比如PageSourceProvider添加到PageSourceManager管理中。
<b>我们关心的从哪里加载数据，应该是PageSourceProvider作用</b>
#PageSourceManager类
@Override
public ConnectorPageSource createPageSource(Session session, Split split, List<ColumnHandle> columns)
{
getPageSourceProvider(split).createPageSource(split.getTransactionHandle(), connectorSession, split.getConnectorSplit(), columns);
}
#具体的实现类HivePageSourceProvider
@Override
public ConnectorPageSource createPageSource(ConnectorTransactionHandle transaction, ConnectorSession session, ConnectorSplit split, List<ColumnHandle> columns)
{
//读取列信息
List<HiveColumnHandle> hiveColumns = columns.stream()
.map(HiveColumnHandle::toHiveColumnHandle)
.collect(toList());
//获取hiveSplit路径
HiveSplit hiveSplit = checkType(split, HiveSplit.class, "split");
Path path = new Path(hiveSplit.getPath());
//hive的数据来源
Optional<ConnectorPageSource> pageSource = createHivePageSource(
cursorProviders,
pageSourceFactories,
hiveSplit.getClientId(),
hdfsEnvironment.getConfiguration(path),
session,
path,
hiveSplit.getStart(),
hiveSplit.getLength(),
hiveSplit.getSchema(),
hiveSplit.getEffectivePredicate(),
hiveColumns,
hiveSplit.getPartitionKeys(),
hiveStorageTimeZone,
typeManager);
if (pageSource.isPresent()) {
return pageSource.get();
}
throw new RuntimeException("Could not find a file reader for split " + hiveSplit);
}
好了，我们已经知道了他是如何获取数据的了，下一节介绍什么时候去拉取数据。待续~
