Driver类是对
org.apache.hadoop.hive.ql.processors.CommandProcessor.java
接口的实现，重写了run方法，定义了常见sql的执行方式.
public class Driver implements CommandProcessor
具体的方法调用顺序：
run--->runInternal--->(createTxnManager+recordValidTxns)----->compileInternal---> compile--analyzer(BaseSemanticAnalyzer)--->execute
其中compile和execute是两个比较重要的方法：
compile用来完成语法和语义的分析，生成执行计划
execute执行物理计划，即提交相应的mapredjob
通过打印perflog可以看到Driver类的简单地时序图：
下面来看下Driver类的几个常用的方法实现：
1)createTxnManager 用来获取目前设置的用于实现lock的类，比如:
org.apache.hadoop.hive.ql.lockmgr.DummyTxnManager
2)checkConcurrency 用来判断当前hive设置是否支持并发控制:
boolean supportConcurrency = conf.getBoolVar(HiveConf.ConfVars.HIVE_SUPPORT_CONCURRENCY);
主要是通过判断hive.support.concurrency参数，默认是false
3)getClusterStatus 调用JobClient类的getClusterStatus方法来获取集群的状态:
public ClusterStatus getClusterStatus() throws Exception {
ClusterStatus cs;
try {
JobConf job = new JobConf(conf , ExecDriver.class);
JobClient jc = new JobClient(job);
cs = jc.getClusterStatus();
} catch (Exception e) {
e.printStackTrace();
throw e;
}
LOG.info( "Returning cluster status: " + cs.toString());
return cs;
}4）getSchema //返回表的schema信息
doAuthorization/doAuthorizationV2/getHivePrivObjects
用来在开启权限验证情况下对sql的权限检测操作
getLockObjects/acquireReadWriteLocks/releaseLocks
都是和锁相关的方法 ,其中getLockObjects用来获取锁的对象（锁的路径，锁的模式等），最终返回一个包含所有锁的list,acquireReadWriteLocks用来控制获取锁，releaseLocks用来释放锁:
getLockObjects:
private List<HiveLockObj> getLockObjects(Database d, Table t, Partition p, HiveLockMode mode)
throws SemanticException {
List<HiveLockObj> locks = new LinkedList<HiveLockObj>();
HiveLockObjectData lockData =
new HiveLockObjectData( plan.getQueryId(),
String. valueOf(System.currentTimeMillis ()),
"IMPLICIT",
plan.getQueryStr());
if (d != null) {
locks.add( new HiveLockObj(new HiveLockObject(d.getName(), lockData), mode)); //数据库层面的锁
return locks;
}
if (t != null) { // 表层面的锁
locks.add( new HiveLockObj(new HiveLockObject(t.getDbName(), lockData), mode));
locks.add( new HiveLockObj(new HiveLockObject(t, lockData), mode));
mode = HiveLockMode.SHARED;
locks.add( new HiveLockObj(new HiveLockObject(t.getDbName(), lockData), mode));
return locks;
}
if (p != null) { //分区层面的锁
locks.add( new HiveLockObj(new HiveLockObject(p.getTable().getDbName(), lockData), mode));
if (!(p instanceof DummyPartition)) {
locks.add( new HiveLockObj(new HiveLockObject(p, lockData), mode));
}
// All the parents are locked in shared mode
mode = HiveLockMode.SHARED;
// For dummy partitions, only partition name is needed
String name = p.getName();
if (p instanceof DummyPartition) {
name = p.getName().split( "@")[2];
}
String partialName = "";
String[] partns = name.split( "/");
int len = p instanceof DummyPartition ? partns.length : partns.length - 1;
Map<String, String> partialSpec = new LinkedHashMap<String, String>();
for ( int idx = 0; idx < len; idx++) {
String partn = partns[idx];
partialName += partn;
String[] nameValue = partn.split( "=");
assert(nameValue.length == 2);
partialSpec.put(nameValue[0], nameValue[1]);
try {
locks.add( new HiveLockObj(
new HiveLockObject(new DummyPartition(p.getTable(), p.getTable().getDbName()
+ "/" + p.getTable().getTableName()
+ "/" + partialName,
partialSpec), lockData), mode));
partialName += "/";
} catch (HiveException e) {
throw new SemanticException(e.getMessage());
}
}
locks.add( new HiveLockObj(new HiveLockObject(p.getTable(), lockData), mode));
locks.add( new HiveLockObj(new HiveLockObject(p.getTable().getDbName(), lockData), mode));
}
return locks;
}acquireReadWriteLocks调用了锁具体实现类的acquireLocks方法
releaseLocks调用了锁具体实现类的releaseLocks方法
run方法是Driver类的入口方法，调用了runInternal方法，我们主要来看runInternal的方法，大体步骤：
运行hive.exec.driver.run.hooks中设置的hook， 运行HiveDriverRunHook相关类的的preDriverRun方法---->检测是否支持并发，并获取并发实现的类 --->compileInternal---->运行锁相关的操作（判断是否只对mapred job进行锁，获取锁等） ---->调用execute---->释放锁--->运行HiveDriverRunHook相关类的的postDriverRun方法 ---->返回CommandProcessorResponse对象
相关代码：
private CommandProcessorResponse runInternal(String command, boolean alreadyCompiled)
throws CommandNeedRetryException {
errorMessage = null;
SQLState = null;
downstreamError = null;
if (!validateConfVariables()) {
return new CommandProcessorResponse(12, errorMessage , SQLState );
}
HiveDriverRunHookContext hookContext = new HiveDriverRunHookContextImpl(conf , command);
// Get all the driver run hooks and pre-execute them.
List<HiveDriverRunHook> driverRunHooks;
try { //运行hive.exec.driver.run.hooks中设置的hook
driverRunHooks = getHooks(HiveConf.ConfVars.HIVE_DRIVER_RUN_HOOKS,
HiveDriverRunHook. class);
for (HiveDriverRunHook driverRunHook : driverRunHooks) {
driverRunHook.preDriverRun(hookContext); //运行HiveDriverRunHook相关类的的preDriverRun方法
}
} catch (Exception e) {
errorMessage = "FAILED: Hive Internal Error: " + Utilities.getNameMessage(e);
SQLState = ErrorMsg. findSQLState(e.getMessage());
downstreamError = e;
console.printError( errorMessage + "\n"
+ org.apache.hadoop.util.StringUtils.stringifyException(e));
return new CommandProcessorResponse(12, errorMessage , SQLState );
}
// Reset the perf logger
PerfLogger perfLogger = PerfLogger.getPerfLogger( true);
perfLogger.PerfLogBegin( CLASS_NAME, PerfLogger.DRIVER_RUN);
perfLogger.PerfLogBegin( CLASS_NAME, PerfLogger.TIME_TO_SUBMIT);
int ret;
boolean requireLock = false;
boolean ckLock = false;
try {
ckLock = checkConcurrency(); //检测是否支持并发，并获取并发实现的类，比如常用的 org.apache.hadoop.hive.ql.lockmgr.DummyTxnManager
createTxnManager();
} catch (SemanticException e) {
errorMessage = "FAILED: Error in semantic analysis: " + e.getMessage();
SQLState = ErrorMsg. findSQLState(e.getMessage());
downstreamError = e;
console.printError( errorMessage, "\n"
+ org.apache.hadoop.util.StringUtils.stringifyException(e));
ret = 10;
return new CommandProcessorResponse(ret, errorMessage , SQLState );
}
ret = recordValidTxns();
if (ret != 0) return new CommandProcessorResponse(ret, errorMessage, SQLState);
if (!alreadyCompiled) {
ret = compileInternal(command); //调用compileInternal方法
if (ret != 0) {
return new CommandProcessorResponse(ret, errorMessage, SQLState);
}
}
// the reason that we set the txn manager for the cxt here is because each
// query has its own ctx object. The txn mgr is shared across the
// same instance of Driver, which can run multiple queries.
ctx.setHiveTxnManager( txnMgr);
if (ckLock) { //断是否只对mapred job进行锁,参数hive.lock.mapred.only.operation，默认为false
boolean lockOnlyMapred = HiveConf.getBoolVar( conf, HiveConf.ConfVars.HIVE_LOCK_MAPRED_ONLY);
if(lockOnlyMapred) {
Queue<Task<? extends Serializable>> taskQueue = new LinkedList<Task<? extends Serializable>>();
taskQueue.addAll( plan.getRootTasks());
while (taskQueue.peek() != null) {
Task<? extends Serializable> tsk = taskQueue.remove();
requireLock = requireLock || tsk.requireLock();
if(requireLock) {
break;
}
if (tsk instanceof ConditionalTask) {
taskQueue.addAll(((ConditionalTask)tsk).getListTasks());
}
if(tsk.getChildTasks()!= null) {
taskQueue.addAll(tsk.getChildTasks());
}
// does not add back up task here, because back up task should be the same
// type of the original task.
}
} else {
requireLock = true;
}
}
if (requireLock) { //获取锁
ret = acquireReadWriteLocks();
if (ret != 0) {
try {
releaseLocks( ctx.getHiveLocks());
} catch (LockException e) {
// Not much to do here
}
return new CommandProcessorResponse(ret, errorMessage, SQLState);
}
}
ret = execute(); //job运行
if (ret != 0) {
//if needRequireLock is false, the release here will do nothing because there is no lock
try {
releaseLocks( ctx.getHiveLocks());
} catch (LockException e) {
// Nothing to do here
}
return new CommandProcessorResponse(ret, errorMessage , SQLState );
}
//if needRequireLock is false, the release here will do nothing because there is no lock
try {
releaseLocks( ctx.getHiveLocks());
} catch (LockException e) {
errorMessage = "FAILED: Hive Internal Error: " + Utilities.getNameMessage(e);
SQLState = ErrorMsg. findSQLState(e.getMessage());
downstreamError = e;
console.printError( errorMessage + "\n"
+ org.apache.hadoop.util.StringUtils.stringifyException(e));
return new CommandProcessorResponse(12, errorMessage , SQLState );
}
perfLogger.PerfLogEnd( CLASS_NAME, PerfLogger.DRIVER_RUN);
perfLogger.close(LOG, plan);
// Take all the driver run hooks and post-execute them.
try {
for (HiveDriverRunHook driverRunHook : driverRunHooks) { //运行HiveDriverRunHook相关类的的postDriverRun方法
driverRunHook.postDriverRun(hookContext);
}
} catch (Exception e) {
errorMessage = "FAILED: Hive Internal Error: " + Utilities.getNameMessage(e);
SQLState = ErrorMsg. findSQLState(e.getMessage());
downstreamError = e;
console.printError( errorMessage + "\n"
+ org.apache.hadoop.util.StringUtils.stringifyException(e));
return new CommandProcessorResponse(12, errorMessage , SQLState );
}
return new CommandProcessorResponse(ret);
}8）
再来看下compileInternal方法
private static final Object compileMonitor = new Object();
private int compileInternal(String command) {
int ret;
synchronized ( compileMonitor) {
ret = compile(command); //调用compile方法
}
if (ret != 0) {
try {
releaseLocks( ctx.getHiveLocks());
} catch (LockException e) {
LOG.warn("Exception in releasing locks. "
+ org.apache.hadoop.util.StringUtils.stringifyException(e));
}
}
return ret;
}调用了compile方法，compile方法分析命令，生成Task,关于compile的具体实现后面详细讲解
9.execute方法,提交task并等待task运行完毕，并打印task运行的信息，比如消耗的时间等
（这里信息也比较多，后面单独讲解
本文出自 “菜光光的博客” 博客，请务必保留此出处http://caiguangguang.blog.51cto.com/1652935/1571890
hive执行流程(3)-Driver类分析1Driver类整体流程
原文：http://caiguangguang.blog.51cto.com/1652935/1571890