CommandCreator 主要是基于不同业务规则进行conmandrunner 的生成，以下是一个简单说明
CommandCreator 的作用
- 基于request 创建包装的command
- 包装多种conmandrunner （基于用户请求类型，包装不同的commandrunner）
- 构建后变任务处理需要的上下文信息（比如sqlConverter，sqlHandlerConfig）
参考类
CommandRunner 类
参考子类，后边会介绍下，jdbc 以及web 经常会用到HandlerToExec 
调用
实际CommandCreator 的调用是由AttemptManager 的run 方法执行的，同时源头是ForemenWorkManager（和drill 一致）AttemptManager我以前简单介绍过，可以参考
- run 部分处理
对于CommandCreator 的依赖处理核心是使用了CommandPool
@Override
public void run() {
// rename the thread we're using for debugging purposes
final Thread currentThread = Thread.currentThread();
final String originalName = currentThread.getName();
currentThread.setName(queryIdString + ":foreman");
try {
injector.injectChecked(queryContext.getExecutionControls(), INJECTOR_TRY_BEGINNING_ERROR,
ForemanException.class);
observer.beginState(AttemptObserver.toEvent(AttemptEvent.State.PENDING));
observer.queryStarted(queryRequest, queryContext.getSession().getCredentials().getUserName());
String ruleSetEngine = ruleBasedEngineSelector.resolveAndUpdateEngine(queryContext);
ResourceSchedulingProperties resourceSchedulingProperties = new ResourceSchedulingProperties();
resourceSchedulingProperties.setRoutingEngine(queryContext.getSession().getRoutingEngine());
resourceSchedulingProperties.setRuleSetEngine(ruleSetEngine);
final GroupResourceInformation groupResourceInformation =
maestroService.getGroupResourceInformation(queryContext.getOptions(), resourceSchedulingProperties);
queryContext.setGroupResourceInformation(groupResourceInformation);
// Checks for Run Query privileges for the selected Engine
checkRunQueryAccessPrivilege(groupResourceInformation);
// planning is done in the command pool
commandPool.submit(CommandPool.Priority.LOW, attemptId.toString() + ":foreman-planning",
(waitInMillis) -> {
observer.commandPoolWait(waitInMillis);
injector.injectPause(queryContext.getExecutionControls(), INJECTOR_PENDING_PAUSE, logger);
injector.injectChecked(queryContext.getExecutionControls(), INJECTOR_PENDING_ERROR,
ForemanException.class);
plan();
injector.injectPause(queryContext.getExecutionControls(), INJECTOR_PLAN_PAUSE, logger);
injector.injectChecked(queryContext.getExecutionControls(), INJECTOR_PLAN_ERROR,
ForemanException.class);
return null;
}, runInSameThread).get(); // 等待plan()中的创建成功
plan 方法,会等待实际的CommandRunner plan 执行完成
private void plan() throws Exception {
// query parsing and dataset retrieval (both from source and kvstore).
observer.beginState(AttemptObserver.toEvent(AttemptEvent.State.METADATA_RETRIEVAL));
CommandCreator creator = newCommandCreator(queryContext, observer, prepareId);
command = creator.toCommand();
logger.debug("Using command: {}.", command);
injector.injectPause(queryContext.getExecutionControls(), INJECTOR_METADATA_RETRIEVAL_PAUSE, logger);
switch (command.getCommandType()) {
case ASYNC_QUERY:
Preconditions.checkState(command instanceof AsyncCommand, "Asynchronous query must be an AsyncCommand");
command.plan();
break;
case SYNC_QUERY:
case SYNC_RESPONSE:
moveToState(QueryState.STARTING, null);
command.plan();
extraResultData = command.execute();
addToEventQueue(QueryState.COMPLETED, null);
break;
default:
throw new IllegalStateException(
String.format("command type %s not supported in plan()", command.getCommandType()));
}
profileTracker.setPrepareId(prepareId.value);
}
参考资料
sabot/kernel/src/main/java/com/dremio/exec/planner/sql/handlers/commands/CommandCreator.java
https://www.cnblogs.com/rongfengliang/p/15987562.html
sabot/kernel/src/main/java/com/dremio/exec/work/foreman/AttemptManager.java