blackberrier commented on a change in pull request #5572:
URL: https://github.com/apache/dolphinscheduler/pull/5572#discussion_r644825479
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File path:
dolphinscheduler-server/src/main/java/org/apache/dolphinscheduler/server/master/cache/impl/TaskInstanceCacheManagerImpl.java
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@@ -57,7 +86,7 @@
@Override
public TaskInstance getByTaskInstanceId(Integer taskInstanceId) {
TaskInstance taskInstance = taskInstanceCache.get(taskInstanceId);
Review comment:
@ruanwenjun
I think the block may happen on two thread on two key, and the two key share
the same hashcode, which means they are on the same Linkedlist or Red-black
tree, and in `computeIfAbsent` synchronized lock on the head node.
If we write like this,
```
taskInstanceCache.computeIfAbsent(taskInstanceId, k ->
processService.findTaskInstanceById(k));
```
and if the first key access database and wasting time , then the second key
have to wait.
If we take database access out, like
```
taskInstance = processService.findTaskInstanceById(taskInstanceId);
TaskInstance finalTaskInstance = taskInstance;
taskInstanceCache.computeIfAbsent(taskInstanceId, k -> finalTaskInstance);
```
the second key need not wait while the first key is accessing database.
I wonder if my thought is reasonable.
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