Package com.intellij.util.io

Interface BaseDataReader.SleepingPolicy

All Known Implementing Classes:

BaseDataReader.AdaptiveSleepingPolicy

Enclosing class:

BaseDataReader

public static interface BaseDataReader.SleepingPolicy

Blocking

In Java you can only read data from child process's stdout/stderr using blocking InputStream.read(). (Async approach like SelectableChannel is not supported for process's streams, although some native api may be used). Thread stays blocked by InputStream.read() until some data arrived or stream is closed (because of process death). It may lead to issues like IDEA-32376: you can't unlock blocked thread (at least non-daemon) otherwise than by killing process (and you may want to keep it running). Thread.interrupt() doesn't work here. This approach is good for short-living processes. If you know for sure that process will end soon (i.e. helper process) you can enable this behaviour using BLOCKING policy. It is implemented in BaseDataReader.readAvailableBlocking()

Non-blocking

Before reading data, you can call InputStream.available() to see how much data can be read without of blocking. This gives us ability to use simple loop

1. Check <InputStream.available()
2. If not zero then InputStream.read()} which is guaranteed not to block
3. If processTerminated flag set then exit loop
4. Sleep for a while
5. Repeat

This "busy-wait" antipattern is the only way to exit thread leaving process alive. It is required if you want to "disconnect" from user process and used by NON_BLOCKING (aka non-blocking) policy. Drawback is that process may finish (when Process.waitFor() returns) leaving some data unread. It is implemented in BaseDataReader.readAvailableNonBlocking()}

Conclusion

For helper (simple script that is guaranteed to finish soon) and should never be left after Idea is closed use BLOCKING. For user process that may run forever, even after idea is closed, and user should have ability to disconnect from it use NON_BLOCKING. If you see some data lost in stdout/stderr try switching to BLOCKING.

Field Summary

Fields

Modifier and Type	Field and Description
static BaseDataReader.SleepingPolicy	BLOCKING
static BaseDataReader.SleepingPolicy	NON_BLOCKING
static BaseDataReader.SleepingPolicy	SIMPLE Deprecated. use NON_BLOCKING instead
static int	sleepTimeWhenIdle
static int	sleepTimeWhenWasActive

Method Summary

Modifier and Type	Method and Description
int	getTimeToSleep(boolean wasActive)

Field Detail

sleepTimeWhenWasActive

static final int sleepTimeWhenWasActive

See Also:

Constant Field Values

sleepTimeWhenIdle

static final int sleepTimeWhenIdle

See Also:

Constant Field Values

NON_BLOCKING

static final BaseDataReader.SleepingPolicy NON_BLOCKING

BLOCKING

static final BaseDataReader.SleepingPolicy BLOCKING

SIMPLE

@Deprecated
static final BaseDataReader.SleepingPolicy SIMPLE

Deprecated. use NON_BLOCKING instead

Method Detail

getTimeToSleep

int getTimeToSleep(boolean wasActive)