## What do these changes do?
Because the logic of generating `TaskID` in java is different from python's, there are many tests fail when we change the `Ray Core` code.
In this change, I rewrote the logic of generating `TaskID` in java which is the same as the python's.
In java, we call the native method `_generateTaskId()` to generate a `TaskID` which is also used in python. We change `computePutId()`'s logic too.
## Related issue number
[#2608](https://github.com/ray-project/ray/issues/2608)
Currently, log directory in Java is a relative path . This PR changes it to `/tmp/raylogs` (with the same format as Python, e.g., `local_scheduler-2018-51-17_17-8-6-05164.err`). It also cleans up some relative code.
* Support building Java and Python version at the same time.
* Remove duplicated definition.
* Refine the building process of local_scheduler
* Refine
* Add comment for languages
* Modify instruction and add python,jave building to CI.
* change according to comment
## What do these changes do?
This implements basic task reconstruction in raylet. There are two parts to this PR:
1. Reconstruction suppression through the `TaskReconstructionLog`. This prevents two raylets from reconstructing the same task if they decide simultaneously (via the logic in #2497) that reconstruction is necessary.
2. Task resubmission once a raylet becomes responsible for reconstructing a task.
Reconstruction is quite slow in this PR, especially for long chains of dependent tasks. This is mainly due to the lease table mechanism, where nodes may wait too long before trying to reconstruct a task. There are two ways to improve this:
1. Expire entries in the lease table using Redis `PEXPIRE`. This is a WIP and I may include it in this PR.
2. Introduce a "fast path" for reconstructing dependencies of a re-executed task. Normally, we wait for an initial timeout before checking whether a task requires reconstruction. However, if a task requires reconstruction, then it's likely that its dependencies also require reconstruction. In this case, we could skip the initial timeout before checking the GCS to see whether reconstruction is necessary (e.g., if the object has been evicted).
Since handling failures of other raylets is probably not yet complete in master, this only turns back on Python tests for reconstructing evicted objects.
* add java code lint check and fix the java code lint error
* add java doc lint check and fix the java doc lint error
* add java code and doc lint to the CI
* Enable java worker support
--------------------------
This commit includes a tailored version of the Java worker implementation from Ant Financial.
The changes for build system, python module, src module and arrow are in other commits, this commit consists of the following modules:
- java/api: Ray API definition
- java/common: utilities
- java/hook: binary rewrite of the Java byte-code for remote execution
- java/runtime-common: common implementation of the runtime in worker
- java/runtime-dev: a pure-java mock implementation of the runtime for fast development
- java/runtime-native: a native implementation of the runtime
- java/test: various tests
Contributors for this work:
Guyang Song, Peng Cao, Senlin Zhu,Xiaoying Chu, Yiming Yu, Yujie Liu, Zhenyu Guo
* change the format of java help document from markdown to RST
* update the vesion of Arrow for java worker
* adapt the new version of plasma java client from arrow which use byte[] instead of custom type
* add java worker test to ci
* add the example module for better usage guide
