## What do these changes do?
Fix the misleading comments in code for:
- `EPISODES_THIS_ITER`
- `EPISODES_TOTAL`
Had noted it before and planned to fix it along with some other changes but seemed very relevant to stay next to #3058 so sending this now.
* bugfix: env exists check error
* support to avoid re-build pyarrow in project
* bugfix: adapt gtest for centos lib64
* bugfix: check gtest lib exists in the directory
* bugfix: find gtest with checking all libs exists
* prefix RAY_ to thirdparty env variables to avoid conflicts with other module
* arrow use glog from ray
* change the glog and gtest install dir
## What do these changes do?
1. Add a configuration item `driver.resource-path`.
2. Load driver resources from the local path which is specified in the `ray.conf`.
Before this change, we should add all driver resources(like user's jar package, dependencies package and config files) into `classpath`.
After this change, we should add the driver resources into the mount path which we can configure it in `ray.conf`, and we shouldn't configure `classpath` for driver resources any more.
## Related issue number
N/A
This commit fix some small defects.
1. Remove a comment that should have been removed in #3003
2. Remove `redis_protected_mode` that is never used in `ray.init()`
3. Fix `object_id_seed` that is forgotten to be passed into `ray._init()`
4. Remove several redundant brackets.
This tests the case in which a worker is blocked in a call to ray.get or ray.wait, and then the worker dies. Then later, the object that the worker was waiting for becomes available. We need to make sure not to try to send a message to the dead worker and then die. Related to #2790.
## What do these changes do?
```c++
// Try to execute the worker command.
int rv = execvp(worker_command_args[0],
const_cast<char *const *>(worker_command_args.data()));
// The worker failed to start. This is a fatal error.
RAY_LOG(FATAL) << "Failed to start worker with return value " << rv;
```
When starting a process fails, the return value `rv` always be set to -1.
It is useless for us.
The log message should show some meaningful infos.
For example, If we did't install java. The message showed for us should be:
```shell
Failed to start worker: No such file or directory.
```
This could help us to locate issue quickly.
## Related issue number
N/A
If we set `ray.home` configuration item to `""`.
The current `RayConfig` will set it to current work directory, like `/User/My/Ray`.
But the some other configuration items(like `redisServerExecutablePath`) will be set to `/User/My/Ray//build/src/common/thirdparty/redis/src/redis-server` by mistake.
Note: There are 2 `/` between current work directory and `build/src/common....`
This PR will fix this issue.
Adds a tmux flag that can be used to support background execution of experiments. Cannot be used together with screen. Seems to be useful feature that has shown up with different users.
