Starting LocalDatastoreHelper stalls if beta gcloud component is not installed

[pomu0325]

Environment details

• OS type and version: Debian GNU/Linux 10 (buster) (on Docker)
• Java version: openjdk version "1.8.0_275"
• datastore version(s): com.google.cloud:google-cloud-datastore:jar:1.105.0

Steps to reproduce

1. Remove beta component: gcloud components remove beta
2. Run the code which uses LocalDatastoreHelper

Code example

import com.google.cloud.datastore.testing.LocalDatastoreHelper;

public class Test {
  public static void main(String[] args) throws Exception {
    LocalDatastoreHelper emulator = LocalDatastoreHelper.create();
    emulator.start();

    System.out.println("Started!");
  }
}

How I found this

• Removed beta component

root@17224e8a6010:/app# gcloud components remove beta --quiet
┌──────────────────────────────────────────┐
│    These components will be removed.     │
├──────────────────────┬────────────┬──────┤
│         Name         │  Version   │ Size │
├──────────────────────┼────────────┼──────┤
│ gcloud Beta Commands │ 2019.05.17 │      │
└──────────────────────┴────────────┴──────┘
...
Uninstall done!

• Run code example, then it stalls.

root@17224e8a6010:/app# mvn exec:java -Dexec.mainClass=Test

• Ctrl+Z and run ps to find out what command is executed via LocalDatastoreHelper

^Z
[1]+  Stopped                 mvn exec:java -Dexec.mainClass=Test
root@17224e8a6010:/app# ps -ef 
...
root      1840  1795  0 17:40 pts/1    00:00:00 python2 -S /root/google-cloud-sdk/lib/gcloud.py beta emulators datastore start --host-port=localhost:40079 --consistency=0.9

• Execute the same command at the terminal, then it prompts whether continue to install beta component

root@17224e8a6010:/app# python2 -S /root/google-cloud-sdk/lib/gcloud.py beta emulators datastore start --host-port=localhost:40079 --consistency=0.9
You do not currently have this command group installed.  Using it 
requires the installation of components: [beta]


Your current Cloud SDK version is: 322.0.0
Installing components from version: 322.0.0

┌─────────────────────────────────────────────┐
│     These components will be installed.     │
├──────────────────────┬────────────┬─────────┤
│         Name         │  Version   │   Size  │
├──────────────────────┼────────────┼─────────┤
│ gcloud Beta Commands │ 2019.05.17 │ < 1 MiB │
└──────────────────────┴────────────┴─────────┘

For the latest full release notes, please visit:
  https://cloud.google.com/sdk/release_notes

Do you want to continue (Y/n)?  

Possible solution

Add --quiet option to run emulator, so as to silently install beta component.
pomu0325@e2cb8f2

[crwilcox]

It seems the issue here is likely that the process is blocking on https://github.com/googleapis/java-datastore/blob/master/google-cloud-datastore/src/main/java/com/google/cloud/datastore/testing/LocalDatastoreHelper.java#L273
which never occurs as the components aren't present.

Perhaps this method https://github.com/googleapis/java-core/blob/375983090b3700b3fb6a1953626db7efca49cc51/google-cloud-core/src/main/java/com/google/cloud/testing/BaseEmulatorHelper.java#L94 needs a timeout?

[meredithslota]

@prash-mi Can you or @jainsahab take a look?