[BEAM-4665] Allow joining a running dataflow pipeline without throwing

[damccorm]

Right now, if you try to run a dataflow pipeline with a defined name in async mode multiple times in a row it throws the second time because a job already exists:

This updates the behavior to just join the existing pipeline and not throw:

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ValidatesRunner compliance status (on master branch)

Lang	ULR	Dataflow	Flink	Samza	Spark	Twister2
Go	---					---
Java
Python	---					---
XLang						---

Examples testing status on various runners

Lang	ULR	Dataflow	Flink	Samza	Spark	Twister2
Go	---	---	---	---	---	---	---
Java	---		---	---	---	---	---
Python	---	---	---	---	---	---	---
XLang	---	---	---	---	---	---	---

Post-Commit SDK/Transform Integration Tests Status (on master branch)

Go	Java	Python

Pre-Commit Tests Status (on master branch)

---	Java	Python	Go	Website	Whitespace	Typescript
Non-portable
Portable	---			---	---	---

See .test-infra/jenkins/README for trigger phrase, status and link of all Jenkins jobs.

GitHub Actions Tests Status (on master branch)

See CI.md for more information about GitHub Actions CI.

[codecov]

Codecov Report

Merging #16689 (a0ebe95) into master (cc0b2c5) will decrease coverage by 0.04%.
The diff coverage is 0.00%.

@@            Coverage Diff             @@
##           master   #16689      +/-   ##
==========================================
- Coverage   46.43%   46.38%   -0.05%     
==========================================
  Files         202      202              
  Lines       19810    19828      +18     
==========================================
  Hits         9198     9198              
- Misses       9625     9643      +18     
  Partials      987      987              

Impacted Files	Coverage Δ
...o/pkg/beam/runners/dataflow/dataflowlib/execute.go	0.00% <0.00%> (ø)
...ks/go/pkg/beam/runners/dataflow/dataflowlib/job.go	14.76% <0.00%> (-1.22%)	⬇️

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[damccorm]

R: @lostluck

[damccorm]

Run GoPortable PreCommit

[damccorm]

Looks like the portable precommit check is being flaky? Either that or I'm not understanding what its trying to tell me 😬

[lostluck]

The portable failure looks like an unrelated failure, introduced this morning-ish. https://ci-beam.apache.org/job/beam_PreCommit_GoPortable_Cron/1317/
It's being discussed and worked on, so it'll probably be fine for a re-run later.

Not that this PR should be affecting the portable precommit anyway. Since this is dataflow specific we need to run the postcommit (which runs the same suite, on dataflow).

[lostluck]

Run Go Postcommit

[lostluck]

LGTM. I'll wait on the post commit just in case, but otherwise thanks!
This is great! Heck this allows anyone on the same project to get status/monitoring information for an active job, but that's a goal for a different time...

[damccorm]

Run Go Postcommit

[damccorm]

@lostluck looks like the integration failures were fixed by #16692, tests are passing again 🎉

[lostluck]

LGTM Thanks!