remove not used plugin heartbeat.lua

[mtx2d]

Fix #1176

Pre-submission checklist:

Please answer each of these after submitting your pull request:

• Did you explain what problem does this PR solve? Or what new features have been added?
  change: remove the plugin heartbeat #1776 Says that heartbeat is no longer needed, we can remove this.
• Have you added corresponding test cases?
  Checked that there is not test cases related to heartbeat.
  Removing this file does not break existing test suit.
• Have you modified the corresponding document?
  Link to document including heartbeart.
  There are three instances, two of them in the change log, and last one discussing in general service discovery.
  No need to modify any one of them.
• Is this PR backward compatible?
  Not sure how to check this.

[membphis]

@mtx2d please take a look at the output of CI, eg: https://github.com/apache/incubator-apisix/pull/1845/checks?check_run_id=871655239#step:6:272

[mtx2d]

@mtx2d please take a look at the output of CI, eg: https://github.com/apache/incubator-apisix/pull/1845/checks?check_run_id=871655239#step:6:272

Cannot run the test locally, so running this with CI.
In the meantime, could you please say more on why we no longer need heartbeat?
I can read the test failure and all, but design wise understanding the motivation will help me to create the correct PR.

[mtx2d]

Trying to figure out how to trigger CI.

[mtx2d]

@moonming @membphis , is it possible to force trigger a CI?
I made new commit to my local repo mtx2d/incubato-apisix, but the CI still looks at the old states.(my master should be 11 commits ahead but the CI still believes I am only 5 commits ahead).

How can I force trigger a CI?

[mtx2d]

@moonming @membphis , is it possible to force trigger a CI?
I made new commit to my local repo mtx2d/incubato-apisix, but the CI still looks at the old states.(my master should be 11 commits ahead but the CI still believes I am only 5 commits ahead).

How can I force trigger a CI?

Seems like the CI picks it up now.

[mtx2d]

The CI fails due to CI server network issue: https://github.com/apache/incubator-apisix/pull/1845/checks?check_run_id=874200614#step:3:68

Will make a small change and trigger another CI run.

[mtx2d]

According to this doc, we can close and reopen, which will trigger a new CI run without making changes.

[mtx2d]

Hi @membphis,
Do we think this is PR good to move forward :D?

[moonming]

LGTM

[membphis]

@mtx2d many thx, merged already