[AIRFLOW-5528] end_of_log_mark should not be a log record

[pingzh]

Make sure you have checked all steps below.

Jira

• My PR addresses the following Airflow Jira issues and references them in the PR title. For example, "[AIRFLOW-5528] My Airflow PR"
  • https://issues.apache.org/jira/browse/AIRFLOW-5528
  • In case you are fixing a typo in the documentation you can prepend your commit with [AIRFLOW-XXX], code changes always need a Jira issue.
  • In case you are proposing a fundamental code change, you need to create an Airflow Improvement Proposal (AIP).
  • In case you are adding a dependency, check if the license complies with the ASF 3rd Party License Policy.

Description

• Here are some details about my PR, including screenshots of any UI changes:

When the end_of_log_mark is wrapped in a log record, the end_of_log_mark can no longer be able to match the log line in _read:

        metadata['end_of_log'] = False if not logs \
            else logs[-1].message == self.end_of_log_mark.strip()

It leads to the UI keeps calling backend and generates lots of load to ES.

Tests

• My PR adds the following unit tests OR does not need testing for this extremely good reason:

Commits

• My commits all reference Jira issues in their subject lines, and I have squashed multiple commits if they address the same issue. In addition, my commits follow the guidelines from "How to write a good git commit message":
  1. Subject is separated from body by a blank line
  2. Subject is limited to 50 characters (not including Jira issue reference)
  3. Subject does not end with a period
  4. Subject uses the imperative mood ("add", not "adding")
  5. Body wraps at 72 characters
  6. Body explains "what" and "why", not "how"

Documentation

• In case of new functionality, my PR adds documentation that describes how to use it.
  • All the public functions and the classes in the PR contain docstrings that explain what it does
  • If you implement backwards incompatible changes, please leave a note in the Updating.md so we can assign it to a appropriate release

@KevinYang21

[codecov-io]

Codecov Report

Merging #6159 into master will increase coverage by <.01%.
The diff coverage is 100%.

@@            Coverage Diff             @@
##           master    #6159      +/-   ##
==========================================
+ Coverage   80.09%   80.09%   +<.01%     
==========================================
  Files         606      606              
  Lines       35039    35039              
==========================================
+ Hits        28063    28065       +2     
+ Misses       6976     6974       -2

Impacted Files	Coverage Δ
airflow/utils/log/es_task_handler.py	91.74% <100%> (ø)	⬆️
airflow/jobs/scheduler_job.py	74.58% <0%> (+0.3%)	⬆️

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