[Bug] Task log can't be shown on Web-Server when the task runs failed

[huozhanfeng]

Apache Airflow version:

Kubernetes version (if you are using kubernetes) (use kubectl version):

Environment:

• Cloud provider or hardware configuration: Aliyun
• OS (e.g. from /etc/os-release): CentOS Linux" VERSION="7 (Core)
• Kernel (e.g. uname -a): Linux 3.10.0-514.21.1.el7.x86_64
• Install tools: celery 4.4.7 rabbitmq 3.8.17
• Others:

What happened:
Task log can't be shown on Web-Server when the task runs failed, while log can be shown normally when the task success

*** Log file does not exist: /home/airflow/airflow/logs/dag_id/task_id/2021-06-28T00:00:00+08:00/28.log
*** Fetching from: http://:8793/log/dag_id/task_id/2021-06-28T00:00:00+08:00/28.log
*** Failed to fetch log file from worker. Unsupported URL protocol 

What you expected to happen:
The task log should be shown normally when the task runs failed.

The Hostname info doesn't be written into the task instance table, so the webserver can't get the corresponding hostname.

How to reproduce it:
Just run a dag and make its task fail to reproduce the bug.

Anything else we need to know:
I have fixed it in my env and will commit a PR to fix it.

[boring-cyborg]

Thanks for opening your first issue here! Be sure to follow the issue template!

[uranusjr]

Looks like another duplicate to #13692.

[huozhanfeng]

Looks like another duplicate to #13692.

Sure, I will track it on the other issue.