Implement New design of Observer, includes a newly designed logging system#11

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JohnDing1995 wants to merge 2 commits intomasterfrom

ruiyang/improvement/new_observer

Commits on Aug 21, 2019

Implement New design of Observer, includes a newly designed logging system:
JohnDing1995
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Fix 0cdd8a8d39687e89ef2123639b4c923653e856f5: Cache all log in one step and dump them to database in the end of each step.
JohnDing1995
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