worker, utils: show same master status in one response

[lance6716]

What problem does this PR solve?

fix #727

What is changed and how it works?

when one response contains multiple relay and syncer status, use the larger master binlog position overwrite them and re-check status.

Check List

Tests

• Unit test

Code changes

• Has exported function/method change

Side effects

Related changes

• Need to cherry-pick to the master branch (doing)

[GMHDBJD]

Will this cause global point greater than master point?

[lance6716]

Yes. What's a better way? use larger master position and re-check two units? GMHDBJD <notifications@github.com> 于 2020年7月23日周四 15:20写道：

…

***@***.**** commented on this pull request. ------------------------------ In pkg/utils/db.go <#817 (comment)>: > // GetMasterStatus gets status from master func GetMasterStatus(db *sql.DB, flavor string) (gmysql.Position, gtid.Set, error) { + masterMu.Lock() + defer masterMu.Unlock() + + if useMasterStatusCache && masterStatusCached { + return masterPosCache, masterGTIDCache, nil Will this cause global point greater <https://github.com/pingcap/dm/blob/7ec79aed1816481099f01fcf0aaf48c7b783c96a/syncer/status.go#L79> than master point? — You are receiving this because you authored the thread. Reply to this email directly, view it on GitHub <#817 (review)>, or unsubscribe <https://github.com/notifications/unsubscribe-auth/AAM4RJWRVGSUKA6MSWIA45TR47QETANCNFSM4PFJ7FCA> .

[GMHDBJD]

Yes. What's a better way? use larger master position and re-check two units?

How about use the last one master position for same worker?

[lance6716]

last is larger position or something? not very understand GMHDBJD <notifications@github.com> 于 2020年7月23日周四 17:29写道：

…

Yes. What's a better way? use larger master position and re-check two units? How about use the last master position? — You are receiving this because you authored the thread. Reply to this email directly, view it on GitHub <#817 (comment)>, or unsubscribe <https://github.com/notifications/unsubscribe-auth/AAM4RJVAUPEHIGEQ5FLLSQTR477JBANCNFSM4PFJ7FCA> .

[GMHDBJD]

last is larger position or something? not very understand

Yes，use the largest one

[codecov]

Codecov Report

Merging #817 into release-1.0 will decrease coverage by 0.0273%.
The diff coverage is 70.4545%.

@@                 Coverage Diff                 @@
##           release-1.0       #817        +/-   ##
===================================================
- Coverage      57.7345%   57.7072%   -0.0274%     
===================================================
  Files              168        168                
  Lines            16756      16757         +1     
===================================================
- Hits              9674       9670         -4     
- Misses            6200       6204         +4     
- Partials           882        883         +1     

[GMHDBJD]

rest LGTM

[GMHDBJD]

/run-all-tests

[GMHDBJD]

LGTM

[csuzhangxc]

rest LGTM.

Should we need to re-implement this in master branch?

[lance6716]

Should we need to re-implement this in master branch?

yes, in description of this PR I added cherry-pick to master😂, will add a "wrong" tag to remind myself

[csuzhangxc]

LGTM