pdms: support primary/transfer api for scheduling and tso

[HuSharp]

What problem does this PR solve?

For tiup

1. When we have 3 pdms, pdms-0/pdms-1/pdms-2, and pdms-2 is primary
2. upgrade pdms-2 firstly maybe transfer primary to pdms-0
3. uprade pdms-0 will transfer primary again

We can upgrade pdms primary in last place(named defer feature) can avoid unnecessary primary transfer

Ref https://github.com/pingcap/tiup/pull/2414

For operator

tidb-operator does not have the ability to defer feature, it can only upgrade the pods in order.

Furthermore, Thinking about this situation:

1. When we have 3 pdms, pdms-0/pdms-1/pdms-2, and pdms-2 is primary
2. upgrade pdms-2 firstly maybe transfer primary to pdms-1
3. upgrade pdms-1 maybe transfer primary to pdms-0.

To fix it, Assume that current primary ordinal is x, and range is [0, n]

1. Find the max suitable ordinal in (x, n], because they have been upgraded
2. If no suitable ordinal, find the min suitable ordinal in [0, x) to reduce the count of transfer

Ref https://github.com/pingcap/tidb-operator/pull/5643

Issue Number: Close #7995, Ref #5766, #7519

What is changed and how does it work?

1. Add primaryWatch for the primary watch only, which is used to reuse Watch interface in Leadership.
2. primaryWatch watches /ms/primary/transfer API whether changed the primary.
   1. modify the expected primary flag to the new primary
   2. modify memory status
   3. exit the primary watch loop
   4. delete the leader key
3. Expected primary flag is the path to store the expected primary , ONLY Triggered BY /ms/primary/transfer API.
   • This flag likes a fence to avoid exited 2 primaries in the cluster simultaneously.
   • Since follower will campaign a new primary when it found the leader_key is deleted.
   • We can ensure expected_primary is set before deleting the leader_key.
   • Old primary will set expected_primary firstly,then delete the leader_key which will trigger the follower to campaign a new primary.
4. support /ms/primary/transfer API to change primary

$ curl --location --request GET 'http://127.0.0.1:2379/pd/api/v2/ms/primary/tso'
"http://127.0.0.1:2382"%

$ curl --location --request POST 'http://127.0.0.1:2379/pd/api/v2/ms/primary/transfer/tso' \
--header 'Content-Type: text/plain' \
--data-raw '{
    "new_primary": "tso-0"
}'
"success"%

$ curl --location --request GET 'http://127.0.0.1:2379/pd/api/v2/ms/primary/tso'
"http://127.0.0.1:2384"

$ curl --location --request POST 'http://127.0.0.1:2379/pd/api/v2/ms/primary/transfer/tso' \
--header 'Content-Type: application/json' \
--data-raw '{
    "new_primary": ""
}'
"success"

$ curl --location --request GET 'http://127.0.0.1:2379/pd/api/v2/ms/primary/tso'
"http://127.0.0.1:2382"

the members info are

curl --location --request GET 'http://127.0.0.1:2379/pd/api/v2/ms/members/tso'

get

[
    {
        "name": "tso-0",
        "service-addr": "http://127.0.0.1:2384",
        "version": "v8.2.0-alpha-23-gdd72b9c19-dirty",
        "git-hash": "dd72b9c19707ccbdb1801d379b3982a7944df23f",
        "deploy-path": "/Users/pingcap/CS/PingCAP/pd/bin",
        "start-timestamp": 1715577605,
        "member-value": "ChtodHRwOi8vMTI3LjAuMC4xOjIzODQtMDAwMDAQp+L2iMCp3NUaGhVodHRwOi8vMTI3LjAuMC4xOjIzODQ="
    },
    {
        "name": "tso-1",
        "service-addr": "http://127.0.0.1:2386",
        "version": "v8.2.0-alpha-23-gdd72b9c19-dirty",
        "git-hash": "dd72b9c19707ccbdb1801d379b3982a7944df23f",
        "deploy-path": "/Users/pingcap/CS/PingCAP/pd/bin",
        "start-timestamp": 1715577605,
        "member-value": "ChtodHRwOi8vMTI3LjAuMC4xOjIzODYtMDAwMDAQj9ro5Yq9mY8mGhVodHRwOi8vMTI3LjAuMC4xOjIzODY="
    }
]

Check List

Tests

• Unit test
• Manual test (add detailed scripts or steps below)

Release note

None.

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[codecov[bot]]

Codecov Report

Attention: Patch coverage is 75.70093% with 52 lines in your changes missing coverage. Please review.

Project coverage is 77.49%. Comparing base (3f32f54) to head (2d9a3b0). Report is 2 commits behind head on master.

Additional details and impacted files

@@            Coverage Diff             @@
##           master    #8157      +/-   ##
==========================================
+ Coverage   77.40%   77.49%   +0.08%     
==========================================
  Files         472      473       +1     
  Lines       61821    61934     +113     
==========================================
+ Hits        47854    47993     +139     
+ Misses      10400    10373      -27     
- Partials     3567     3568       +1     

Flag	Coverage Δ
unittests	77.49% <75.70%> (+0.08%)	:arrow_up:

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[HuSharp]

@JmPotato @lhy1024 PTAL, thx!

[HuSharp]

@rleungx @JmPotato @lhy1024 friendly ping :)

[ti-chi-bot[bot]]

[LGTM Timeline notifier]

Timeline:

• 2024-07-04 08:12:07.112911669 +0000 UTC m=+1484853.598400502: :ballot_box_with_check: agreed by JmPotato.
• 2024-07-08 08:11:01.07454411 +0000 UTC m=+258758.309778223: :ballot_box_with_check: agreed by rleungx.

[HuSharp]

/hold Need to prepare tiup&operator pr

[HuSharp]

@JmPotato @rleungx Can you put in a lgtm to indicate that you have agreed? Then I'll cancel the hold label. :) Thx!

[ti-chi-bot[bot]]

[APPROVALNOTIFIER] This PR is APPROVED

This pull-request has been approved by: JmPotato, rleungx

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[HuSharp]

Completed manual testing of operator and tiup

[HuSharp]

/unhold

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