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 pingcap/tiup#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 pingcap/tidb-operator#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]

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%)	⬆️

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[rleungx]

Shall we need a default name?

[HuSharp]

default name set by this code, which is like TSO-localhost

pd/pkg/mcs/tso/server/config.go

Lines 185 to 195 in a39300e

	func (c *Config) Adjust(meta *toml.MetaData) error {
	configMetaData := configutil.NewConfigMetadata(meta)
	if err := configMetaData.CheckUndecoded(); err != nil {
	c.WarningMsgs = append(c.WarningMsgs, err.Error())
	}
	if c.Name == "" {
	hostname, err := os.Hostname()
	if err != nil {
	return err
	}
	configutil.AdjustString(&c.Name, fmt.Sprintf("%s-%s", defaultName, hostname))

And your commented snippet is for testing to avoid using the same name for the same machine for local testing, I used addr here

pd/tests/testutil.go

Lines 87 to 88 in 51708b5

	cfg.Name = cfg.ListenAddr
	cfg, err := tso.GenerateConfig(cfg)

[rleungx]

got

[rleungx]

Please revert this change.

[HuSharp]

Need to check why our static doesn't detect it here. 🤔

[JmPotato]

Suggested change

	func KeepExpectedPrimaryAlive(ctx context.Context, cli *clientv3.Client, exitPrimary chan struct{},
	func KeepExpectedPrimaryAlive(ctx context.Context, cli *clientv3.Client, exitPrimary chan<- struct{},

[HuSharp]

nice catch

[HuSharp]

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

[JmPotato]

I think here we can optimize the case that if the updated primary is still itself, no need to return to campaign again.

[HuSharp]

https://github.com/HuSharp/pd/blob/43830ec9ea80d92008be663ec5c26b3d137373a9/pkg/mcs/utils/expected_primary.go#L141-L146

I skipped the member on the outer layer(in transfer primary) which is not the same as oldPrimary, do you think I still need to add the restriction inside the watch?

Maybe the expected primary flag should not be modified when the leader is itself, because this flag must keep the lease alive after campaigning new leader, which means that it requires the Primary to quit the current watch.

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[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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