[TASK] Refactor: phase 2 cleanup — remove legacy master-worker scheduler dead code

[bitflicker64]

Background

PR #3082 soft-disabled the pre-PD master-worker scheduling path and intentionally left
deprecated config handling, role-election wiring, and ServerInfoManager persistence as
compatibility scaffolding. This issue tracks the follow-up physical removal ("phase 2")
called out in the merge comment ("TODO: cleanup legacy code/configs in phrase2").

Scope of removal

1. Deprecated config warnings + transition tests (low risk)

• task.scheduler_type warning block in StandardHugeGraph
• ENABLE_SERVER_ROLE_ELECTION warning in GraphManager.initNodeRole()
• ServerOptions.ENABLE_SERVER_ROLE_ELECTION config key declaration
• Transition-only tests: testOpenGraphWithDeprecatedTaskSchedulerType and
  testGraphManagerWarnsOnRoleElection

2. Role election infrastructure (medium risk — touches HugeGraph interface)

All of the following are dead code — nothing starts the state machine after #3082:

• StandardHugeGraph.initRoleStateMachine(Id) and the roleElectionStateMachine field
• roleElectionStateMachine() from the HugeGraph interface and HugeGraphAuthProxy
• GraphManager.initRoleStateMachine() and GraphManager.supportRoleElection() (never called)
• StandardRoleListener class (never instantiated)
• TaskManager.onAsRoleMaster() / onAsRoleWorker() no-ops
• TaskManager.schedulerExecutor (task-scheduler-%d) zombie thread pool and closeSchedulerTx()
• RoleElectionOptions config key declarations

3. ServerInfoManager dead persistence path + HugeServerInfo deletion (medium risk)

• ServerInfoManager.init() (no-op), heartbeat() (no-op), tx(), call(), and the
  dbExecutor field — the live methods (selfNodeId, selfIsMaster, initServerInfo, etc.)
  must be kept since DistributedTaskScheduler still uses them
• HugeServerInfo.java — entire class, including ~server vertex schema and load tracking
• serverInfoDbExecutor thread pool and SERVER_INFO_DB_WORKER constant from TaskManager
• serverInfoDbExecutor parameter from StandardTaskScheduler, TaskAndResultScheduler,
  and DistributedTaskScheduler constructors
• Update ServerInfoManagerTest and TaskSchedulerServerInfoTest accordingly

Suggested PR split

PR	Scope	Risk
PR A	Deprecated config warnings + transition tests	Low
PR B	Role election infrastructure	Medium
PR C	ServerInfoManager surgery + HugeServerInfo deletion	Medium

Important constraints

• ServerInfoManager itself is not deleted — DistributedTaskScheduler still uses
  selfNodeId() for task lock scoping.
• TaskScheduler.serverManager() interface method stays for the same reason.
• StandardHugeGraph.serverStarted() must keep the initServerInfo(nodeInfo) call —
  only the initRoleStateMachine(nodeInfo.nodeId()) call is removed.
• Before deleting HugeServerInfo, audit HugeVertex.java for fromVertex dispatch
  references and any initSchemaIfNeeded() call sites in system init.

Related

• refactor(server): disable legacy master-worker scheduler logic #3082

[bitflicker64]

Implementation Plan

Splitting into 3 PRs ordered by risk. Each PR is independently reviewable and mergeable.

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PR A — Remove deprecated config warnings + transition tests

Files to change:

• hugegraph-server/hugegraph-core/src/main/java/org/apache/hugegraph/StandardHugeGraph.java

  • Delete the task.scheduler_type containsKey warning block (~lines 229-234)

• hugegraph-server/hugegraph-api/src/main/java/org/apache/hugegraph/core/GraphManager.java

  • In initNodeRole(): remove the enableRoleElection local variable and the if (enableRoleElection) warning block; keep only the SERVER_ROLE read and initNodeRole() call

• hugegraph-server/hugegraph-api/src/main/java/org/apache/hugegraph/config/ServerOptions.java

  • Delete the ENABLE_SERVER_ROLE_ELECTION config key declaration

• hugegraph-server/hugegraph-test/.../core/MultiGraphsTest.java

  • Delete testOpenGraphWithDeprecatedTaskSchedulerType

• hugegraph-server/hugegraph-test/.../unit/core/TaskSchedulerServerInfoTest.java

  • Delete testGraphManagerWarnsOnRoleElection

No interface changes. Compile + existing tests should pass as-is.

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PR B — Remove role election infrastructure

Files to change:

• StandardHugeGraph.java

  • In serverStarted(): remove the this.initRoleStateMachine(nodeInfo.nodeId()) call (keep initServerInfo)
  • Delete the entire initRoleStateMachine(Id serverId) private method
  • Delete the roleElectionStateMachine field declaration
  • Delete the roleElectionStateMachine() public method

• HugeGraph.java (interface)

  • Remove the roleElectionStateMachine() method declaration

• HugeGraphAuthProxy.java

  • Remove the roleElectionStateMachine() override and its delegate call

• GraphManager.java

  • Delete initRoleStateMachine() method entirely (never called)
  • Delete supportRoleElection() method entirely (never called)
  • In serverStarted(): delete the dead if (!this.globalNodeRoleInfo.nodeRole().computer() && ...) block

• TaskManager.java

  • Delete onAsRoleMaster() and onAsRoleWorker() no-op methods
  • Delete schedulerExecutor field and TASK_SCHEDULER constant
  • Delete schedulerExecutor allocation in constructor
  • Delete closeSchedulerTx() private method
  • Remove closeSchedulerTx(graph) call inside closeScheduler()
  • Delete schedulerExecutor shutdown block in shutdown()

• StandardRoleListener.java — delete entire file

• RoleElectionOptions.java — remove all config key declarations (or delete the class if nothing else references it; grep first)

Verify: HugeGraph interface has multiple implementations — make sure all of them compile after removing roleElectionStateMachine().

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PR C — Slim ServerInfoManager, delete HugeServerInfo, drop serverInfoDbExecutor

Important constraint: ServerInfoManager is NOT deleted. DistributedTaskScheduler still uses selfNodeId() and selfIsMaster(). The serverManager() method on the TaskScheduler interface stays.

Files to change:

• ServerInfoManager.java

  • Remove dbExecutor field
  • Remove dbExecutor parameter from constructor (and its E.checkNotNull guard)
  • Delete init() method
  • Delete heartbeat() method
  • Delete tx() private method
  • Delete call() private method
  • Remove dead imports (Callable, ExecutorService, GraphTransaction, HugeException)
  • close() stays but simplify to just this.closed = true

• StandardTaskScheduler.java

  • Remove serverInfoDbExecutor parameter from constructor
  • Change new ServerInfoManager(graph, serverInfoDbExecutor) → new ServerInfoManager(graph)
  • If synchronized (this.serverManager) is used as a monitor in tx(), replace with synchronized (this) or a dedicated lock field

• TaskAndResultScheduler.java

  • Remove serverInfoDbExecutor parameter from constructor
  • Change new ServerInfoManager(graph, serverInfoDbExecutor) → new ServerInfoManager(graph)

• DistributedTaskScheduler.java

  • Remove serverInfoDbExecutor parameter from constructor
  • Update super(graph, serverInfoDbExecutor) → super(graph)

• TaskManager.java

  • Delete serverInfoDbExecutor field and SERVER_INFO_DB_WORKER constant
  • Delete serverInfoDbExecutor allocation in constructor
  • Remove serverInfoDbExecutor argument from both addScheduler() constructor calls
  • Delete serverInfoDbExecutor shutdown block in shutdown()

• HugeVertex.java

  • Audit for HugeServerInfo references (2 matches) — likely a fromVertex dispatch case; remove it

• StandardHugeGraph.java

  • Audit for initSchemaIfNeeded() call on HugeServerInfo.Schema in initSystemInfo() — remove it

• HugeServerInfo.java — delete entire file (after removing all call sites above)

• ServerInfoManagerTest.java

  • Delete testInitDoesNotAccessBackendStore (method no longer exists)
  • Update constructor calls: remove the executor argument everywhere

• TaskSchedulerServerInfoTest.java

  • Remove serverInfoDbExecutor local variable, its shutdownNow() call, and the constructor argument from the remaining tests

• TaskAndResultSchedulerTest.java

  • Same: remove serverInfoDbExecutor from all constructor calls (~10 occurrences)

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Checklist before each PR merges

• mvn compile passes
• mvn test -pl hugegraph-server/hugegraph-test passes
• No remaining references to deleted classes/methods (grep for HugeServerInfo, roleElectionStateMachine, schedulerExecutor, serverInfoDbExecutor as appropriate)