refactor(plugin-iceberg): Fix thread safety in Iceberg procedures

[agrawalreetika]

Description

Fix thread safety in Iceberg procedures

Motivation and Context

Fix thread safety in Iceberg procedures

Impact

Fix thread safety in Iceberg procedures

Test Plan

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Release Notes

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Summary by Sourcery

Bug Fixes:

• Wrap Iceberg snapshot management operations in a thread context class loader to avoid thread-safety issues when invoking these procedures.

[sourcery-ai]

Reviewer's Guide

Wraps Iceberg snapshot/branch management procedures in a ThreadContextClassLoader to fix thread-safety issues related to the context class loader during metadata and snapshot operations.

Sequence diagram for Iceberg procedure execution with ThreadContextClassLoader

sequenceDiagram
    participant PrestoEngine
    participant SetCurrentSnapshotProcedure
    participant ThreadContextClassLoader
    participant IcebergTransactionMetadata
    participant IcebergTable

    PrestoEngine->>SetCurrentSnapshotProcedure: setCurrentSnapshot(session, schema, table, snapshotId, reference)
    activate SetCurrentSnapshotProcedure

    SetCurrentSnapshotProcedure->>ThreadContextClassLoader: new ThreadContextClassLoader(procedureClassLoader)
    activate ThreadContextClassLoader
    SetCurrentSnapshotProcedure->>ThreadContextClassLoader: enter try_with_resources

    SetCurrentSnapshotProcedure->>SetCurrentSnapshotProcedure: checkState(snapshotId xor reference)

    SetCurrentSnapshotProcedure->>IcebergTransactionMetadata: metadataFactory.create()
    activate IcebergTransactionMetadata
    IcebergTransactionMetadata-->>SetCurrentSnapshotProcedure: metadata

    SetCurrentSnapshotProcedure->>IcebergTransactionMetadata: getIcebergTable(metadata, session, schemaTableName)
    IcebergTransactionMetadata-->>SetCurrentSnapshotProcedure: IcebergTable
    activate IcebergTable

    SetCurrentSnapshotProcedure->>SetCurrentSnapshotProcedure: resolve targetSnapshotId

    SetCurrentSnapshotProcedure->>IcebergTable: manageSnapshots().setCurrentSnapshot(targetSnapshotId).commit()

    SetCurrentSnapshotProcedure->>IcebergTransactionMetadata: commit()
    deactivate IcebergTransactionMetadata
    deactivate IcebergTable

    SetCurrentSnapshotProcedure->>ThreadContextClassLoader: close() (restore previous context loader)
    deactivate ThreadContextClassLoader

    SetCurrentSnapshotProcedure-->>PrestoEngine: return
    deactivate SetCurrentSnapshotProcedure

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Class diagram for Iceberg procedures using ThreadContextClassLoader

classDiagram
    class SetCurrentSnapshotProcedure {
        - IcebergTransactionMetadataFactory metadataFactory
        + Procedure get()
        + void setCurrentSnapshot(ConnectorSession clientSession, String schema, String table, Long snapshotId, String reference)
    }

    class FastForwardBranchProcedure {
        - IcebergTransactionMetadataFactory metadataFactory
        + Procedure get()
        + void fastForwardToBranch(ConnectorSession clientSession, String schemaName, String tableName, String fromBranch, String targetBranch)
    }

    class RollbackToSnapshotProcedure {
        - IcebergTransactionMetadataFactory metadataFactory
        + Procedure get()
        + void rollbackToSnapshot(ConnectorSession clientSession, String schema, String table, Long snapshotId)
    }

    class ThreadContextClassLoader {
        - ClassLoader newContextClassLoader
        - ClassLoader previousContextClassLoader
        + ThreadContextClassLoader(ClassLoader newContextClassLoader)
        + void close()
    }

    class IcebergTransactionMetadataFactory {
        + IcebergTransactionMetadata create()
    }

    class IcebergTransactionMetadata {
        + void commit()
    }

    class Table {
        + SnapshotManager manageSnapshots()
    }

    class SnapshotManager {
        + SnapshotManager setCurrentSnapshot(long snapshotId)
        + SnapshotManager rollbackTo(long snapshotId)
        + SnapshotManager fastForwardBranch(String fromBranch, String targetBranch)
        + void commit()
    }

    SetCurrentSnapshotProcedure --> ThreadContextClassLoader : uses
    FastForwardBranchProcedure --> ThreadContextClassLoader : uses
    RollbackToSnapshotProcedure --> ThreadContextClassLoader : uses

    SetCurrentSnapshotProcedure --> IcebergTransactionMetadataFactory : uses
    FastForwardBranchProcedure --> IcebergTransactionMetadataFactory : uses
    RollbackToSnapshotProcedure --> IcebergTransactionMetadataFactory : uses

    IcebergTransactionMetadataFactory --> IcebergTransactionMetadata : creates
    IcebergTransactionMetadata --> Table : provides
    Table --> SnapshotManager : provides

    SetCurrentSnapshotProcedure --> Table : obtains via metadata
    FastForwardBranchProcedure --> Table : obtains via metadata
    RollbackToSnapshotProcedure --> Table : obtains via metadata

    SetCurrentSnapshotProcedure --> SnapshotManager : manageSnapshots()
    FastForwardBranchProcedure --> SnapshotManager : manageSnapshots()
    RollbackToSnapshotProcedure --> SnapshotManager : manageSnapshots()

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File-Level Changes

Change	Details	Files
Ensure Iceberg snapshot-setting procedure executes with a controlled thread context class loader.	Wrap the body of setCurrentSnapshot in a try-with-resources using ThreadContextClassLoader(getClass().getClassLoader()) Keep existing validation that exactly one of snapshotId or reference is provided Perform Iceberg table lookup, snapshot ID resolution, snapshot switch, and transaction commit within the protected context	presto-iceberg/src/main/java/com/facebook/presto/iceberg/procedure/SetCurrentSnapshotProcedure.java
Ensure Iceberg fast-forward branch procedure runs under a deterministic thread context class loader.	Wrap the body of fastForwardToBranch in a try-with-resources using ThreadContextClassLoader(getClass().getClassLoader()) Perform table lookup, fast-forward branch operation, and metadata commit inside this context	presto-iceberg/src/main/java/com/facebook/presto/iceberg/procedure/FastForwardBranchProcedure.java
Ensure Iceberg rollback-to-snapshot procedure runs under a deterministic thread context class loader.	Wrap the body of rollbackToSnapshot in a try-with-resources using ThreadContextClassLoader(getClass().getClassLoader()) Perform table lookup, snapshot rollback, and metadata commit inside this context	presto-iceberg/src/main/java/com/facebook/presto/iceberg/procedure/RollbackToSnapshotProcedure.java

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[sourcery-ai]

Hey - I've left some high level feedback:

• The new ThreadContextClassLoader wrapping pattern is duplicated across three procedures; consider extracting a small helper (e.g., withIcebergClassLoader(Runnable) or similar) so future changes to the classloader handling are centralized.
• If other Iceberg procedures invoke manageSnapshots() or similar Iceberg APIs, it may be worth standardizing on the same ThreadContextClassLoader usage there as well to avoid subtle inconsistencies in thread-safety behavior across procedures.
• Consider whether the ThreadContextClassLoader scope can be narrowed to just the Iceberg manageSnapshots() calls rather than the whole method body (including metadataFactory.create()), to minimize the surface area where the thread context classloader is altered.

Prompt for AI Agents

Please address the comments from this code review:

## Overall Comments
- The new `ThreadContextClassLoader` wrapping pattern is duplicated across three procedures; consider extracting a small helper (e.g., `withIcebergClassLoader(Runnable)` or similar) so future changes to the classloader handling are centralized.
- If other Iceberg procedures invoke `manageSnapshots()` or similar Iceberg APIs, it may be worth standardizing on the same `ThreadContextClassLoader` usage there as well to avoid subtle inconsistencies in thread-safety behavior across procedures.
- Consider whether the `ThreadContextClassLoader` scope can be narrowed to just the Iceberg `manageSnapshots()` calls rather than the whole method body (including `metadataFactory.create()`), to minimize the surface area where the thread context classloader is altered.

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[hantangwangd]

Thanks @agrawalreetika