[pull] master from netdata:master

[pull]

See Commits and Changes for more details.

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Created by pull[bot] (v2.0.0-alpha.1)

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Summary by Sourcery

Improve the metadata cleanup process and update documentation with new examples.

New Features:

• Add support for connecting to PostgreSQL using a Unix socket with a custom port.

Enhancements:

• Improve the efficiency of metadata cleanup operations by removing unnecessary steps and optimizing database queries.
• Remove unnecessary chart label deletion logic during node unregistration.
• Restructure metadata scanning and storage to reduce overhead and improve performance.

Tests:

• Add tests to verify the correctness of metadata cleanup operations.

[sourcery-ai]

Reviewer's Guide by Sourcery

This pull request focuses on improving the metadata cleanup process by introducing several changes to how metadata is stored and deleted. It also includes changes to the database vacuuming process and the way labels are handled.

Sequence diagram for improved metadata cleanup process

sequenceDiagram
    participant Host
    participant MetadataWorker
    participant SQLite

    Host->>MetadataWorker: Queue metadata update
    activate MetadataWorker
    MetadataWorker->>MetadataWorker: Begin transaction
    MetadataWorker->>SQLite: Store host metadata
    MetadataWorker->>SQLite: Store chart metadata
    MetadataWorker->>SQLite: Store dimension metadata
    MetadataWorker->>MetadataWorker: Commit transaction
    MetadataWorker->>MetadataWorker: Run cleanup loop
    MetadataWorker->>SQLite: Vacuum database if needed
    deactivate MetadataWorker

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Class diagram for metadata storage changes

classDiagram
    class MetadataWorker {
        -wc: metadata_wc*
        -work_buffer: BUFFER*
        -pending_ae_list: judy_list_t*
        -pending_ctx_cleanup_list: judy_list_t*
        -pending_uuid_deletion: judy_list_t*
        +store_metadata()
        +run_cleanup_loop()
        +vacuum_database()
    }

    class SQLiteMetadata {
        +store_chart_metadata()
        +store_dimension_metadata()
        +store_host_systeminfo()
        +check_dimension_metadata()
        +check_chart_metadata()
        +check_label_metadata()
    }

    MetadataWorker --> SQLiteMetadata: uses

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State diagram for metadata cleanup process

stateDiagram-v2
    [*] --> Idle
    Idle --> ProcessingMetadata: Metadata update queued
    ProcessingMetadata --> StoringData: Begin transaction
    StoringData --> RunningCleanup: Commit transaction
    RunningCleanup --> VacuumingDB: Cleanup completed
    VacuumingDB --> Idle: Vacuum completed

    note right of ProcessingMetadata: Improved batch processing
    note right of RunningCleanup: Removed MAX_METADATA_CLEANUP limit
    note right of VacuumingDB: New vacuum frequency control

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File-Level Changes

Change	Details	Files
Refactored metadata cleanup to use row IDs and avoid unnecessary full table scans.	Introduced row ID tracking for dimensions, charts, and labels. Modified cleanup loops to use row IDs for more efficient processing. Removed the limit on the number of metadata cleanup operations. Added a check to avoid running cleanup if there are no new rows to process.	src/database/sqlite/sqlite_metadata.c
Removed chart and dimension check intervals.	Removed METADATA_DIM_CHECK_INTERVAL and METADATA_CHART_CHECK_INTERVAL constants. Adjusted the logic to use a single maintenance repeat interval.	src/database/sqlite/sqlite_metadata.c
Consolidated chart and dimension metadata storage.	Modified store_chart_metadata and store_dimension_metadata to use thread-local prepared statements. Removed the SQLITE_RESET calls after each insert. Added error handling for failed metadata storage.	src/database/sqlite/sqlite_metadata.c
Improved database vacuuming.	Introduced a new constant DATABASE_VACUUM_FREQUENCY_SECONDS to control vacuum frequency. Modified the vacuuming logic to run periodically instead of on every cleanup. Added a check to avoid vacuuming if the free pages are below the threshold.	src/database/sqlite/sqlite_metadata.c
Removed the deletion of chart labels during host unregistration.	Removed the delete_host_chart_labels function. Removed the call to metadata_delete_host_chart_labels from sql_unregister_node. Removed the METADATA_DELETE_HOST_CHART_LABELS event. Removed the metadata_delete_host_chart_labels function.	src/database/sqlite/sqlite_metadata.c src/database/sqlite/sqlite_aclk.c
Added a dedicated worker for storing host metadata.	Introduced a new worker UV_EVENT_STORE_HOST. Moved the host metadata storage logic to the new worker. Added a new worker for storing chart metadata UV_EVENT_STORE_CHART. Added a new worker for storing dimension metadata UV_EVENT_STORE_DIMENSION.	src/database/sqlite/sqlite_metadata.c src/daemon/libuv_workers.c src/daemon/libuv_workers.h
Improved host label handling.	Modified the host label storage to use a single SQL statement with ON CONFLICT clause. Added a check to avoid storing labels if the host does not have the RRDHOST_FLAG_METADATA_LABELS flag set.	src/database/sqlite/sqlite_metadata.c
Added a new worker for alert queue processing.	Introduced a new worker WORKER_HEALTH_JOB_ALARM_LOG_QUEUE. Added a new worker WORKER_HEALTH_JOB_WAIT_EXEC. Moved the alert queue processing logic to the new worker.	src/health/health_event_loop.c src/daemon/libuv_workers.c src/daemon/libuv_workers.h
Updated libsensors vendoring.	Updated the minimum required CMake version for libsensors. Removed the FindLibSensors.cmake file.	src/collectors/debugfs.plugin/libsensors/CMakeLists.txt packaging/cmake/Modules/FindLibSensors.cmake

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