Skip to content

02-platform-architecture.md

Latest commit

 

History

History
226 lines (167 loc) · 7.84 KB

02-platform-architecture.md

File metadata and controls

226 lines (167 loc) · 7.84 KB
layout default
title Chapter 2: Platform Architecture
nav_order 2
parent Langflow Tutorial

Chapter 2: Platform Architecture

Welcome to Chapter 2: Platform Architecture. In this part of Langflow Tutorial: Visual AI Agent and Workflow Platform, you will build an intuitive mental model first, then move into concrete implementation details and practical production tradeoffs.

Langflow combines a visual editor, execution runtime, and deployment surfaces in one platform.

Architecture View

flowchart LR
    A[Flow Builder UI] --> B[Flow Graph Engine]
    B --> C[Model and Tool Integrations]
    C --> D[Playground and Testing]
    D --> E[API and MCP Exposure]
Loading

Core Layers

Layer Purpose
visual authoring rapid flow composition and iteration
flow runtime executes node graph with state
integrations models, vector stores, tool connectors
deployment surfaces API endpoints and MCP server exposure

Source References

Summary

You now understand where to place design, logic, and deployment concerns in Langflow.

Next: Chapter 3: Visual Flow Builder

Depth Expansion Playbook

Source Code Walkthrough

scripts/generate_migration.py

The upgrade function in scripts/generate_migration.py handles a key part of this chapter's functionality:

def upgrade() -> None:
    """
    EXPAND PHASE: Add new schema elements (backward compatible)
    - All new columns must be nullable or have defaults
    - No breaking changes to existing schema
    - Services using old schema continue to work
    """
    bind = op.get_bind()
    inspector = inspect(bind)

    # Get existing columns for idempotency
        columns = [col['name'] for col in inspector.get_columns('{table_name}')]
    }

    # Add new nullable column (always check existence first)
    if '{column_name}' not in columns:
        op.add_column('{table_name}',
            sa.Column('{column_name}', sa.{column_type}(), nullable=True{default_value})
        )

        print(f"✅ Added column '{column_name}' to table '{table_name}'")

        # Optional: Add index for performance
        # op.create_index('ix_{table_name}_{column_name}', '{table_name}', ['{column_name}'])
    else:
        print(f"⏭️  Column '{column_name}' already exists in table '{table_name}'")

    # Verify the change
    result = bind.execute(text(
        "SELECT COUNT(*) as cnt FROM {table_name}"

This function is important because it defines how Langflow Tutorial: Visual AI Agent and Workflow Platform implements the patterns covered in this chapter.

scripts/migrate_secret_key.py

The get_default_config_dir function in scripts/migrate_secret_key.py handles a key part of this chapter's functionality:

def get_default_config_dir() -> Path:
    """Get the default Langflow config directory using platformdirs."""
    return Path(user_cache_dir("langflow", "langflow"))


def get_config_dir() -> Path:
    """Get the Langflow config directory from environment or default."""
    config_dir = os.environ.get("LANGFLOW_CONFIG_DIR")
    if config_dir:
        return Path(config_dir)
    return get_default_config_dir()


def set_secure_permissions(file_path: Path) -> None:
    """Set restrictive permissions on a file (600 on Unix)."""
    if platform.system() in {"Linux", "Darwin"}:
        file_path.chmod(0o600)
    elif platform.system() == "Windows":
        try:
            import win32api
            import win32con
            import win32security

            user, _, _ = win32security.LookupAccountName("", win32api.GetUserName())
            sd = win32security.GetFileSecurity(str(file_path), win32security.DACL_SECURITY_INFORMATION)
            dacl = win32security.ACL()
            dacl.AddAccessAllowedAce(
                win32security.ACL_REVISION,
                win32con.GENERIC_READ | win32con.GENERIC_WRITE,
                user,

This function is important because it defines how Langflow Tutorial: Visual AI Agent and Workflow Platform implements the patterns covered in this chapter.

scripts/migrate_secret_key.py

The get_config_dir function in scripts/migrate_secret_key.py handles a key part of this chapter's functionality:

def get_config_dir() -> Path:
    """Get the Langflow config directory from environment or default."""
    config_dir = os.environ.get("LANGFLOW_CONFIG_DIR")
    if config_dir:
        return Path(config_dir)
    return get_default_config_dir()


def set_secure_permissions(file_path: Path) -> None:
    """Set restrictive permissions on a file (600 on Unix)."""
    if platform.system() in {"Linux", "Darwin"}:
        file_path.chmod(0o600)
    elif platform.system() == "Windows":
        try:
            import win32api
            import win32con
            import win32security

            user, _, _ = win32security.LookupAccountName("", win32api.GetUserName())
            sd = win32security.GetFileSecurity(str(file_path), win32security.DACL_SECURITY_INFORMATION)
            dacl = win32security.ACL()
            dacl.AddAccessAllowedAce(
                win32security.ACL_REVISION,
                win32con.GENERIC_READ | win32con.GENERIC_WRITE,
                user,
            )
            sd.SetSecurityDescriptorDacl(1, dacl, 0)
            win32security.SetFileSecurity(str(file_path), win32security.DACL_SECURITY_INFORMATION, sd)
        except ImportError:
            print("Warning: Could not set secure permissions on Windows (pywin32 not installed)")

This function is important because it defines how Langflow Tutorial: Visual AI Agent and Workflow Platform implements the patterns covered in this chapter.

scripts/migrate_secret_key.py

The set_secure_permissions function in scripts/migrate_secret_key.py handles a key part of this chapter's functionality:

def set_secure_permissions(file_path: Path) -> None:
    """Set restrictive permissions on a file (600 on Unix)."""
    if platform.system() in {"Linux", "Darwin"}:
        file_path.chmod(0o600)
    elif platform.system() == "Windows":
        try:
            import win32api
            import win32con
            import win32security

            user, _, _ = win32security.LookupAccountName("", win32api.GetUserName())
            sd = win32security.GetFileSecurity(str(file_path), win32security.DACL_SECURITY_INFORMATION)
            dacl = win32security.ACL()
            dacl.AddAccessAllowedAce(
                win32security.ACL_REVISION,
                win32con.GENERIC_READ | win32con.GENERIC_WRITE,
                user,
            )
            sd.SetSecurityDescriptorDacl(1, dacl, 0)
            win32security.SetFileSecurity(str(file_path), win32security.DACL_SECURITY_INFORMATION, sd)
        except ImportError:
            print("Warning: Could not set secure permissions on Windows (pywin32 not installed)")


def read_secret_key_from_file(config_dir: Path) -> str | None:
    """Read the secret key from the config directory."""
    secret_file = config_dir / "secret_key"
    if secret_file.exists():
        return secret_file.read_text(encoding="utf-8").strip()
    return None

This function is important because it defines how Langflow Tutorial: Visual AI Agent and Workflow Platform implements the patterns covered in this chapter.

How These Components Connect

flowchart TD
    A[upgrade]
    B[get_default_config_dir]
    C[get_config_dir]
    D[set_secure_permissions]
    A --> B
    B --> C
    C --> D
Loading