Key-Value Storage

Stores and retrieves key-value pairs to/from a file.

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Overview

This node provides simple key-value storage functionality using JSON files. It allows users to save a value under a specific key or read a value by its key from a named file. This is useful for persisting small amounts of data between workflow executions without requiring an external database or service.

Common scenarios include:

  • Caching API tokens or temporary data.
  • Storing user preferences or state information.
  • Sharing data between different parts of a workflow or across workflows.

For example, you can save a session token with a key "sessionToken" in a file named "myFile", and later read it back when needed.

Properties

Name Meaning
File The name of the JSON file where key-value pairs are saved or read from (e.g., "myFile").
Key The key string used to save or retrieve a value (e.g., "exampleKey").

Note: For the "Read" operation, only "File" and "Key" are required inputs.

Output

The node outputs a single JSON object with the following structure depending on the operation:

  • Save operation:

    {
  "<key>": {
    "value": "<saved_value>",
    "operation": "save",
    "status": "Saved"
  }
}

    Where <key> is the key used to save the value.

  • Read operation:

    {
  "key": "<key>",
  "value": "<retrieved_value_or_null>",
  "operation": "read"
}

    If the key does not exist in the file, the value will be null.

The output is always returned as an array containing one item with this JSON data.

Dependencies

  • Uses Node.js built-in fs and path modules for file system operations.
  • Stores data in JSON files located in a subdirectory named data relative to the node's source directory.
  • No external APIs or credentials are required.

Troubleshooting

  • File access errors: Ensure the n8n process has write/read permissions to the data directory where files are stored.
  • Missing keys on read: If a key does not exist in the file, the node returns null for the value. Verify the key spelling and that the save operation was successful.
  • Corrupted JSON files: Manual edits or concurrent writes might corrupt the JSON file causing parse errors. Deleting or fixing the file may resolve issues.
  • Concurrent writes: Since the node reads and writes the entire JSON file, simultaneous executions could cause race conditions leading to lost data.

Links and References

Discussion