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The Knowledge Retriever component allows plugins to provide external knowledge base retrieval capabilities for LangBot. When users create an external knowledge base in LangBot, they can choose a knowledge retriever provided by a plugin to retrieve knowledge.
Adding a Knowledge Retriever Component
A single plugin can add any number of knowledge retrievers. Execute the command lbp comp KnowledgeRetriever in the plugin directory and follow the prompts to enter the knowledge retriever configuration.
➜ FastGPTRetriever > lbp comp KnowledgeRetriever
Generating component KnowledgeRetriever...
KnowledgeRetriever name: fastgpt
KnowledgeRetriever description: Retrieve knowledge from FastGPT knowledge bases
Component KnowledgeRetriever generated successfully.
fastgpt.yaml and fastgpt.py files in the components/knowledge_retriever/ directory. The .yaml file defines the basic information and configuration parameters of the knowledge retriever, and the .py file is the handler for this retriever:
➜ FastGPTRetriever > tree
...
├── components
│ ├── __init__.py
│ └── knowledge_retriever
│ ├── __init__.py
│ ├── fastgpt.py
│ └── fastgpt.yaml
...
Manifest File: Knowledge Retriever
apiVersion: v1 # Do not modify
kind: KnowledgeRetriever # Do not modify
metadata:
name: fastgpt # Knowledge retriever name, used to identify this retriever
label:
en_US: FastGPT Knowledge Base # Retriever display name, shown in LangBot's UI, supports multiple languages
zh_Hans: FastGPT 知识库
ja_JP: FastGPT ナレッジベース
description:
en_US: 'Retrieve knowledge from FastGPT knowledge bases' # Retriever description, shown in LangBot's UI, supports multiple languages. Optional
zh_Hans: '从 FastGPT 知识库中检索知识'
ja_JP: 'FastGPT ナレッジベースから知識を取得'
icon: assets/icon.svg # Retriever icon, displayed on the external knowledge base configuration page
spec:
config: # Retriever configuration parameters, users need to fill in these parameters when creating an external knowledge base
- name: api_base_url # Parameter name
type: string # Parameter type: string, number, boolean, select
label:
en_US: API Base URL
zh_Hans: API 基础地址
ja_JP: API ベース URL
description:
en_US: 'Base URL for FastGPT API'
zh_Hans: 'FastGPT API 基础地址'
ja_JP: 'FastGPT API ベース URL'
default: 'http://localhost:3000' # Default parameter value
required: true # Whether required
- name: api_key
type: string
label:
en_US: FastGPT API Key
zh_Hans: FastGPT API Key
ja_JP: FastGPT API キー
description:
en_US: 'API key from your FastGPT instance'
zh_Hans: '从您的 FastGPT 实例获取的 API Key'
ja_JP: 'FastGPT インスタンスから取得した API Key'
default: ''
required: true
- name: search_mode # Example of select type parameter
type: select
label:
en_US: Search Mode
zh_Hans: 搜索模式
ja_JP: 検索モード
description:
en_US: 'The search method to use'
zh_Hans: '使用的搜索方法'
ja_JP: '使用する検索方法'
default: 'embedding'
options: # Select type parameters need to define an option list
- name: 'embedding'
label:
en_US: 'Embedding Search'
zh_Hans: '向量搜索'
ja_JP: '埋め込み検索'
- name: 'fullTextRecall'
label:
en_US: 'Full-Text Recall'
zh_Hans: '全文检索'
ja_JP: '全文検索'
- name: using_rerank # Example of boolean type parameter
type: boolean
label:
en_US: Use Re-ranking
zh_Hans: 使用重排序
ja_JP: リランキングを使用
description:
en_US: 'Whether to use re-ranking'
zh_Hans: '是否使用重排序'
ja_JP: 'リランキングを使用するかどうか'
default: false
required: false
execution:
python:
path: fastgpt.py # Retriever handler, do not modify
attr: FastGPT # Class name of the retriever handler, consistent with the class name in fastgpt.py
Plugin Handler
The following code will be generated by default (components/knowledge_retriever/<retriever_name>.py). You need to implement the knowledge retrieval logic in the retrieve method of the FastGPT class. Complete code can be found in langbot-plugin-demo.
# Auto generated by LangBot Plugin SDK.
# Please refer to https://docs.langbot.app/en/plugin/dev/tutor.html for more details.
...
class FastGPT(KnowledgeRetriever):
async def retrieve(self, context: RetrievalContext) -> list[RetrievalResultEntry]:
"""Retrieve knowledge from FastGPT knowledge base"""
# 1. Get configuration parameters
api_base_url = self.config.get('api_base_url', 'http://localhost:3000')
api_key = self.config.get('api_key')
dataset_id = self.config.get('dataset_id')
search_mode = self.config.get('search_mode', 'embedding')
using_rerank = self.config.get('using_rerank', False)
# 2. Parameter validation
if not api_key or not dataset_id:
logger.error("Missing required configuration: api_key or dataset_id")
return []
# 3. Build API request
url = f"{api_base_url.rstrip('/')}/api/core/dataset/searchTest"
headers = {
"Authorization": f"Bearer {api_key}",
"Content-Type": "application/json"
}
payload = {
"datasetId": dataset_id,
"text": context.query, # Get query text from RetrievalContext
"searchMode": search_mode,
"usingReRank": using_rerank,
}
try:
# 4. Call external API
async with httpx.AsyncClient() as client:
response = await client.post(url, json=payload, headers=headers, timeout=30.0)
response.raise_for_status()
result = response.json()
# 5. Parse response and convert to RetrievalResultEntry
results = []
for record in result.get('data', []):
# Combine main data and auxiliary data as content
content_text = '\n'.join([
record.get('q', ''),
record.get('a', '')
]).strip()
# Create retrieval result entry
entry = RetrievalResultEntry(
id=record.get('id', ''),
content=[ContentElement.from_text(content_text)],
metadata={
'dataset_id': record.get('datasetId', ''),
'source_name': record.get('sourceName', ''),
'score': record.get('score', 0.0),
},
# Convert similarity score to distance (higher score = smaller distance)
distance=1.0 - float(record.get('score', 0.0)),
)
results.append(entry)
logger.info(f"Retrieved {len(results)} chunks from FastGPT dataset {dataset_id}")
return results
except httpx.HTTPStatusError as e:
logger.error(f"HTTP error from FastGPT API: {e.response.status_code} - {e.response.text}")
return []
except httpx.RequestError as e:
logger.error(f"Request error when calling FastGPT API: {str(e)}")
return []
except Exception as e:
traceback.print_exc()
logger.error(f"Unexpected error during retrieval: {str(e)}")
return []
Retrieval Context
RetrievalContext contains context information for this retrieval:
class RetrievalContext(pydantic.BaseModel):
"""Knowledge retrieval context"""
query: str
"""Query text, the user's retrieval question"""
Retrieval Results
Retrieval results need to be converted to a list of RetrievalResultEntry objects, each representing a retrieved knowledge chunk:
class RetrievalResultEntry(pydantic.BaseModel):
"""Single retrieval result entry"""
id: str
"""Result ID, uniquely identifies this entry"""
content: list[ContentElement]
"""Result content, create text content using ContentElement.from_text()"""
metadata: dict[str, Any]
"""Result metadata, can contain any key-value pairs, such as source, score, etc."""
distance: float
"""Distance score, indicates relevance to the query (smaller is more relevant)
Usually calculated as 1.0 - similarity_score"""
Getting Configuration Parameters
Get user-configured parameter values using self.config.get(parameter_name, default_value):
# Get string parameter
api_base_url = self.config.get('api_base_url', 'http://localhost:3000')
# Get number parameters
limit = self.config.get('limit', 5000)
similarity = self.config.get('similarity', 0.0)
# Get boolean parameter
using_rerank = self.config.get('using_rerank', False)
# Get select parameter
search_mode = self.config.get('search_mode', 'embedding')
Testing the Retriever
After creation, execute the command lbp run in the plugin directory to start debugging. Then in LangBot:
- Go to the “Knowledge Base” page
- Add an external knowledge base
- Select the knowledge retriever provided by your plugin and fill in the configuration
After saving, you can select this knowledge base in the LangBot pipeline.