How Do Pipelines Work?

Pipelines are composed of connected components. Each component processes a piece of your data, such as documents, and performs specific tasks before passing the output to the next component. For example, a basic RAG pipeline may include:

• A TextEmbedder that takes the user query and turns it into a vector.
• A Retriever that receives the vector from the TextEmbedder and uses it to fetch relevant documents from the document store.
• A PromptBuilder that injects the user query and the documents from the Retriever into the prompt.
• A Generator that uses the prompt from the PromptBuilder, including the documents, to generate the response.

Components function like modular building blocks that you can mix, match, and replace to form various pipeline configurations, such as loops, branches, or simultaneous flows. When connecting the components, it's crucial to ensure the output type of one component matches the input type of the next. Each component receives only the data it needs, which speeds up the pipeline and makes it easier to debug.

For component compatibility, check individual pages under Pipeline Components. When building in Pipeline Builder, you can check compatible connections if you hover your mouse over the connection point of a component.

deepset AI Platform uses Haystack pipelines, which means pipelines accept Haystack objects as input and output. For more information, see Haystack documentation.

Connection Types

Pipelines in deepset AI Platform are flexible and multifunctional. While you can still create simple pipelines performing one function, like answering queries, you can also use them to build complex workflows.

Connection Validation

When you connect components in a pipeline, it validates that their outputs and inputs match and are explicitly indicated and, if needed, produces detailed errors.

Branches

Pipelines can branch to process data simultaneously. For example, each pipeline branch can have a different converter, each dedicated to a specific file type, allowing for efficient parallel processing.

Loops

In loops, components operate iteratively, with a set limit on repetitions. This is useful in scenarios such as self-correcting loops, where a validator component checks the generator's output and potentially cycles it back for correction until it meets the quality standard and can be sent further down the pipeline.

How Do Pipelines Use Your Data?

Pipelines run on the documents produced by the indexes they're connected to. An index preprocesses the files from a deepset workspace, converts them into documents, and writes them into a document store where a pipeline can access them. A single pipeline can be connected to multiple indexes. For details, see Indexes.

One file may produce multiple documents. Documents inherit metadata from files. Your indexing pipeline defines the exact steps for preprocessing the files.

See also Data Flow in deepset AI Platform.

Building Pipelines

Pipelines contain recipes for how to execute a query. A typical pipeline that runs on your files in deepset, receives the user query, retrieves the relevant documents, and processes them through the components to arrive at an answer.

components:
    bm25_retriever: # Selects the most similar documents from the document store
      type: haystack_integrations.components.retrievers.opensearch.bm25_retriever.OpenSearchBM25Retriever
      init_parameters:
        document_store:
          init_parameters:
            use_ssl: True
            verify_certs: False
            hosts:
              - ${OPENSEARCH_HOST}
            http_auth:
              - "${OPENSEARCH_USER}"
              - "${OPENSEARCH_PASSWORD}"
          type: haystack_integrations.document_stores.opensearch.document_store.OpenSearchDocumentStore
        top_k: 20 # The number of results to return

    query_embedder:
      type: haystack.components.embedders.sentence_transformers_text_embedder.SentenceTransformersTextEmbedder
      init_parameters:
        model: "intfloat/e5-base-v2"
        device: null

    embedding_retriever: # Selects the most similar documents from the document store
      type: haystack_integrations.components.retrievers.opensearch.embedding_retriever.OpenSearchEmbeddingRetriever
      init_parameters:
        document_store:
          init_parameters:
            use_ssl: True
            verify_certs: False
            http_auth:
              - "${OPENSEARCH_USER}"
              - "${OPENSEARCH_PASSWORD}"
          type: haystack_integrations.document_stores.opensearch.document_store.OpenSearchDocumentStore
        top_k: 20 # The number of results to return

    document_joiner:
      type: haystack.components.joiners.document_joiner.DocumentJoiner
      init_parameters:
        join_mode: concatenate

    ranker:
      type: haystack.components.rankers.transformers_similarity.TransformersSimilarityRanker
      init_parameters:
        model: "intfloat/simlm-msmarco-reranker"
        top_k: 8
        device: null
        model_kwargs:
          torch_dtype: "torch.float16"

    prompt_builder:
      type: haystack.components.builders.prompt_builder.PromptBuilder
      init_parameters:
        template: |-
          You are a technical expert.
          You answer questions truthfully based on provided documents.
          Ignore typing errors in the question.
          For each document check whether it is related to the question.
          Only use documents that are related to the question to answer it.
          Ignore documents that are not related to the question.
          If the answer exists in several documents, summarize them.
          Only answer based on the documents provided. Don't make things up.
          Don't reference documents.
          Just output the structured, informative and precise answer and nothing else.
          If the documents can't answer the question, say so.
          These are the documents:
          {% for document in documents %}
          Document[{{ loop.index }}]:
          {{ document.content }}
          {% endfor %}
          Question: {{question}}
          Answer:

    llm:
      type: haystack.components.generators.openai.OpenAIGenerator
      init_parameters:
        api_key: {"type": "env_var", "env_vars": ["OPENAI_API_KEY"], "strict": False}
        model: "gpt-4o"
        generation_kwargs:
          max_tokens: 400
          temperature: 0.0
          seed: 0

    answer_builder:
      init_parameters: {}
      type: haystack.components.builders.answer_builder.AnswerBuilder

connections:  # Defines how the components are connected
  - sender: bm25_retriever.documents
    receiver: document_joiner.documents
  - sender: query_embedder.embedding
    receiver: embedding_retriever.query_embedding
  - sender: embedding_retriever.documents
    receiver: document_joiner.documents
  - sender: document_joiner.documents
    receiver: ranker.documents
  - sender: ranker.documents
    receiver: prompt_builder.documents
  - sender: ranker.documents
    receiver: answer_builder.documents
  - sender: prompt_builder.prompt
    receiver: llm.prompt
  - sender: llm.replies
    receiver: answer_builder.replies

max_loops_allowed: 100

inputs:  # Define the inputs for your pipeline
   query:  # These components will receive the query as input
    - "bm25_retriever.query"
    - "query_embedder.text"
    - "ranker.query"
    - "prompt_builder.question"
    - "answer_builder.query"

   filters:  # These components will receive a potential query filter as input
    - "bm25_retriever.filters"
    - "embedding_retriever.filters"

outputs:  # Defines the output of your pipeline
    documents: "ranker.documents"  # The output of the pipeline is the retrieved documents
    answers: "answer_builder.answers"  # The output of the pipeline is the generated answer

Inputs

Pipelines always take query as the required input. Optionally, they can also take in filters. When working in Pipeline Builder, drag Query and Filters from the Inputs group onto the canvas and then connect them to the components that should receive them.

When working in the YAML editor, you must explicitly list the inputs and the components that receive them:

inputs:  # Define the inputs for your pipeline
  query:  # These components will receive the query as input
  - "bm25_retriever.query"
  - "query_embedder.text"
  - "ranker.query"
  - "prompt_builder.question"
  - "answer_builder.query"

  filters:  # These components will receive a potential query filter as input
  - "bm25_retriever.filters"
  - "embedding_retriever.filters"

Filters are documents' metadata keys by default. This means that if your documents have the following metadata: {"category": "news"}, when searching in Playground, users can narrow down the search to the documents matching this category. You can also pass filters at search time with the Search endpoint. For more information about filters, see Working with Metadata.

Outputs

The output of pipelines matches the output of the last component. However, it must be one of the following data classes:

• List of Document objects (usually document search pipelines)
• List of Answer objects, including the following subclasses:
  • List of ExtractedAnswer objects (usually extractive question answering pipelines)
  • List of GeneratedAnswer objects (usually RAG pipelines or pipelines that use large language models to generate answers)

The output can be a list of documents, a list of answers, or both. Ensure the last component in your pipeline produces one or both of these outputs. For example, you may need to add an AnswerBuilder after a Generator to produce a list of GeneratedAnswerobjects. For more information, see Pipeline Components. To learn more about data classes, see Haystack data classes.

In Pipeline Builder, to finalize the pipeline with the correct output, drag the Output component onto the canvas and connect it to the components that produce the documents or answers you want to include:

When working in the YAML editor, you must explicitly specify the outputs and the components that provide them:

outputs:  # Defines the output of your pipeline
  documents: "ranker.documents"  # The output of the pipeline is the retrieved documents
  answers: "answer_builder.answers"  # The output of the pipeline is the generated answers

Pipeline Service Levels

To save costs and meet your infrastructure and service requirements, your pipelines are assigned service levels. There are three service levels available:

• Draft: This is a service level automatically assigned to new and undeployed pipelines, so that you can easily distinguish them from the deployed ones.
• Development: Pipelines at this level are designed for testing and running experiments. They have no replicas by default, and their time to standby is short, so they can save resources whenever these pipelines aren’t used. When you deploy a draft pipeline, it becomes a development pipeline.
• Production: This level is recommended for business-critical scenarios where you need the pipeline to be scalable and reliable. Pipelines at this level include one replica by default and a longer time-to-standby period than other service levels. With heavy traffic, the number of replicas grows up to 10.

This table gives an overview of the settings that come with each service level:

Time to standby is the time after which an unused pipeline enters a standby mode to save resources. Inactive pipelines don’t use up the pipeline hours included in your plan.
To use a pipeline that is on standby, activate it either on the Pipelines page or by initiating a search using that pipeline.

Replicas are the number of duplicate versions of a pipeline that are available. In case there is a spike in demand, deepset AI Platform seamlessly switches to a functioning replica to maintain uninterrupted service. Pricing plans with production pipelines automatically include one replica. The pipeline hours (the hours your pipeline is deployed) of this replica are not billed separately.

For heavy pipelines, we can increase the maximum number of replicas on request. Contact your deepset representative to change this setting.

You can change the service level of your pipeline at any time. For details, see Change the Pipeline's Service Level.

The Pipelines Page

All the pipelines created by your organization are listed on the Pipelines page. The pipelines listed under Deployed are the ones that you can run your search with. The pipelines under In Development are drafts you must deploy before you can use them for your search.

Clicking a pipeline opens Pipeline Details, where you can check all the information about your pipeline, including pipeline logs and search history.

Pipeline Status

When you deploy a pipeline, it changes its status as follows:

• Deploying: The pipeline is being deployed.
• Deployed: The pipeline is ready to resolve queries.
• Failed to deploy: It's a fatal state. Your pipeline was not deployed, and your files are not indexed. For ideas on how to fix it, see Troubleshoot Pipeline Deployment.