|
| 1 | +--- |
| 2 | +title: "VLLMDocumentEmbedder" |
| 3 | +id: vllmdocumentembedder |
| 4 | +slug: "/vllmdocumentembedder" |
| 5 | +description: "This component computes the embeddings of a list of documents using models served with vLLM." |
| 6 | +--- |
| 7 | + |
| 8 | +# VLLMDocumentEmbedder |
| 9 | + |
| 10 | +This component computes the embeddings of a list of documents using models served with [vLLM](https://docs.vllm.ai/). |
| 11 | + |
| 12 | +<div className="key-value-table"> |
| 13 | + |
| 14 | +| | | |
| 15 | +| --- | --- | |
| 16 | +| **Most common position in a pipeline** | Before a [`DocumentWriter`](../writers/documentwriter.mdx) in an indexing pipeline | |
| 17 | +| **Mandatory init variables** | `model`: The name of the model served by vLLM | |
| 18 | +| **Mandatory run variables** | `documents`: A list of documents | |
| 19 | +| **Output variables** | `documents`: A list of documents (enriched with embeddings) | |
| 20 | +| **API reference** | [vLLM](/reference/integrations-vllm) | |
| 21 | +| **GitHub link** | https://github.com/deepset-ai/haystack-core-integrations/tree/main/integrations/vllm | |
| 22 | + |
| 23 | +</div> |
| 24 | + |
| 25 | +## Overview |
| 26 | + |
| 27 | +[vLLM](https://docs.vllm.ai/) is a high-throughput and memory-efficient inference and serving engine for LLMs. It exposes an OpenAI-compatible HTTP server, which `VLLMDocumentEmbedder` uses to compute embeddings through the Embeddings API. |
| 28 | + |
| 29 | +`VLLMDocumentEmbedder` computes the embeddings of a list of documents and stores the obtained vectors in the `embedding` field of each document. It expects a vLLM server to be running and accessible at the `api_base_url` parameter (by default, `http://localhost:8000/v1`). To embed a string (such as a query), use the [`VLLMTextEmbedder`](vllmtextembedder.mdx). |
| 30 | + |
| 31 | +The vectors computed by this component are necessary to perform embedding retrieval on a collection of documents. At retrieval time, the vector that represents the query is compared with those of the documents to find the most similar or relevant ones. |
| 32 | + |
| 33 | +If the vLLM server was started with `--api-key`, provide the API key through the `VLLM_API_KEY` environment variable or the `api_key` init parameter using Haystack's [Secret](../../concepts/secret-management.mdx) API. |
| 34 | + |
| 35 | +### Compatible models |
| 36 | + |
| 37 | +vLLM supports a range of embedding models. Check the [vLLM pooling models docs](https://docs.vllm.ai/en/stable/models/pooling_models) for the list of supported architectures and models. |
| 38 | + |
| 39 | +### vLLM-specific parameters |
| 40 | + |
| 41 | +You can pass vLLM-specific parameters through the `extra_parameters` dictionary. These are forwarded as `extra_body` to the OpenAI-compatible embeddings endpoint. Use this to pass parameters that are not part of the standard OpenAI Embeddings API, such as `truncate_prompt_tokens` or `truncation_side`. See the [vLLM Embeddings API docs](https://docs.vllm.ai/en/stable/models/pooling_models/embed/#openai-compatible-embeddings-api) for details. |
| 42 | + |
| 43 | +```python |
| 44 | +embedder = VLLMDocumentEmbedder( |
| 45 | + model="google/embeddinggemma-300m", |
| 46 | + extra_parameters={"truncate_prompt_tokens": 256, "truncation_side": "right"}, |
| 47 | +) |
| 48 | +``` |
| 49 | + |
| 50 | +### Matryoshka embeddings |
| 51 | + |
| 52 | +If the model was trained with Matryoshka Representation Learning, you can reduce the dimensionality of the output vector through the `dimensions` parameter. See the [vLLM Matryoshka docs](https://docs.vllm.ai/en/stable/models/pooling_models/embed/#matryoshka-embeddings) for details. |
| 53 | + |
| 54 | +### Batching and failure handling |
| 55 | + |
| 56 | +`VLLMDocumentEmbedder` encodes documents in batches. Use `batch_size` (default `32`) to control how many documents are sent in a single request to the vLLM server, and `progress_bar` to toggle the progress indicator. |
| 57 | + |
| 58 | +By default (`raise_on_failure=False`), failed embedding requests are logged and processing continues with the remaining documents. Set `raise_on_failure=True` to raise an exception instead. |
| 59 | + |
| 60 | +### Instructions |
| 61 | + |
| 62 | +Some embedding models require prepending the document text with an instruction to work better for retrieval. For example, if you use [intfloat/e5-large-v2](https://huggingface.co/intfloat/e5-large-v2), you should prefix your document with the following instruction: "passage:". |
| 63 | + |
| 64 | +This is how it works with `VLLMDocumentEmbedder`: |
| 65 | + |
| 66 | +```python |
| 67 | +instruction = "passage:" |
| 68 | +embedder = VLLMDocumentEmbedder( |
| 69 | + model="intfloat/e5-large-v2", |
| 70 | + prefix=instruction, |
| 71 | +) |
| 72 | +``` |
| 73 | + |
| 74 | +### Embedding metadata |
| 75 | + |
| 76 | +Documents often come with a set of metadata. If they are distinctive and semantically meaningful, you can embed them along with the text of the document to improve retrieval. Pass the relevant fields through `meta_fields_to_embed`; they are concatenated to the document text using `embedding_separator` (a newline by default): |
| 77 | + |
| 78 | +```python |
| 79 | +from haystack import Document |
| 80 | +from haystack_integrations.components.embedders.vllm import VLLMDocumentEmbedder |
| 81 | + |
| 82 | +doc = Document(content="some text", meta={"title": "relevant title", "page_number": 18}) |
| 83 | + |
| 84 | +embedder = VLLMDocumentEmbedder( |
| 85 | + model="google/embeddinggemma-300m", |
| 86 | + meta_fields_to_embed=["title"], |
| 87 | +) |
| 88 | + |
| 89 | +docs_with_embeddings = embedder.run(documents=[doc])["documents"] |
| 90 | +``` |
| 91 | + |
| 92 | +## Usage |
| 93 | + |
| 94 | +Install the `vllm-haystack` package to use the `VLLMDocumentEmbedder`: |
| 95 | + |
| 96 | +```shell |
| 97 | +pip install vllm-haystack |
| 98 | +``` |
| 99 | + |
| 100 | +### Starting the vLLM server |
| 101 | + |
| 102 | +Before using this component, start a vLLM server with an embedding model: |
| 103 | + |
| 104 | +```bash |
| 105 | +vllm serve google/embeddinggemma-300m |
| 106 | +``` |
| 107 | + |
| 108 | +For details on server options, see the [vLLM CLI docs](https://docs.vllm.ai/en/stable/cli/serve/). |
| 109 | + |
| 110 | +### On its own |
| 111 | + |
| 112 | +```python |
| 113 | +from haystack import Document |
| 114 | +from haystack_integrations.components.embedders.vllm import VLLMDocumentEmbedder |
| 115 | + |
| 116 | +doc = Document(content="I love pizza!") |
| 117 | + |
| 118 | +document_embedder = VLLMDocumentEmbedder(model="google/embeddinggemma-300m") |
| 119 | + |
| 120 | +result = document_embedder.run([doc]) |
| 121 | +print(result["documents"][0].embedding) |
| 122 | + |
| 123 | +## [-0.0215301513671875, 0.01499176025390625, ...] |
| 124 | +``` |
| 125 | + |
| 126 | +### In a pipeline |
| 127 | + |
| 128 | +```python |
| 129 | +from haystack import Document, Pipeline |
| 130 | +from haystack.components.retrievers.in_memory import InMemoryEmbeddingRetriever |
| 131 | +from haystack.components.writers import DocumentWriter |
| 132 | +from haystack.document_stores.in_memory import InMemoryDocumentStore |
| 133 | +from haystack.document_stores.types import DuplicatePolicy |
| 134 | +from haystack_integrations.components.embedders.vllm import ( |
| 135 | + VLLMDocumentEmbedder, |
| 136 | + VLLMTextEmbedder, |
| 137 | +) |
| 138 | + |
| 139 | +document_store = InMemoryDocumentStore(embedding_similarity_function="cosine") |
| 140 | + |
| 141 | +documents = [ |
| 142 | + Document(content="My name is Wolfgang and I live in Berlin"), |
| 143 | + Document(content="I saw a black horse running"), |
| 144 | + Document(content="Germany has many big cities"), |
| 145 | +] |
| 146 | + |
| 147 | +document_embedder = VLLMDocumentEmbedder(model="google/embeddinggemma-300m") |
| 148 | +writer = DocumentWriter(document_store=document_store, policy=DuplicatePolicy.OVERWRITE) |
| 149 | + |
| 150 | +indexing_pipeline = Pipeline() |
| 151 | +indexing_pipeline.add_component("document_embedder", document_embedder) |
| 152 | +indexing_pipeline.add_component("writer", writer) |
| 153 | +indexing_pipeline.connect("document_embedder", "writer") |
| 154 | + |
| 155 | +indexing_pipeline.run({"document_embedder": {"documents": documents}}) |
| 156 | + |
| 157 | +query_pipeline = Pipeline() |
| 158 | +query_pipeline.add_component( |
| 159 | + "text_embedder", |
| 160 | + VLLMTextEmbedder(model="google/embeddinggemma-300m"), |
| 161 | +) |
| 162 | +query_pipeline.add_component( |
| 163 | + "retriever", |
| 164 | + InMemoryEmbeddingRetriever(document_store=document_store), |
| 165 | +) |
| 166 | +query_pipeline.connect("text_embedder.embedding", "retriever.query_embedding") |
| 167 | + |
| 168 | +query = "Who lives in Berlin?" |
| 169 | + |
| 170 | +result = query_pipeline.run({"text_embedder": {"text": query}}) |
| 171 | + |
| 172 | +print(result["retriever"]["documents"][0]) |
| 173 | + |
| 174 | +## Document(id=..., content: 'My name is Wolfgang and I live in Berlin', score: ...) |
| 175 | +``` |
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