Merge #4456

4456: Add Ollama as an embeddings provider r=dureuill a=jakobklemm

# Pull Request

## Related issue
[Related Discord Thread](https://discord.com/channels/1006923006964154428/1211977150316683305)

## What does this PR do?
- Adds Ollama as a provider of Embeddings besides HuggingFace and OpenAI under the name `ollama`
- Adds the environment variable `MEILI_OLLAMA_URL` to set the embeddings URL of an Ollama instance with a default value of `http://localhost:11434/api/embeddings` if no variable is set
- Changes some of the structs and functions in `openai.rs` to be public so that they can be shared.
- Added more error variants for Ollama specific errors
- It uses the model `nomic-embed-text` as default, but any string value is allowed, however it won't automatically check if the model actually exists or is an embedding model

Tested against Ollama version `v0.1.27` and the `nomic-embed-text` model.

## PR checklist
Please check if your PR fulfills the following requirements:
- [x] Does this PR fix an existing issue, or have you listed the changes applied in the PR description (and why they are needed)?
- [x] Have you read the contributing guidelines?
- [x] Have you made sure that the title is accurate and descriptive of the changes?

Co-authored-by: Jakob Klemm <jakob@jeykey.net>
Co-authored-by: Louis Dureuil <louis.dureuil@gmail.com>

milli/src/vector/mod.rs

@@ -10,6 +10,8 @@ pub mod manual;
 pub mod openai;
 pub mod settings;
 
+pub mod ollama;
+
 pub use self::error::Error;
 
 pub type Embedding = Vec<f32>;
@@ -76,6 +78,7 @@ pub enum Embedder {
     HuggingFace(hf::Embedder),
     OpenAi(openai::Embedder),
     UserProvided(manual::Embedder),
+    Ollama(ollama::Embedder),
 }
 
 #[derive(Debug, Clone, Default, serde::Deserialize, serde::Serialize)]
@@ -127,6 +130,7 @@ impl IntoIterator for EmbeddingConfigs {
 pub enum EmbedderOptions {
     HuggingFace(hf::EmbedderOptions),
     OpenAi(openai::EmbedderOptions),
+    Ollama(ollama::EmbedderOptions),
     UserProvided(manual::EmbedderOptions),
 }
 
@@ -144,6 +148,10 @@ impl EmbedderOptions {
     pub fn openai(api_key: Option<String>) -> Self {
         Self::OpenAi(openai::EmbedderOptions::with_default_model(api_key))
     }
+
+    pub fn ollama() -> Self {
+        Self::Ollama(ollama::EmbedderOptions::with_default_model())
+    }
 }
 
 impl Embedder {
@@ -151,6 +159,7 @@ impl Embedder {
         Ok(match options {
             EmbedderOptions::HuggingFace(options) => Self::HuggingFace(hf::Embedder::new(options)?),
             EmbedderOptions::OpenAi(options) => Self::OpenAi(openai::Embedder::new(options)?),
+            EmbedderOptions::Ollama(options) => Self::Ollama(ollama::Embedder::new(options)?),
             EmbedderOptions::UserProvided(options) => {
                 Self::UserProvided(manual::Embedder::new(options))
             }
@@ -167,6 +176,10 @@ impl Embedder {
                 let client = embedder.new_client()?;
                 embedder.embed(texts, &client).await
             }
+            Embedder::Ollama(embedder) => {
+                let client = embedder.new_client()?;
+                embedder.embed(texts, &client).await
+            }
             Embedder::UserProvided(embedder) => embedder.embed(texts),
         }
     }
@@ -181,6 +194,7 @@ impl Embedder {
         match self {
             Embedder::HuggingFace(embedder) => embedder.embed_chunks(text_chunks),
             Embedder::OpenAi(embedder) => embedder.embed_chunks(text_chunks),
+            Embedder::Ollama(embedder) => embedder.embed_chunks(text_chunks),
             Embedder::UserProvided(embedder) => embedder.embed_chunks(text_chunks),
         }
     }
@@ -189,6 +203,7 @@ impl Embedder {
         match self {
             Embedder::HuggingFace(embedder) => embedder.chunk_count_hint(),
             Embedder::OpenAi(embedder) => embedder.chunk_count_hint(),
+            Embedder::Ollama(embedder) => embedder.chunk_count_hint(),
             Embedder::UserProvided(_) => 1,
         }
     }
@@ -197,6 +212,7 @@ impl Embedder {
         match self {
             Embedder::HuggingFace(embedder) => embedder.prompt_count_in_chunk_hint(),
             Embedder::OpenAi(embedder) => embedder.prompt_count_in_chunk_hint(),
+            Embedder::Ollama(embedder) => embedder.prompt_count_in_chunk_hint(),
             Embedder::UserProvided(_) => 1,
         }
     }
@@ -205,6 +221,7 @@ impl Embedder {
         match self {
             Embedder::HuggingFace(embedder) => embedder.dimensions(),
             Embedder::OpenAi(embedder) => embedder.dimensions(),
+            Embedder::Ollama(embedder) => embedder.dimensions(),
             Embedder::UserProvided(embedder) => embedder.dimensions(),
         }
     }
@@ -213,6 +230,7 @@ impl Embedder {
         match self {
             Embedder::HuggingFace(embedder) => embedder.distribution(),
             Embedder::OpenAi(embedder) => embedder.distribution(),
+            Embedder::Ollama(embedder) => embedder.distribution(),
             Embedder::UserProvided(_embedder) => None,
         }
     }