Introduction to OpenSearch Models

Introduction to OpenSearch Models

With the OpenSearch models feature, developers can improve the search relevancy of their data via pre-trained, custom, and external models. Learn here everything about this exciting new feature of OpenSearch.

Ricardo Ferreira
Amazon Employee
Published Dec 21, 2023
OpenSearch is largely known in the industry for being a tool for builders interested in search and analytics. There are a great number of use cases around the world fully leveraging OpenSearch. All of this is possible thanks to the well-designed architecture of OpenSearch that allows for distributed work execution capable of delivering sub-second responses. Moreover, being heavily centered around open source roots is another key characteristic of OpenSearch because it allows for the technology to evolve at a faster pace around the community of developers.
You may already know all of this. But there's something you probably don't know. OpenSearch can also improve the search relevancy of your data using Generative AI. You can leverage groundbreaking Large Language Models (LLM) along with semantic search to force multiply the ability to find data based on their meaning—more than just matching words. This technology also fuels exciting new approaches, such as multimodal searches. Models can be locally hosted or cloud hosted. You can use LLM providers like Cohere, OpenAI ChatGPT, and AI21 Labs. You can also use services like Amazon SageMaker, Amazon Bedrock, or APIs from your own infrastructure. Once deployed, there are limitless possibilities about how can you use these models with OpenSearch for search, aggregation, and data analysis.
This series will introduce you to the engine that makes all of this possible. The first part provides a basic understanding of the most important concepts. Parts two and three of this series will be more hands-on, and will provide you with tutorials so you can learn how to do things yourself. Part four provides you with tips and tricks on how to troubleshoot things.

Motivations for OpenSearch models

Say My Name is a popular song from the band Destiny's Child, often associated with the pop singer super star Beyoncé since she was part of the band during the late 90s. At least this is what most search engines may give back to you. They are based on keyword-based retrieval systems, such as BM25, which use ranking functions to estimate the relevance of documents to a given search query. The problem of it is that it cannot provide answers beyond keyword similarities, and for us human beings, this is not enough.
We understand relevance in a far broader sense, which involves semantics, contextual awareness, and general world knowledge. Therefore, we need to augment existing search engines with semantic search. Using semantic search, you would also get as a result a reference to the seventh episode from the fifth season of the TV show Breaking Bad. This is the episode where the character Walter White confirms for the first time that he is the infamous Heisenberg.
The support for semantic search was introduced into OpenSearch version 2.9, and it allows ML developers to train and deploy models into OpenSearch clusters. This support is provided by the OpenSearch ML Commons Framework. The idea behind this project is to simplify the process of defining, deploying, and using models using REST APIs, a programming model that is known and accessible to many developers. No more learning specialized ML frameworks. With OpenSearch, your development lifecycle is essentially invoking REST APIs and indexing documents as usual.
Consider this tutorial as an example of a pre-trained model based on Hugging Face that can be invoked using the prediction API. In the example below, the identifier cleMb4kBJ1eYAeTMFFg4 represents the model deployed on OpenSearch. This is how a developer can invoke this model with a search:
By having developers use OpenSearch for their needs, the learning curve to implement AI use cases is drastically reduced as OpenSearch now acts as the middleware responsible for management, deployment, and execution of ML related tasks. It is a great way for organizations to democratize AI operations among teams, whether internal and external ones. If you work for a company whose main purpose is to provide services for developers based on your own models, then OpenSearch provides everything you need to get your team focused on what matters.

Same architecture, multiple deployment options

One of the coolest things provided by the ML Commons Framework is the support for different types of models. Using the same APIs for managing the lifecycle of your models, you can work with models that are deployed in your OpenSearch cluster, or available via an external API. This provides you with a seamless experience to work with models, as you can start working with models with OpenSearch using a local deployment model, and migrate to models available externally without changing a single line of your code.
This level of flexibility is also relevant for model training. You can use pre-trained models with OpenSearch, where you can simply reuse a trained model and deploy to OpenSearch. Alternatively, you can switch to deploy your own custom models, maybe because you identified edge cases where the pre-trained models are not adequate. Switching from one approach to another won't break your applications, as the interaction design is the same.
But what if you work for a company who doesn't have expertise in AI? In this scenario, it doesn't make much sense to use pre-trained or custom models deployed locally. Moreover, using models deployed locally requires your OpenSearch cluster to have compute nodes dedicated to ML related tasks. Not only this will increase the infrastructure footprint of your clusters, but it will be a workload that may compete with your other OpenSearch applications. In these situations, you can use externally available models.
External models allow models to be trained outside OpenSearch. This means doing the training of the model without any changes in the cluster. Additionally, the people responsible for the model training can perform their job without necessarily worrying about OpenSearch-related aspects. Data scientists, which are usually the people responsible for training models, don't necessarily need to learn OpenSearch in order to complete their duties. They can innovate using the approaches they are familiar with, which is great for keeping them focused on the business problem.
Just like models deployed locally at OpenSearch, externally available models are handled the same way. You can leverage the same REST APIs to deploy and use models.
external models
OpenSearch will transparently invoke the external models via the registered connectors, taking care of the details regarding networking, security, work scheduling, and integration. It is important to clarify that using external models doesn't forbid you to deploy models locally. Both deployment options can be used at the same time, which is ideal for situations you started with local models but you plan to move to external ones to reduce cost, improve your efficiency, and scale your workloads.

Connectors and Connector blueprints

To take advantage of external models, you must create a connector. A connector defines the service to which OpenSearch will function as a client. Therefore, they need to include information about how to invoke the service, which parameters are expected, and how the result is provided. Moreover, connectors provide technology providers with a way to integrate their AI technologies with OpenSearch with minimal effort and becoming part of our open source community.
There are two types of connectors: standalone and the ones created for a specific model. The key criteria to decide which one to use depends on their level of reusability. If you want that, a connector can be used in different models, then you must create a standalone one. This means the connector can be the implementation path of one or multiple models. Otherwise, if you don't intend to reuse the connector as much and plan to use it for a single model, then you may choose to create a specific one.
connector types
Because standalone connectors intend to be reused across multiple models, they are stored in a dedicated index called .plugins-ml-connector. This way, even if a model is deleted, it won't affect the other models using the connector, as the lifecycle of the connector is not dependent on the model. Consequentially, when an internal connector is created, they are stored in the same index that also stores the models, an index called .plugins-ml-model.
To create a connector, you must provide the configuration of the connector with a connector blueprint. This is a JSON document containing all the metadata required to connect with the external model. Usually, the connector blueprint is created by ML developers who understand how the external model works and know their API contract works. The API contract is everything related to how messages will be exchanged, such as what are the data required to perform the request, as well as what are the data returned when a response is generated.
Think about connector blueprints as templates for connectors. Once the template is created and shared, one or multiple connectors can be created based on it. For instance, take this connector blueprint for an Amazon SageMaker API as an example.
As you can notice, the connector blueprint provides the guidance necessary to whoever is going to create a connector from this template to know which parameters to provide. All the parameters fall into sections that are self-descriptive—such as the credential, parameters, and actions. ML developers creating connector blueprints must be as detailed as possible, to make sure that connectors created out of it will work as expected. A complete summary of all possible sections and fields of a connector blueprint can be seen here.

Model groups and models

In the software development world, Domain-Driven Design (DDD) is a common approach to design software-intensive systems. DDD aims to unify the language used by system implementers and users to facilitate communication and achieve understanding. This is important for keeping different teams aligned and enabling them to discuss system development and evolution without getting caught up in semantic details. Now, you may wonder, what does this have to do with OpenSearch?
There are a few concepts we can borrow from DDD to better understand how models work. One of them is the concept of a bounded context. When dealing with large models and teams, it is often a good idea to delineate a bounded context to group a set of related terms and concepts together. Different people will use subtly different vocabularies in different parts of a large organization. This is where creating a bounded context helps. They function as a container for all connected items from a domain model perspective, and provide a convenient way to search for them.
At OpenSearch, you can use the concept of model groups to define bounded contexts. Use model groups to define how models will work together to design your use case. From the OpenSearch perspective, model groups' primary job is to manage model versions. This means that a model group is essentially a way to group a set of model versions. Moreover, model groups in OpenSearch are used to enforce security. Just like a bounded context, model groups must specify clear boundaries about who can access the models within that model group, given a set of permissions.
Using the same line of thinking based on DDD, you can see models as your possible entities or services that your domain model will contain. In your design model, there may be entities whose job is to represent something concrete from the real world. They have attributes and qualifiers, but they don't have any behavior associated. Similarly, your domain model may need services to represent what your system will require as behavior, something that, given an input, will produce an output. A model in OpenSearch can be used to either represent an entity or a service from your domain model.
Here is one example. Say you want to build a use case based on RAG and semantic searches. Here, you will need an entity to represent the model used to implement the RAG, as well as the entities from the search that are going to leverage RAG to augment the data.
model groups
There is no special formula that you can use to decide which components of your design will be entities, services, and how they should belong to a bounded context. It requires a thoughtful analysis of your domain model and what you are trying to model. What you need to keep in mind is the relationship between model groups and bounded contexts, as well as models with entities and services.


In this first part of the series, you were introduced to the concept of models from OpenSearch. You have learned this feature creates the right approach for you to democratize the usage of AI within your organization, as OpenSearch takes care of much of what would be custom engineering implementation with no business value associated. By using models, you and your team can jump straight to what matters without having to worry about losing your investment because you decided to change the deployment model used.
In the second part, you will practice everything you learned here. You will learn how to spin up a development OpenSearch cluster, connect this OpenSearch cluster with the AI21 Labs Jurassic 2 foundation model via the Amazon Bedrock service, and test running inferences against the model.

Any opinions in this post are those of the individual author and may not reflect the opinions of AWS.