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dynamodb.ts
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dynamodb.ts
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import {
DynamoDBClient,
DynamoDBClientConfig,
GetItemCommand,
GetItemCommandInput,
UpdateItemCommand,
UpdateItemCommandInput,
DeleteItemCommand,
DeleteItemCommandInput,
AttributeValue,
} from "@aws-sdk/client-dynamodb";
import { BaseListChatMessageHistory } from "@langchain/core/chat_history";
import {
BaseMessage,
StoredMessage,
mapChatMessagesToStoredMessages,
mapStoredMessagesToChatMessages,
} from "@langchain/core/messages";
/**
* Interface defining the fields required to create an instance of
* `DynamoDBChatMessageHistory`. It includes the DynamoDB table name,
* session ID, partition key, sort key, message attribute name, and
* DynamoDB client configuration.
*/
export interface DynamoDBChatMessageHistoryFields {
tableName: string;
sessionId: string;
partitionKey?: string;
sortKey?: string;
messageAttributeName?: string;
config?: DynamoDBClientConfig;
key?: Record<string, AttributeValue>;
}
/**
* Interface defining the structure of a chat message as it is stored in
* DynamoDB.
*/
interface DynamoDBSerializedChatMessage {
M: {
type: {
S: string;
};
text: {
S: string;
};
role?: {
S: string;
};
};
}
/**
* Class providing methods to interact with a DynamoDB table to store and
* retrieve chat messages. It extends the `BaseListChatMessageHistory`
* class.
*/
export class DynamoDBChatMessageHistory extends BaseListChatMessageHistory {
lc_namespace = ["langchain", "stores", "message", "dynamodb"];
get lc_secrets(): { [key: string]: string } | undefined {
return {
"config.credentials.accessKeyId": "AWS_ACCESS_KEY_ID",
"config.credentials.secretAccessKey": "AWS_SECRETE_ACCESS_KEY",
"config.credentials.sessionToken": "AWS_SESSION_TOKEN",
};
}
private tableName: string;
private sessionId: string;
private client: DynamoDBClient;
private partitionKey = "id";
private sortKey?: string;
private messageAttributeName = "messages";
private dynamoKey: Record<string, AttributeValue> = {};
constructor({
tableName,
sessionId,
partitionKey,
sortKey,
messageAttributeName,
config,
key = {},
}: DynamoDBChatMessageHistoryFields) {
super();
this.tableName = tableName;
this.sessionId = sessionId;
this.client = new DynamoDBClient(config ?? {});
this.partitionKey = partitionKey ?? this.partitionKey;
this.sortKey = sortKey;
this.messageAttributeName =
messageAttributeName ?? this.messageAttributeName;
this.dynamoKey = key;
// override dynamoKey with partition key and sort key when key not specified
if (Object.keys(this.dynamoKey).length === 0) {
this.dynamoKey[this.partitionKey] = { S: this.sessionId };
if (this.sortKey) {
this.dynamoKey[this.sortKey] = { S: this.sortKey };
}
}
}
/**
* Retrieves all messages from the DynamoDB table and returns them as an
* array of `BaseMessage` instances.
* @returns Array of stored messages
*/
async getMessages(): Promise<BaseMessage[]> {
const params: GetItemCommandInput = {
TableName: this.tableName,
Key: this.dynamoKey,
};
const response = await this.client.send(new GetItemCommand(params));
const items = response.Item
? response.Item[this.messageAttributeName]?.L ?? []
: [];
const messages = items
.map((item) => ({
type: item.M?.type.S,
data: {
role: item.M?.role?.S,
content: item.M?.text.S,
},
}))
.filter(
(x): x is StoredMessage =>
x.type !== undefined && x.data.content !== undefined
);
return mapStoredMessagesToChatMessages(messages);
}
/**
* Deletes all messages from the DynamoDB table.
*/
async clear(): Promise<void> {
const params: DeleteItemCommandInput = {
TableName: this.tableName,
Key: this.dynamoKey,
};
await this.client.send(new DeleteItemCommand(params));
}
/**
* Adds a new message to the DynamoDB table.
* @param message The message to be added to the DynamoDB table.
*/
async addMessage(message: BaseMessage) {
const messages = mapChatMessagesToStoredMessages([message]);
const params: UpdateItemCommandInput = {
TableName: this.tableName,
Key: this.dynamoKey,
ExpressionAttributeNames: {
"#m": this.messageAttributeName,
},
ExpressionAttributeValues: {
":empty_list": {
L: [],
},
":m": {
L: messages.map((message) => {
const dynamoSerializedMessage: DynamoDBSerializedChatMessage = {
M: {
type: {
S: message.type,
},
text: {
S: message.data.content,
},
},
};
if (message.data.role) {
dynamoSerializedMessage.M.role = { S: message.data.role };
}
return dynamoSerializedMessage;
}),
},
},
UpdateExpression:
"SET #m = list_append(if_not_exists(#m, :empty_list), :m)",
};
await this.client.send(new UpdateItemCommand(params));
}
}