SDK for JavaScript Streaming Quickstart

This quickstart shows you how to use the Oracle Cloud Infrastructure (OCI) SDK for TypeScript and JavaScript and Oracle Cloud Infrastructure Streaming to publish and consume messages.

Refer to the Overview of Streaming for key concepts and more Streaming details. For more information about using the OCI SDKs, see the SDK Guides.

Prerequisites

  1. To use the SDK for TypeScript and JavaScript, you must have the following:

    • An Oracle Cloud Infrastructure account.
    • A user created in that account, in a group with a policy that grants the required permissions. This user can be yourself, or another person/system that needs to call the API. For an example of how to set up a new user, group, compartment, and policy, see Adding Users. For a list of typical policies you may want to use, see Common Policies.
    • A key pair used for signing API requests, with the public key uploaded to Oracle. Only the user calling the API should possess the private key. For more information, see Getting Started.
  2. Collect the Messages endpoint and OCID of a stream. See Listing Streams and Stream Pools for instructions on viewing stream details. For the purposes of this quickstart, the stream should use a public endpoint and let Oracle manage encryption. Refer to Creating Streams and Creating Stream Pools if you do not have an existing stream.
  3. Node.js version 8.x or later. Download the latest long-term support (LTS) version.
  4. Visual Code Studio (recommended) or any other integrated development environment (IDE).
  5. Open a command prompt that has npm in its path, change to the directory where you want to keep your code for this quickstart (wd, for example), and then run the following command to install the OCI SDK for JavaScript:

    npm install oci-sdk
  6. Ensure that you have a valid SDK configuration file. For production environments, you should use instance principal authorization.

Producing Messages

  1. Open your favorite editor, such as Visual Studio Code, from the directory wd. You should already have oci-sdk packages for JavaScript installed in this directory after you've met the prerequisites.
  2. Create a file named Producer.js in the wd directory with following code. Replace values of variables ociConfigFile, ociProfileName,ociStreamOcid, and ociMessageEndpointForStream in the following code snippet with the values applicable for your tenancy.

    const common = require("oci-common");
    const st = require("oci-streaming"); // OCI SDK package for OSS
    
    const ociConfigFile = "<config_file_path>";
    const ociProfileName = "<config_file_profile_name>";
    const ociMessageEndpointForStream = "<stream_message_endpoint>";
    const ociStreamOcid = "<stream_OCID>";
    
    // provide authentication for OCI and OSS
    const provider = new common.ConfigFileAuthenticationDetailsProvider(ociConfigFile, ociProfileName);
      
    async function main() {
      // OSS client to produce and consume messages from a Stream in OSS
      const client = new st.StreamClient({ authenticationDetailsProvider: provider });
    
      client.endpoint = ociMessageEndpointForStream;
    
      // build up a putRequest and publish some messages to the stream
      let messages = [];
      for (let i = 1; i <= 3; i++) {
        let entry = {
          key: Buffer.from("messageKey" + i).toString("base64"),
          value: Buffer.from("messageValue" + i).toString("base64")
        };
        messages.push(entry);
      }
    
      console.log("Publishing %s messages to stream %s.", messages.length, ociStreamOcid);
      const putMessageDetails = { messages: messages };
      const putMessagesRequest = {
        putMessagesDetails: putMessageDetails,
        streamId: ociStreamOcid
      };
      const putMessageResponse = await client.putMessages(putMessagesRequest);
      for (var entry of putMessageResponse.putMessagesResult.entries)
        console.log("Published messages to parition %s, offset %s", entry.partition, entry.offset);
    
    }
    
    main().catch((err) => {
      console.log("Error occurred: ", err);
    });
  3. From the wd directory, run the following command:

    node run Producer.js
  4. Use the Console to see the latest messages sent to the stream to verify that production was successful.

Consuming Messages

  1. First, ensure that the stream you want to consume messages from contains messages. You could use the Console to produce a test message, or use the stream and messages we created in this quickstart.
  2. Open your favorite editor, such as Visual Studio Code, from the directory wd. You should already have the oci-sdk packages for JavaScript installed in this directory after you've met the prerequisites.
  3. Create a file named Consumer.js in directory wd with following code. Replace values of variables ociConfigFile, ociProfileName,ociStreamOcid, and ociMessageEndpointForStream in the following code snippet with the values applicable for your tenancy.

    const common = require("oci-common");
    const st = require("oci-streaming"); // OCI SDK package for OSS
    
    const ociConfigFile = "<config_file_path>";
    const ociProfileName = "<config_file_profile_name>";
    const ociMessageEndpointForStream = "<stream_message_endpoint>";
    const ociStreamOcid = "<stream_OCID>";
    
    // provide authentication for OCI and OSS
    const provider = new common.ConfigFileAuthenticationDetailsProvider(ociConfigFile, ociProfileName);
      
    const consumerGroupName = "exampleGroup";
    const consumerGroupInstanceName = "exampleInstance-1";
    
    async function main() {
      // OSS client to produce and consume messages from a Stream in OSS
      const client = new st.StreamClient({ authenticationDetailsProvider: provider });
      client.endpoint = ociMessageEndpointForStream;
    
      // A cursor can be created as part of a consumer group.
      // Committed offsets are managed for the group, and partitions
      // are dynamically balanced amongst consumers in the group.
      console.log("Starting a simple message loop with a group cursor");
      const groupCursor = await getCursorByGroup(client, ociStreamOcid, consumerGroupName, consumerGroupInstanceName);
      await consumerMsgLoop(client, ociStreamOcid, groupCursor);
    }
    
    main().catch((err) => {
        console.log("Error occurred: ", err);
    }); 
    
    async function consumerMsgLoop(client, streamId, initialCursor) {
        let cursor = initialCursor;
        for (var i = 0; i < 10; i++) {
          const getRequest = {
            streamId: streamId,
            cursor: cursor,
            limit: 2
          };
          const response = await client.getMessages(getRequest);
          console.log("Read %s messages.", response.items.length);
          for (var message of response.items) {
            if (message.key !== null)  {         
                console.log("%s: %s",
                Buffer.from(message.key, "base64").toString(),
                Buffer.from(message.value, "base64").toString());
            }
           else{
                console.log("Null: %s",
                    Buffer.from(message.value, "base64").toString() );
           }
          }
          // getMessages is a throttled method; clients should retrieve sufficiently large message
          // batches, as to avoid too many http requests.
          await delay(2);
          cursor = response.opcNextCursor;
        }
      }
      
    
    async function getCursorByGroup(client, streamId, groupName, instanceName) {
        console.log("Creating a cursor for group %s, instance %s.", groupName, instanceName);
        const cursorDetails = {
          groupName: groupName,
          instanceName: instanceName,
          type: st.models.CreateGroupCursorDetails.Type.TrimHorizon,
          commitOnGet: true
        };
        const createCursorRequest = {
          createGroupCursorDetails: cursorDetails,
          streamId: streamId
        };
        const response = await client.createGroupCursor(createCursorRequest);
        return response.cursor.value;
    }
    
    async function delay(s) {
        return new Promise(resolve => setTimeout(resolve, s * 1000));
    }
  4. From the wd directory, run the following command:

    node run Consumer.js
  5. You should see messages similar to the following:

    Starting a simple message loop with a group cursor
    Creating a cursor for group exampleGroup, instance exampleInstance-1.
    Read 1 messages.
    Null: Example Test Message 0
    Read 1 messages.
    Null: Example Test Message 0
    Read 1 messages.
    Null: Example Test Message 0
    Read 2 messages.
    Null: Example Test Message 0
    Null: Example Test Message 0
    Read 2 messages.
    Null: Example Test Message 0
    Null: Example Test Message 0
    Note

    If you used the Console to produce a test message, the key for each message is Null