Exercise - Broker messages using Streams

  • 15 minutes

Your retail application currently uses server-side files to record pertinent information from mobile devices when running in-house software. Unfortunately, there have been multiple issues with scaling this solution out; including concurrency between numerous clients, missing data, and locks preventing reading or writing actions. Your team has decided to move forward with a middleware solution that can serve as a message broker.

In this exercise, implement Streams in an Azure Cache for Redis instance.

Add entries to a stream

Entries are added to a new or existing stream using the XADD command. The stream is automatically created if it doesn't already exists.

  1. Sign in to the Azure portal using the same account you used to activate the sandbox.

  2. Within the Azure services category, select More services, select the Databases category and then select Azure Cache for Redis.

  3. Select the Azure Cache for Redis instance you created in a previous exercise.

  4. In the resource pane, select Console to open the Redis console.

  5. In the console, use the XADD command to add the following new entries:

    Stream Key Data
    org.logs.clientapp 1324092248593-0 device-id mobile error unknown-crash
    org.logs.clientapp 1481945061467-0 worker-process 1788 status success 
    XADD org.logs.clientapp 1324092248593-0 device-id mobile error unknown-crash

XADD org.logs.clientapp 1481945061467-0 worker-process 1788 status success

  6. Observe the output from the two invocations of the XADD command. The output includes the key of the newly added entries.

    "1324092248593-0"

"1481945061467-0"

  7. Use the XADD command to add another new entry with an automatically generated identifier:

    Stream Data
    org.logs.clientapp application-status started 
    XADD org.logs.clientapp * application-status started

  8. Observe the output from the invocation of the XADD command. The output includes a newly generated key based on the current Unix time in milliseconds and a sequence number. For example, if the key is 1638502526759-0, then the output would be:

    "1638502526759-0"

Retrieve and count all entires in a stream

The XLEN command counts the number of entries in a stream. Once you're ready to query the entries, you can use the XRANGE command to get entries within the stream.

  1. Use the XLEN command to count the number of entries in the org.logs.clientapp stream:

    XLEN org.logs.clientapp

  2. Observe the output from the XLEN command. The output is an integer with a value of 3 for the entries created earlier in this exercise.

    (integer) 3

  3. Use the XRANGE command and both the + and - operators to get a range of all data in the org.logs.clientapp stream:

    XRANGE org.logs.clientapp - +

  4. Observe the output from invoking the XRANGE command. This output includes all three entries in the stream.

    1) 1) "1324092248593-0"
   2) 1) "device-id"
      2) "mobile"
      3) "error"
      4) "unknown-crash"
2) 1) "1481945061467-0"
   2) 1) "worker-process"
      2) "1788"
      3) "status"
      4) "success"
3) 1) "1638502526759-0"
   2) 1) "application-status"
      2) "started"

    Note

    Your last key will not exactly match the identifier used in this example.

Retrieve a subset of entries in a stream

The XRANGE command includes a + and - operator. These operators can be used with keys to query a subset of the data in a stream based on a time range.

  1. Invoke the XRANGE command using the - operator and the key of the second entry (1481945061467-0):

    XRANGE org.logs.clientapp - 1481945061467-0

  2. Observe the output of the invocation of the XRANGE command. The output includes all entries from the start of the stream, chronologically, up to the second entry.

    1) 1) "1324092248593-0"
   2) 1) "device-id"
      2) "mobile"
      3) "error"
      4) "unknown-crash"
2) 1) "1481945061467-0"
   2) 1) "worker-process"
      2) "1788"
      3) "status"
      4) "success"

  3. Invoke the XRANGE command using the key of the second entry (1481945061467-0) and the + operator:

    XRANGE org.logs.clientapp 1481945061467-0 +

  4. Observe the output of the invocation of the XRANGE command. The output includes the second entry, and then all entries up to the end of the stream, chronologically.

    1) 1) "1481945061467-0"
   2) 1) "worker-process"
      2) "1788"
      3) "status"
      4) "success"
2) 1) "1638502526759-0"
   2) 1) "application-status"
      2) "started"

    Note

    The last key will not exactly match the one used in this example.