Using the Profile Log Service

Creating and Writing To a New Profile Name

CNC allows users of Azul Prime to record and distribute ReadyNow profiles with intervention of a CNC administrator. All of the necessary options can be specified as command-line arguments to the Java process at the time of deployment.

When using ReadyNow with CNC, responsibilities are split between the JVM and CNC:

Profile Log Service Commands

The following options are available in Azul Prime when using the Profile Log Service with CNC:

Profile Log Service Global Defaults

CNC admins can also set the following global defaults for ReadyNow profiles:

Basic Profile Recording with Server Defaults

In its most basic form, you just let the server-side defaults do all the work. By default, CNC will nominate profile logs after three full generations and does not place a limit on log size. Suppose you want to record a new profile while deploying code to a fleet running in production. Run with the following options:

 
java -XX:CNCHost=TestEnvCncHost \
    -XX:ProfileLogName=cnc://MyApp-v3 \
    -jar myapp.jar

In this case, all JVMs nominate their logs for promotion after two minutes of recording and keep recording until the JVM shuts down. For best results, do a test run in a canary instance for at least two minutes and if possible a full ten minutes. This creates generation 1 of your profile. Then restart your fleet as normal. As JVMs start up, they receive a profile from CNC and check the generation number. If that number is less than the server-side default maximum of 3, the JVM writes out the next generation of the profile. Once there is a valid generation 3 of the profile on CNC, none of the JVMs write any more output.

Capping Profile Log Recording and Maximum Generations

We can make our example above more complex:

A profile needs to record for at least 2 minutes to be nominated. After 10 minutes you want to stop recording. You want to record two generations of the profile. Start your JVM with the following parameters:

 
java -XX:CNCHost=TestEnvCncHost \
    -XX:ProfileLogName=cnc://MyApp-v3 \
    -XX:ProfileLogTimeLimitSeconds=600 \
    -XX:ProfileLogMaxNominatedGenerationCount=2 \
    -jar myapp.jar

Continuing to Record After Promotion

You often want to keep recording after you have a valid profile that your JVMs can use. This allows you to review your ReadyNow information later to analyze new traffic patterns or debug unwanted application behavior. To continue recording after the maximum generation has been reached, CNC Admin sets StopRecordingOnMaxGeneration=false. In the above example, all JVMs who start and receive a valid generation 3 profile write out a profile log to generation 4 of MyApp-v3 but never nominates them for use by other JVMs. CNC will never send generation 4 of a profile to a JVM. You can access these diagnostic profiles through the administrative REST APIs.

Using a Previous Profile as the Basis of a New Profile Recording

When you’re deploying version 3 of MyApp, you often have a valid profile for version 2. In most cases, you change a small portion of your code between versions and most of the previous profile is still valid for your new version. When you feed in the previous version of the profile as input to recording the new version of the profile, you can in most cases eliminate the need to do multiple training iterations.

Using our above example, perform one run of the full ten minutes in a canary with the following settings:

 
java -XX:CNCHost=TestEnvCncHost \
    -XX:ProfileLogIn=cnc://MyApp-v2 \
    -XX:ProfileLogOut=cnc://MyApp-v3 \
    -XX:ProfileLogTimeLimitSeconds=600 \
    -XX:ProfileLogMaxNominatedGenerationCount=1 \
    -jar myapp.jar

To restart the rest of your fleet with the following settings:

 
java -XX:CNCHost=TestEnvCncHost \
    -XX:ProfileLogName=cnc://MyApp-v3 \
    -XX:ProfileLogTimeLimitSeconds=600 \
    -XX:ProfileLogMaxNominatedGenerationCount=1 \
    -jar myapp.jar