JFR Analytics

An exploration for running analytics on JDK Flight Recorder recordings.

There's two areas of interest:

• Pull-based SQL queries on JFR recording files, using Apache Calcite (work in progress)
• Streaming queries on realtime JFR event streams (implementation tbd., e.g. via Apache Flink or Akka Streams; not started yet)

Running SQL Queries on JFR Recordings

Each JFR event type gets mapped to a table named after the type, e.g. jdk.ObjectAllocationSample, jdk.ClassLoad, etc. Each event attribute gets mapped to a table column. These tables can be queried programmatically using JDBC or ad-hoc using SQLLine. See here for a list of all built-in JFR event types and their attributes.

Running Queries Via JDBC

Queries against a JFR file can be run using standard JDBC like shown below (this query retrieves the ten top allocating stacktraces):

Path jfrFile = ...; // path to some-recording.jfr

Properties properties = new Properties();
properties.put("model", JfrSchemaFactory.INLINE_MODEL.formatted(jfrFile));

try (Connection connection = DriverManager.getConnection("jdbc:calcite:", properties)) {
    PreparedStatement statement = connection.prepareStatement("""
            SELECT TRUNCATE_STACKTRACE("stackTrace", 40), SUM("weight")
            FROM "JFR"."jdk.ObjectAllocationSample"
            GROUP BY TRUNCATE_STACKTRACE("stackTrace", 40)
            ORDER BY SUM("weight") DESC
            LIMIT 10
            """);

    try (ResultSet rs = statement.executeQuery()) {
        while (rs.next()) {
            System.out.println("Trace : " + rs.getString(1));
            System.out.println("Weight: " + rs.getLong(2));
        }
    }
}

Running Queries Using SQLLine

Using SQLLine, you can run ad-hoc SQL queries against a given JFR file. First build the project using the sqlline profile, which will copy SQLLine and all the project dependencies into the target/lib folder. Then run SQLLine as shown below:

mvn clean verify -Psqlline -Dquick
java --class-path "target/lib/*:target/jfr-analytics-1.0.0-SNAPSHOT.jar" sqlline.SqlLine

Within SQLLine, you can "connect" to a given JFR recording file like so:

!connect jdbc:calcite:schemaFactory=org.moditect.jfranalytics.JfrSchemaFactory;schema.file=src/test/resources/object-allocations.jfr dummy dummy

!tables # shows all tables (i.e. JFR event types)
!columns "jdk.ObjectAllocationSample" # shows all columns (i.e. JFR event attributes)
!outputformat vertical # vertical output, useful when displaying stack traces

SELECT TRUNCATE_STACKTRACE("stackTrace", 40), SUM("weight")
FROM "jdk.ObjectAllocationSample"
WHERE "startTime" > (SELECT "startTime" FROM "jfrunit.Reset")
GROUP BY TRUNCATE_STACKTRACE("stackTrace", 40)
ORDER BY SUM("weight") DESC
LIMIT 10;

Built-in Functions

There's a set of functions for working with JFR attribute types such as jdk.jfr.consumer.RecordedClass and jdk.jfr.consumer.RecordedStackTrace.

Function	Description
VARCHAR CLASS_NAME(RecordedClass)	Obtains the fully-qualified class name from the given jdk.jfr.consumer.RecordedClass
VARCHAR TRUNCATE_STACKTRACE(RecordedStackTrace, INT)	Truncates the stacktrace of the given jdk.jfr.consumer.RecordedStackTrace to the given depth
BOOL HAS_MATCHING_FRAME(RecordedStackTrace, VARCHAR)	Returns true if the given jdk.jfr.consumer.RecordedStackTrace contains a frame matching the given regular expression, false otherwise

Built-in Types

The following struct types are provided by JFR Analtics:

Function	Attributes
RecordedThread	osName, osThreadId, javaName, javaThreadId, group

Build

Run the following command to build this project:

mvn clean verify

Pass the -Dquick option to skip all non-essential plug-ins and create the output artifact as quickly as possible:

mvn clean verify -Dquick

Run the following command to format the source code and organize the imports as per the project's conventions:

mvn process-sources

Using as a library

The easiest way to consume JFR Analytics as a library is to add it as a local dependency, along with Calcite as a transitive dependency. For example, in this Gradle (Kotlin) snippet:

  implementation(files("lib/jfr-analytics.jar"))
  implementation("org.apache.calcite:calcite-core:1.29.0")

License

This code base is available under the Apache License, version 2.