Overview of testing with load actors

Testing system performance is an important stage of adding changes to the YDB core. With load testing, you can:

• Determine the performance metrics and compare them to the values before the changes.
• Test how the system runs under high or peak loads.

The task to load a high-performance distributed system is non-trivial. A software developer often has to run multiple client instances to achieve the required server load. YDB implements a simple and convenient load generation mechanism: load actors. Actors are created and run directly on a cluster, which allows avoiding the use of additional resources for starting client instances. Load actors can be run on arbitrary cluster nodes: one, all, or only selected ones. You can create any number of actors on any node.

With load actors, you can test both the entire system and its individual components:

For example, you can generate a load on Distributed Storage without using tablet and Query Processor layers. This lets you test different system layers separately and find bottlenecks in an efficient way. By combining a variety of actor types, you can run different types of load.

Actor types

Running a load

You can run load using the following tools:

• Cluster Embedded UI: Allows you to create, based on a configuration, and start a load actor either on the current node or all tenant nodes at once.
• The ydbd utility: Allows you to send the actor configuration to any cluster node specifying the nodes to create and run the actor on.

The use case described below shows how to create and run the KqpLoad actor. The actor accesses the /slice/db database as a key-value store using 64 threads with a 30-second load. Before the test, the actor creates the necessary tables and deletes them once the test is completed. When being created, the actor is automatically assigned a tag. The same tag will be assigned to the test result.

KqpLoad: {
  DurationSeconds: 30
  WindowDuration: 1
  WorkingDir: "/slice/db"
  NumOfSessions: 64
  UniformPartitionsCount: 1000
  DeleteTableOnFinish: 1
  WorkloadType: 0
  Kv: {
    InitRowCount: 1000
    PartitionsByLoad: true
    MaxFirstKey: 18446744073709551615
    StringLen: 8
    ColumnsCnt: 2
    RowsCnt: 1
  }
}

{"status":"OK","tag":1}

NodeId: 1
Event: {
  KqpLoad: {
    DurationSeconds: 30
    WindowDuration: 1
    WorkingDir: "/slice/db"
    NumOfSessions: 64
    UniformPartitionsCount: 1000
    DeleteTableOnFinish: 1
    WorkloadType: 0
    Kv: {
      InitRowCount: 1000
      PartitionsByLoad: true
      MaxFirstKey: 18446744073709551615
      StringLen: 8
      ColumnsCnt: 2
      RowsCnt: 1
    }
  }
}

NodeId: 1
NodeId: 2
...
NodeId: N
Event: {
...

ydbd load-test --server <endpoint> --protobuf "$(cat <proto_file>)"

Viewing test results

You can view the test results using the Embedded UI. For a description of output parameters, see the documentation of the respective actor.