stages

Commentary

added in 0.6.0

Executes generators in a sequence (instead of the normal round-robin behavior), where each step in the sequence is called a stage.

At a minimum, each stage must name which generators will run. You specify those generators by supplying a name attribute on the generator definition itself. ¹

The generators in each stage will only begin running after the previous stage's generators have all terminated. You can terminate with a generator with maxEvents, maxMs, or a stateMachine with a transition that has no further states.

In addition to being able to name what generators should run in each stage, you can also specify overrides so that a generator will behave differently in two different stages. ²

---

Examples

Defining stages

Set a name on each generator you want to schedule. In this example, that's simply a and b.

Then, under the stages key of schedule, name the generators to run. Notice in the output how a runs to completion, and then b takes over.

{
    "generators": [
        {
            "name": "a",
            "topic": "generatorA",
            "value": {
                "_gen": "oneOf",
                "choices": [
                    1,
                    2,
                    3
                ]
            },
            "localConfigs": {
                "maxEvents": 3
            }
        },
        {
            "name": "b",
            "topic": "generatorB",
            "value": {
                "_gen": "boolean"
            },
            "localConfigs": {
                "maxEvents": 2
            }
        }
    ],
    "schedule": {
        "stages": [
            {
                "generators": [
                    "a"
                ]
            },
            {
                "generators": [
                    "b"
                ]
            }
        ]
    },
    "connections": {
        "kafka": {
            "kind": "kafka",
            "producerConfigs": {
                "bootstrap.servers": "localhost:9092",
                "key.serializer": "io.shadowtraffic.kafka.serdes.JsonSerializer",
                "value.serializer": "io.shadowtraffic.kafka.serdes.JsonSerializer"
            }
        }
    }
}

[
    3,
    2,
    1,
    false,
    true
]

Overriding generators

Use the overrides key in a stage to change the behavior of a generator when that stage executes. This is useful if you want to quickly seed some data by setting throttleMs to 0, and then generate it more sporadically later on.

overrides must be a map of generator name to object. The contents of override will be merged into the base generator definition.

In this example, generator a is overriden to produce only 5 events, and b only 4.

{
    "generators": [
        {
            "name": "a",
            "topic": "generatorA",
            "value": {
                "_gen": "oneOf",
                "choices": [
                    1,
                    2,
                    3
                ]
            }
        },
        {
            "name": "b",
            "topic": "generatorB",
            "value": {
                "_gen": "boolean"
            }
        }
    ],
    "schedule": {
        "stages": [
            {
                "generators": [
                    "a"
                ],
                "overrides": {
                    "a": {
                        "localConfigs": {
                            "maxEvents": 5
                        }
                    }
                }
            },
            {
                "generators": [
                    "b"
                ],
                "overrides": {
                    "b": {
                        "localConfigs": {
                            "maxEvents": 4
                        }
                    }
                }
            }
        ]
    },
    "connections": {
        "kafka": {
            "kind": "kafka",
            "producerConfigs": {
                "bootstrap.servers": "localhost:9092",
                "key.serializer": "io.shadowtraffic.kafka.serdes.JsonSerializer",
                "value.serializer": "io.shadowtraffic.kafka.serdes.JsonSerializer"
            }
        }
    }
}

[
    1,
    2,
    1,
    1,
    3,
    false,
    true,
    false,
    true
]

---

Specification

JSON schema

{
    "type": "array",
    "minItems": 1,
    "items": {
        "type": "object",
        "properties": {
            "generators": {
                "type": "array",
                "minItems": 1,
                "items": {
                    "type": "string"
                }
            },
            "overrides": {
                "type": "object",
                "additionalProperties": {
                    "type": "object"
                }
            }
        },
        "required": [
            "generators"
        ]
    }
}