Single View Trigger Generator

The Single View Trigger Generator has 3 fundamental parts:

• The consumption of pr-update messages
• The strategy execution
• The production of sv-trigger messages or pc records

For each part we will need to configure a set of environment variables and config maps.

Environment variables

The following table indicates all the available environment variables for you to customize the service to your needs.

note

When creating the service from the marketplace the following environment variables will be added for you with some default values but you still need to properly update them to make the service work

Name	Required	Description	Default value
LOG_LEVEL	✓	Level to use for logging; to choose from: error, fatal, warn, info, debug, trace, silent	silent
MONGODB_URL	✓	MongoDB URL where the projections are stored	-
MONGODB_NAME	✓	MongoDB Database name where the projections are stored	-
EVENT_STORE_CONFIG_PATH	✓	Path to the Event Store Config file	-
EVENT_STORE_TARGET	✓	Kafka topic to send the sv-trigger messages or MongoDB collection to save the pc records	-
SINGLE_VIEW_NAME	✓	The name of the Single View	-
KAFKA_PROJECTION_UPDATES_FOLDER	✓	Path to the Kafka Projection Updates folder	-
ER_SCHEMA_FOLDER	✓	Path to the ER Schema folder	-
PROJECTION_CHANGES_SCHEMA_FOLDER	✓	Path to the Projection Changes Schema folder	-
MANUAL_STRATEGIES_FOLDER	-	Path to the custom strategies folder where the custom strategies scripts are stored	-
TRIGGER_CUSTOM_FUNCTIONS_FOLDER	-	Path to the custom functions folder used in __fromFile__ values	''

Attaching a Service to a Single View

To simplify the configuration of the Single View Trigger Generator service, you can attach a previously created Single View Trigger Generator service from the marketplace to a Single View. Here's how to do it:

• create your Single View and attach a Single View Creator Service to it from the dedicated configuration page. This is necessary because the Single View Trigger Generator can work with only one Single View Creator Service.
• within the Single View Creator tab of the Single View modal, enter the configuration page of the Single View Creator that you've configured.
• in the Single View Trigger Generator tab, you can choose a Single View Trigger Generator from the available services.

Once the service has been attached, you can manage the content of the Projection Changes Schema config map and the Kafka Projection Updates config map.

Any updates to these configurations will be reflected in the service config maps after saving the configuration.

Shared ER Schema

Additionally, when a service is attached to a Single View, the ER Schema config map will be shared between the Single View Creator and the Single View Trigger Generator.

Also, the environment variable SINGLE_VIEW_NAME will be set automatically to the name of the Single View.

danger

When a Single View Trigger Generator is attached to a Single View, the environment variable SINGLE_VIEW_NAME will be set to "read-only" mode, as well as the config maps for the ER Schema, Projection Changes Schema, and Kafka Projection Updates.

If you prefer to manually configure these services, you can always detach the service in the Single View Trigger Generator tab via the Detach microservice button on the top-right side of the page. After saving the configuration, the environment variable and the config maps will be again editable from the Microservices section.

config maps

The service can use the following 3 config maps:

note

When creating the service from the marketplace the following config maps will be created for you with some default values. The Event Store Config must be manually modified from the Microservice page to include all the missing configuration, but the ER Schema, the Projection Changes Schema and the Kafka Projection Updates configuration can be simplified by attaching the service to a Single View: in this case, the environment variables and config maps for these three config maps will be automatically managed by the application.

ER Schema

The ER Schema config map contains the erSchema.json file which describes the relationships between each projection of the System of Records.

Remember to copy/paste the mount path into the ER_SCHEMA_FOLDER environment variable so the service can read the file. To know more on how to configure the file please go to the ER Schema page.

Projection Changes Schema

The Projection Changes Schema config map contains the projectionChangesSchema.json file which defines how to get to the base projection of the single view starting from the projection in which we received the ingestion message.

Remember to copy/paste the mount path into the PROJECTION_CHANGES_SCHEMA_FOLDER environment variable so the service can read the file. If you need more info on how to configure the projectionChangesSchema.json file, please refer to the Projection Changes Schema page.

Kafka Projection Updates

The Kafka Projection Updates config map contains the kafkaProjectionUpdates.json file which defines the topics from where to consume the Projection Updates and the strategy to apply to each message.

Remember to copy/paste the mount path into the KAFKA_PROJECTION_UPDATES_FOLDER environment variable so the service can read the file. If you need more info on how to configure the kafkaProjectionUpdates.json file, please refer to the Kafka Projection Updates page.

danger

If you attach the service to a Single View, the Kafka Projection Updates config map can be modified to support only automatic strategies.

If you need to use manual strategies for one or more projections, please detach the service and configure the config maps from the Microservices page.

Event Store Config

The Event Store Config is a JSON file containing the configuration of the consumer and producer of the service itself and it has the following format:

{
  "consumer": {
    "kafka": {
      // Kafka consumer configuration (see below)
    }
  },
  "producer": {
    "<kafka | mongo>": {
      // Kafka or mongo producer configuration (see below)
    }
  }
}

caution

Mind that only one producer and consumer must be configured at a time so the service knows which kind to use. Providing more than one consumer or producer will fail the configmap validation and shut down the service at start up.

Consumers

At the moment you can only configure your consumer with kafka which will read pr-update messages from the Real-Time Updater. To configure it you must follow the JsonSchema specification below.

Kafka consumer config JsonSchema

{
  "type": "object",
  "required": [
    "brokers",
    "consumerGroupId"
  ],
  "properties": {
    "brokers": {
      "type": "string"
    },
    "consumerGroupId": {
      "type": "string"
    },
    "consumeFromBeginning": {
      "type": "boolean",
      "description": "specify whether the consumer group should start to consume from the beginning of the topic whenever the group id is created for the first time",
      "default": false
    },
    "ssl": {
      "description": "https://kafka.js.org/docs/configuration#ssl",
      "oneOf": [
        {
          "type": "boolean"
        },
        {
          "type": "object",
          "additionalProperties": true,
          "properties": {
            "ca": {
              "type": "string",
              "description": "path to the file containing the CA certificate in PEM format"
            },
            "key": {
                "type": "string",
              "description": "path to the file containing the client private key in PEM format"
            },
            "passphrase": {
              "type": "string",
              "description": "password necessary to unlock the private key"
            },
            "cert": {
              "type": "string",
              "description": "path to the file containing the client certificate in PEM format"
            }
          }
        }
      ]
    },
    "sasl": {
      "type": "object",
      "properties": {
        "mechanism": {
          "type": "string",
          "enum": [
            "plain",
            "scram-sha-256",
            "scram-sha-512"
          ]
        },
        "username": {
          "type": "string"
        },
        "password": {
          "type": "string"
        }
      }
    },
    "clientId": {
      "type": "string"
    },
    "connectionTimeout": {
      "type": "number"
    },
    "authenticationTimeout": {
      "type": "number"
    },
    "reauthenticationThreshold": {
      "type": "number"
    },
    "requestTimeout": {
      "type": "number"
    },
    "enforceRequestTimeout": {
      "type": "boolean"
    },
    "retry": {
      "type": "object",
      "properties": {
        "maxRetryTime": {
          "type": "number"
        },
        "initialRetryTime": {
          "type": "number"
        },
        "factor": {
          "type": "number"
        },
        "multiplier": {
          "type": "number"
        },
        "retries": {
          "type": "number"
        }
      }
    },
    "logLevel": {
      "type": "string",
      "enum": [
        "NOTHING",
        "ERROR",
        "WARN",
        "INFO",
        "DEBUG"
      ]
    }
  }
}

Producers

For the producers you can choose between two options: Kafka or MongoDB (sv-trigger vs. pc). With MongoDB you will save Projection Changes on the DB just like the Real-Time Updater does. With Kafka instead it will send sv-trigger messages which will also be read by the Single View Creator by changing its configuration to do so. Here's the configuration specification for both:

MongoDB producer config JsonSchema

{
  "type": "object",
  "required": ["url", "dbName"],
  "properties": {
    "url": {
      "type": "string"
    },
    "dbName": {
      "type": "string"
    }
  }
}

Kafka producer config JsonSchema

{
  "type": "object",
  "required": ["brokers"],
  "properties": {
    "brokers": {
      "type": "string"
    },
    "ssl": {
      "description": "https://kafka.js.org/docs/configuration#ssl",
      "oneOf": [
        {
          "type": "boolean"
        },
        {
          "type": "object",
          "additionalProperties": true,
          "properties": {
            "ca": {
              "type": "string",
              "description": "path to the file containing the CA certificate in PEM format"
            },
            "key": {
              "type": "string",
              "description": "path to the file containing the client private key in PEM format"
            },
            "passphrase": {
              "type": "string",
              "description": "password necessary to unlock the private key"
            },
            "cert": {
              "type": "string",
              "description": "path to the file containing the client certificate in PEM format"
            }
          }
        }
      ]
    },
    "sasl": {
      "type": "object",
      "properties": {
        "mechanism": {
          "type": "string",
          "enum": ["plain", "scram-sha-256", "scram-sha-512"]
        },
        "username": {
          "type": "string"
        },
        "password": {
          "type": "string"
        }
      }
    },
    "clientId": {
      "type": "string"
    },
    "connectionTimeout": {
      "type": "number"
    },
    "authenticationTimeout": {
      "type": "number"
    },
    "reauthenticationThreshold": {
      "type": "number"
    },
    "requestTimeout": {
      "type": "number"
    },
    "enforceRequestTimeout": {
      "type": "boolean"
    },
    "retry": {
      "type": "object",
      "properties": {
        "maxRetryTime": {
          "type": "number"
        },
        "initialRetryTime": {
          "type": "number"
        },
        "factor": {
          "type": "number"
        },
        "multiplier": {
          "type": "number"
        },
        "retries": {
          "type": "number"
        }
      }
    },
    "logLevel": {
      "type": "string",
      "enum": ["NOTHING", "ERROR", "WARN", "INFO", "DEBUG"]
    }
  }
}

An example of a complete configuration would be:

{
  "consumer": {
    "kafka": {
      "brokers": "localhost:9092,localhost:9093",
      "clientId": "client-id",
      "consumerGroupId": "group-id",
      "consumeFromBeginning": true,
      "logLevel": "NOTHING"
    }
  },
  "producer": {
    "mongo": {
      "url": "mongodb://localhost:27017",
      "dbName": "pc-sv-books-test"
    }
  }
}