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Version: 12.x (Current)

Single View Creator

The Single View Creator is the service that keeps the Single View updated with data retrieved from Projections. This service is available as a plugin or as a template:

  • plugin: it allows you to use the Single View Creator as a black-box. You just need to configure it through the Config Maps and environment variables
  • template: it gives you access to the source code of the Single View Creator, which will be hosted on a Git repository. You will need to update its dependencies and maintain the code.
tip

We strongly recommend using the plugin. The template is supposed to be used only for advanced use cases where the plugin cannot be used.

Environment Variables

NameRequiredDescriptionDefault value
CONFIGURATION_FOLDER-Folder where configuration files are mounted/home/node/app/src/
LOG_LEVELLevel to use for logging-
HTTP_PORT-Port exposed by the service3000
TYPEIdentifies the type of projection changes that need to be read. It should be the same as the Single View name you want to update.-
SCHEDULING_TIME-a quantity of time in milliseconds, every X milliseconds the service wake up and check if there are some projections changes in NEW state to work on. The service continue working until no more new projections changes are found, if so he goes to sleep for X milliseconds.60000
PROJECTIONS_MONGODB_URLMongoDB connection string where projections are stored. Must be a valid uri-
SINGLE_VIEWS_MONGODB_URLMongoDB connection string where single view must be stored. Must be a valid uri-
PROJECTIONS_CHANGES_MONGODB_URL-The db from where projections changes are read. If not set, PROJECTIONS_MONGODB_URL is used.-
PROJECTIONS_CHANGES_DATABASEThe db from where projections changes are read.-
PROJECTIONS_DATABASEThe db from where projections are read. If not set, PROJECTIONS_CHANGES_DATABASE is used.-
PROJECTIONS_CHANGES_COLLECTION-if you have set a custom projection change collection name from advanced, then set its name. Otherwise, it is fd-pc-SYSTEM_ID where SYSTEM_ID is the id of the System of Record this single view creator is responsible for.-
SINGLE_VIEWS_DATABASEThe db from where single views are written.-
SINGLE_VIEWS_COLLECTIONIt must be equals to the Single View name the service is in charge of keeping updated.-
SINGLE_VIEWS_PORTFOLIO_ORIGINName that should represent the source of any request received by the Single View Creator (in case the SVC receives requests from one System of Record, we suggest to use the name of said SoR). This will be used as an identifier for debugging, tracking requests and categorizing metrics;
-
SINGLE_VIEWS_ERRORS_COLLECTIONName of a MongoDB CRUD you want to use as collection for single view errors.-
KAFKA_CONSUMER_GROUP_ID-@deprecated - in favor of KAFKA_GROUP_ID. The Kafka consumer group identifier-
KAFKA_GROUP_ID-defines the Kafka group id (it is suggested to use a syntax like {'{tenant}.{environment}.{projectName}.{system}.{singleViewName}.single-view-creator'})-
KAFKA_CLIENT_ID-The Kafka client identifier-
KAFKA_BROKERS_LIST-@deprecated - in favor of KAFKA_BROKERS. list of brokers the service needs to connect to-
KAFKA_BROKERS-list of brokers the service needs to connect to-
KAFKA_SASL_MECHANISM-The Kafka SASL mechanism to be used. Can be one of the following: "plain", "PLAIN", "scram-sha-256", "SCRAM-SHA-256", "scram-sha-512", "SCRAM-SHA-512"plain
KAFKA_SASL_USERNAME-username to use for logging into Kafka-
KAFKA_SASL_PASSWORD-password to use for logging into Kafka-
KAFKA_SVC_EVENTS_TOPIC-topic used to queue Single View Creator state changes (e.g. single view creation). This feature is deprecated in favor of KAFKA_SV_UPDATE_TOPIC and it will be removed soon-
SEND_BA_TO_KAFKA-true if you want to send to Kafka the before-after information about the update changes of the single view. This feature is deprecated in favor of ADD_BEFORE_AFTER_CONTENT using the 'sv-update' event and it will be removed soonfalse
KAFKA_BA_TOPIC-topic where to send the before-after messages which represent the single view document before and after a change. This feature is deprecated in favor of ADD_BEFORE_AFTER_CONTENT using the 'sv-update' event and it will be removed soon-
SEND_SV_UPDATE_TO_KAFKA-true if you want to send to Kafka the sv-update message about the update changes of the single viewfalse
ADD_BEFORE_AFTER_CONTENT-true if you want to add the before and after content to the sv-update message, works only if SEND_SV_UPDATE_TO_KAFKA is set to truefalse
KAFKA_SV_UPDATE_TOPIC-topic where to send the sv-update message-
UPSERT_STRATEGY-(v3.1.0 or higher) Strategy name or file path to update/insert Single View records, for more info checkout Upsert and Delete strategies.replace
DELETE_STRATEGY-(v3.1.0 or higher) Strategy name or file path to delete Single View records, for more info checkout Upsert and Delete strategies.delete
SINGLE_VIEWS_MAX_PROCESSING_MINUTES-(v3.4.2 or higher) time to wait before processing again a Projection with state IN_PROGRESS30
CA_CERT_PATH-The path to the CA certificate, which should include the file name as well, e.g. /home/my-ca.pem-
ER_SCHEMA_FOLDER-The path to the ER Schema folder, e.g. /home/node/app/erSchema-
AGGREGATION_FOLDER-The path to the Aggregation folder, e.g. /home/node/app/aggregation-
USE_AUTOMATIC-Whether to use the low code architecture for the Single View Creator service or not-
PROJECTIONS_CHANGES_SOURCE-System to use to handle the Projection Changes, supported methods are KAFKA or MONGOMONGO
READ_TOPIC_FROM_BEGINNING-Available from v.5.5.0 of the Single View Creator Plugin. If set to true, the Single View Creator will start reading from messages in the Projection Changes topic from the beginning, instead of the message with the latest commmitted offset. This will happen only the first time connecting to the topic, and it has effect only if PROJECTIONS_CHANGES_SOURCE is set to KAFKA.false
KAFKA_PROJECTION_CHANGES_TOPICS-Comma separated list of projection changes topics. Remember to set the PROJECTIONS_CHANGES_SOURCE to KAFKA to properly enable the consumer.-
KAFKA_SV_RETRY_TOPIC-Topic name for the Single View Retry mechanism. This enables the system which uses a Kafka consumer and a Kafka producer.-
KAFKA_SV_RETRY_MAX_ATTEMPTS-Number of attempts allowed for a failed Projection Change. Defining 0 will not retry the failed aggregations but will send the retry message to the KAFKA_SV_RETRY_TOPIC5
KAFKA_SV_RETRY_DELAY-Time in milliseconds in which the service buffers the retry messages before sending them. This is meant to reduce the impact on performace of sending the retry messages.5000
KAFKA_PROJECTION_UPDATE_TOPICS-Comma separated list of projection update topics-
SV_TRIGGER_HANDLER_CUSTOM_CONFIG-Path to the config defining SV-Patch actions-
USE_UPDATE_MANY_SV_PATCH-Use the MongoDB updateMany operation instead of the findOneAndUpdate with cursors in the sv patch operation. This will speed up the Single View creation/update process but it will not fire the kafka events of Single View Creation/Update. As a natural consequence, if enabled, the following environment vairables will be ignored: SEND_BA_TO_KAFKA, KAFKA_BA_TOPIC, SEND_SV_UPDATE_TO_KAFKA, KAFKA_SV_UPDATE_TOPIC, ADD_BEFORE_AFTER_CONTENT, KAFKA_SVC_EVENTS_TOPICfalse
KAFKA_CONSUMER_MAX_WAIT_TIME_MS-(v6.2.1 or higher) The maximum amount of time in milliseconds the server will block before answering the fetch request if there isn't sufficient data to immediately satisfy the requirement given by minBytes [1 byte]500
SV_UPDATE_VERSION-(v6.2.1 or higher) Define which version of the sv-update event should be emitted by the service. Accepted values are v1.0.0 and v2.0.0. By default, for retro-compatibility, version v1.0.0 is employedv1.0.0
CONTROL_PLANE_ACTIONS_TOPIC-Topic where the Single View Creator expects to receive the action commands of pause and resume.-
CONTROL_PLANE_KAFKA_GROUP_ID-The Kafka Consumer Group Identifier for the action commands client.-
note

Setting up both the variable CONTROL_PLANE_ACTIONS_TOPIC and CONTROL_PLANE_KAFKA_GROUP_ID enables the communication between the Single View Creator and the Runtime Management. This means that the Single View Creator will receive and execute the commands from the latter. Check the Runtime Management section of this page for more information.

caution

If you want to enable any mechanism that uses Kafka in the Single View Creator, like the Single View Patch, remember to declare the following environment variables:

  • KAFKA_BROKERS (required)
  • KAFKA_CLIENT_ID (required)
  • KAFKA_GROUP_ID (required if the machanism needs a consumer)
  • KAFKA_SASL_USERNAME
  • KAFKA_SASL_PASSWORD
  • KAFKA_SASL_MECHANISM

Consuming from Kafka

As you can see, the Single View Creator lets you configure what channel is used as input through the PROJECTIONS_CHANGES_SOURCE environment variable. The default channel is MongoDB for the Projection Changes but this might not always be what you need. The service gives you the alternative to listen from Apache Kafka instead, this can be useful in two different cases:

In both of the cases you have to configure all the required environment variables related to kafka. First you need to configure the KAFKA_BROKERS and KAFKA_GROUP_ID, then you probably need to configure your authentication credentials with KAFKA_SASL_MECHANISM, KAFKA_SASL_USERNAME and KAFKA_SASL_PASSWORD.

Once this is done remember to set the PROJECTIONS_CHANGES_SOURCE environment variable to KAFKA and to check out the configuration page of the system you need to complete the necessary steps.

Handling Connections with Self Signed Certificates

Sometimes MongoDB or Kafka instances may have a TLS connection with a self-signed certification authority.

Since service version 3.9.0, you can include additional certification authority certificates by providing the absolute path of a certification file in the environment variable CA_CERT_PATH. This file should be included in your project as a Secret.

Error handling

When generating a Single View, every error that occurs is saved in MongoDB following the Single View Error format which satisfies the schema requirements of the CRUD service, so that you can handle those errors using the Console. It is highly recommended to use a TTL index to enable the automatic deletion of older messages, which can be done directly using the Console, as explained here.

Errors are categorized with a code that you will find in the errorType property of the Single View Error record.

These are the currently emitted codes:

CodeDescriptionRetryable
NO_SV_GENERATEDHappens when the aggregation pipeline unexpectedly does not find the base projection record and thus returns empty
VALIDATION_ERRORHappens when the result of an aggregation does not pass the validation defined by the user in the validator.js
ERROR_SEND_SVC_EVENTHappens when service fails to send a Kafka message to notify a successful aggregation
SINGLE_VIEW_AGGREGATION_MAX_TIMEHappens when aggregation pipeline takes too long and goes over the maximum established time defined on the SINGLE_VIEWS_MAX_PROCESSING_MINUTES environment variable
UNKNOWN_ERRORHappens with an unexpected error, such as a connection error with Apache Kafka or MongoDB

Notice the column retryable indicates which types of errors are sent to the retry queue when the Single View Retry system is enabled.

Single View Retry

info

This feature is supported from version 6.3.0 of the Single View Creator

The Single View Retry mechanism lets you configure a Kafka topic as a DLQ where to send the failed aggregation attempts. Once a message is sent to that topic it will be consumed by all the Single View Creators with the Single View Retry enabled and connected to that topic, then an attempt to aggregate the failed Single View record will be performed.

First thing you need to do to enable the mechanism is to define the KAFKA_SV_RETRY_TOPIC alongside with all the Kafka related variables to make Kafka work in the service. The messages sent to that topic have the Single View Trigger format, that's why, if you are already listening to Single View Trigger messages on Kafka as the main input of the service you can re-use the same exact topic.

To customize the system we also offer you the environment variables KAFKA_SV_RETRY_MAX_ATTEMPTS and KAFKA_SV_RETRY_DELAY. Check them out on the Environment Variables table.

Runtime Management

info

This feature is supported from version 6.4.0 of the Single View Creator

By specifying the environment variables CONTROL_PLANE_ACTIONS_TOPIC and CONTROL_PLANE_KAFKA_GROUP_ID you enable the Single View Creator to receive and execute the commands from the Runtime Management.

By design, every service interacting with the Control Plane starts up in a paused state, unless a resume command that can apply to the specific service is already present in the topic. Therefore, when the Single View Creator starts up, the aggregation process will not start automatically. In this case, you just need to send a resume command to the resource name (namely, the Single View name) managed by the Single View Creator.

tip

Read the Interacting with the Frontend section of the Runtime Management documentation page to learn more about the Control Plane and how to use it.