Cookbook: SOW and Delta Subscribe

This section presents common recipes for atomic SOW and Delta Subscribe in AMPS using the Command or Message interfaces. This section provides information on how to configure the request to AMPS. You can adapt this information to your application and the specific interface you are using.

Command: sow_and_delta_subscribe

Basic SOW and Delta Subscribe

In its simplest form, a SOW and Delta Subscribe needs only the topic to query and subscribe to.

Header	Comment
topic (required)	Sets the topic to query and subscribe to. The topic specified can be the literal topic name, or a regular expression that matches multiple topics.

SOW and Delta Subscribe with Options

In its simplest form, a SOW and Delta Subscribe needs only the topic to query and subscribe to. To add options to the subscription, set the Options header on the Command.

Header	Comment
topic (required)	Sets the topic to query and subscribe to. The topic specified can be the literal topic name, or a regular expression that matches multiple topics.
opts	A comma-delimited set of options for this command. See the sow_and_delta_subscribe section for a full description of supported options. The most common options for this command are: oof - Request out of focus notifications. timestamp - Include timestamps on messages.

SOW and Delta Subscribe with Content Filter

To provide a content filter on a SOW and Delta Subscribe, set the Filter property on the command. The AMPS User Guide provides details on the filter syntax.

Header	Comment
topic (required)	Sets the topic to query and subscribe to. The topic specified can be the literal topic name, or a regular expression that matches multiple topics.
filter	Sets the content filter to be applied to the query. Only messages that match the content filter will be returned in response to the query.

Paginated SOW and Delta Subscribe

To request a paginated subscription for a SOW and Delta Subscribe, set the Options property on the command to specify the number of records to return and the number of records to skip before returning records. Most paginated subscriptions also specify the oof option to be notified when a record is out of focus.

Header	Comment
topic (required)	Sets the topic to query and subscribe to. The topic specified can be the literal topic name, or a regular expression that matches multiple topics.
orderby	Specifies how to order the results within the paginated result set. If the OrderBy is not provided, the results are ordered by the SowKey for the messages.
opts	A comma-separated list of options for the command. Set the number of results returned with top_n, and the starting point within the result set with skip_n. For example, to display records 31-50 of the result set, you could provide the following option: top_n=20,skip_n=30,oof This tells AMPS to skip the first 30 records of the result set, and then provide the top 20 records from the remaining results. Out of focus notifications will be provided.

Aggregated SOW and Delta Subscribe

An Aggregated SOW and Delta Subscribe is a command that provides aggregation options. To add these options to the command, set the Options header on the Command.

Header	Comment
topic (required)	Sets the topic to query and subscribe to. The topic specified can be the literal topic name, or a regular expression that matches multiple topics.
opts	A comma-delimited set of options for this command. For an aggregated SOW and delta subscribe, the options provide the projection and grouping for the command. A SOW and delta subscribe can provide options in addition to the projection and grouping. The most common additional options are: oof - Request out of focus notifications. timestamp - Include timestamps. no_empties - Do not send a delta message if the update does not change the value of a field.