delta_publish
The delta_publish
command is a way of publishing an incremental update to a record. If a client uses delta_publish
to publish an update, AMPS first extracts the key fields from the record and does a look up for the record in the SOW. AMPS will then apply the update to the SOW record overwriting any field that has a newer value in the update and appending to the record any new fields that were not previously in the SOW record.
If delta_publish
is used on a record that does not currently exist in the SOW or if it is used on a topic that does not have a SOW topic store defined, then delta_publish
will behave like a standard publish
command.
A delta_publish
is transparent to other clients and the merged record will be forwarded to matching subscriptions.
Header Fields
The following table contains the header fields available to a delta_publish
command.
Field | Description |
| Command to be executed.
Value: |
| The SOW topic to publish the message to. |
| Acknowledgment type for the given command. Value is a comma separated list of one or more of the following: |
| If specified with an AMPS command which requests an acknowledgment message, all requested acknowledgment messages will contain the |
| An interval used to define the lifetime of a |
| A monotonically increasing number used to identify published messages in a high availability environment. |
| A user-provided string that will be passed, verbatim, to subscribers. If this header is not present, subscribers receive no value for the |
| For SOW topics that use an explicit key, the SOW key to use for the message. The contents of this header must consist of characters that are legal in Base64 encoding. |
Returns
For a delta_publish
message, AMPS will send acknowledgment messages for the following AckType
fields: received
, processed
and persisted
along with a populated Status
header field describing the acknowledgment.
The following table contains the acknowledgment messages that can be returned by a delta_publish
.
In general, 60East recommends only requesting persisted
acknowledgments for delta_publish
commands, since these acknowledgments can be conflated when commands succeed.
Acknowledgment | Description |
| No |
| AMPS has processed the message and, if necessary enqueued the message for persistence and replication. This acknowledgment includes the steps acknowledged by the |
| When AMPS returns an acknowledgment message of 1. All downstream synchronous replications have acknowledged that the message(s) have been delivered to their respective SOW Topic(s). 2. When the publish message has been sent to all available downstream asynchronous replications. If no replication is configured for this topic, this acknowledgment applies only to local persistence. If no persistence is configured for this topic, this acknowledgment is still provided when requested. |
| AMPS has processed the message(s) to be published to the SOW. Any errors which occur in the message will be returned to the client in this acknowledgment message. This includes processing entitlement checks, and parsing the message but does not guarantee that the message has been replicated or persisted. |
| The |
| Not supported at this time. |
Errors
Any errors that occur while processing this command will be returned in the status of a processed
acknowledgment message and logged to the log file. Regardless of success or failure, the processed
acknowledgment message will be returned only if requested by specifying processed
in the AckType
field.
Errors that occur during the processing command or after processing the command will be returned in the status of a persisted
acknowledgment message if one is requested. This acknowledgment is returned at the point that the message can be considered safely persisted in AMPS.
The configuration of the AMPS instance controls when persisted
acknowledgments are returned, and persisted
acknowledgments can be conflated to apply to multiple publish
commands. See the AMPS User Guide for details.
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