/AWS1/CL_SWF=>POLLFORDECISIONTASK()
¶
About PollForDecisionTask¶
Used by deciders to get a DecisionTask from the specified decision
taskList
. A decision task may be returned for any open workflow execution that
is using the specified task list. The task includes a paginated view of the history of the
workflow execution. The decider should use the workflow type and the history to determine how
to properly handle the task.
This action initiates a long poll, where the service holds the HTTP connection open and responds as soon a task becomes available. If no decision task is available in the specified task list before the timeout of 60 seconds expires, an empty result is returned. An empty result, in this context, means that a DecisionTask is returned, but that the value of taskToken is an empty string.
Deciders should set their client side socket timeout to at least 70 seconds (10 seconds higher than the timeout).
Because the number of workflow history events for a single workflow execution might
be very large, the result returned might be split up across a number of pages. To retrieve
subsequent pages, make additional calls to PollForDecisionTask
using the
nextPageToken
returned by the initial call. Note that you do
not call GetWorkflowExecutionHistory
with this
nextPageToken
. Instead, call PollForDecisionTask
again.
Access Control
You can use IAM policies to control this action's access to Amazon SWF resources as follows:
-
Use a
Resource
element with the domain name to limit the action to only specified domains. -
Use an
Action
element to allow or deny permission to call this action. -
Constrain the
taskList.name
parameter by using aCondition
element with theswf:taskList.name
key to allow the action to access only certain task lists.
If the caller doesn't have sufficient permissions to invoke the action, or the
parameter values fall outside the specified constraints, the action fails. The associated
event attribute's cause
parameter is set to OPERATION_NOT_PERMITTED
.
For details and example IAM policies, see Using IAM to Manage Access to Amazon SWF
Workflows in the Amazon SWF Developer Guide.
Method Signature¶
IMPORTING¶
Required arguments:¶
IV_DOMAIN
TYPE /AWS1/SWFDOMAINNAME
/AWS1/SWFDOMAINNAME
¶
The name of the domain containing the task lists to poll.
IO_TASKLIST
TYPE REF TO /AWS1/CL_SWFTASKLIST
/AWS1/CL_SWFTASKLIST
¶
Specifies the task list to poll for decision tasks.
The specified string must not contain a
:
(colon),/
(slash),|
(vertical bar), or any control characters (\u0000-\u001f
|\u007f-\u009f
). Also, it must not be the literal stringarn
.
Optional arguments:¶
IV_IDENTITY
TYPE /AWS1/SWFIDENTITY
/AWS1/SWFIDENTITY
¶
Identity of the decider making the request, which is recorded in the DecisionTaskStarted event in the workflow history. This enables diagnostic tracing when problems arise. The form of this identity is user defined.
IV_NEXTPAGETOKEN
TYPE /AWS1/SWFPAGETOKEN
/AWS1/SWFPAGETOKEN
¶
If
NextPageToken
is returned there are more results available. The value ofNextPageToken
is a unique pagination token for each page. Make the call again using the returned token to retrieve the next page. Keep all other arguments unchanged. Each pagination token expires after 24 hours. Using an expired pagination token will return a400
error: "Specified token has exceeded its maximum lifetime
".The configured
maximumPageSize
determines how many results can be returned in a single call.The
nextPageToken
returned by this action cannot be used with GetWorkflowExecutionHistory to get the next page. You must call PollForDecisionTask again (with thenextPageToken
) to retrieve the next page of history records. Calling PollForDecisionTask with anextPageToken
doesn't return a new decision task.
IV_MAXIMUMPAGESIZE
TYPE /AWS1/SWFPAGESIZE
/AWS1/SWFPAGESIZE
¶
The maximum number of results that are returned per call. Use
nextPageToken
to obtain further pages of results.This is an upper limit only; the actual number of results returned per call may be fewer than the specified maximum.
IV_REVERSEORDER
TYPE /AWS1/SWFREVERSEORDER
/AWS1/SWFREVERSEORDER
¶
When set to
true
, returns the events in reverse order. By default the results are returned in ascending order of theeventTimestamp
of the events.
IV_STRTATPREVIOUSSTRTEDEVENT
TYPE /AWS1/SWFSTRTATPREVIOUSSTRTE00
/AWS1/SWFSTRTATPREVIOUSSTRTE00
¶
When set to
true
, returns the events witheventTimestamp
greater than or equal toeventTimestamp
of the most recentDecisionTaskStarted
event. By default, this parameter is set tofalse
.