Polling Settings

Source connectors that poll for data (Database Reader, File Reader, JavaScript Reader) support configurable polling schedules. This page covers the available scheduling options.

Polling schedule types

Interval

Polls at a fixed interval. The schedule is built when the source connector starts, and poll times are aligned to the start of the day's Active Time range, or to midnight when Active Time is All Day or the range crosses midnight. The first poll lands on the next multiple of the interval measured from that point, not one interval after the connector starts. A 6-hour interval polls at 00:00, 06:00, 12:00, and 18:00 no matter when the channel came up.

Setting	Description
Interval	Time between polls. Enter a number and select the unit: milliseconds, seconds, minutes, or hours. The value must be greater than zero and less than 24 hours. It is stored in the channel as pollingFrequency, in milliseconds.

Example: Poll every 5 seconds.

The schedule exists only while the source connector is running. Deploying a channel starts the connector unless the channel's initial state is Stopped or Paused, and a channel deployed in either of those states does not poll until it is started. With Active Time set to All Day the polls continue around the clock. Enable Poll Once on Start to get a poll the moment the connector starts, ahead of the aligned schedule.

Time

Polls once per day at a specific time.

Setting	Description
Time	The time of day to poll (hour and minute)

Example: Poll once daily at 6:00 AM.

Use this when data should be picked up at the same time each day.

Cron

Polls according to one or more cron expressions, providing the most flexible scheduling.

Setting	Description
Cron Jobs	A table of cron expressions, each with an optional description

Cron expression format

The engine hands each expression to Quartz, which needs six fields plus an optional seventh field for the year:

second minute hour day-of-month month day-of-week [year]

Note: Quartz cannot combine a day-of-month value with a day-of-week value, so one of the two fields must be ?. An expression that sets both is rejected as invalid.

Field	Values	Special Characters
Second	0-59	, - * /
Minute	0-59	, - * /
Hour	0-23	, - * /
Day of Month	1-31	, - * ? / L W
Month	1-12 or JAN-DEC	, - * /
Day of Week	1-7 or SUN-SAT	, - * ? / L #
Year (optional)	Up to 100 years after the current year (a later year is accepted but never fires)	, - * /

Examples

Expression	Schedule
0 0/5 * * * ?	Every 5 minutes
0 0 8 * * ?	Daily at 8:00 AM
0 0 8,17 * * ?	Daily at 8:00 AM and 5:00 PM
0 0 */2 * * ?	Every 2 hours
0 0 9-17 ? * MON-FRI	Hourly from 9 AM to 5 PM, weekdays only
0 30 6 ? * MON	Every Monday at 6:30 AM
0 0 0 1 * ?	First day of every month at midnight

Common settings

These settings are available regardless of which schedule type is selected:

Setting	Description
Schedule Type	Interval, Time, or Cron
Poll Once on Start	Execute a poll immediately when the channel starts, before the scheduled poll

Poll Once on Start

When enabled, the connector immediately polls for data when the channel is started or deployed, without waiting for the first scheduled poll time. This is useful for catching up on data that arrived while the channel was stopped.

Advanced polling settings

The Advanced Settings dialog (wrench icon) is available for Interval and Time schedule types, but not for Cron. It provides additional control over when polling occurs.

Active Days

Controls which days polling is allowed to occur.

Mode	Description
Weekly	Select specific days of the week (Sunday through Saturday) when polling is active. At least one day must be selected.
Monthly	Select a specific day of the month (1-31) when polling is active.

Active Time (Interval only)

Controls the time window during which interval-based polling is active. This setting is not available for Time schedule type (since Time already specifies a single poll time).

Mode	Description
All Day	Polling may occur at any time during the day (default).
Range	Polling only occurs during the specified time range (e.g., 8:00 AM - 5:00 PM).

Polling vs. listener connectors

Behavior	Polling (Reader)	Listener
Initiation	OIE pulls data on a schedule	External system pushes data
Connectors	Database Reader, File Reader, JavaScript Reader	TCP Listener, HTTP Listener, Channel Reader, JMS Listener, Web Service Listener, DICOM Listener
Schedule	Interval, time, or cron	N/A (always listening)
Resource usage	Active only during polls	Continuous
Latency	Depends on poll interval	Near real-time