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Setting the scan_subscriber_queue_size

asked 2013-05-03 10:05:46 -0500

Ernest gravatar image

Hi, I'm trying to set a good scan_subscriber_queue_size for my hector_mapping node. According to the wiki:

~scan_subscriber_queue_size (int, default: 5) The queue size of the scan subscriber. This should be set to high values (for example 50) if logfiles are played back to hector_mapping at faster than realtime speeds.

I'm not sure what logfiles being played back means; my node just take in scans from hokuyo_node, so is it ok to leave the default value of 5?

Thanks,

Ernest

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answered 2013-05-03 11:57:56 -0500

this post is marked as community wiki

This post is a wiki. Anyone with karma >75 is welcome to improve it.

Incoming messages are buffered in a queue of the size you can specify via the scan_subscriber_queue_size parameter. The smaller your queue size is, the earlier a message might be processed in a callback (as there are potentially less other messages in the queue that have to be processed before). On the other hand, if callbacks take longer than the time between incoming messages on average, the queue will fill up and messages will eventually be dropped. In that case, there will also be some delay between a message entering the queue and it finally being processed.

We noted that increasing the queue size helps when playing back bagfiles at faster than real-time speeds. If a callback takes longer than normal in that scenario, it can quickly happen that some scan messages are dropped. In normal operation (e.g. using the hokuyo_node directly) the queue size shouldn't have to be increased however.

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OK - thank you Stefan!

Ernest gravatar image Ernest  ( 2013-05-03 13:23:02 -0500 )edit

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Asked: 2013-05-03 10:05:46 -0500

Seen: 243 times

Last updated: May 03 '13