I have been running InfluxDB+Telegraf to monitor servers for a month or two, with the default system Telegraf plugin, no custom metrics yet. I didn’t add retention policies or continuous queries, so my InfluxDB database grew to 3.5GB by now. Clearly it’s useless to store the CPU usage every 5 seconds going back 2 months! I want to add downsampling now, but it’s not totally clear to me how it works. If I understand correctly: retention policies can make data expire after X time, and continuous queries aggregate new data and store the aggregated result into a different RP that expires after Y time (or never). The downsampling guide also says: We perform the following steps before writing the data to the database food_data. We do this before inserting any data because CQs only run against recent data So it seems like if I add a CQ now, it won’t aggregate my existing data, and if I change the retention duration, it will immediately wipe my old data. How do I aggregate the data I already have into a new RP, before changing the duration of the default RP?

That works great, thanks. Now I just need to fight my inner data packrat and decide how much data I really need to keep!

Well with compression to ~2 bytes per float or integer value you shouldn’t have to throw out too much! I generally just use CQ to optimize queries that are taking too long to return and try to keep as much data as possible.

Downsampling existing data

Systems

jackzampolin June 7, 2017, 11:57pm 2

@nicolas17 You can run raw INTO queries without the CQ syntax to accomplish this. I just did this on one of our instances today!

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Downsampling existing data

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