Synchronize SQL database time stamps?

ComputerSmiths — Tue, 12 Mar 2019 13:30:47 +0000

Hi All,

I've got several SQL databases from machines logging sunlight data that I'd like to synchronize for solar power studies. One example is:

mysql> select ComputerTime, Pac, IntSolIrr from SMA where ComputerTime >= (unix_timestamp(now())-(60*10)) order by ComputerTime;
+--------------+------+-----------+
| ComputerTime | Pac | IntSolIrr |
+--------------+------+-----------+
| 1552395307 | 3738 | 557 |
| 1552395366 | 3869 | 583 |
| 1552395425 | 3813 | 578 |
| 1552395487 | 3874 | 586 |
| 1552395546 | 3853 | 587 |
| 1552395607 | 3917 | 598 |
| 1552395666 | 3998 | 611 |
| 1552395728 | 4054 | 621 |
| 1552395785 | 4114 | 633 |
| 1552395846 | 4149 | 634 |
+--------------+------+-----------+
10 rows in set (0.84 sec)

While another nearby one is:

MariaDB [Weather]> select Epoch,WF$UDP$obs_sky$obs$SolarRadiation_Wpm2 from WeatherFlow where Epoch >= (unix_timestamp(now())-(60*10)) order by Epoch;
+------------+----------------------------------------+
| Epoch | WF$UDP$obs_sky$obs$SolarRadiation_Wpm2 |
+------------+----------------------------------------+
| 1552395304 | 433 |
| 1552395364 | 433 |
| 1552395424 | 445 |
| 1552395484 | 442 |
| 1552395544 | 448 |
| 1552395604 | 450 |
| 1552395664 | 457 |
| 1552395724 | 467 |
| 1552395784 | 476 |
| 1552395844 | 483 |
+------------+----------------------------------------+
10 rows in set (0.82 sec)

As you can see, they are logging on one-minute intervals, but can be off from each other by a few seconds.

Is there an easy way in SQL to get these measurements synchronized? My brute force approach would probably be to look for the closest one-minute timestamp by subtracting and then ordering by delta and taking the last one, but for one-minute intervals over several year that's going to take a long time... 8*}

Alternately, I can read them into separate arrays and do the math outside SQL, but if there's an easy way to say "to the closest Epoch/60" or something, that might be easier...

Many thanks in advance for any pointers to real programming techniques as eventually I'll have a dozen or more datasets to sync up...

Synchronize program start over network

ComputerSmiths — Sat, 09 Feb 2019 12:46:41 +0000

I'm trying to get two computers to start a program (to play a video) simultaneously using a network connection in Python.

I'm starting down the path of opening a socket server on one machine, connecting to it on the other, and sending some kind of communication saying "Now!", which is do-able, but seems unnecessarily complicated.

Is there some easy thing I'm missing here? Ideally I'd have a program called "Block.py" that I'd start from a bash script on one machine, which would wait till I run it on the other machine, and they'd then both continue on to the omxplayer command...

Both machines have static IPs, if that helps simplify things.

Many Thanks in advance!

DEV Community: ComputerSmiths

Synchronize SQL database time stamps?

Synchronize program start over network