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56 lines
1.8 KiB
Markdown
56 lines
1.8 KiB
Markdown
Introduction
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============
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This project is simple ORM for working with the [ClickHouse database](https://clickhouse.yandex/).
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It allows you to define model classes whose instances can be written to the database and read from it.
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Let's jump right in with a simple example of monitoring CPU usage. First we need to define the model class,
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connect to the database and create a table for the model:
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```python
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from infi.clickhouse_orm import Database, Model, DateTimeField, UInt16Field, Float32Field, Memory, F
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class CPUStats(Model):
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timestamp = DateTimeField()
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cpu_id = UInt16Field()
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cpu_percent = Float32Field()
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engine = Memory()
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db = Database('demo')
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db.create_table(CPUStats)
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```
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Now we can collect usage statistics per CPU, and write them to the database:
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```python
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import psutil, time, datetime
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psutil.cpu_percent(percpu=True) # first sample should be discarded
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while True:
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time.sleep(1)
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stats = psutil.cpu_percent(percpu=True)
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timestamp = datetime.datetime.now()
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db.insert([
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CPUStats(timestamp=timestamp, cpu_id=cpu_id, cpu_percent=cpu_percent)
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for cpu_id, cpu_percent in enumerate(stats)
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])
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```
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Querying the table is easy, using either the query builder or raw SQL:
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```python
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# Calculate what percentage of the time CPU 1 was over 95% busy
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queryset = CPUStats.objects_in(db)
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total = queryset.filter(CPUStats.cpu_id == 1).count()
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busy = queryset.filter(CPUStats.cpu_id == 1, CPUStats.cpu_percent > 95).count()
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print('CPU 1 was busy {:.2f}% of the time'.format(busy * 100.0 / total))
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# Calculate the average usage per CPU
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for row in queryset.aggregate(CPUStats.cpu_id, average=F.avg(CPUStats.cpu_percent)):
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print('CPU {row.cpu_id}: {row.average:.2f}%'.format(row=row))
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```
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To learn more please visit the [documentation](docs/toc.md).
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