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92d4a9c2b9
* Split MetricRouter and MetricAggregator * Missing change in MetricCache * Add README for MetricAggregator
38 lines
3.0 KiB
Markdown
38 lines
3.0 KiB
Markdown
# The MetricAggregator
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In some cases, further combination of metrics or raw values is required. For that strings like `foo + 1` with runtime dependent `foo` need to be evaluated. The MetricAggregator relies on the [`gval`](https://github.com/PaesslerAG/gval) Golang package to perform all expression evaluation. The `gval` package provides the basic arithmetic operations but the MetricAggregator defines additional ones.
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**Note**: To get an impression which expressions can be handled by `gval`, see its [README](https://github.com/PaesslerAG/gval/blob/master/README.md)
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## Simple expression evaluation
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For simple expression evaluation, the MetricAggregator provides two function for different use-cases:
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- `EvalBoolCondition(expression string, params map[string]interface{}`: Used by the MetricRouter to match metrics like `metric.Name() == 'mymetric'`
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- `EvalFloat64Condition(expression string, params map[string]interface{})`: Used by the MetricRouter and LikwidCollector to derive new values like `(PMC0+PMC1)/PMC3`
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## MetricAggregator extensions for `gval`
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The MetricAggregator provides these functions additional to the `Full` language in `gval`:
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- `sum(array)`: Sum up values in an array like `sum(values)`
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- `min(array)`: Get the minimum value in an array like `min(values)`
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- `avg(array)`: Get the mean value in an array like `avg(values)`
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- `mean(array)`: Get the mean value in an array like `mean(values)`
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- `max(array)`: Get the maximum value in an array like `max(values)`
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- `len(array)`: Get the length of an array like `len(values)`
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- `median(array)`: Get the median value in an array like `mean(values)`
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- `in`: Check existence in an array like `0 in getCpuList()` to check whether there is an entry `0`. Also substring matching works like `temp in metric.Name()`
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- `match`: Regular-expression matching like `match('temp_cores_%d+', metric.Name())`. **Note** all `\` in an regex has to be replaced with `%`
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- `getCpuCore(cpuid)`: For a CPU id, the the corresponding CPU core id like `getCpuCore(0)`
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- `getCpuSocket(cpuid)`: For a CPU id, the the corresponding CPU socket id
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- `getCpuNuma(cpuid)`: For a CPU id, the the corresponding NUMA domain id
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- `getCpuDie(cpuid)`: For a CPU id, the the corresponding CPU die id
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- `getSockCpuList(sockid)`: For a given CPU socket id, the list of CPU ids is returned like the CPUs on socket 1 `getSockCpuList(1)`
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- `getNumaCpuList(numaid)`: For a given NUMA node id, the list of CPU ids is returned
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- `getDieCpuList(dieid)`: For a given CPU die id, the list of CPU ids is returned
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- `getCoreCpuList(coreid)`: For a given CPU core id, the list of CPU ids is returned
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- `getCpuList`: Get the list of all CPUs
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## Limitations
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- Since the metrics are written in JSON files which do not allow `""` without proper escaping inside of JSON strings, you have to use `''` for strings.
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- Since `\` is interpreted by JSON as escape character, it cannot be used in metrics. But it is required to write regular expressions. So instead of `/`, use `%` and the MetricAggregator replaces them after reading the JSON file. |