Registering a Prometheus metric in Python ONLY if it doesn't already exist

user_76487 0
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I'm making use of the multiprocess prometheus collector (in python), but likely this problem would exist for single process as well.

Is there a way to check if a Counter Metric already exists, to prevent the attempt of registering a duplicate ? Multiple calls to the below code generate the appended error. Or alternatively to check if a given metric exists, and get it.

Some kind of look up in the Registry ? The docs seems rather lacking.

Code:

logging_counter = prometheus_client.Counter('test', 'test')

Error generated:

ValueError: Duplicated timeseries in CollectorRegistry: {'test', 'test_total', 'test_created'}

prometheus python
2 Answers

Ended up being an issue with how MultiProcessCollector was setup ... make sure that at the subprocess level you initialize with CollectorRegistry and not Registry.

Proper Solution:

prometheus_client.multiprocess.MultiProcessCollector(prometheus_client.registry.REGISTRY)

Incorrect Solution:

prometheus_client.multiprocess.MultiProcessCollector(CollectorRegistry())
user_764870

This might be a very hacky way to do this but this is how I made it work for a single process;

self.registry = CollectorRegistry()

def collect_metrics(self):
    sorted_keys = sorted(self.stat_msg_dict.keys())
    for key in sorted_keys:
        ..... getting metric_key, metric_name, current_value .....
        gauge = self.registry._names_to_collectors.get(metric_key, None)
        if gauge is None:
            gauge = Gauge(metric_key, metric_name, registry=self.registry)
        gauge.set(current_value)

In this particular instance all my collectors are gauges.

user_5152560
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