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Discovery Client - Support "ClusterId" environment variable without prefix #247

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Discovery Client - Support "ClusterId" environment variable without prefix #247

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Support "CLUSTERID" without the prefix.
hunter-ni Dec 1, 2025
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hunter-ni Dec 1, 2025
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hunter-ni Dec 1, 2025
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Merge branch 'main' into users/hunter-ni/clusterid-env-var
hunter-ni Dec 17, 2025
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Make environment variable specification use Pascal Case for consisten…
hunter-ni Dec 17, 2025
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11 changes: 10 additions & 1 deletion ...easurementlink.discovery.v1.client/src/ni/measurementlink/discovery/v1/client/_support.py
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Expand Up @@ -29,9 +29,18 @@
_START_SERVICE_TIMEOUT = 30.0
_START_SERVICE_POLLING_INTERVAL = 100e-3

_DISCOVERY_SERVICE_ENV_VAR_PREFIX = "NIDiscovery_"
_DISCOVERY_SERVICE_CLUSTER_ID_ENV_VAR = "ClusterId"


def _get_discovery_service_address() -> str:
cluster_id = os.environ.get("NIDISCOVERY_CLUSTERID")
# To support operating systems other than Windows (and match Discovery Service behavior),
# we would likely want to make this check case-insensitive.
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@jfriedri-ni jfriedri-ni Dec 17, 2025

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How do we document this for users? If we use shout-case there, then all OSes have the same casing for this variable and we can use os.environ directly.

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@hunter-ni hunter-ni Dec 17, 2025

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I believe @nick-beer's original comment (precipitating this change + comment) was that we would want to match here whatever the Discovery Service itself would be anticipated to actually support, which would be the environment variable of this given name (with optional prefix) irrespective of case. I don't have any specific insight on the question of existing documentation.

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@bkeryan bkeryan Dec 17, 2025

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If the server is going to use PascalCase, then you're better off using PascalCase in the Python and LV packages so that it works regardless of whether environment variables are case-sensitive or case-insensitive. However, a lot of software avoids this situation by using all-caps for environment variables everywhere.

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@hunter-ni hunter-ni Dec 17, 2025

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To summarize (and confirm that I'm on the same page):

Nick's comment indicates that the Discovery Service itself is explicitly designed to look for this environment variable in a case-insensitive manner (regardless of operating system). To your point though, existing Discovery Service code does use PascalCase when it needs to reference ClusterId and the NIDiscovery prefix, so we can use that casing here for consistency with the server code.

cluster_id = os.environ.get(
_DISCOVERY_SERVICE_ENV_VAR_PREFIX + _DISCOVERY_SERVICE_CLUSTER_ID_ENV_VAR
)
if not cluster_id:
cluster_id = os.environ.get(_DISCOVERY_SERVICE_CLUSTER_ID_ENV_VAR)
key_file_path = _get_key_file_path(cluster_id)
_ensure_discovery_service_started(key_file_path)
_logger.debug("Discovery service key file path: %s", key_file_path)
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