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Key elements of the measurement to define:

• The attribute and the entity to measure.
• The important scope or scopes in which this kind of entity exists, and in which each meter will measure the attribute.
• The conditions that govern whether to measure the attribute and how to report the measurements.

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Define the Scope of the Measurement

When you define a measurement, clearly identify the key scope or scopes in which the measurement is made. Look for two common kinds of scopes:

• The entity about which the measurement is made.
• The boundaries within which the measurement is made.

Boundaries. Each meter measures within one or more boundaries of interest to your audience.

Example: Each geode.cache.entries gauge measures within several boundaries:

Each measurement measures within one or more scopes of interest to your audience. To identify those scopes, look for various boundaries that encompass the entity being measured, or in which the entity participates.

Example: Each geode.cache.entries gauge measures within several scopes:

• The region that holds the entries counted by the meter.
• The region that holds the entries counted by the meter.
• The cache server in which the region holds the entries counted by the meter.
• The host on which the server is running.
• The cluster in which the server is a member.

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• The region is an example of an entity boundary. The entity (as described above) is typically the smallest scope for your meter.
• The cache server is an example of a process boundary.
• The host is an example of a hardware or virtual machine boundary.
• The cluster is an example of a conceptual or domain boundary.

The example also shows that:

• Some scopes may form part of the identity of the entity being measured. The cluster in which a region participates is an essential part of the identity of a region.
• Scopes may Boundaries may be nested. A given host may encompass several cache servers.
• Boundaries Scopes may overlap. A region holds entries across numerous servers, and a server may hold entries for numerous regions.
• Some boundaries serve to uniquely identify the attribute being measured. The cluster is an essential part of the identity of a region.

Audience focus. Identify scopes of interest to your audience—those scopes that your audience may wish to use to select and sort measurements for display and analysis. Of particular interest are the scopes necessary that help to uniquely identify the attribute  attribute being measured.

Rationale. Defining the scope of the measurement will help you:

• Name and describe the meter.
• Identify tags to add to the meter to help identify and describe the source of the measurement.
• Identify and evaluate potential instrumentation sites.

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