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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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Each meter measures some attribute of some entity. Identify and describe the entity attribute and the attributetype of entity.

The entity. Each measurement is about some entity. Each meter measures some attribute of that entity or on behalf of that entity or in relation to that entityattribute. The attribute is the characteristic that we want to measure about some entity.

Example: Each A geode.cache.entries gauge reports measures the number of entries in a particular region. The measurement is about that region. The gauge includes a region tag that identifies which region it measures.

The attribute. 

• Identify the attribute to measure.
• Identify the kind of entity for which
• Identify the operations, events, or conditions that cause the attribute to change.

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.

some local region.

Example: A jvm.memory.used gauge measures the amount memory in use from some pool of memory.

The type of entity. The entity is the thing whose attribute we want to measure.

Example: Each geode.cache.entries gauge reports the number of entries in a particular local region: That part of a region served by a particular cache server. The measurement is about that local region. The type of entity in this case is local region. We use a region tag to identify the particular local region measured by each meter.

Example: Each jvm.memory.used gauge measures the amount memory in use in a particular pool of memory. The measurement is about that pool of memory. The type of entity is in this case pool of memory. We use an id tag to identify the particular pool of memory measured by each meter.

The smallest entity. In general, we want to identify the smallest entity that we are interested in that has the attribute. This gives users insight into  Because we will add tags that identify interesting scopes that encompass the entity, the user's monitoring system can aggregate the meters from the individually measured entities to compute metrics the measured attribute in larger scopes.

Example: Each geode.cache.entries gauge reports the number of entries in a particular local region. Later we will add tags to each meter that identify larger scopes, and the user can use those tags aggregate these local region entry counts. The user can, for example:

• Sum geode.cache.entries for all regions in a given server.
• Sum geode.cache.entries for a given region across all servers.
• Sum geode.cache.entries for all regions across all servers in a given cluster.

What affects the attribute. Identify the operations, events, or conditions that cause the attribute to change. Focus on causes that are meaningful to your audience. The user will use your meter to make inferences about those operations, events, and conditions. Identifying these causes will be useful as you identify potential instrumentation sites.

Define the Scope of the Measurement

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

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

• 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:

• 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 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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