Allocation model
Allocation answers "who owns this cost?" Costfluent keeps it separate from filtering and from tagging, because each answers a different question.
Four tools, four questions
| Tool | Question it answers | Where it lives |
|---|---|---|
| Filter | Which cost is in this report? | One cost report |
| Tag | What did the resource's owner write on it? | Your cloud accounts; Costfluent reads it |
| Virtual tag | What value should this cost line carry, whatever the source tags say? | A workspace; see Virtual tags |
| Allocation rule | Which segment owns this cost line? | A workspace; see Segments and allocation rules |
A filter narrows one report and leaves every other report alone. Tags and virtual tags describe cost lines; a report can filter or group by them. Allocation rules assign each cost line to a segment, and a report grouped by Segment shows the result.
Segments
A segment is one owner that cost can be assigned to. Team, product and cost centre together identify it, so the same owner cannot be typed two ways and split a report. A segment can instead be a shared cost bucket, for cost that belongs to no single owner.
Ordered rules, one claim per cost line
Rules are evaluated in order, top first. The first rule that matches a cost line claims it, and no later rule can claim it again, so no cost is counted twice. A rule matches on one field (account or subscription, resource group, resource name or a tag) with one literal comparison: equals, starts with, ends with or contains. There are no wildcards and no regular expressions.
Shared cost
A rule pointing at a shared cost bucket marks cost as shared. Shared cost is spread across the direct segments in proportion to their direct cost in the same period. If there is no direct cost to spread it across, it stays unallocated rather than being absorbed silently.
Exact totals and visible unallocated cost
Allocation never creates or loses money: the direct, shared and unallocated amounts always add up to the workspace total. Cost no rule claims is reported as unallocated, and the coverage figure on the Segments page shows how much of the total is assigned.
Evaluated when a report is read
Rules are never written onto cost records. They are compiled into each query, so adding, disabling, reordering or deleting a rule restates every past month at once, without collecting anything again. The same holds for virtual tags. Preview a rule before saving it to see what it would move.