Documentation
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Overview ¶
Package routing implements a routing table for resolving incoming requests to handlers. The table data model is structured for efficient use by the runtime code during actual dispatch. At a high-level, the structure of table is as follows:
Table: map[variety]varietyTable varietyTable: map[namespace]NamespaceTable NamespaceTable: list(Destination) Destination: unique(handler&template) + list(InstanceGroup) InstanceGroup: condition + list(InstanceBuilders) + list(OutputMappers)
The call into table.GetDestinations performs a lookup on the first map by the variety (i.e. quota, check, report, apa etc.), followed by a lookup on the second map for the namespace, and a NamespaceTable struct is returned.
The returned NamespaceTable holds all the handlers that should be dispatched to, along with conditions and builders for the instances. These include handlers that were defined for the namespace of the request, as well as the handlers from the default namespace. If there were no explicit rules in the request's namespace, then only the handlers from the default namespace is applied. Similarly, if the request is for the default namespace, then only the handlers from the default namespace is applied.
Beneath the namespace layer, the same handler can appear multiple times in this list for each template that is supported by the handler. This helps caller to ensure that each dispatch to the handler will use a unique template.
The client code is expected to work as follows:
- Call GetDestinations(variety, namespace) to get a NamespaceTable.
- Go through the list of entries in the NamespaceTable.
- For each entry begin a dispatch session to the associated handler.
- Go through the InstanceGroup
- For each InstanceGroup, check the condition and see if the inputs/outputs apply.
- If applies, then call InstanceBuilders to create instances
- Depending on the variety, either aggregate all instances in the group, and send them all at once, or dispatch for every instance individually to the adapter.
Index ¶
Constants ¶
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Variables ¶
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Functions ¶
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Types ¶
type Destination ¶
type Destination struct {
// Handler to invoke
Handler adapter.Handler
// HandlerName is the name of the handler. Used for monitoring/logging purposes.
HandlerName string
// AdapterName is the name of the adapter. Used for monitoring/logging purposes.
AdapterName string
// Template of the handler.
Template *template.Info
// InstanceGroups that should be (conditionally) applied to the handler.
InstanceGroups []*InstanceGroup
// FriendlyName is the friendly name of this configured handler entry. Used for monitoring/logging purposes.
FriendlyName string
// Perf counters for keeping track of dispatches to adapters/handlers.
Counters DestinationCounters
// contains filtered or unexported fields
}
Destination contains a target handler, and instances to send, grouped by the conditional match that applies to them.
func (*Destination) MaxInstances ¶
func (d *Destination) MaxInstances() int
MaxInstances returns the maximum number of instances that can be built from this Destination.
type DestinationCounters ¶
type DestinationCounters struct {
// contains filtered or unexported fields
}
DestinationCounters are used to track the total/failed dispatch counts and dispatch duration for a target destination, based on the template/handler/adapter label set.
type InstanceGroup ¶
type InstanceGroup struct {
// Condition for applying this instance group.
Condition compiled.Expression
// TODO(Issue #2139): This should be removed when we stop doing resource-type based checks.
// ResourceType is the resource type condition for this instance group.
ResourceType config.ResourceType
// Builders for the instances in this group for each instance that should be applied.
Builders []template.InstanceBuilderFn
// Mappers for attribute-generating adapters that map output attributes into the main attribute set.
Mappers []template.OutputMapperFn
// contains filtered or unexported fields
}
InstanceGroup is a set of instances that needs to be sent to a handler, grouped by a condition expression.
type NamespaceTable ¶
type NamespaceTable struct {
// contains filtered or unexported fields
}
NamespaceTable contains a list of destinations that should be targeted for a given namespace.
func (*NamespaceTable) Count ¶
func (d *NamespaceTable) Count() int
Count returns the number of entries contained.
func (*NamespaceTable) Entries ¶
func (d *NamespaceTable) Entries() []*Destination
Entries in the table.
type Table ¶
type Table struct {
// contains filtered or unexported fields
}
Table is the main routing table. It is used to find the set of handlers that should be invoked, along with the instance builders and match conditions.
func BuildTable ¶
func BuildTable( handlers *handler.Table, config *config.Snapshot, expb *compiled.ExpressionBuilder, defaultConfigNamespace string, debugInfo bool) *Table
BuildTable builds and returns a routing table. If debugInfo is set, the returned table will have debugging information attached, which will show up in String() call.
func (*Table) GetDestinations ¶
func (t *Table) GetDestinations(variety tpb.TemplateVariety, namespace string) *NamespaceTable
GetDestinations returns the set of destinations (handlers) for the given template variety and for the given namespace.
Source Files