Involved Source Filescontext.go
Package tag contains OpenCensus tags.
Tags are key-value pairs. Tags provide additional cardinality to
the OpenCensus instrumentation data.
Tags can be propagated on the wire and in the same
process via context.Context. Encode and Decode should be
used to represent tags into their binary propagation form.
key.gomap.gomap_codec.gometadata.goprofile_19.govalidate.go
Code Examples
package main
import (
"context"
"go.opencensus.io/tag"
"log"
)
var (
tagMap *tag.Map
ctx context.Context
key tag.Key
)
func main() {
ctx, err := tag.New(ctx,
tag.Insert(key, "macOS-10.12.5"),
tag.Upsert(key, "macOS-10.12.7"),
)
if err != nil {
log.Fatal(err)
}
tag.Do(ctx, func(ctx context.Context) {
_ = ctx // use context
})
}
package main
import (
"context"
"go.opencensus.io/tag"
)
var (
tagMap *tag.Map
ctx context.Context
key tag.Key
)
func main() {
tagMap := tag.FromContext(ctx)
_ = tagMap // use the tag map
}
package main
import (
"go.opencensus.io/tag"
)
func main() {
key := tag.MustNewKey("example.com/keys/user-os")
_ = key // use key
}
package main
import (
"context"
"go.opencensus.io/tag"
"log"
)
var (
tagMap *tag.Map
ctx context.Context
key tag.Key
)
func main() {
osKey := tag.MustNewKey("example.com/keys/user-os")
userIDKey := tag.MustNewKey("example.com/keys/user-id")
ctx, err := tag.New(ctx,
tag.Insert(osKey, "macOS-10.12.5"),
tag.Upsert(userIDKey, "cde36753ed"),
)
if err != nil {
log.Fatal(err)
}
_ = ctx // use context
}
package main
import (
"context"
"go.opencensus.io/tag"
)
var (
tagMap *tag.Map
ctx context.Context
key tag.Key
)
func main() {
// Propagate the tag map in the current context.
ctx := tag.NewContext(context.Background(), tagMap)
_ = ctx // use context
}
package main
import (
"go.opencensus.io/tag"
"log"
)
func main() {
// Get a key to represent user OS.
key, err := tag.NewKey("example.com/keys/user-os")
if err != nil {
log.Fatal(err)
}
_ = key // use key
}
package main
import (
"context"
"go.opencensus.io/tag"
"log"
)
var (
tagMap *tag.Map
ctx context.Context
key tag.Key
)
func main() {
ctx, err := tag.New(ctx,
tag.Insert(key, "macOS-10.12.5"),
tag.Upsert(key, "macOS-10.12.7"),
)
if err != nil {
log.Fatal(err)
}
_ = ctx // use context
}
Package-Level Type Names (total 12, in which 6 are exported)
TTL is metadata that specifies number of hops a tag can propagate.
Details about TTL metadata is specified at https://github.com/census-instrumentation/opencensus-specs/blob/master/tags/TagMap.md#tagmetadata
ttlint
func WithTTL(ttl TTL) Metadata
var TTLNoPropagation
var TTLUnlimitedPropagation
Package-Level Functions (total 20, in which 14 are exported)
Decode decodes the given []byte into a tag map.
DecodeEach decodes the given serialized tag map, calling handler for each
tag key and value decoded.
Delete returns a mutator that deletes
the value associated with k.
Do is similar to pprof.Do: a convenience for installing the tags
from the context as Go profiler labels. This allows you to
correlated runtime profiling with stats.
It converts the key/values from the given map to Go profiler labels
and calls pprof.Do.
Do is going to do nothing if your Go version is below 1.9.
Encode encodes the tag map into a []byte. It is useful to propagate
the tag maps on wire in binary format.
FromContext returns the tag map stored in the context.
Insert returns a mutator that inserts a
value associated with k. If k already exists in the tag map,
mutator doesn't update the value.
Metadata applies metadata to the tag. It is optional.
Metadatas are applied in the order in which it is provided.
If more than one metadata updates the same attribute then
the update from the last metadata prevails.
MustNewKey returns a key with the given name, and panics if name is an invalid key name.
New returns a new context that contains a tag map
originated from the incoming context and modified
with the provided mutators.
NewContext creates a new context with the given tag map.
To propagate a tag map to downstream methods and downstream RPCs, add a tag map
to the current context. NewContext will return a copy of the current context,
and put the tag map into the returned one.
If there is already a tag map in the current context, it will be replaced with m.
NewKey creates or retrieves a string key identified by name.
Calling NewKey more than once with the same name returns the same key.
Update returns a mutator that updates the
value of the tag associated with k with v. If k doesn't
exists in the tag map, the mutator doesn't insert the value.
Metadata applies metadata to the tag. It is optional.
Metadatas are applied in the order in which it is provided.
If more than one metadata updates the same attribute then
the update from the last metadata prevails.
Upsert returns a mutator that upserts the
value of the tag associated with k with v. It inserts the
value if k doesn't exist already. It mutates the value
if k already exists.
Metadata applies metadata to the tag. It is optional.
Metadatas are applied in the order in which it is provided.
If more than one metadata updates the same attribute then
the update from the last metadata prevails.
valid are restricted to US-ASCII subset (range 0x20 (' ') to 0x7e ('~')).
valueTTLNoPropagation prevents tag from propagating.
valueTTLUnlimitedPropagation allows tag to propagate without any limits on number of hops.
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