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New encoding for OpenTSDB tag values (and metric names).
Change-Id: I0f4393f638c6e2bb2b2ce14e58e38b49ce456da8
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Bjoern Rabenstein
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Mar 21, 2014
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| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -0,0 +1,144 @@ | ||
| package opentsdb | ||
|
|
||
| import ( | ||
| "bytes" | ||
| "fmt" | ||
|
|
||
| clientmodel "github.com/prometheus/client_golang/model" | ||
| ) | ||
|
|
||
| // TagValue is a clientmodel.LabelValue that implements json.Marshaler and | ||
| // json.Unmarshaler. These implementations avoid characters illegal in | ||
| // OpenTSDB. See the MarshalJSON for details. TagValue is used for the values of | ||
| // OpenTSDB tags as well as for OpenTSDB metric names. | ||
| type TagValue clientmodel.LabelValue | ||
|
|
||
| // MarshalJSON marshals this TagValue into JSON that only contains runes allowed | ||
| // in OpenTSDB. It implements json.Marshaler. The runes allowed in OpenTSDB are | ||
| // all single-byte. This function encodes the arbitrary byte sequence found in | ||
| // this TagValue in the following way: | ||
| // | ||
| // - The string that underlies TagValue is scanned byte by byte. | ||
| // | ||
| // - If a byte represents a legal OpenTSDB rune with the exception of '_', that | ||
| // byte is directly copied to the resulting JSON byte slice. | ||
| // | ||
| // - If '_' is encountered, it is replaced by '__'. | ||
| // | ||
| // - If ':' is encountered, it is replaced by '_.'. | ||
| // | ||
| // - All other bytes are replaced by '_' followed by two bytes containing the | ||
| // uppercase ASCII representation of their hexadecimal value. | ||
| // | ||
| // This encoding allows to save arbitrary Go strings in OpenTSDB. That's | ||
| // required because Prometheus label values can contain anything, and even | ||
| // Prometheus metric names may (and often do) contain ':' (which is disallowed | ||
| // in OpenTSDB strings). The encoding uses '_' as an escape character and | ||
| // renders a ':' more or less recognizable as '_.' | ||
| // | ||
| // Examples: | ||
| // | ||
| // "foo-bar-42" -> "foo-bar-42" | ||
| // | ||
| // "foo_bar_42" -> "foo__bar__42" | ||
| // | ||
| // "http://example.org:8080" -> "http_.//example.org_.8080" | ||
| // | ||
| // "Björn's email: bjoern@soundcloud.com" -> | ||
| // "Bj_C3_B6rn_27s_20email_._20bjoern_40soundcloud.com" | ||
| // | ||
| // "日" -> "_E6_97_A5" | ||
| func (tv TagValue) MarshalJSON() ([]byte, error) { | ||
| length := len(tv) | ||
| // Need at least two more bytes than in tv. | ||
| result := bytes.NewBuffer(make([]byte, 1, length+2)) | ||
| result.WriteByte('"') | ||
| for i := 0; i < length; i++ { | ||
| b := tv[i] | ||
| switch { | ||
| case (b >= '-' && b <= '9') || // '-', '.', '/', 0-9 | ||
| (b >= 'A' && b <= 'Z') || | ||
| (b >= 'a' && b <= 'z'): | ||
| result.WriteByte(b) | ||
| case b == '_': | ||
| result.WriteString("__") | ||
| case b == ':': | ||
| result.WriteString("_.") | ||
| default: | ||
| result.WriteString(fmt.Sprintf("_%X", b)) | ||
| } | ||
| } | ||
| result.WriteByte('"') | ||
| return result.Bytes(), nil | ||
| } | ||
|
|
||
| // UnmarshalJSON unmarshals JSON strings coming from OpenTSDB into Go strings | ||
| // by applying the inverse of what is described for the MarshalJSON method. | ||
| func (tv *TagValue) UnmarshalJSON(json []byte) error { | ||
| escapeLevel := 0 // How many bytes after '_'. | ||
| var parsedByte byte | ||
|
|
||
| // Might need fewer bytes, but let's avoid realloc. | ||
| result := bytes.NewBuffer(make([]byte, 0, len(json)-2)) | ||
|
|
||
| for i, b := range json { | ||
| if i == 0 { | ||
| if b != '"' { | ||
| return fmt.Errorf("expected '\"', got %q", b) | ||
| } | ||
| continue | ||
| } | ||
| if i == len(json)-1 { | ||
| if b != '"' { | ||
| return fmt.Errorf("expected '\"', got %q", b) | ||
| } | ||
| break | ||
| } | ||
| switch escapeLevel { | ||
| case 0: | ||
| if b == '_' { | ||
| escapeLevel = 1 | ||
| continue | ||
| } | ||
| result.WriteByte(b) | ||
| case 1: | ||
| switch { | ||
| case b == '_': | ||
| result.WriteByte('_') | ||
| escapeLevel = 0 | ||
| case b == '.': | ||
| result.WriteByte(':') | ||
| escapeLevel = 0 | ||
| case b >= '0' && b <= '9': | ||
| parsedByte = (b - 48) << 4 | ||
| escapeLevel = 2 | ||
| case b >= 'A' && b <= 'F': // A-F | ||
| parsedByte = (b - 55) << 4 | ||
| escapeLevel = 2 | ||
| default: | ||
| return fmt.Errorf( | ||
| "illegal escape sequence at byte %d (%c)", | ||
| i, b, | ||
| ) | ||
| } | ||
| case 2: | ||
| switch { | ||
| case b >= '0' && b <= '9': | ||
| parsedByte += b - 48 | ||
| case b >= 'A' && b <= 'F': // A-F | ||
| parsedByte += b - 55 | ||
| default: | ||
| return fmt.Errorf( | ||
| "illegal escape sequence at byte %d (%c)", | ||
| i, b, | ||
| ) | ||
| } | ||
| result.WriteByte(parsedByte) | ||
| escapeLevel = 0 | ||
| default: | ||
| panic("unexpected escape level") | ||
| } | ||
| } | ||
| *tv = TagValue(result.String()) | ||
| return nil | ||
| } |
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| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -0,0 +1,51 @@ | ||
| package opentsdb | ||
|
|
||
| import ( | ||
| "bytes" | ||
| "encoding/json" | ||
| "testing" | ||
| ) | ||
|
|
||
| var stringtests = []struct { | ||
| tv TagValue | ||
| json []byte | ||
| }{ | ||
| {TagValue("foo-bar-42"), []byte(`"foo-bar-42"`)}, | ||
| {TagValue("foo_bar_42"), []byte(`"foo__bar__42"`)}, | ||
| {TagValue("http://example.org:8080"), []byte(`"http_.//example.org_.8080"`)}, | ||
| {TagValue("Björn's email: bjoern@soundcloud.com"), []byte(`"Bj_C3_B6rn_27s_20email_._20bjoern_40soundcloud.com"`)}, | ||
| {TagValue("日"), []byte(`"_E6_97_A5"`)}, | ||
| } | ||
|
|
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| func TestTagValueMarshaling(t *testing.T) { | ||
| for i, tt := range stringtests { | ||
| json, err := json.Marshal(tt.tv) | ||
| if err != nil { | ||
| t.Errorf("%d. Marshal(%q) returned err: %s", i, tt.tv, err) | ||
| } else { | ||
| if !bytes.Equal(json, tt.json) { | ||
| t.Errorf( | ||
| "%d. Marshal(%q) => %q, want %q", | ||
| i, tt.tv, json, tt.json, | ||
| ) | ||
| } | ||
| } | ||
| } | ||
| } | ||
|
|
||
| func TestTagValueUnMarshaling(t *testing.T) { | ||
| for i, tt := range stringtests { | ||
| var tv TagValue | ||
| err := json.Unmarshal(tt.json, &tv) | ||
| if err != nil { | ||
| t.Errorf("%d. Unmarshal(%q, &str) returned err: %s", i, tt.json, err) | ||
| } else { | ||
| if tv != tt.tv { | ||
| t.Errorf( | ||
| "%d. Unmarshal(%q, &str) => str==%q, want %q", | ||
| i, tt.json, tv, tt.tv, | ||
| ) | ||
| } | ||
| } | ||
| } | ||
| } |