Documentation

Overview

    Package dsl is the Domain Specific Language for the series query. Presently it mostly mimics the Graphite API functions. The parser used for the language is Go standard lib parser.ParseExpr(), which basically means the syntax is Go, and so the user of this package might need to ensure to wrap series names in quotes, etc.

    For example, consider

    scale(foo.bar.baz, 2)
    

    is a valid Go expression. foo.bar.baz is called a selector expression. However,

    scale(foo.1bar.baz, 2)
    

    is not valid because an identifier cannot begin with a digit. In any case,

    scale("foo.1bar.b*", 2)
    

    is always valid, and is the preferred method.

    Tgres DSL also supports function chaining, e.g.:

    group("foo.*").scale(2)
    

    Internally this is done by taking the return value of the preceeding function and inserting it as the first argument to the current one, thus the above expression is equivalent to:

    scale(group("foo.*", 2))
    

    Index

    Constants

    This section is empty.

    Variables

    This section is empty.

    Functions

    func NewNamedDSFetcher

    func NewNamedDSFetcher(db dsFetcherSearcher, dsc watcher, lruCap int) *namedDsFetcher

      Returns a new instance of a NamedDSFetcher. The current implementation will re-fetch all series names any time a series cannot be found. TODO: Make this better.

      func NewNamedDSFetcherMap

      func NewNamedDSFetcherMap(dss map[string]rrd.DataSourcer) *namedDsFetcher

        Creates a NamedDsFetcher from a map of DataSourcers. This is useful to bootstrap a DSL Context without any database.

        Types

        type AliasSeries

        type AliasSeries interface {
        	series.Series
        	// With argument sets the alias. Returns the alias.
        	Alias(s ...string) string
        }

          A Series which supports Alias()

          type DataPoint

          type DataPoint struct {
          	serde.Ident
          	T time.Time
          	V float64
          }

          type FsFindNode

          type FsFindNode struct {
          	Name       string
          	Leaf       bool
          	Expandable bool
          	// contains filtered or unexported fields
          }

          type NamedDSFetcher

          type NamedDSFetcher interface {
          	// contains filtered or unexported methods
          }

            A NamedDSFetcher is a serde.Fetcher which also implements a method for finding DS's by its dotted name using filepath.Match-like syntax.

            type NamedDsFetcherStats

            type NamedDsFetcherStats struct {
            	LruEvictions int
            	LruSize      int
            	LruHits      int
            	LruMisses    int
            }

            type SeriesMap

            type SeriesMap map[string]AliasSeries

              SeriesMap is a map and should not be confused with series.SeriesSlice. The key distinction is that you cannot "see" beyond a SeriesSlice, it encapsulates and hides all Series within it. E.g. when we compute avg(a, b), we end up with a new series and no longer have access to a or b. This is done by way of SeriesSlice.

              The test is whether a "new" series is created. E.g. scale() is given a bunch of series, and returns a bunch of series, so it should use SeriesMap. avg() takes a bunch of series and returns only one series, so it's a SeriesSlice.

              SeriesSlice

              - based on []Series
              - satisfies Series interface
              - aligns Series' within it to match on group by
              - series in it are not associated with a name (key)
              - it's a "mix of series" that can be treated as a series
              - supports duplicates
              

              SeriesMap

              - alias for map[string]Series
              - does NOT implement Series, it's a container of series, but not a series
              - is how we give Series names - the key is the name
              - does not support duplicates - same series would need different names
              

              func ParseDsl

              func ParseDsl(db ctxDSFetcher, src string, from, to time.Time, maxPoints int64) (SeriesMap, error)

                Parse a DSL expression given by src and other params.

                func (SeriesMap) SortedKeys

                func (sm SeriesMap) SortedKeys() []string