Docker Swarm Code Analysis Note (--filter)

This is a creation in Article, where the information may have evolved or changed.

Docker Swarm manageThe options of the command are filter used to specify scheduler Docker Engine the selected filter, whose variables are defined as follows ( cli/flags.go ):

// hack for go vetflFilterValue = cli.StringSlice(filter.List())// DefaultFilterNumber is exportedDefaultFilterNumber = len(flFilterValue)flFilter = cli.StringSliceFlag{    Name:  "filter, f",    Usage: "filter to use [" + strings.Join(filter.List(), ", ") + "]",    Value: &flFilterValue,}

filterthe code to get the value is as follows ( cli/manage.go ):

// see https://github.com/codegangsta/cli/issues/160names := c.StringSlice("filter")if c.IsSet("filter") || c.IsSet("f") {    names = names[DefaultFilterNumber:]}fs, err := filter.New(names)if err != nil {    log.Fatal(err)}

By default, all filter () are obtained scheduler/filter/filter.go :

func init() {    filters = []Filter{        &HealthFilter{},        &PortFilter{},        &SlotsFilter{},        &DependencyFilter{},        &AffinityFilter{},        &ConstraintFilter{},    }}

And Filter is a interface ( scheduler/filter/filter.go ):

// Filter is exportedtype Filter interface {    Name() string    // Return a subset of nodes that were accepted by the filtering policy.    Filter(*cluster.ContainerConfig, []*node.Node, bool) ([]*node.Node, error)    // Return a list of constraints/filters provided    GetFilters(*cluster.ContainerConfig) ([]string, error)}

Where the Filter method is used to filter the qualifying Docker Engine , GetFilters A string that describes the filter condition is returned.

In scheduler/filter/filter.go , applyfilters to filter Docker Engine ; Listallfilters Returns all filter conditions:

Applyfilters applies a set of filters in Batch.func applyfilters (filters []filter, config *cluster. Containerconfig, nodes []*node. Node, soft bool) ([]*node.        Node, error) {var (err error candidates = nodes) for _, Filter: = Range Filters { Candidates, err = filter.            Filter (config, candidates, soft) if err! = Nil {//special case for when no healthy nodes is found If filter. Name () = = "Health" {return nil, err} return nil, FMT. Errorf ("Unable to find a node that satisfies the following conditions%s", listallfilters (filters, config, filter.) Name ())}} return candidates, nil}//Listallfilters creates a string containing all applied Filtersfunc lis Tallfilters (filters []filter, config *cluster. Containerconfig, Lastfilter String) string {allfilters: = "" For _, Filter: = Range Filters {list, err: = f Ilter. Getfilters (config) if err = = Nil && lEn (list) > 0 {allfilters = fmt. Sprintf ("%s\n%v", Allfilters, List)} if filter. Name () = = Lastfilter {return allfilters}} return Allfilters}