consul/command/agent/ui_endpoint.go

package agent

import (
	"github.com/hashicorp/consul/consul/structs"
	"net/http"
	"strings"
)

// UINodes is used to list the nodes in a given datacenter. We return a
// NodeDump which provides overview information for all the nodes
func (s *HTTPServer) UINodes(resp http.ResponseWriter, req *http.Request) (interface{}, error) {
	// Get the datacenter
	var dc string
	s.parseDC(req, &dc)

	// Try to ge ta node dump
	var dump structs.NodeDump
	if err := s.getNodeDump(resp, dc, "", &dump); err != nil {
		return nil, err
	}

	return dump, nil
}

// UINodeInfo is used to get info on a single node in a given datacenter. We return a
// NodeInfo which provides overview information for the node
func (s *HTTPServer) UINodeInfo(resp http.ResponseWriter, req *http.Request) (interface{}, error) {
	// Get the datacenter
	var dc string
	s.parseDC(req, &dc)

	// Verify we have some DC, or use the default
	node := strings.TrimPrefix(req.URL.Path, "/v1/internal/ui/node/")
	if node == "" {
		resp.WriteHeader(400)
		resp.Write([]byte("Missing node name"))
		return nil, nil
	}

	// Try to get a node dump
	var dump structs.NodeDump
	if err := s.getNodeDump(resp, dc, node, &dump); err != nil {
		return nil, err
	}

	// Return only the first entry
	if len(dump) > 0 {
		return dump[0], nil
	}
	return nil, nil
}

// getNodeDump is used to get a dump of all node data. We make a best effort by
// reading stale data in the case of an availability outage.
func (s *HTTPServer) getNodeDump(resp http.ResponseWriter, dc, node string, dump *structs.NodeDump) error {
	var args interface{}
	var method string
	var allowStale *bool

	if node == "" {
		raw := structs.DCSpecificRequest{Datacenter: dc}
		method = "Internal.NodeDump"
		allowStale = &raw.AllowStale
		args = &raw
	} else {
		raw := &structs.NodeSpecificRequest{Datacenter: dc, Node: node}
		method = "Internal.NodeInfo"
		allowStale = &raw.AllowStale
		args = &raw
	}
	var out structs.IndexedNodeDump
	defer setMeta(resp, &out.QueryMeta)

START:
	if err := s.agent.RPC(method, args, &out); err != nil {
		// Retry the request allowing stale data if no leader. The UI should continue
		// to function even during an outage
		if strings.Contains(err.Error(), structs.ErrNoLeader.Error()) && !*allowStale {
			*allowStale = true
			goto START
		}
		return err
	}

	// Set the result
	*dump = out.Dump
	return nil
}