// GetAllocs is used to lookup a set of allocations
func (a *Alloc) GetAllocs(args *structs.AllocsGetRequest,
	reply *structs.AllocsGetResponse) error {
	if done, err := a.srv.forward("Alloc.GetAllocs", args, args, reply); done {
		return err
	}
	defer metrics.MeasureSince([]string{"nomad", "alloc", "get_alloc"}, time.Now())

	// Lookup the allocations
	snap, err := a.srv.fsm.State().Snapshot()
	if err != nil {
		return err
	}

	allocs := make([]*structs.Allocation, len(args.AllocIDs))
	for i, alloc := range args.AllocIDs {
		out, err := snap.AllocByID(alloc)
		if err != nil {
			return err
		}
		if out == nil {
			return fmt.Errorf("unknown alloc id %q", alloc)
		}

		allocs[i] = out
		if reply.Index < out.ModifyIndex {
			reply.Index = out.ModifyIndex
		}
	}

	// Set the response
	a.srv.setQueryMeta(&reply.QueryMeta)
	reply.Allocs = allocs
	return nil
}

// watchAllocations is used to scan for updates to allocations
func (c *Client) watchAllocations(updates chan *allocUpdates) {
	// The request and response for getting the map of allocations that should
	// be running on the Node to their AllocModifyIndex which is incremented
	// when the allocation is updated by the servers.
	req := structs.NodeSpecificRequest{
		NodeID: c.Node().ID,
		QueryOptions: structs.QueryOptions{
			Region:     c.Region(),
			AllowStale: true,
		},
	}
	var resp structs.NodeClientAllocsResponse

	// The request and response for pulling down the set of allocations that are
	// new, or updated server side.
	allocsReq := structs.AllocsGetRequest{
		QueryOptions: structs.QueryOptions{
			Region:     c.Region(),
			AllowStale: true,
		},
	}
	var allocsResp structs.AllocsGetResponse

	for {
		// Get the allocation modify index map, blocking for updates. We will
		// use this to determine exactly what allocations need to be downloaded
		// in full.
		resp = structs.NodeClientAllocsResponse{}
		err := c.RPC("Node.GetClientAllocs", &req, &resp)
		if err != nil {
			c.logger.Printf("[ERR] client: failed to query for node allocations: %v", err)
			retry := c.retryIntv(getAllocRetryIntv)
			select {
			case <-time.After(retry):
				continue
			case <-c.shutdownCh:
				return
			}
		}

		// Check for shutdown
		select {
		case <-c.shutdownCh:
			return
		default:
		}

		// Filter all allocations whose AllocModifyIndex was not incremented.
		// These are the allocations who have either not been updated, or whose
		// updates are a result of the client sending an update for the alloc.
		// This lets us reduce the network traffic to the server as we don't
		// need to pull all the allocations.
		var pull []string
		filtered := make(map[string]struct{})
		runners := c.getAllocRunners()
		for allocID, modifyIndex := range resp.Allocs {
			// Pull the allocation if we don't have an alloc runner for the
			// allocation or if the alloc runner requires an updated allocation.
			runner, ok := runners[allocID]
			if !ok || runner.shouldUpdate(modifyIndex) {
				pull = append(pull, allocID)
			} else {
				filtered[allocID] = struct{}{}
			}
		}

		c.logger.Printf("[DEBUG] client: updated allocations at index %d (pulled %d) (filtered %d)",
			resp.Index, len(pull), len(filtered))

		// Pull the allocations that passed filtering.
		allocsResp.Allocs = nil
		if len(pull) != 0 {
			// Pull the allocations that need to be updated.
			allocsReq.AllocIDs = pull
			allocsResp = structs.AllocsGetResponse{}
			if err := c.RPC("Alloc.GetAllocs", &allocsReq, &allocsResp); err != nil {
				c.logger.Printf("[ERR] client: failed to query updated allocations: %v", err)
				retry := c.retryIntv(getAllocRetryIntv)
				select {
				case <-time.After(retry):
					continue
				case <-c.shutdownCh:
					return
				}
			}

			// Check for shutdown
			select {
			case <-c.shutdownCh:
				return
			default:
			}
		}

		// Update the query index.
		if resp.Index > req.MinQueryIndex {
			req.MinQueryIndex = resp.Index
		}

//.........这里部分代码省略.........