Pick makes the routing decision for every outbound RPC.
(info balancer.PickInfo)
| 80 | |
| 81 | // Pick makes the routing decision for every outbound RPC. |
| 82 | func (p *rlsPicker) Pick(info balancer.PickInfo) (balancer.PickResult, error) { |
| 83 | if name := info.FullMethodName; !isFullMethodNameValid(name) { |
| 84 | return balancer.PickResult{}, fmt.Errorf("rls: method name %q is not of the form '/service/method", name) |
| 85 | } |
| 86 | |
| 87 | // Build the request's keys using the key builders from LB config. |
| 88 | md, _ := metadata.FromOutgoingContext(info.Ctx) |
| 89 | reqKeys := p.kbm.RLSKey(md, p.origEndpoint, info.FullMethodName) |
| 90 | |
| 91 | p.lb.cacheMu.Lock() |
| 92 | var pr balancer.PickResult |
| 93 | var err error |
| 94 | |
| 95 | // Record metrics without the cache mutex held, to prevent lock contention |
| 96 | // between concurrent RPC's and their Pick calls. Metrics Recording can |
| 97 | // potentially be expensive. |
| 98 | metricsCallback := func() {} |
| 99 | defer func() { |
| 100 | p.lb.cacheMu.Unlock() |
| 101 | metricsCallback() |
| 102 | }() |
| 103 | |
| 104 | // Lookup data cache and pending request map using request path and keys. |
| 105 | cacheKey := cacheKey{path: info.FullMethodName, keys: reqKeys.Str} |
| 106 | dcEntry := p.lb.dataCache.getEntry(cacheKey) |
| 107 | pendingEntry := p.lb.pendingMap[cacheKey] |
| 108 | now := time.Now() |
| 109 | |
| 110 | switch { |
| 111 | // No data cache entry. No pending request. |
| 112 | case dcEntry == nil && pendingEntry == nil: |
| 113 | throttled := p.sendRouteLookupRequestLocked(cacheKey, &backoffState{bs: defaultBackoffStrategy}, reqKeys.Map, rlspb.RouteLookupRequest_REASON_MISS, "") |
| 114 | if throttled { |
| 115 | pr, metricsCallback, err = p.useDefaultPickIfPossible(info, errRLSThrottled) |
| 116 | return pr, err |
| 117 | } |
| 118 | return balancer.PickResult{}, balancer.ErrNoSubConnAvailable |
| 119 | |
| 120 | // No data cache entry. Pending request exits. |
| 121 | case dcEntry == nil && pendingEntry != nil: |
| 122 | return balancer.PickResult{}, balancer.ErrNoSubConnAvailable |
| 123 | |
| 124 | // Data cache hit. No pending request. |
| 125 | case dcEntry != nil && pendingEntry == nil: |
| 126 | if dcEntry.expiryTime.After(now) { |
| 127 | if !dcEntry.staleTime.IsZero() && dcEntry.staleTime.Before(now) && dcEntry.backoffTime.Before(now) { |
| 128 | p.sendRouteLookupRequestLocked(cacheKey, dcEntry.backoffState, reqKeys.Map, rlspb.RouteLookupRequest_REASON_STALE, dcEntry.headerData) |
| 129 | } |
| 130 | // Delegate to child policies. |
| 131 | pr, metricsCallback, err = p.delegateToChildPoliciesLocked(dcEntry, info) |
| 132 | return pr, err |
| 133 | } |
| 134 | |
| 135 | // We get here only if the data cache entry has expired. If entry is in |
| 136 | // backoff, delegate to default target or fail the pick. |
| 137 | if dcEntry.backoffState != nil && dcEntry.backoffTime.After(now) { |
| 138 | // Avoid propagating the status code received on control plane RPCs to the |
| 139 | // data plane which can lead to unexpected outcomes as we do not control |
nothing calls this directly
no test coverage detected