Golang BatchRequest.IsReadOnly方法代碼示例

// sendAttempt gathers and rearranges the replicas, and makes an RPC call.
func (ds *DistSender) sendAttempt(trace *tracer.Trace, ba roachpb.BatchRequest, desc *roachpb.RangeDescriptor) (*roachpb.BatchResponse, *roachpb.Error) {
	defer trace.Epoch("sending RPC")()

	leader := ds.leaderCache.Lookup(roachpb.RangeID(desc.RangeID))

	// Try to send the call.
	replicas := newReplicaSlice(ds.gossip, desc)

	// Rearrange the replicas so that those replicas with long common
	// prefix of attributes end up first. If there's no prefix, this is a
	// no-op.
	order := ds.optimizeReplicaOrder(replicas)

	// If this request needs to go to a leader and we know who that is, move
	// it to the front.
	if !(ba.IsReadOnly() && ba.ReadConsistency == roachpb.INCONSISTENT) &&
		leader.StoreID > 0 {
		if i := replicas.FindReplica(leader.StoreID); i >= 0 {
			replicas.MoveToFront(i)
			order = rpc.OrderStable
		}
	}

	br, err := ds.sendRPC(trace, desc.RangeID, replicas, order, ba)
	if err != nil {
		return nil, roachpb.NewError(err)
	}
	// Untangle the error from the received response.
	pErr := br.Error
	br.Error = nil // scrub the response error
	return br, pErr
}

// sendSingleRange gathers and rearranges the replicas, and makes an RPC call.
func (ds *DistSender) sendSingleRange(
	ctx context.Context, ba roachpb.BatchRequest, desc *roachpb.RangeDescriptor,
) (*roachpb.BatchResponse, *roachpb.Error) {
	// Hack: avoid formatting the message passed to Span.LogEvent for
	// opentracing.noopSpans. We can't actually tell if we have a noopSpan, but
	// we can see if the span as a NoopTracer. Note that this particular
	// invocation is expensive because we're pretty-printing keys.
	//
	// TODO(tschottdorf): This hack can go away when something like
	// Span.LogEventf is added.
	sp := opentracing.SpanFromContext(ctx)
	if sp != nil && sp.Tracer() != (opentracing.NoopTracer{}) {
		sp.LogEvent(fmt.Sprintf("sending RPC to [%s, %s)", desc.StartKey, desc.EndKey))
	}

	// Try to send the call.
	replicas := newReplicaSlice(ds.gossip, desc)

	// Rearrange the replicas so that those replicas with long common
	// prefix of attributes end up first. If there's no prefix, this is a
	// no-op.
	order := ds.optimizeReplicaOrder(replicas)

	// If this request needs to go to a leader and we know who that is, move
	// it to the front.
	if !(ba.IsReadOnly() && ba.ReadConsistency == roachpb.INCONSISTENT) {
		if leader := ds.leaderCache.Lookup(roachpb.RangeID(desc.RangeID)); leader.StoreID > 0 {
			if i := replicas.FindReplica(leader.StoreID); i >= 0 {
				replicas.MoveToFront(i)
				order = orderStable
			}
		}
	}

	// TODO(tschottdorf): should serialize the trace here, not higher up.
	br, pErr := ds.sendRPC(ctx, desc.RangeID, replicas, order, ba)
	if pErr != nil {
		return nil, pErr
	}

	// If the reply contains a timestamp, update the local HLC with it.
	if br.Error != nil && br.Error.Now != roachpb.ZeroTimestamp {
		ds.clock.Update(br.Error.Now)
	} else if br.Now != roachpb.ZeroTimestamp {
		ds.clock.Update(br.Now)
	}

	// Untangle the error from the received response.
	pErr = br.Error
	br.Error = nil // scrub the response error
	return br, pErr
}

// sendSingleRange gathers and rearranges the replicas, and makes an RPC call.
func (ds *DistSender) sendSingleRange(
	ctx context.Context, ba roachpb.BatchRequest, desc *roachpb.RangeDescriptor,
) (*roachpb.BatchResponse, *roachpb.Error) {
	log.Trace(ctx, fmt.Sprintf("sending RPC to [%s, %s)", desc.StartKey, desc.EndKey))

	// Try to send the call.
	replicas := newReplicaSlice(ds.gossip, desc)

	// Rearrange the replicas so that those replicas with long common
	// prefix of attributes end up first. If there's no prefix, this is a
	// no-op.
	order := ds.optimizeReplicaOrder(replicas)

	// If this request needs to go to a leader and we know who that is, move
	// it to the front.
	if !(ba.IsReadOnly() && ba.ReadConsistency == roachpb.INCONSISTENT) {
		if leader := ds.leaderCache.Lookup(roachpb.RangeID(desc.RangeID)); leader.StoreID > 0 {
			if i := replicas.FindReplica(leader.StoreID); i >= 0 {
				replicas.MoveToFront(i)
				order = orderStable
			}
		}
	}

	// TODO(tschottdorf): should serialize the trace here, not higher up.
	br, pErr := ds.sendRPC(ctx, desc.RangeID, replicas, order, ba)
	if pErr != nil {
		return nil, pErr
	}

	// If the reply contains a timestamp, update the local HLC with it.
	if br.Error != nil && br.Error.Now != roachpb.ZeroTimestamp {
		ds.clock.Update(br.Error.Now)
	} else if br.Now != roachpb.ZeroTimestamp {
		ds.clock.Update(br.Now)
	}

	// Untangle the error from the received response.
	pErr = br.Error
	br.Error = nil // scrub the response error
	return br, pErr
}

// sendSingleRange gathers and rearranges the replicas, and makes an RPC call.
func (ds *DistSender) sendSingleRange(trace opentracing.Span, ba roachpb.BatchRequest, desc *roachpb.RangeDescriptor) (*roachpb.BatchResponse, *roachpb.Error) {
	trace.LogEvent(fmt.Sprintf("sending RPC to [%s, %s)", desc.StartKey, desc.EndKey))

	leader := ds.leaderCache.Lookup(roachpb.RangeID(desc.RangeID))

	// Try to send the call.
	replicas := newReplicaSlice(ds.gossip, desc)

	// Rearrange the replicas so that those replicas with long common
	// prefix of attributes end up first. If there's no prefix, this is a
	// no-op.
	order := ds.optimizeReplicaOrder(replicas)

	// If this request needs to go to a leader and we know who that is, move
	// it to the front.
	if !(ba.IsReadOnly() && ba.ReadConsistency == roachpb.INCONSISTENT) &&
		leader.StoreID > 0 {
		if i := replicas.FindReplica(leader.StoreID); i >= 0 {
			replicas.MoveToFront(i)
			order = orderStable
		}
	}

	// Increase the sequence counter in the per-range loop (not
	// outside) since we might hit the same range twice by
	// accident. For example, we might send multiple requests to
	// the same Replica if (1) the descriptor cache has post-split
	// descriptors that are still write intents and (2) the split
	// has not yet been completed.
	ba.SetNewRequest()

	// TODO(tschottdorf): should serialize the trace here, not higher up.
	br, pErr := ds.sendRPC(trace, desc.RangeID, replicas, order, ba)
	if pErr != nil {
		return nil, pErr
	}
	// Untangle the error from the received response.
	pErr = br.Error
	br.Error = nil // scrub the response error
	return br, pErr
}

// Send implements the batch.Sender interface. If the request is part of a
// transaction, the TxnCoordSender adds the transaction to a map of active
// transactions and begins heartbeating it. Every subsequent request for the
// same transaction updates the lastUpdate timestamp to prevent live
// transactions from being considered abandoned and garbage collected.
// Read/write mutating requests have their key or key range added to the
// transaction's interval tree of key ranges for eventual cleanup via resolved
// write intents; they're tagged to an outgoing EndTransaction request, with
// the receiving replica in charge of resolving them.
func (tc *TxnCoordSender) Send(ctx context.Context, ba roachpb.BatchRequest) (*roachpb.BatchResponse, *roachpb.Error) {
	if err := tc.maybeBeginTxn(&ba); err != nil {
		return nil, roachpb.NewError(err)
	}
	ba.CmdID = ba.GetOrCreateCmdID(tc.clock.PhysicalNow())
	var startNS int64

	// This is the earliest point at which the request has a ClientCmdID and/or
	// TxnID (if applicable). Begin a Trace which follows this request.
	trace := tc.tracer.NewTrace(tracer.Coord, &ba)
	defer trace.Finalize()
	defer trace.Epoch("sending batch")()
	ctx = tracer.ToCtx(ctx, trace)

	var id string // optional transaction ID
	if ba.Txn != nil {
		// If this request is part of a transaction...
		id = string(ba.Txn.ID)
		// Verify that if this Transaction is not read-only, we have it on
		// file. If not, refuse writes - the client must have issued a write on
		// another coordinator previously.
		if ba.Txn.Writing && ba.IsTransactionWrite() {
			tc.Lock()
			_, ok := tc.txns[id]
			tc.Unlock()
			if !ok {
				return nil, roachpb.NewError(util.Errorf("transaction must not write on multiple coordinators"))
			}
		}

		// Set the timestamp to the original timestamp for read-only
		// commands and to the transaction timestamp for read/write
		// commands.
		if ba.IsReadOnly() {
			ba.Timestamp = ba.Txn.OrigTimestamp
		} else {
			ba.Timestamp = ba.Txn.Timestamp
		}

		if rArgs, ok := ba.GetArg(roachpb.EndTransaction); ok {
			et := rArgs.(*roachpb.EndTransactionRequest)
			if len(et.Key) != 0 {
				return nil, roachpb.NewError(util.Errorf("EndTransaction must not have a Key set"))
			}
			et.Key = ba.Txn.Key
			// Remember when EndTransaction started in case we want to
			// be linearizable.
			startNS = tc.clock.PhysicalNow()
			if len(et.Intents) > 0 {
				// TODO(tschottdorf): it may be useful to allow this later.
				// That would be part of a possible plan to allow txns which
				// write on multiple coordinators.
				return nil, roachpb.NewError(util.Errorf("client must not pass intents to EndTransaction"))
			}
			tc.Lock()
			txnMeta, metaOK := tc.txns[id]
			if id != "" && metaOK {
				et.Intents = txnMeta.intents()
			}
			tc.Unlock()

			if intents := ba.GetIntents(); len(intents) > 0 {
				// Writes in Batch, so EndTransaction is fine. Should add
				// outstanding intents to EndTransaction, though.
				// TODO(tschottdorf): possible issues when the batch fails,
				// but the intents have been added anyways.
				// TODO(tschottdorf): some of these intents may be covered
				// by others, for example {[a,b), a}). This can lead to
				// some extra requests when those are non-local to the txn
				// record. But it doesn't seem worth optimizing now.
				et.Intents = append(et.Intents, intents...)
			} else if !metaOK {
				// If we don't have the transaction, then this must be a retry
				// by the client. We can no longer reconstruct a correct
				// request so we must fail.
				//
				// TODO(bdarnell): if we had a GetTransactionStatus API then
				// we could lookup the transaction and return either nil or
				// TransactionAbortedError instead of this ambivalent error.
				return nil, roachpb.NewError(util.Errorf("transaction is already committed or aborted"))
			}
			if len(et.Intents) == 0 {
				// If there aren't any intents, then there's factually no
				// transaction to end. Read-only txns have all of their state in
				// the client.
				return nil, roachpb.NewError(util.Errorf("cannot commit a read-only transaction"))
			}
			if log.V(1) {
				for _, intent := range et.Intents {
					trace.Event(fmt.Sprintf("intent: [%s,%s)", intent.Key, intent.EndKey))
				}
//.........這裏部分代碼省略.........

// Send implements the batch.Sender interface. If the request is part of a
// transaction, the TxnCoordSender adds the transaction to a map of active
// transactions and begins heartbeating it. Every subsequent request for the
// same transaction updates the lastUpdate timestamp to prevent live
// transactions from being considered abandoned and garbage collected.
// Read/write mutating requests have their key or key range added to the
// transaction's interval tree of key ranges for eventual cleanup via resolved
// write intents; they're tagged to an outgoing EndTransaction request, with
// the receiving replica in charge of resolving them.
func (tc *TxnCoordSender) Send(ctx context.Context, ba roachpb.BatchRequest) (*roachpb.BatchResponse, *roachpb.Error) {
	// Start new or pick up active trace and embed its trace metadata into
	// header for use by RPC recipients. From here on, there's always an active
	// Trace, though its overhead is small unless it's sampled.
	sp, cleanupSp := tracing.SpanFromContext(opTxnCoordSender, tc.tracer, ctx)
	defer cleanupSp()
	// TODO(tschottdorf): To get rid of the spurious alloc below we need to
	// implement the carrier interface on ba.Header or make Span non-nullable,
	// both of which force all of ba on the Heap. It's already there, so may
	// not be a big deal, but ba should live on the stack. Also not easy to use
	// a buffer pool here since anything that goes into the RPC layer could be
	// used by goroutines we didn't wait for.
	if ba.Header.Trace == nil {
		ba.Header.Trace = &tracing.Span{}
	}
	if err := tc.tracer.Inject(sp, basictracer.Delegator, ba.Trace); err != nil {
		return nil, roachpb.NewError(err)
	}

	if err := tc.maybeBeginTxn(&ba); err != nil {
		return nil, roachpb.NewError(err)
	}
	var startNS int64
	ba.SetNewRequest()

	// This is the earliest point at which the request has an ID (if
	// applicable). Begin a Trace which follows this request.
	ctx = opentracing.ContextWithSpan(ctx, sp)

	if ba.Txn != nil {
		// If this request is part of a transaction...
		txnID := *ba.Txn.ID
		// Verify that if this Transaction is not read-only, we have it on
		// file. If not, refuse writes - the client must have issued a write on
		// another coordinator previously.
		if ba.Txn.Writing && ba.IsTransactionWrite() {
			tc.Lock()
			_, ok := tc.txns[txnID]
			tc.Unlock()
			if !ok {
				return nil, roachpb.NewErrorf("transaction must not write on multiple coordinators")
			}
		}

		// Set the timestamp to the original timestamp for read-only
		// commands and to the transaction timestamp for read/write
		// commands.
		if ba.IsReadOnly() {
			ba.Timestamp = ba.Txn.OrigTimestamp
		} else {
			ba.Timestamp = ba.Txn.Timestamp
		}

		if rArgs, ok := ba.GetArg(roachpb.EndTransaction); ok {
			et := rArgs.(*roachpb.EndTransactionRequest)
			if len(et.Key) != 0 {
				return nil, roachpb.NewErrorf("EndTransaction must not have a Key set")
			}
			et.Key = ba.Txn.Key
			// Remember when EndTransaction started in case we want to
			// be linearizable.
			startNS = tc.clock.PhysicalNow()
			if len(et.IntentSpans) > 0 {
				// TODO(tschottdorf): it may be useful to allow this later.
				// That would be part of a possible plan to allow txns which
				// write on multiple coordinators.
				return nil, roachpb.NewErrorf("client must not pass intents to EndTransaction")
			}
			tc.Lock()
			txnMeta, metaOK := tc.txns[txnID]
			if metaOK {
				et.IntentSpans = txnMeta.intentSpans()
			}
			tc.Unlock()

			if intentSpans := ba.GetIntentSpans(); len(intentSpans) > 0 {
				// Writes in Batch, so EndTransaction is fine. Should add
				// outstanding intents to EndTransaction, though.
				// TODO(tschottdorf): possible issues when the batch fails,
				// but the intents have been added anyways.
				// TODO(tschottdorf): some of these intents may be covered
				// by others, for example {[a,b), a}). This can lead to
				// some extra requests when those are non-local to the txn
				// record. But it doesn't seem worth optimizing now.
				et.IntentSpans = append(et.IntentSpans, intentSpans...)
			} else if !metaOK {
				// If we don't have the transaction, then this must be a retry
				// by the client. We can no longer reconstruct a correct
				// request so we must fail.
				//
				// TODO(bdarnell): if we had a GetTransactionStatus API then
//.........這裏部分代碼省略.........