129 lines
3.1 KiB
Go
129 lines
3.1 KiB
Go
package nats
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import (
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"context"
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"errors"
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"fmt"
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"sync"
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"github.com/nats-io/nats.go"
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addressSDK "github.com/nspcc-dev/neofs-sdk-go/object/address"
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"go.uber.org/zap"
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)
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// Writer is a NATS object notification writer.
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// It handles NATS JetStream connections and allows
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// sending string representation of the address to
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// the NATS server.
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//
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// For correct operation must be created via New function.
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// new(Writer) or Writer{} construction leads to undefined
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// behaviour and is not safe.
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type Writer struct {
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log *zap.Logger
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js nats.JetStreamContext
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nc *nats.Conn
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m *sync.RWMutex
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createdStreams map[string]struct{}
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}
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type opts struct {
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logger *zap.Logger
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nOpts []nats.Option
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}
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type Option func(*opts)
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var errConnIsClosed = errors.New("connection to the server is closed")
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// Notify sends object address's string representation to the provided topic.
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// Uses first 4 bytes of object ID as a message ID to support 'exactly once message'
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// delivery.
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//
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// Returns error only if:
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// 1. underlying connection was closed and has not established again;
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// 2. NATS server could not respond that is has saved the message.
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func (n *Writer) Notify(topic string, address *addressSDK.Address) error {
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if !n.nc.IsConnected() {
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return errConnIsClosed
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}
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// use first 4 byte of the encoded string as
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// message ID for the exactly-once delivery
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messageID := address.ObjectID().String()[:4]
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// check if the stream was previously created
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n.m.RLock()
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_, created := n.createdStreams[topic]
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n.m.RUnlock()
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if !created {
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_, err := n.js.AddStream(&nats.StreamConfig{
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Name: topic,
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})
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if err != nil {
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return fmt.Errorf("could not add stream: %w", err)
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}
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n.m.Lock()
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n.createdStreams[topic] = struct{}{}
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n.m.Unlock()
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}
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_, err := n.js.Publish(topic, []byte(address.String()), nats.MsgId(messageID))
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if err != nil {
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return err
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}
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return nil
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}
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// New creates and inits new Writer.
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// Connection is closed when passed context is done.
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//
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// Returns error only if fails to open connection to a NATS server
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// with provided configuration.
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func New(ctx context.Context, endpoint string, oo ...Option) (*Writer, error) {
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opts := &opts{
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logger: zap.L(),
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nOpts: make([]nats.Option, 0, len(oo)+3),
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}
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for _, o := range oo {
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o(opts)
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}
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opts.nOpts = append(opts.nOpts,
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nats.NoCallbacksAfterClientClose(), // do not call callbacks when it was planned writer stop
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nats.DisconnectErrHandler(func(conn *nats.Conn, err error) {
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opts.logger.Error("nats: connection was lost", zap.Error(err))
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}),
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nats.ReconnectHandler(func(conn *nats.Conn) {
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opts.logger.Warn("nats: reconnected to the server")
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}),
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)
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nc, err := nats.Connect(endpoint, opts.nOpts...)
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if err != nil {
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return nil, fmt.Errorf("could not connect to server: %w", err)
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}
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// usage w/o options is error-free
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js, _ := nc.JetStream()
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go func() {
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<-ctx.Done()
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opts.logger.Info("nats: closing connection as the context is done")
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nc.Close()
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}()
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return &Writer{
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js: js,
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nc: nc,
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log: opts.logger,
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m: &sync.RWMutex{},
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createdStreams: make(map[string]struct{}),
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}, nil
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}
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