forked from mongodb/mongo-go-driver
/
client.go
814 lines (735 loc) · 26.8 KB
/
client.go
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// Copyright (C) MongoDB, Inc. 2017-present.
//
// Licensed under the Apache License, Version 2.0 (the "License"); you may
// not use this file except in compliance with the License. You may obtain
// a copy of the License at http://www.apache.org/licenses/LICENSE-2.0
package mongo
import (
"context"
"crypto/tls"
"errors"
"strconv"
"strings"
"time"
"go.mongodb.org/mongo-driver/bson"
"go.mongodb.org/mongo-driver/bson/bsoncodec"
"go.mongodb.org/mongo-driver/event"
"go.mongodb.org/mongo-driver/mongo/options"
"go.mongodb.org/mongo-driver/mongo/readconcern"
"go.mongodb.org/mongo-driver/mongo/readpref"
"go.mongodb.org/mongo-driver/mongo/writeconcern"
"go.mongodb.org/mongo-driver/x/bsonx/bsoncore"
"go.mongodb.org/mongo-driver/x/mongo/driver"
"go.mongodb.org/mongo-driver/x/mongo/driver/auth"
"go.mongodb.org/mongo-driver/x/mongo/driver/connstring"
"go.mongodb.org/mongo-driver/x/mongo/driver/description"
"go.mongodb.org/mongo-driver/x/mongo/driver/operation"
"go.mongodb.org/mongo-driver/x/mongo/driver/session"
"go.mongodb.org/mongo-driver/x/mongo/driver/topology"
"go.mongodb.org/mongo-driver/x/mongo/driver/uuid"
)
const defaultLocalThreshold = 15 * time.Millisecond
const batchSize = 10000
// keyVaultCollOpts specifies options used to communicate with the key vault collection
var keyVaultCollOpts = options.Collection().SetReadConcern(readconcern.Majority()).
SetWriteConcern(writeconcern.New(writeconcern.WMajority()))
// Client is a handle representing a pool of connections to a MongoDB deployment. It is safe for concurrent use by
// multiple goroutines.
//
// The Client type opens and closes connections automatically and maintains a pool of idle connections. For
// connection pool configuration options, see documentation for the ClientOptions type in the mongo/options package.
type Client struct {
id uuid.UUID
topologyOptions []topology.Option
deployment driver.Deployment
connString connstring.ConnString
localThreshold time.Duration
retryWrites bool
retryReads bool
clock *session.ClusterClock
readPreference *readpref.ReadPref
readConcern *readconcern.ReadConcern
writeConcern *writeconcern.WriteConcern
registry *bsoncodec.Registry
marshaller BSONAppender
monitor *event.CommandMonitor
sessionPool *session.Pool
// client-side encryption fields
keyVaultClient *Client
keyVaultColl *Collection
mongocryptd *mcryptClient
crypt *driver.Crypt
}
// Connect creates a new Client and then initializes it using the Connect method. This is equivalent to calling
// NewClient followed by Client.Connect.
//
// When creating an options.ClientOptions, the order the methods are called matters. Later Set*
// methods will overwrite the values from previous Set* method invocations. This includes the
// ApplyURI method. This allows callers to determine the order of precedence for option
// application. For instance, if ApplyURI is called before SetAuth, the Credential from
// SetAuth will overwrite the values from the connection string. If ApplyURI is called
// after SetAuth, then its values will overwrite those from SetAuth.
//
// The opts parameter is processed using options.MergeClientOptions, which will overwrite entire
// option fields of previous options, there is no partial overwriting. For example, if Username is
// set in the Auth field for the first option, and Password is set for the second but with no
// Username, after the merge the Username field will be empty.
//
// The NewClient function does not do any I/O and returns an error if the given options are invalid.
// The Client.Connect method starts background goroutines to monitor the state of the deployment and does not do
// any I/O in the main goroutine to prevent the main goroutine from blocking. Therefore, it will not error if the
// deployment is down.
//
// The Client.Ping method can be used to verify that the deployment is successfully connected and the
// Client was correctly configured.
func Connect(ctx context.Context, opts ...*options.ClientOptions) (*Client, error) {
c, err := NewClient(opts...)
if err != nil {
return nil, err
}
err = c.Connect(ctx)
if err != nil {
return nil, err
}
return c, nil
}
// NewClient creates a new client to connect to a deployment specified by the uri.
//
// When creating an options.ClientOptions, the order the methods are called matters. Later Set*
// methods will overwrite the values from previous Set* method invocations. This includes the
// ApplyURI method. This allows callers to determine the order of precedence for option
// application. For instance, if ApplyURI is called before SetAuth, the Credential from
// SetAuth will overwrite the values from the connection string. If ApplyURI is called
// after SetAuth, then its values will overwrite those from SetAuth.
//
// The opts parameter is processed using options.MergeClientOptions, which will overwrite entire
// option fields of previous options, there is no partial overwriting. For example, if Username is
// set in the Auth field for the first option, and Password is set for the second but with no
// Username, after the merge the Username field will be empty.
func NewClient(opts ...*options.ClientOptions) (*Client, error) {
clientOpt := options.MergeClientOptions(opts...)
id, err := uuid.New()
if err != nil {
return nil, err
}
client := &Client{id: id}
err = client.configure(clientOpt)
if err != nil {
return nil, err
}
if client.deployment == nil {
client.deployment, err = topology.New(client.topologyOptions...)
if err != nil {
return nil, replaceErrors(err)
}
}
return client, nil
}
// Connect initializes the Client by starting background monitoring goroutines.
// If the Client was created using the NewClient function, this method must be called before a Client can be used.
//
// Connect starts background goroutines to monitor the state of the deployment and does not do any I/O in the main
// goroutine. The Client.Ping method can be used to verify that the connection was created successfully.
func (c *Client) Connect(ctx context.Context) error {
if connector, ok := c.deployment.(driver.Connector); ok {
err := connector.Connect()
if err != nil {
return replaceErrors(err)
}
}
if c.mongocryptd != nil {
if err := c.mongocryptd.connect(ctx); err != nil {
return err
}
}
if c.keyVaultClient != nil {
if err := c.keyVaultClient.Connect(ctx); err != nil {
return err
}
}
var updateChan <-chan description.Topology
if subscriber, ok := c.deployment.(driver.Subscriber); ok {
sub, err := subscriber.Subscribe()
if err != nil {
return replaceErrors(err)
}
updateChan = sub.Updates
}
c.sessionPool = session.NewPool(updateChan)
return nil
}
// Disconnect closes sockets to the topology referenced by this Client. It will
// shut down any monitoring goroutines, close the idle connection pool, and will
// wait until all the in use connections have been returned to the connection
// pool and closed before returning. If the context expires via cancellation,
// deadline, or timeout before the in use connections have returned, the in use
// connections will be closed, resulting in the failure of any in flight read
// or write operations. If this method returns with no errors, all connections
// associated with this Client have been closed.
func (c *Client) Disconnect(ctx context.Context) error {
if ctx == nil {
ctx = context.Background()
}
c.endSessions(ctx)
if c.mongocryptd != nil {
if err := c.mongocryptd.disconnect(ctx); err != nil {
return err
}
}
if c.keyVaultClient != nil {
if err := c.keyVaultClient.Disconnect(ctx); err != nil {
return err
}
}
if c.crypt != nil {
c.crypt.Close()
}
if disconnector, ok := c.deployment.(driver.Disconnector); ok {
return replaceErrors(disconnector.Disconnect(ctx))
}
return nil
}
// Ping sends a ping command to verify that the client can connect to the deployment.
//
// The rp paramter is used to determine which server is selected for the operation.
// If it is nil, the client's read preference is used.
//
// If the server is down, Ping will try to select a server until the client's server selection timeout expires.
// This can be configured through the ClientOptions.SetServerSelectionTimeout option when creating a new Client.
// After the timeout expires, a server selection error is returned.
//
// Using Ping reduces application resilience because applications starting up will error if the server is temporarily
// unavailable or is failing over (e.g. during autoscaling due to a load spike).
func (c *Client) Ping(ctx context.Context, rp *readpref.ReadPref) error {
if ctx == nil {
ctx = context.Background()
}
if rp == nil {
rp = c.readPreference
}
db := c.Database("admin")
res := db.RunCommand(ctx, bson.D{
{"ping", 1},
}, options.RunCmd().SetReadPreference(rp))
return replaceErrors(res.Err())
}
// StartSession starts a new session configured with the given options.
//
// If the DefaultReadConcern, DefaultWriteConcern, or DefaultReadPreference options are not set, the client's read
// concern, write concern, or read preference will be used, respectively.
func (c *Client) StartSession(opts ...*options.SessionOptions) (Session, error) {
if c.sessionPool == nil {
return nil, ErrClientDisconnected
}
sopts := options.MergeSessionOptions(opts...)
coreOpts := &session.ClientOptions{
DefaultReadConcern: c.readConcern,
DefaultReadPreference: c.readPreference,
DefaultWriteConcern: c.writeConcern,
}
if sopts.CausalConsistency != nil {
coreOpts.CausalConsistency = sopts.CausalConsistency
}
if sopts.DefaultReadConcern != nil {
coreOpts.DefaultReadConcern = sopts.DefaultReadConcern
}
if sopts.DefaultWriteConcern != nil {
coreOpts.DefaultWriteConcern = sopts.DefaultWriteConcern
}
if sopts.DefaultReadPreference != nil {
coreOpts.DefaultReadPreference = sopts.DefaultReadPreference
}
if sopts.DefaultMaxCommitTime != nil {
coreOpts.DefaultMaxCommitTime = sopts.DefaultMaxCommitTime
}
sess, err := session.NewClientSession(c.sessionPool, c.id, session.Explicit, coreOpts)
if err != nil {
return nil, replaceErrors(err)
}
sess.RetryWrite = c.retryWrites
sess.RetryRead = c.retryReads
return &sessionImpl{
clientSession: sess,
client: c,
deployment: c.deployment,
}, nil
}
func (c *Client) endSessions(ctx context.Context) {
if c.sessionPool == nil {
return
}
ids := c.sessionPool.IDSlice()
idx, idArray := bsoncore.AppendArrayStart(nil)
for i, id := range ids {
idDoc, _ := id.MarshalBSON()
idArray = bsoncore.AppendDocumentElement(idArray, strconv.Itoa(i), idDoc)
}
idArray, _ = bsoncore.AppendArrayEnd(idArray, idx)
op := operation.NewEndSessions(idArray).ClusterClock(c.clock).Deployment(c.deployment).
ServerSelector(description.ReadPrefSelector(readpref.PrimaryPreferred())).CommandMonitor(c.monitor).
Database("admin").Crypt(c.crypt)
idx, idArray = bsoncore.AppendArrayStart(nil)
totalNumIDs := len(ids)
for i := 0; i < totalNumIDs; i++ {
idDoc, _ := ids[i].MarshalBSON()
idArray = bsoncore.AppendDocumentElement(idArray, strconv.Itoa(i), idDoc)
if ((i+1)%batchSize) == 0 || i == totalNumIDs-1 {
idArray, _ = bsoncore.AppendArrayEnd(idArray, idx)
_ = op.SessionIDs(idArray).Execute(ctx)
idArray = idArray[:0]
idx = 0
}
}
}
func (c *Client) configure(opts *options.ClientOptions) error {
if err := opts.Validate(); err != nil {
return err
}
var connOpts []topology.ConnectionOption
var serverOpts []topology.ServerOption
var topologyOpts []topology.Option
// TODO(GODRIVER-814): Add tests for topology, server, and connection related options.
// AppName
var appName string
if opts.AppName != nil {
appName = *opts.AppName
}
// Compressors & ZlibLevel
var comps []string
if len(opts.Compressors) > 0 {
comps = opts.Compressors
connOpts = append(connOpts, topology.WithCompressors(
func(compressors []string) []string {
return append(compressors, comps...)
},
))
for _, comp := range comps {
switch comp {
case "zlib":
connOpts = append(connOpts, topology.WithZlibLevel(func(level *int) *int {
return opts.ZlibLevel
}))
case "zstd":
connOpts = append(connOpts, topology.WithZstdLevel(func(level *int) *int {
return opts.ZstdLevel
}))
}
}
serverOpts = append(serverOpts, topology.WithCompressionOptions(
func(opts ...string) []string { return append(opts, comps...) },
))
}
// Handshaker
var handshaker = func(driver.Handshaker) driver.Handshaker {
return operation.NewIsMaster().AppName(appName).Compressors(comps)
}
// Auth & Database & Password & Username
if opts.Auth != nil {
cred := &auth.Cred{
Username: opts.Auth.Username,
Password: opts.Auth.Password,
PasswordSet: opts.Auth.PasswordSet,
Props: opts.Auth.AuthMechanismProperties,
Source: opts.Auth.AuthSource,
}
mechanism := opts.Auth.AuthMechanism
if len(cred.Source) == 0 {
switch strings.ToUpper(mechanism) {
case auth.MongoDBX509, auth.GSSAPI, auth.PLAIN:
cred.Source = "$external"
default:
cred.Source = "admin"
}
}
authenticator, err := auth.CreateAuthenticator(mechanism, cred)
if err != nil {
return err
}
handshakeOpts := &auth.HandshakeOptions{
AppName: appName,
Authenticator: authenticator,
Compressors: comps,
}
if mechanism == "" {
// Required for SASL mechanism negotiation during handshake
handshakeOpts.DBUser = cred.Source + "." + cred.Username
}
if opts.AuthenticateToAnything != nil && *opts.AuthenticateToAnything {
// Authenticate arbiters
handshakeOpts.PerformAuthentication = func(serv description.Server) bool {
return true
}
}
handshaker = func(driver.Handshaker) driver.Handshaker {
return auth.Handshaker(nil, handshakeOpts)
}
}
connOpts = append(connOpts, topology.WithHandshaker(handshaker))
// ConnectTimeout
if opts.ConnectTimeout != nil {
serverOpts = append(serverOpts, topology.WithHeartbeatTimeout(
func(time.Duration) time.Duration { return *opts.ConnectTimeout },
))
connOpts = append(connOpts, topology.WithConnectTimeout(
func(time.Duration) time.Duration { return *opts.ConnectTimeout },
))
}
// Dialer
if opts.Dialer != nil {
connOpts = append(connOpts, topology.WithDialer(
func(topology.Dialer) topology.Dialer { return opts.Dialer },
))
}
// Direct
if opts.Direct != nil && *opts.Direct {
topologyOpts = append(topologyOpts, topology.WithMode(
func(topology.MonitorMode) topology.MonitorMode { return topology.SingleMode },
))
}
// HeartbeatInterval
if opts.HeartbeatInterval != nil {
serverOpts = append(serverOpts, topology.WithHeartbeatInterval(
func(time.Duration) time.Duration { return *opts.HeartbeatInterval },
))
}
// Hosts
hosts := []string{"localhost:27017"} // default host
if len(opts.Hosts) > 0 {
hosts = opts.Hosts
}
topologyOpts = append(topologyOpts, topology.WithSeedList(
func(...string) []string { return hosts },
))
// LocalThreshold
c.localThreshold = defaultLocalThreshold
if opts.LocalThreshold != nil {
c.localThreshold = *opts.LocalThreshold
}
// MaxConIdleTime
if opts.MaxConnIdleTime != nil {
connOpts = append(connOpts, topology.WithIdleTimeout(
func(time.Duration) time.Duration { return *opts.MaxConnIdleTime },
))
}
// MaxPoolSize
if opts.MaxPoolSize != nil {
serverOpts = append(
serverOpts,
topology.WithMaxConnections(func(uint64) uint64 { return *opts.MaxPoolSize }),
)
}
// MinPoolSize
if opts.MinPoolSize != nil {
serverOpts = append(
serverOpts,
topology.WithMinConnections(func(uint64) uint64 { return *opts.MinPoolSize }),
)
}
// PoolMonitor
if opts.PoolMonitor != nil {
serverOpts = append(
serverOpts,
topology.WithConnectionPoolMonitor(func(*event.PoolMonitor) *event.PoolMonitor { return opts.PoolMonitor }),
)
}
// Monitor
if opts.Monitor != nil {
c.monitor = opts.Monitor
connOpts = append(connOpts, topology.WithMonitor(
func(*event.CommandMonitor) *event.CommandMonitor { return opts.Monitor },
))
}
// ReadConcern
c.readConcern = readconcern.New()
if opts.ReadConcern != nil {
c.readConcern = opts.ReadConcern
}
// ReadPreference
c.readPreference = readpref.Primary()
if opts.ReadPreference != nil {
c.readPreference = opts.ReadPreference
}
// Registry
c.registry = bson.DefaultRegistry
if opts.Registry != nil {
c.registry = opts.Registry
}
// ReplicaSet
if opts.ReplicaSet != nil {
topologyOpts = append(topologyOpts, topology.WithReplicaSetName(
func(string) string { return *opts.ReplicaSet },
))
}
// RetryWrites
c.retryWrites = true // retry writes on by default
if opts.RetryWrites != nil {
c.retryWrites = *opts.RetryWrites
}
c.retryReads = true
if opts.RetryReads != nil {
c.retryReads = *opts.RetryReads
}
// ServerSelectionTimeout
if opts.ServerSelectionTimeout != nil {
topologyOpts = append(topologyOpts, topology.WithServerSelectionTimeout(
func(time.Duration) time.Duration { return *opts.ServerSelectionTimeout },
))
}
// SocketTimeout
if opts.SocketTimeout != nil {
connOpts = append(
connOpts,
topology.WithReadTimeout(func(time.Duration) time.Duration { return *opts.SocketTimeout }),
topology.WithWriteTimeout(func(time.Duration) time.Duration { return *opts.SocketTimeout }),
)
}
// TLSConfig
if opts.TLSConfig != nil {
connOpts = append(connOpts, topology.WithTLSConfig(
func(*tls.Config) *tls.Config {
return opts.TLSConfig
},
))
}
// WriteConcern
if opts.WriteConcern != nil {
c.writeConcern = opts.WriteConcern
}
// AutoEncryptionOptions
if opts.AutoEncryptionOptions != nil {
if err := c.configureAutoEncryption(opts.AutoEncryptionOptions); err != nil {
return err
}
}
// ClusterClock
c.clock = new(session.ClusterClock)
serverOpts = append(
serverOpts,
topology.WithClock(func(*session.ClusterClock) *session.ClusterClock { return c.clock }),
topology.WithConnectionOptions(func(...topology.ConnectionOption) []topology.ConnectionOption { return connOpts }),
)
c.topologyOptions = append(topologyOpts, topology.WithServerOptions(
func(...topology.ServerOption) []topology.ServerOption { return serverOpts },
))
// Deployment
if opts.Deployment != nil {
if len(serverOpts) > 2 || len(topologyOpts) > 1 {
return errors.New("cannot specify topology or server options with a deployment")
}
c.deployment = opts.Deployment
}
return nil
}
func (c *Client) configureAutoEncryption(opts *options.AutoEncryptionOptions) error {
if err := c.configureKeyVault(opts); err != nil {
return err
}
if err := c.configureMongocryptd(opts); err != nil {
return err
}
return c.configureCrypt(opts)
}
func (c *Client) configureKeyVault(opts *options.AutoEncryptionOptions) error {
// parse key vault options and create new client if necessary
if opts.KeyVaultClientOptions != nil {
var err error
c.keyVaultClient, err = NewClient(opts.KeyVaultClientOptions)
if err != nil {
return err
}
}
dbName, collName := splitNamespace(opts.KeyVaultNamespace)
client := c.keyVaultClient
if client == nil {
client = c
}
c.keyVaultColl = client.Database(dbName).Collection(collName, keyVaultCollOpts)
return nil
}
func (c *Client) configureMongocryptd(opts *options.AutoEncryptionOptions) error {
var err error
c.mongocryptd, err = newMcryptClient(opts.ExtraOptions)
return err
}
func (c *Client) configureCrypt(opts *options.AutoEncryptionOptions) error {
// convert schemas in SchemaMap to bsoncore documents
cryptSchemaMap := make(map[string]bsoncore.Document)
for k, v := range opts.SchemaMap {
schema, err := transformBsoncoreDocument(c.registry, v)
if err != nil {
return err
}
cryptSchemaMap[k] = schema
}
// configure options
var bypass bool
if opts.BypassAutoEncryption != nil {
bypass = *opts.BypassAutoEncryption
}
kr := keyRetriever{coll: c.keyVaultColl}
cir := collInfoRetriever{client: c}
cryptOpts := &driver.CryptOptions{
CollInfoFn: cir.cryptCollInfo,
KeyFn: kr.cryptKeys,
MarkFn: c.mongocryptd.markCommand,
KmsProviders: opts.KmsProviders,
BypassAutoEncryption: bypass,
SchemaMap: cryptSchemaMap,
}
var err error
c.crypt, err = driver.NewCrypt(cryptOpts)
return err
}
// validSession returns an error if the session doesn't belong to the client
func (c *Client) validSession(sess *session.Client) error {
if sess != nil && !uuid.Equal(sess.ClientID, c.id) {
return ErrWrongClient
}
return nil
}
// Database returns a handle for a database with the given name configured with the given DatabaseOptions.
func (c *Client) Database(name string, opts ...*options.DatabaseOptions) *Database {
return newDatabase(c, name, opts...)
}
// ListDatabases executes a listDatabases command and returns the result.
//
// The filter parameter must be a document containing query operators and can be used to select which
// databases are included in the result. It cannot be nil. An empty document (e.g. bson.D{}) should be used to include
// all databases.
//
// The opts paramter can be used to specify options for this operation (see the options.ListDatabasesOptions documentation).
//
// For more information about the command, see https://docs.mongodb.com/manual/reference/command/listDatabases/.
func (c *Client) ListDatabases(ctx context.Context, filter interface{}, opts ...*options.ListDatabasesOptions) (ListDatabasesResult, error) {
if ctx == nil {
ctx = context.Background()
}
sess := sessionFromContext(ctx)
err := c.validSession(sess)
if sess == nil && c.sessionPool != nil {
sess, err = session.NewClientSession(c.sessionPool, c.id, session.Implicit)
if err != nil {
return ListDatabasesResult{}, err
}
defer sess.EndSession()
}
err = c.validSession(sess)
if err != nil {
return ListDatabasesResult{}, err
}
filterDoc, err := transformBsoncoreDocument(c.registry, filter)
if err != nil {
return ListDatabasesResult{}, err
}
selector := description.CompositeSelector([]description.ServerSelector{
description.ReadPrefSelector(readpref.Primary()),
description.LatencySelector(c.localThreshold),
})
selector = makeReadPrefSelector(sess, selector, c.localThreshold)
ldo := options.MergeListDatabasesOptions(opts...)
op := operation.NewListDatabases(filterDoc).
Session(sess).ReadPreference(c.readPreference).CommandMonitor(c.monitor).
ServerSelector(selector).ClusterClock(c.clock).Database("admin").Deployment(c.deployment).Crypt(c.crypt)
if ldo.NameOnly != nil {
op = op.NameOnly(*ldo.NameOnly)
}
retry := driver.RetryNone
if c.retryReads {
retry = driver.RetryOncePerCommand
}
op.Retry(retry)
err = op.Execute(ctx)
if err != nil {
return ListDatabasesResult{}, replaceErrors(err)
}
return newListDatabasesResultFromOperation(op.Result()), nil
}
// ListDatabaseNames executes a listDatabases command and returns a slice containing the names of all of the databases
// on the server.
//
// The filter parameter must be a document containing query operators and can be used to select which databases
// are included in the result. It cannot be nil. An empty document (e.g. bson.D{}) should be used to include all
// databases.
//
// The opts parameter can be used to specify options for this operation (see the options.ListDatabasesOptions
// documentation.)
//
// For more information about the command, see https://docs.mongodb.com/manual/reference/command/listDatabases/.
func (c *Client) ListDatabaseNames(ctx context.Context, filter interface{}, opts ...*options.ListDatabasesOptions) ([]string, error) {
opts = append(opts, options.ListDatabases().SetNameOnly(true))
res, err := c.ListDatabases(ctx, filter, opts...)
if err != nil {
return nil, err
}
names := make([]string, 0)
for _, spec := range res.Databases {
names = append(names, spec.Name)
}
return names, nil
}
// WithSession creates a new SessionContext from the ctx and sess parameters and uses it to call the fn callback. The
// SessionContext must be used as the Context parameter for any operations in the fn callback that should be executed
// under the session.
//
// If the ctx parameter already contains a Session, that Session will be replaced with the one provided.
//
// Any error returned by the fn callback will be returned without any modifications.
func WithSession(ctx context.Context, sess Session, fn func(SessionContext) error) error {
return fn(contextWithSession(ctx, sess))
}
// UseSession creates a new Session and uses it to create a new SessionContext, which is used to call the fn callback.
// The SessionContext parameter must be used as the Context parameter for any operations in the fn callback that should
// be executed under a session. After the callback returns, the created Session is ended, meaning that any in-progress
// transactions started by fn will be aborted even if fn returns an error.
//
// If the ctx parameter already contains a Session, that Session will be replaced with the newly created one.
//
// Any error returned by the fn callback will be returned without any modifications.
func (c *Client) UseSession(ctx context.Context, fn func(SessionContext) error) error {
return c.UseSessionWithOptions(ctx, options.Session(), fn)
}
// UseSessionWithOptions operates like UseSession but uses the given SessionOptions to create the Session.
func (c *Client) UseSessionWithOptions(ctx context.Context, opts *options.SessionOptions, fn func(SessionContext) error) error {
defaultSess, err := c.StartSession(opts)
if err != nil {
return err
}
defer defaultSess.EndSession(ctx)
sessCtx := sessionContext{
Context: context.WithValue(ctx, sessionKey{}, defaultSess),
Session: defaultSess,
}
return fn(sessCtx)
}
// Watch returns a change stream for all changes on the deployment. See
// https://docs.mongodb.com/manual/changeStreams/ for more information about change streams.
//
// The client must be configured with read concern majority or no read concern for a change stream to be created
// successfully.
//
// The pipeline parameter must be an array of documents, each representing a pipeline stage. The pipeline cannot be
// nil or empty. The stage documents must all be non-nil. See https://docs.mongodb.com/manual/changeStreams/ for a list
// of pipeline stages that can be used with change streams. For a pipeline of bson.D documents, the mongo.Pipeline{}
// type can be used.
//
// The opts parameter can be used to specify options for change stream creation (see the options.ChangeStreamOptions
// documentation).
func (c *Client) Watch(ctx context.Context, pipeline interface{},
opts ...*options.ChangeStreamOptions) (*ChangeStream, error) {
if c.sessionPool == nil {
return nil, ErrClientDisconnected
}
csConfig := changeStreamConfig{
readConcern: c.readConcern,
readPreference: c.readPreference,
client: c,
registry: c.registry,
streamType: ClientStream,
}
return newChangeStream(ctx, csConfig, pipeline, opts...)
}
// NumberSessionsInProgress returns the number of sessions that have been started for this client but have not been
// closed (i.e. EndSession has not been called).
func (c *Client) NumberSessionsInProgress() int {
return c.sessionPool.CheckedOut()
}