event

Documentation

Overview

Package event is a library for monitoring events from the MongoDB Go driver. Monitors can be set for commands sent to the MongoDB cluster, connection pool changes, or changes on the MongoDB cluster.

Monitoring commands requires specifying a CommandMonitor when constructing a mongo.Client. A CommandMonitor can be set to monitor started, succeeded, and/or failed events. A CommandStartedEvent can be correlated to its matching CommandSucceededEvent or CommandFailedEvent through the RequestID field. For example, the following code collects the names of started events:

var commandStarted []string
cmdMonitor := &event.CommandMonitor{
  Started: func(_ context.Context, evt *event.CommandStartedEvent) {
    commandStarted = append(commandStarted, evt.CommandName)
  },
}
clientOpts := options.Client().ApplyURI("mongodb://localhost:27017").SetMonitor(cmdMonitor)
client, err := mongo.Connect(context.Background(), clientOpts)

Monitoring the connection pool requires specifying a PoolMonitor when constructing a mongo.Client. The following code tracks the number of checked out connections:

var int connsCheckedOut
poolMonitor := &event.PoolMonitor{
  Event: func(evt *event.PoolEvent) {
    switch evt.Type {
    case event.GetSucceeded:
      connsCheckedOut++
    case event.ConnectionReturned:
      connsCheckedOut--
    }
  },
}
clientOpts := options.Client().ApplyURI("mongodb://localhost:27017").SetPoolMonitor(poolMonitor)
client, err := mongo.Connect(context.Background(), clientOpts)

Monitoring server changes specifying a ServerMonitor object when constructing a mongo.Client. Different functions can be set on the ServerMonitor to monitor different kinds of events. See ServerMonitor for more details. The following code appends ServerHeartbeatStartedEvents to a slice:

   var heartbeatStarted []*event.ServerHeartbeatStartedEvent
   svrMonitor := &event.ServerMonitor{
     ServerHeartbeatStarted: func(e *event.ServerHeartbeatStartedEvent) {
	      heartbeatStarted = append(heartbeatStarted, e)
     }
   }
   clientOpts := options.Client().ApplyURI("mongodb://localhost:27017").SetServerMonitor(svrMonitor)
   client, err := mongo.Connect(context.Background(), clientOpts)

Index

• Constants
• type CommandFailedEvent
• type CommandFinishedEvent
• type CommandMonitor
• type CommandStartedEvent
• type CommandSucceededEvent
• type MonitorPoolOptions
• type PoolEvent
• type PoolMonitor
• type ServerClosedEvent
• type ServerDescriptionChangedEvent
• type ServerHeartbeatFailedEvent
• type ServerHeartbeatStartedEvent
• type ServerHeartbeatSucceededEvent
• type ServerMonitor
• type ServerOpeningEvent
• type TopologyClosedEvent
• type TopologyDescriptionChangedEvent
• type TopologyOpeningEvent

Examples

• CommandMonitor

Constants

const (
	ReasonIdle              = "idle"
	ReasonPoolClosed        = "poolClosed"
	ReasonStale             = "stale"
	ReasonConnectionErrored = "connectionError"
	ReasonTimedOut          = "timeout"
	ReasonError             = "error"
)

strings for pool command monitoring reasons

const (
	PoolCreated        = "ConnectionPoolCreated"
	PoolReady          = "ConnectionPoolReady"
	PoolCleared        = "ConnectionPoolCleared"
	PoolClosedEvent    = "ConnectionPoolClosed"
	ConnectionCreated  = "ConnectionCreated"
	ConnectionReady    = "ConnectionReady"
	ConnectionClosed   = "ConnectionClosed"
	GetStarted         = "ConnectionCheckOutStarted"
	GetFailed          = "ConnectionCheckOutFailed"
	GetSucceeded       = "ConnectionCheckedOut"
	ConnectionReturned = "ConnectionCheckedIn"
)

strings for pool command monitoring types

Types

type CommandFailedEvent

type CommandFailedEvent struct {
	CommandFinishedEvent
	Failure string
}

CommandFailedEvent represents an event generated when a command's execution fails.

type CommandFinishedEvent

type CommandFinishedEvent struct {
	DurationNanos int64
	CommandName   string
	RequestID     int64
	ConnectionID  string
	// ServerConnectionID contains the connection ID from the server of the operation. If the server does not return
	// this value (e.g. on MDB < 4.2), it is unset.
	ServerConnectionID *int32
	// ServiceID contains the ID of the server to which the command was sent if it is running behind a load balancer.
	// Otherwise, it is unset.
	ServiceID *primitive.ObjectID
}

CommandFinishedEvent represents a generic command finishing.

type CommandMonitor

type CommandMonitor struct {
	Started   func(context.Context, *CommandStartedEvent)
	Succeeded func(context.Context, *CommandSucceededEvent)
	Failed    func(context.Context, *CommandFailedEvent)
}

CommandMonitor represents a monitor that is triggered for different events.

Example

CommandMonitor represents a monitor that is triggered for different events.

package main

import (
	"context"
	"log"

	"go.mongodb.org/mongo-driver/bson"
	"go.mongodb.org/mongo-driver/event"
	"go.mongodb.org/mongo-driver/mongo"
	"go.mongodb.org/mongo-driver/mongo/options"
)

func main() {
	// If the application makes multiple concurrent requests, it would have to
	// use a concurrent map like sync.Map
	startedCommands := make(map[int64]bson.Raw)
	cmdMonitor := &event.CommandMonitor{
		Started: func(_ context.Context, evt *event.CommandStartedEvent) {
			startedCommands[evt.RequestID] = evt.Command
		},
		Succeeded: func(_ context.Context, evt *event.CommandSucceededEvent) {
			log.Printf("Command: %v Reply: %v\n",
				startedCommands[evt.RequestID],
				evt.Reply,
			)
		},
		Failed: func(_ context.Context, evt *event.CommandFailedEvent) {
			log.Printf("Command: %v Failure: %v\n",
				startedCommands[evt.RequestID],
				evt.Failure,
			)
		},
	}
	clientOpts := options.Client().ApplyURI("mongodb://localhost:27017").SetMonitor(cmdMonitor)
	client, err := mongo.Connect(context.Background(), clientOpts)
	if err != nil {
		log.Fatal(err)
	}
	defer func() {
		if err = client.Disconnect(context.TODO()); err != nil {
			log.Fatal(err)
		}
	}()
}

type CommandStartedEvent

type CommandStartedEvent struct {
	Command      bson.Raw
	DatabaseName string
	CommandName  string
	RequestID    int64
	ConnectionID string
	// ServerConnectionID contains the connection ID from the server of the operation. If the server does not return
	// this value (e.g. on MDB < 4.2), it is unset.
	ServerConnectionID *int32
	// ServiceID contains the ID of the server to which the command was sent if it is running behind a load balancer.
	// Otherwise, it is unset.
	ServiceID *primitive.ObjectID
}

CommandStartedEvent represents an event generated when a command is sent to a server.

type CommandSucceededEvent

type CommandSucceededEvent struct {
	CommandFinishedEvent
	Reply bson.Raw
}

CommandSucceededEvent represents an event generated when a command's execution succeeds.

type MonitorPoolOptions

type MonitorPoolOptions struct {
	MaxPoolSize        uint64 `json:"maxPoolSize"`
	MinPoolSize        uint64 `json:"minPoolSize"`
	WaitQueueTimeoutMS uint64 `json:"maxIdleTimeMS"`
}

MonitorPoolOptions contains pool options as formatted in pool events

type PoolEvent

type PoolEvent struct {
	Type         string              `json:"type"`
	Address      string              `json:"address"`
	ConnectionID uint64              `json:"connectionId"`
	PoolOptions  *MonitorPoolOptions `json:"options"`
	Reason       string              `json:"reason"`
	// ServiceID is only set if the Type is PoolCleared and the server is deployed behind a load balancer. This field
	// can be used to distinguish between individual servers in a load balanced deployment.
	ServiceID *primitive.ObjectID `json:"serviceId"`
}

PoolEvent contains all information summarizing a pool event

type PoolMonitor

type PoolMonitor struct {
	Event func(*PoolEvent)
}

PoolMonitor is a function that allows the user to gain access to events occurring in the pool

type ServerClosedEvent

type ServerClosedEvent struct {
	Address    address.Address
	TopologyID primitive.ObjectID // A unique identifier for the topology this server is a part of
}

ServerClosedEvent is an event generated when the server is closed.

type ServerDescriptionChangedEvent

type ServerDescriptionChangedEvent struct {
	Address             address.Address
	TopologyID          primitive.ObjectID // A unique identifier for the topology this server is a part of
	PreviousDescription description.Server
	NewDescription      description.Server
}

ServerDescriptionChangedEvent represents a server description change.

type ServerHeartbeatFailedEvent

type ServerHeartbeatFailedEvent struct {
	DurationNanos int64
	Failure       error
	ConnectionID  string // The address this heartbeat was sent to with a unique identifier
	Awaited       bool   // If this heartbeat was awaitable
}

ServerHeartbeatFailedEvent is an event generated when the heartbeat fails.

type ServerHeartbeatStartedEvent

type ServerHeartbeatStartedEvent struct {
	ConnectionID string // The address this heartbeat was sent to with a unique identifier
	Awaited      bool   // If this heartbeat was awaitable
}

ServerHeartbeatStartedEvent is an event generated when the heartbeat is started.

type ServerHeartbeatSucceededEvent

type ServerHeartbeatSucceededEvent struct {
	DurationNanos int64
	Reply         description.Server
	ConnectionID  string // The address this heartbeat was sent to with a unique identifier
	Awaited       bool   // If this heartbeat was awaitable
}

ServerHeartbeatSucceededEvent is an event generated when the heartbeat succeeds.

type ServerMonitor

type ServerMonitor struct {
	ServerDescriptionChanged func(*ServerDescriptionChangedEvent)
	ServerOpening            func(*ServerOpeningEvent)
	ServerClosed             func(*ServerClosedEvent)
	// TopologyDescriptionChanged is called when the topology is locked, so the callback should
	// not attempt any operation that requires server selection on the same client.
	TopologyDescriptionChanged func(*TopologyDescriptionChangedEvent)
	TopologyOpening            func(*TopologyOpeningEvent)
	TopologyClosed             func(*TopologyClosedEvent)
	ServerHeartbeatStarted     func(*ServerHeartbeatStartedEvent)
	ServerHeartbeatSucceeded   func(*ServerHeartbeatSucceededEvent)
	ServerHeartbeatFailed      func(*ServerHeartbeatFailedEvent)
}

ServerMonitor represents a monitor that is triggered for different server events. The client will monitor changes on the MongoDB deployment it is connected to, and this monitor reports the changes in the client's representation of the deployment. The topology represents the overall deployment, and heartbeats are sent to individual servers to check their current status.

type ServerOpeningEvent

type ServerOpeningEvent struct {
	Address    address.Address
	TopologyID primitive.ObjectID // A unique identifier for the topology this server is a part of
}

ServerOpeningEvent is an event generated when the server is initialized.

type TopologyClosedEvent

type TopologyClosedEvent struct {
	TopologyID primitive.ObjectID // A unique identifier for the topology this server is a part of
}

TopologyClosedEvent is an event generated when the topology is closed.

type TopologyDescriptionChangedEvent

type TopologyDescriptionChangedEvent struct {
	TopologyID          primitive.ObjectID // A unique identifier for the topology this server is a part of
	PreviousDescription description.Topology
	NewDescription      description.Topology
}

TopologyDescriptionChangedEvent represents a topology description change.

type TopologyOpeningEvent

type TopologyOpeningEvent struct {
	TopologyID primitive.ObjectID // A unique identifier for the topology this server is a part of
}

TopologyOpeningEvent is an event generated when the topology is initialized.