connectionPoolSettings = ConnectionPoolSettings.builder()
                            .minSize(getMinConnectionsPerHost())
                            .maxSize(getConnectionsPerHost())
                            .maxWaitQueueSize(getThreadsAllowedToBlockForConnectionMultiplier()
                                     * getConnectionsPerHost())
                            .maxWaitTime(getMaxWaitTime(), MILLISECONDS)
                            .maxConnectionIdleTime(getMaxConnectionIdleTime(), MILLISECONDS)
                            .maxConnectionLifeTime(getMaxConnectionLifeTime(), MILLISECONDS)
                            .build();

  public static class Builder {
    private String description;
    private String applicationName;
    //讀取偏好, 這里默認(rèn)的是從主節(jié)點(diǎn)讀取.
    private ReadPreference readPreference = ReadPreference.primary();
    //使用服務(wù)器默認(rèn)的寫(xiě)關(guān)注?
    private WriteConcern writeConcern = WriteConcern.ACKNOWLEDGED;
    //使用服務(wù)的默認(rèn)讀關(guān)注,默認(rèn)是local
    private ReadConcern readConcern = ReadConcern.DEFAULT;
    private CodecRegistry codecRegistry = MongoClient.getDefaultCodecRegistry();
    private final List<CommandListener> commandListeners = new ArrayList<CommandListener>();
    private final List<ClusterListener> clusterListeners = new ArrayList<ClusterListener>();
    private final List<ServerListener> serverListeners = new ArrayList<ServerListener>();
    private final List<ServerMonitorListener> serverMonitorListeners = new ArrayList<ServerMonitorListener>();

    private int minConnectionsPerHost;
    private int maxConnectionsPerHost = 100;
    private int threadsAllowedToBlockForConnectionMultiplier = 5;
    //設(shè)置服務(wù)器選擇超時(shí)（以毫秒為單位），它定義驅(qū)動(dòng)程序在拋出異常之前等待服務(wù)器選擇成功的時(shí)間
    //值為0表示如果沒(méi)有可用的服務(wù)器，它將立即超時(shí)。 負(fù)值意味著無(wú)限期等待
    private int serverSelectionTimeout = 1000 * 30;
    //線程等待連接變?yōu)榭捎玫淖铋L(zhǎng)時(shí)間
    private int maxWaitTime = 1000 * 60 * 2;
    // 線程池中連接的最大空閑時(shí)間
    private int maxConnectionIdleTime;
    private int maxConnectionLifeTime;
    //連接超時(shí)時(shí)間,必須大于0
    private int connectTimeout = 1000 * 10;
    //socket超時(shí)時(shí)間
    private int socketTimeout = 0;
    //socket是否保活
    private boolean socketKeepAlive = false;
    private boolean sslEnabled = false;
    private boolean sslInvalidHostNameAllowed = false;
    private boolean alwaysUseMBeans = false;
    //設(shè)置心跳頻率。 這是驅(qū)動(dòng)程序?qū)L試確定群集中每個(gè)服務(wù)器的當(dāng)前狀態(tài)的頻率。 默認(rèn)值為10,000毫秒
    private int heartbeatFrequency = 10000;
    //設(shè)置最小心跳頻率。 如果驅(qū)動(dòng)程序必須經(jīng)常重新檢查服務(wù)器的可用性，它將至少在上一次檢查后等待很長(zhǎng)時(shí)間，以避免浪費(fèi)精力。 默認(rèn)值為500毫秒。
    private int minHeartbeatFrequency = 500;
    //設(shè)置用于集群心跳的連接的連接超時(shí)
    private int heartbeatConnectTimeout = 20000;
    //設(shè)置用于集群心跳的連接的套接字超時(shí)
    private int heartbeatSocketTimeout = 20000;
    //本地閾值
    private int localThreshold = 15;

    private String requiredReplicaSetName;
    private DBDecoderFactory dbDecoderFactory = DefaultDBDecoder.FACTORY;
    private DBEncoderFactory dbEncoderFactory = DefaultDBEncoder.FACTORY;
    private SocketFactory socketFactory;
    private boolean cursorFinalizerEnabled = true;
...}

//讀取偏好, 首先從從節(jié)點(diǎn)讀取.
private ReadPreference readPreference = ReadPreference.secondaryPreferred();
//寫(xiě)關(guān)注為1 ,寫(xiě)入主節(jié)點(diǎn)即返回.
private WriteConcern writeConcern = WriteConcern.W1;
//使用服務(wù)的默認(rèn)讀關(guān)注,默認(rèn)是local(決定到某個(gè)讀取數(shù)據(jù)時(shí)，能讀到什么樣的數(shù)據(jù))
private ReadConcern readConcern = ReadConcern.LOCAL;

//線程池空閑時(shí)保持的最小連接數(shù)

minConnectionsPerHost=20

//線程池允許的最大連接數(shù)

connectionsPerHost=100

//connectionsPerHost* 5 =最大隊(duì)列數(shù)

threadsAllowedToBlockForConnectionMultiplier=5

//線程池中連接的最大空閑時(shí)間,5分鐘

maxConnectionIdleTime = 5*60*1000

 // 線程池中連接的最長(zhǎng)生存時(shí)間,采用默認(rèn)值

maxConnectionLifeTime

//設(shè)置服務(wù)器選擇超時(shí)（以毫秒為單位），它定義驅(qū)動(dòng)程序在拋出異常之前等待服務(wù)器選擇成功的時(shí)間
//值為0表示如果沒(méi)有可用的服務(wù)器，它將立即超時(shí)。 負(fù)值意味著無(wú)限期等待
private int serverSelectionTimeout = 1000 * 30;

//連接超時(shí)時(shí)間,必須大于0
private int connectTimeout = 1000 * 5;

//線程等待連接變?yōu)榭捎玫淖铋L(zhǎng)時(shí)間.

maxWaitTime=6000