import com.allanbank.mongodb.bson.Document; //导入方法依赖的package包/类

/**

* Extract the number of seconds this Server is behind the primary by

* comparing its latest optime with that of the absolute latest optime.

*

* To account for idle servers we use the optime for each server and assign

* a value of zero to the "latest" optime and then subtract the remaining

* servers from that optime.

*

*

* Lastly, the state of the server is also checked and the seconds behind is

* set to {@link Double#MAX_VALUE} if not in the primary (

* {@value #PRIMARY_STATE}) or secondary ({@value #SECONDARY_STATE}).

*

*

* @param replicaStateDoc

* The document to extract the seconds behind from.

*/

private void updateSecondsBehind(final Document replicaStateDoc) {

final State oldValue = myState;

final NumericElement state = replicaStateDoc.get(NUMERIC_TYPE,

"myState");

if (state != null) {

final int value = state.getIntValue();

if (value == PRIMARY_STATE) {

myState = State.WRITABLE;

mySecondsBehind = 0;

}

else if (value == SECONDARY_STATE) {

myState = State.READ_ONLY;

TimestampElement serverTimestamp = null;

final StringElement expectedName = new StringElement("name",

myCanonicalName);

for (final DocumentElement member : replicaStateDoc.find(

DOCUMENT_TYPE, "members", ".*")) {

if (expectedName.equals(member.get("name"))

&& (member.get(TIMESTAMP_TYPE, "optimeDate") != null)) {

serverTimestamp = member.get(TIMESTAMP_TYPE,

"optimeDate");

}

}

if (serverTimestamp != null) {

TimestampElement latestTimestamp = serverTimestamp;

for (final TimestampElement time : replicaStateDoc.find(

TIMESTAMP_TYPE, "members", ".*", "optimeDate")) {

if (latestTimestamp.getTime() < time.getTime()) {

latestTimestamp = time;

}

}

final double msBehind = latestTimestamp.getTime()

- serverTimestamp.getTime();

mySecondsBehind = (msBehind / TimeUnit.SECONDS.toMillis(1));

}

}

else {

// "myState" != 1 and "myState" != 2

mySecondsBehind = Double.MAX_VALUE;

myState = State.UNAVAILABLE;

}

}

myEventSupport.firePropertyChange(STATE_PROP, oldValue, myState);

}