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Prioritize electionId over setVersion on 6.0+ servers #1010

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Merged
jyemin merged 10 commits into from
Oct 13, 2022
Merged

Prioritize electionId over setVersion on 6.0+ servers #1010

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195b2c7
Prioritize electionId over setVersion on 6.0+ servers
jyemin Oct 5, 2022
bb49d9b
Use local variables consistently
jyemin Oct 6, 2022
fe19a91
Fix over-logging bug and hopefully clarify the code too
jyemin Oct 12, 2022
d7934f7
Simplify the logging
jyemin Oct 13, 2022
e801065
Simplify the code
jyemin Oct 13, 2022
396d539
Revert to original method name isStalePrimary
jyemin Oct 13, 2022
80a91c1
A bit more
jyemin Oct 13, 2022
412238c
Add clarifying parens
jyemin Oct 13, 2022
c84470b
Use local variables
jyemin Oct 13, 2022
88d0aec
Revise conditional statements
jyemin Oct 13, 2022
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84 changes: 46 additions & 38 deletions driver-core/src/main/com/mongodb/internal/connection/AbstractMultiServerCluster.java
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Original file line number Diff line number Diff line change
Expand Up @@ -45,6 +45,7 @@
import static com.mongodb.connection.ServerType.REPLICA_SET_GHOST;
import static com.mongodb.connection.ServerType.SHARD_ROUTER;
import static com.mongodb.connection.ServerType.STANDALONE;
import static com.mongodb.internal.operation.ServerVersionHelper.SIX_DOT_ZERO_WIRE_VERSION;
import static java.lang.String.format;

public abstract class AbstractMultiServerCluster extends BaseCluster {
Expand Down Expand Up @@ -224,9 +225,7 @@ private boolean handleReplicaSetMemberChanged(final ServerDescription newDescrip
}

if (newDescription.getType() == REPLICA_SET_GHOST) {
if (LOGGER.isInfoEnabled()) {
LOGGER.info(format("Server %s does not appear to be a member of an initiated replica set.", newDescription.getAddress()));
}
LOGGER.info(format("Server %s does not appear to be a member of an initiated replica set.", newDescription.getAddress()));
return true;
}

Expand All @@ -247,46 +246,43 @@ private boolean handleReplicaSetMemberChanged(final ServerDescription newDescrip
if (newDescription.getCanonicalAddress() != null
&& !newDescription.getAddress().equals(new ServerAddress(newDescription.getCanonicalAddress()))
&& !newDescription.isPrimary()) {
if (LOGGER.isInfoEnabled()) {
LOGGER.info(format("Canonical address %s does not match server address. Removing %s from client view of cluster",
newDescription.getCanonicalAddress(), newDescription.getAddress()));
}
LOGGER.info(format("Canonical address %s does not match server address. Removing %s from client view of cluster",
newDescription.getCanonicalAddress(), newDescription.getAddress()));
removeServer(newDescription.getAddress());
return true;
}

if (newDescription.isPrimary()) {
ObjectId electionId = newDescription.getElectionId();
Integer setVersion = newDescription.getSetVersion();
if (setVersion != null && electionId != null) {
if (isStalePrimary(newDescription)) {
if (LOGGER.isInfoEnabled()) {
LOGGER.info(format("Invalidating potential primary %s whose (set version, election id) tuple of (%d, %s) "
+ "is less than one already seen of (%d, %s)",
newDescription.getAddress(),
setVersion, electionId,
maxSetVersion, maxElectionId));
}
addressToServerTupleMap.get(newDescription.getAddress()).server.resetToConnecting();
if (newDescription.getMaxWireVersion() >= SIX_DOT_ZERO_WIRE_VERSION) {
if (nullSafeCompareTo(electionId, maxElectionId) > 0
|| (nullSafeCompareTo(electionId, maxElectionId) == 0 && nullSafeCompareTo(setVersion, maxSetVersion) >= 0)) {
LOGGER.info(format("Setting max election id to %s and max set version to %d from replica set primary %s",
newDescription.getElectionId(), newDescription.getSetVersion(), newDescription.getAddress()));
maxElectionId = newDescription.getElectionId();
maxSetVersion = newDescription.getSetVersion();
} else {
invalidatePotentialPrimary(newDescription);
return false;
}

if (!electionId.equals(maxElectionId)) {
if (LOGGER.isInfoEnabled()) {
LOGGER.info(format("Setting max election id to %s from replica set primary %s", electionId,
newDescription.getAddress()));
} else {
if (setVersion != null && electionId != null) {
if (nullSafeCompareTo(maxSetVersion, setVersion) <= 0
&& (nullSafeCompareTo(maxSetVersion, setVersion) != 0 || nullSafeCompareTo(maxElectionId, electionId) <= 0)) {
LOGGER.info(format("Setting max election id to %s from replica set primary %s",
newDescription.getElectionId(), newDescription.getAddress()));
maxElectionId = newDescription.getElectionId();
} else {
invalidatePotentialPrimary(newDescription);
return false;
}
maxElectionId = electionId;
}
}

if (setVersion != null
&& (maxSetVersion == null || setVersion.compareTo(maxSetVersion) > 0)) {
if (LOGGER.isInfoEnabled()) {
LOGGER.info(format("Setting max set version to %d from replica set primary %s", setVersion,
newDescription.getAddress()));
if (nullSafeCompareTo(setVersion, maxSetVersion) > 0) {
LOGGER.info(format("Setting max set version to %d from replica set primary %s",
newDescription.getSetVersion(), newDescription.getAddress()));
maxSetVersion = setVersion;
}
maxSetVersion = setVersion;
}

if (isNotAlreadyPrimary(newDescription.getAddress())) {
Expand All @@ -297,14 +293,26 @@ private boolean handleReplicaSetMemberChanged(final ServerDescription newDescrip
return true;
}

private boolean isStalePrimary(final ServerDescription newDescription) {
if (maxSetVersion == null || maxElectionId == null) {
return false;
}
private void invalidatePotentialPrimary(final ServerDescription newDescription) {
LOGGER.info(format("Invalidating potential primary %s whose (set version, election id) tuple of (%d, %s) "
+ "is less than one already seen of (%d, %s)",
newDescription.getAddress(), newDescription.getSetVersion(), newDescription.getElectionId(),
maxSetVersion, maxElectionId));
addressToServerTupleMap.get(newDescription.getAddress()).server.resetToConnecting();
}

Integer setVersion = newDescription.getSetVersion();
return (setVersion == null || maxSetVersion.compareTo(setVersion) > 0
|| (maxSetVersion.equals(setVersion) && maxElectionId.compareTo(newDescription.getElectionId()) > 0));
/**
* Implements the same contract as {@link Comparable#compareTo(Object)}, except that a null value is always considers less-than any
* other value (except null, which it considers as equal-to).
*/
private static <T extends Comparable<T>> int nullSafeCompareTo(final T first, final T second) {
if (first == null) {
return second == null ? 0 : -1;
}
if (second == null) {
return 1;
}
return first.compareTo(second);
}

private boolean isNotAlreadyPrimary(final ServerAddress address) {
Expand Down
1 change: 1 addition & 0 deletions driver-core/src/main/com/mongodb/internal/operation/ServerVersionHelper.java
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Original file line number Diff line number Diff line change
Expand Up @@ -30,6 +30,7 @@ public final class ServerVersionHelper {
public static final int FOUR_DOT_TWO_WIRE_VERSION = 8;
public static final int FOUR_DOT_FOUR_WIRE_VERSION = 9;
public static final int FIVE_DOT_ZERO_WIRE_VERSION = 12;
public static final int SIX_DOT_ZERO_WIRE_VERSION = 17;

public static boolean serverIsAtLeastVersionFourDotZero(final ConnectionDescription description) {
return description.getMaxWireVersion() >= FOUR_DOT_ZERO_WIRE_VERSION;
Expand Down
92 changes: 92 additions & 0 deletions ...c/test/resources/server-discovery-and-monitoring/rs/electionId_precedence_setVersion.json
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Original file line number Diff line number Diff line change
@@ -0,0 +1,92 @@
{
"description" : "ElectionId is considered higher precedence than setVersion",
"uri" : "mongodb://a/?replicaSet=rs",
"phases" : [
{
"responses" : [
[
"a:27017",
{
"ok" : 1,
"helloOk" : true,
"isWritablePrimary" : true,
"hosts" : [
"a:27017",
"b:27017"
],
"setName" : "rs",
"setVersion" : 1,
"electionId" : {
"$oid" : "000000000000000000000001"
},
"minWireVersion" : 0,
"maxWireVersion" : 17
}
],
[
"b:27017",
{
"ok" : 1,
"helloOk" : true,
"isWritablePrimary" : true,
"hosts" : [
"a:27017",
"b:27017"
],
"setName" : "rs",
"setVersion" : 2,
"electionId" : {
"$oid" : "000000000000000000000001"
},
"minWireVersion" : 0,
"maxWireVersion" : 17
}
],
[
"a:27017",
{
"ok" : 1,
"helloOk" : true,
"isWritablePrimary" : true,
"hosts" : [
"a:27017",
"b:27017"
],
"setName" : "rs",
"setVersion" : 1,
"electionId" : {
"$oid" : "000000000000000000000002"
},
"minWireVersion" : 0,
"maxWireVersion" : 17
}
]
],
"outcome" : {
"servers" : {
"a:27017" : {
"type" : "RSPrimary",
"setName" : "rs",
"setVersion" : 1,
"electionId" : {
"$oid" : "000000000000000000000002"
}
},
"b:27017" : {
"type" : "Unknown",
"setName" : null,
"setVersion" : null,
"electionId" : null
}
},
"topologyType" : "ReplicaSetWithPrimary",
"logicalSessionTimeoutMinutes" : null,
"setName" : "rs",
"maxSetVersion" : 1,
"maxElectionId" : {
"$oid" : "000000000000000000000002"
}
}
}
]
}
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