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grpclb: skip fallback if the LB is already in fallback mode #8253

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merged 3 commits into from Jun 11, 2021
Merged

grpclb: skip fallback if the LB is already in fallback mode #8253

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3c77985
Skip fallback if the LB is already in fallback mode. This can be trig…
voidzcy Jun 10, 2021
a766d51
Inline entering fallback if no LB address is given by resolver.
voidzcy Jun 11, 2021
67387e1
Update comment to more precisely describe the fallback behavior whene…
voidzcy Jun 11, 2021
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15 changes: 11 additions & 4 deletions grpclb/src/main/java/io/grpc/grpclb/GrpclbState.java
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Expand Up @@ -259,11 +259,19 @@ void handleAddresses(
serviceName,
newLbAddressGroups,
newBackendServers);
fallbackBackendList = newBackendServers;
if (newLbAddressGroups.isEmpty()) {
// No balancer address: close existing balancer connection and enter fallback mode
// immediately.
// No balancer address: close existing balancer connection and prepare to enter fallback
// mode. If there is no successful backend connection, it enters fallback mode immediately.
// Otherwise, fallback does not happen until backend connections are lost. This behavior
// might be different from other languages (e.g., existing balancer connection is not
// closed in C-core), but we aren't changing it at this time.
shutdownLbComm();
syncContext.execute(new FallbackModeTask(NO_LB_ADDRESS_PROVIDED_STATUS));
if (!usingFallbackBackends) {
fallbackReason = NO_LB_ADDRESS_PROVIDED_STATUS;
cancelFallbackTimer();
maybeUseFallbackBackends();
}
} else {
startLbComm(newLbAddressGroups);
// Avoid creating a new RPC just because the addresses were updated, as it can cause a
Expand All @@ -281,7 +289,6 @@ void handleAddresses(
TimeUnit.MILLISECONDS, timerService);
}
}
fallbackBackendList = newBackendServers;
if (usingFallbackBackends) {
// Populate the new fallback backends to round-robin list.
useFallbackBackends();
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29 changes: 27 additions & 2 deletions grpclb/src/test/java/io/grpc/grpclb/GrpclbLoadBalancerTest.java
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Expand Up @@ -1452,8 +1452,11 @@ public void grpclbFallback_breakLbStreamBeforeFallbackTimerExpires() {
public void grpclbFallback_noBalancerAddress() {
InOrder inOrder = inOrder(helper, subchannelPool);

// Create just backend addresses
List<EquivalentAddressGroup> backendList = createResolvedBackendAddresses(2);
// Create 5 distinct backends
List<EquivalentAddressGroup> backends = createResolvedBackendAddresses(5);

// Name resolver gives the first two backend addresses
List<EquivalentAddressGroup> backendList = backends.subList(0, 2);
deliverResolvedAddresses(backendList, Collections.<EquivalentAddressGroup>emptyList());

assertThat(logs).containsAtLeast(
Expand All @@ -1474,6 +1477,28 @@ public void grpclbFallback_noBalancerAddress() {
.createOobChannel(ArgumentMatchers.<EquivalentAddressGroup>anyList(), anyString());
logs.clear();

/////////////////////////////////////////////////////////////////////////////////////////
// Name resolver sends new resolution results with new backend addr but no balancer addr
/////////////////////////////////////////////////////////////////////////////////////////
// Name resolver then gives the last three backends
backendList = backends.subList(2, 5);
deliverResolvedAddresses(backendList, Collections.<EquivalentAddressGroup>emptyList());

assertThat(logs).containsAtLeast(
"INFO: [grpclb-<api.google.com>] Using fallback backends",
"INFO: [grpclb-<api.google.com>] "
+ "Using RR list=[[[FakeSocketAddress-fake-address-2]/{}], "
+ "[[FakeSocketAddress-fake-address-3]/{}], "
+ "[[FakeSocketAddress-fake-address-4]/{}]], drop=[null, null, null]",
"INFO: [grpclb-<api.google.com>] "
+ "Update balancing state to CONNECTING: picks=[BUFFER_ENTRY], "
+ "drops=[null, null, null]")
.inOrder();

// Shift to use updated backends
fallbackTestVerifyUseOfFallbackBackendLists(inOrder, backendList);
logs.clear();

///////////////////////////////////////////////////////////////////////////////////////
// Name resolver sends new resolution results without any backend addr or balancer addr
///////////////////////////////////////////////////////////////////////////////////////
Expand Down