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core: Enable dns "caching" on Android #12681

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10 changes: 6 additions & 4 deletions core/src/main/java/io/grpc/internal/DnsNameResolver.java
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Original file line number Diff line number Diff line change
Expand Up @@ -100,7 +100,7 @@ public class DnsNameResolver extends NameResolver {
* not installed, the ttl value is {@code null} which falls back to {@link
* #DEFAULT_NETWORK_CACHE_TTL_SECONDS gRPC default value}.
*
* <p>For android, gRPC doesn't attempt to cache; this property value will be ignored.
* <p>For android, gRPC uses a fixed value; this property value will be ignored.
*/
@VisibleForTesting
static final String NETWORKADDRESS_CACHE_TTL_PROPERTY = "networkaddress.cache.ttl";
Expand Down Expand Up @@ -451,12 +451,14 @@ private static final List<String> getHostnamesFromChoice(Map<String, ?> serviceC

/**
* Returns value of network address cache ttl property if not Android environment. For android,
* DnsNameResolver does not cache the dns lookup result.
* DnsNameResolver uses a fixed value.
*/
private static long getNetworkAddressCacheTtlNanos(boolean isAndroid) {
if (isAndroid) {
// on Android, ignore dns cache.
return 0;
// On Android, use fixed value. If the network used changes this value shouldn't matter, as
// channel.enterIdle() should be called and this name resolver instance will be discarded. The
// new name resolver instance will then re-request.
return TimeUnit.SECONDS.toNanos(DEFAULT_NETWORK_CACHE_TTL_SECONDS);
}

String cacheTtlPropertyValue = System.getProperty(NETWORKADDRESS_CACHE_TTL_PROPERTY);
Expand Down
45 changes: 17 additions & 28 deletions core/src/test/java/io/grpc/internal/DnsNameResolverTest.java
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Original file line number Diff line number Diff line change
Expand Up @@ -151,13 +151,6 @@ private RetryingNameResolver newResolver(String name, int defaultPort) {
name, defaultPort, GrpcUtil.NOOP_PROXY_DETECTOR, Stopwatch.createUnstarted());
}

private RetryingNameResolver newResolver(String name, int defaultPort, boolean isAndroid) {
return newResolver(
name, defaultPort, GrpcUtil.NOOP_PROXY_DETECTOR, Stopwatch.createUnstarted(),
isAndroid);
}


private RetryingNameResolver newResolver(
String name,
int defaultPort,
Expand Down Expand Up @@ -227,30 +220,14 @@ public void invalidDnsName_containsUnderscore() {
}
}

@Test
public void resolve_androidIgnoresPropertyValue() throws Exception {
flagResetRule.setSystemPropertyForTest(NETWORKADDRESS_CACHE_TTL_PROPERTY, "2");
resolveNeverCache(true);
}

@Test
public void resolve_androidIgnoresPropertyValueCacheForever() throws Exception {
flagResetRule.setSystemPropertyForTest(NETWORKADDRESS_CACHE_TTL_PROPERTY, "-1");
resolveNeverCache(true);
}

@Test
public void resolve_neverCache() throws Exception {
flagResetRule.setSystemPropertyForTest(NETWORKADDRESS_CACHE_TTL_PROPERTY, "0");
resolveNeverCache(false);
}

private void resolveNeverCache(boolean isAndroid) throws Exception {
final List<InetAddress> answer1 = createAddressList(2);
final List<InetAddress> answer2 = createAddressList(1);
String name = "foo.googleapis.com";

RetryingNameResolver resolver = newResolver(name, 81, isAndroid);
RetryingNameResolver resolver = newResolver(name, 81);
DnsNameResolver dnsResolver = (DnsNameResolver) resolver.getRetriedNameResolver();
AddressResolver mockResolver = mock(AddressResolver.class);
when(mockResolver.resolveAddress(anyString())).thenReturn(answer1).thenReturn(answer2);
Expand Down Expand Up @@ -443,26 +420,38 @@ public void resolve_cacheExpired() throws Exception {
verify(mockResolver, times(2)).resolveAddress(anyString());
}

@Test
public void resolve_androidIgnoresPropertyValue() throws Exception {
flagResetRule.setSystemPropertyForTest(NETWORKADDRESS_CACHE_TTL_PROPERTY, "2");
resolveDefaultValue(true);
}

@Test
public void resolve_androidIgnoresPropertyValueCacheForever() throws Exception {
flagResetRule.setSystemPropertyForTest(NETWORKADDRESS_CACHE_TTL_PROPERTY, "-1");
resolveDefaultValue(true);
}

@Test
public void resolve_invalidTtlPropertyValue() throws Exception {
flagResetRule.setSystemPropertyForTest(NETWORKADDRESS_CACHE_TTL_PROPERTY, "not_a_number");
resolveDefaultValue();
resolveDefaultValue(false);
}

@Test
public void resolve_noPropertyValue() throws Exception {
flagResetRule.clearSystemPropertyForTest(NETWORKADDRESS_CACHE_TTL_PROPERTY);
resolveDefaultValue();
resolveDefaultValue(false);
}

private void resolveDefaultValue() throws Exception {
private void resolveDefaultValue(boolean isAndroid) throws Exception {
final List<InetAddress> answer1 = createAddressList(2);
final List<InetAddress> answer2 = createAddressList(1);
String name = "foo.googleapis.com";
FakeTicker fakeTicker = new FakeTicker();

RetryingNameResolver resolver = newResolver(
name, 81, GrpcUtil.NOOP_PROXY_DETECTOR, Stopwatch.createUnstarted(fakeTicker));
name, 81, GrpcUtil.NOOP_PROXY_DETECTOR, Stopwatch.createUnstarted(fakeTicker), isAndroid);
DnsNameResolver dnsResolver = (DnsNameResolver) resolver.getRetriedNameResolver();
AddressResolver mockResolver = mock(AddressResolver.class);
when(mockResolver.resolveAddress(anyString())).thenReturn(answer1).thenReturn(answer2);
Expand Down