frankvicky commented on code in PR #21080:
URL: https://github.com/apache/kafka/pull/21080#discussion_r3501084974
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clients/src/main/java/org/apache/kafka/clients/NetworkClient.java:
##########
@@ -1210,6 +1280,139 @@ private boolean isTelemetryApi(ApiKeys apiKey) {
return apiKey == ApiKeys.GET_TELEMETRY_SUBSCRIPTIONS || apiKey ==
ApiKeys.PUSH_TELEMETRY;
}
+ public static class BootstrapConfiguration {
+ public static final BootstrapConfiguration DISABLED =
+ new BootstrapConfiguration(List.of(), null, 0, 0);
+
+ public final List<String> bootstrapServers;
+ public final ClientDnsLookup clientDnsLookup;
+ public final long bootstrapResolveTimeoutMs;
+ public final long retryBackoffMs;
+
+ private BootstrapConfiguration(final List<String> bootstrapServers,
+ final ClientDnsLookup clientDnsLookup,
+ final long bootstrapResolveTimeoutMs,
+ final long retryBackoffMs) {
+ this.bootstrapServers = bootstrapServers;
+ this.clientDnsLookup = clientDnsLookup;
+ this.bootstrapResolveTimeoutMs = bootstrapResolveTimeoutMs;
+ this.retryBackoffMs = retryBackoffMs;
+ }
+
+ public static BootstrapConfiguration enabled(final List<String>
bootstrapServers,
+ final ClientDnsLookup
clientDnsLookup,
+ final long
bootstrapResolveTimeoutMs,
+ final long
retryBackoffMs) {
+ for (String url : bootstrapServers) {
+ if (Utils.getHost(url) == null || Utils.getPort(url) == null)
+ throw new ConfigException("Invalid url in " +
CommonClientConfigs.BOOTSTRAP_SERVERS_CONFIG + ": " + url);
+ }
+ return new BootstrapConfiguration(bootstrapServers,
clientDnsLookup, bootstrapResolveTimeoutMs, retryBackoffMs);
+ }
+ }
+
+ /**
+ * Attempts to resolve bootstrap server addresses via DNS and create an
initial bootstrap cluster.
+ * This method is called from {@link #poll(long, long)} and uses a truly
asynchronous approach
+ * to avoid blocking on DNS resolution.
+ *
+ * <p>DNS resolution is performed on a separate thread via {@link
CompletableFuture}. This ensures
+ * the event loop remains responsive even if DNS lookups block or take a
long time. The bootstrap
+ * timeout can interrupt a pending DNS resolution, unlike synchronous
approaches.
+ *
+ * @param currentTimeMs The current time in milliseconds
+ * @throws BootstrapResolutionException if the bootstrap timeout expires
before DNS resolution succeeds
+ */
+ void ensureBootstrapped(final long currentTimeMs) {
+ if (bootstrapConfiguration == BootstrapConfiguration.DISABLED ||
metadataUpdater.isBootstrapped())
+ return;
+
+ if (bootstrapException != null)
+ return;
+
+ if (Thread.interrupted()) {
+ cancelBootstrapResolution();
+ throw new InterruptException(new InterruptedException());
+ }
+
+ // Check if a pending resolution completed before checking the
timeout, so that a
+ // result arriving at the same time as the deadline is not incorrectly
rejected.
+ if (pendingBootstrapResolution != null &&
pendingBootstrapResolution.isDone()) {
+ processBootstrapResolutionResult(currentTimeMs);
+ if (metadataUpdater.isBootstrapped())
+ return;
+ }
+
+ if (bootstrapTimer != null) {
+ bootstrapTimer.update(currentTimeMs);
+ checkBootstrapTimeout();
+ }
+ maybeStartBootstrapResolution(currentTimeMs);
+ }
+
+ /**
+ * Record a permanent bootstrap failure on the metadata if the timeout has
expired.
+ * The error is not thrown here; callers observe it through their metadata
layer
+ * (e.g. {@link Metadata#maybeThrowFatalException()} for
Producer/Consumer, or
+ * {@code AdminMetadataManager#bootstrapFatalException()} for AdminClient).
+ */
+ private void checkBootstrapTimeout() {
+ if (bootstrapTimer.isExpired() && bootstrapException == null) {
+ cancelBootstrapResolution();
+ bootstrapException = new BootstrapResolutionException("Failed to
resolve bootstrap servers after " +
+ bootstrapConfiguration.bootstrapResolveTimeoutMs + "ms. " +
+ "Please check your bootstrap.servers configuration and DNS
settings.");
+ metadataUpdater.bootstrapFailed(bootstrapException);
Review Comment:
Make sense
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