RetryingHttpRequesterFilter: rename ofImmediate to `ofImmediateWi…

…thDefaultLimit`

Motivation:

It's not obvious for users that `BackOffPolicy.ofImmediate()` retries only 3 times.

Modifications:

- Deprecated `BackOffPolicy.ofImmediate()`;
- Introduce `BackOffPolicy.ofImmediateWithDefaultLimit()` that behaves the same way;
- Cache the returning value for `BackOffPolicy.ofImmediateWithDefaultLimit()`;

Result:

Easier for users to understand that immediate `BackOffPolicy` has a limit for
number of retries.

servicetalk-http-netty/src/main/java/io/servicetalk/http/netty/RetryingHttpRequesterFilter.java

@@ -320,6 +320,9 @@ public String toString() {
     public static final class BackOffPolicy {
 
         private static final Duration FULL_JITTER = ofDays(1024);
+        // Subtract 1 because the total strategy anticipates 1 failure from LB not being ready (due to SD available
+        // events not yet arriving), however this level of retry is strictly applied to request/response failures.
+        private static final BackOffPolicy IMMEDIATE_DEFAULT_RETRIES = new BackOffPolicy(DEFAULT_MAX_TOTAL_RETRIES - 1);
 
         // FIXME: 0.43 - change field accessor to default
         /**
@@ -373,12 +376,23 @@ public static final class BackOffPolicy {
 
         /**
          * Creates a new {@link BackOffPolicy} that retries failures instantly up-to 3 max retries.
+         *
          * @return a new {@link BackOffPolicy} that retries failures instantly up-to 3 max retries.
+         * @deprecated Use {@link #ofImmediateWithDefaultLimit()}.
          */
+        @Deprecated
         public static BackOffPolicy ofImmediate() {
-            // Subtract 1 because the total strategy anticipates 1 failure from LB not being ready (due to SD available
-            // events not yet arriving), however this level of retry is strictly applied to request/response failures.
-            return new BackOffPolicy(DEFAULT_MAX_TOTAL_RETRIES - 1);
+            return ofImmediateWithDefaultLimit();
+        }
+
+        /**
+         * Creates a new {@link BackOffPolicy} that retries failures instantly up-to 3 max retries.
+         *
+         * @return a new {@link BackOffPolicy} that retries failures instantly up-to 3 max retries.
+         * @see #ofImmediate(int)
+         */
+        public static BackOffPolicy ofImmediateWithDefaultLimit() {
+            return IMMEDIATE_DEFAULT_RETRIES;
         }
 
         /**
@@ -616,12 +630,12 @@ public static final class Builder {
         private int maxTotalRetries = DEFAULT_MAX_TOTAL_RETRIES;
         private boolean retryExpectationFailed;
 
+        private BiFunction<HttpRequestMetaData, RetryableException, BackOffPolicy>
+                retryRetryableExceptions = (requestMetaData, e) -> BackOffPolicy.ofImmediateWithDefaultLimit();
+
         @Nullable
         private Function<HttpResponseMetaData, HttpResponseException> responseMapper;
 
-        private BiFunction<HttpRequestMetaData, RetryableException, BackOffPolicy>
-                retryRetryableExceptions = (requestMetaData, e) -> BackOffPolicy.ofImmediate();
-
         @Nullable
         private BiFunction<HttpRequestMetaData, IOException, BackOffPolicy>
                 retryIdempotentRequests;
@@ -840,7 +854,7 @@ public RetryingHttpRequesterFilter build() {
                         if (retryExpectationFailed && throwable instanceof ExpectationFailedException &&
                                 requestMetaData.headers().containsIgnoreCase(EXPECT, CONTINUE)) {
                             requestMetaData.headers().remove(EXPECT);
-                            return BackOffPolicy.ofImmediate();
+                            return BackOffPolicy.ofImmediateWithDefaultLimit();
                         }
 
                         if (retryIdempotentRequests != null && throwable instanceof IOException

servicetalk-http-netty/src/test/java/io/servicetalk/http/netty/RetryingHttpRequesterFilterTest.java

@@ -56,6 +56,7 @@
 import static io.servicetalk.http.netty.HttpClients.forSingleAddress;
 import static io.servicetalk.http.netty.HttpServers.forAddress;
 import static io.servicetalk.http.netty.RetryingHttpRequesterFilter.BackOffPolicy.ofImmediate;
+import static io.servicetalk.http.netty.RetryingHttpRequesterFilter.BackOffPolicy.ofImmediateWithDefaultLimit;
 import static io.servicetalk.http.netty.RetryingHttpRequesterFilter.BackOffPolicy.ofNoRetries;
 import static io.servicetalk.http.netty.RetryingHttpRequesterFilter.Builder;
 import static io.servicetalk.http.netty.RetryingHttpRequesterFilter.HttpResponseException;
@@ -139,7 +140,7 @@ void requestRetryingPredicate() {
                 .appendClientFilter(new Builder()
                         .retryRetryableExceptions((requestMetaData, e) -> ofNoRetries())
                         .retryOther((requestMetaData, throwable) ->
-                                requestMetaData.requestTarget().equals("/retry") ? ofImmediate() :
+                                requestMetaData.requestTarget().equals("/retry") ? ofImmediateWithDefaultLimit() :
                                         ofNoRetries()).build())
                 .buildBlocking();
         assertRequestRetryingPred(failingClient);
@@ -151,7 +152,7 @@ void requestRetryingPredicateWithConditionalAppend() {
                 .appendClientFilter((__) -> true, new Builder()
                         .retryRetryableExceptions((requestMetaData, e) -> ofNoRetries())
                         .retryOther((requestMetaData, throwable) ->
-                                requestMetaData.requestTarget().equals("/retry") ? ofImmediate() :
+                                requestMetaData.requestTarget().equals("/retry") ? ofImmediateWithDefaultLimit() :
                                         ofNoRetries()).build())
                 .buildBlocking();
         assertRequestRetryingPred(failingClient);