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Endpoint selection is retried on selection timeout (#4269)
Motivation:
- Differentiate the cases where "endpoint is set to `null`" vs. "endpoint selection timed out" for easier debugging.
- `EmptyEndpointGroupException`: If an `EndpointGroup` sets the endpoint as `null`
- `EndpointSelectionTimeoutException`: If the `Endpoint` selection timed out.
- Add the capability to retry endpoint selection from an `EndpointGroup` if not selected yet.
Modifications:
- Define a helper class `ClientPendingThrowableUtil` which contains helper methods for setting a new attribute `CLIENT_PENDING_THROWABLE`.
- This throwable is thrown after decorators are processed, but before the actual client execution starts.
- This attribute should be removed if a user wants to re-use a derived context.
- An example of this can be seen at `RetryingClient`. `RetryingClient` works by creating a derived context from the original context, and executing requests. If the original context contains `CLIENT_PENDING_THROWABLE`, then derived contexts would also contain the `CLIENT_PENDING_THROWABLE` and the retried requests would fail immediately. Hence, it is necessary that `CLIENT_PENDING_THROWABLE` be cleared in the derived context.
- Set `CLIENT_PENDING_THROWABLE` to `EndpointSelectionTimeoutException` when an `Endpoint` selection times out.
- Modify `RetryingClient`, `RetryingRpcClient`:
- Check if the context has an `EndpointGroup` but doesn't have an `Endpoint` yet, which means previous endpoint selection has failed. If an endpoint hasn't been selected yet, call `initContextAndExecuteWithFallback` which tries another `EndpointSelection`.
Result:
- `EndpointSelectionTimeoutException` is thrown on selection timeout
- Retry is done on selection timeout- Loading branch information
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56 changes: 56 additions & 0 deletions
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...src/main/java/com/linecorp/armeria/client/endpoint/EndpointSelectionTimeoutException.java
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| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -0,0 +1,56 @@ | ||
| /* | ||
| * Copyright 2022 LINE Corporation | ||
| * | ||
| * LINE Corporation licenses this file to you under the Apache License, | ||
| * version 2.0 (the "License"); you may not use this file except in compliance | ||
| * with the License. You may obtain a copy of the License at: | ||
| * | ||
| * https://www.apache.org/licenses/LICENSE-2.0 | ||
| * | ||
| * Unless required by applicable law or agreed to in writing, software | ||
| * distributed under the License is distributed on an "AS IS" BASIS, WITHOUT | ||
| * WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the | ||
| * License for the specific language governing permissions and limitations | ||
| * under the License. | ||
| */ | ||
|
|
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| package com.linecorp.armeria.client.endpoint; | ||
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| import static com.google.common.base.Preconditions.checkArgument; | ||
| import static java.util.Objects.requireNonNull; | ||
|
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| import com.linecorp.armeria.client.Endpoint; | ||
| import com.linecorp.armeria.common.Flags; | ||
| import com.linecorp.armeria.common.annotation.UnstableApi; | ||
|
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| /** | ||
| * An {@link EndpointGroupException} raised when an {@link EndpointGroup} fails to resolve | ||
| * an {@link Endpoint} within a configured selection timeout. | ||
| */ | ||
| @UnstableApi | ||
| public final class EndpointSelectionTimeoutException extends EndpointGroupException { | ||
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| private static final long serialVersionUID = -3079582212067997365L; | ||
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| private static final EndpointSelectionTimeoutException INSTANCE = | ||
| new EndpointSelectionTimeoutException(); | ||
|
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| /** | ||
| * Returns an {@link EndpointSelectionTimeoutException} which prints a message about | ||
| * the {@link EndpointGroup} when thrown. | ||
| */ | ||
| public static EndpointSelectionTimeoutException get(EndpointGroup endpointGroup, | ||
| long selectionTimeoutMillis) { | ||
| requireNonNull(endpointGroup, "endpointGroup"); | ||
| checkArgument(selectionTimeoutMillis >= 0, "selectionTimeoutMillis: %s (expected: >= 0)", | ||
| selectionTimeoutMillis); | ||
| return Flags.verboseExceptionSampler().isSampled(EndpointSelectionTimeoutException.class) ? | ||
| new EndpointSelectionTimeoutException(endpointGroup, selectionTimeoutMillis) : INSTANCE; | ||
| } | ||
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| private EndpointSelectionTimeoutException() {} | ||
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| private EndpointSelectionTimeoutException(EndpointGroup endpointGroup, long selectionTimeoutMillis) { | ||
| super("Failed to select within " + selectionTimeoutMillis + " ms an endpoint from: " + endpointGroup); | ||
| } | ||
| } |
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116 changes: 116 additions & 0 deletions
116
core/src/main/java/com/linecorp/armeria/internal/client/ClientPendingThrowableUtil.java
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| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -0,0 +1,116 @@ | ||
| /* | ||
| * Copyright 2022 LINE Corporation | ||
| * | ||
| * LINE Corporation licenses this file to you under the Apache License, | ||
| * version 2.0 (the "License"); you may not use this file except in compliance | ||
| * with the License. You may obtain a copy of the License at: | ||
| * | ||
| * https://www.apache.org/licenses/LICENSE-2.0 | ||
| * | ||
| * Unless required by applicable law or agreed to in writing, software | ||
| * distributed under the License is distributed on an "AS IS" BASIS, WITHOUT | ||
| * WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the | ||
| * License for the specific language governing permissions and limitations | ||
| * under the License. | ||
| */ | ||
|
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| package com.linecorp.armeria.internal.client; | ||
|
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| import static java.util.Objects.requireNonNull; | ||
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| import com.linecorp.armeria.client.ClientRequestContext; | ||
| import com.linecorp.armeria.common.annotation.Nullable; | ||
| import com.linecorp.armeria.common.util.Exceptions; | ||
|
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| import io.netty.util.AttributeKey; | ||
|
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| /** | ||
| * Sets a pending {@link Throwable} for the specified {@link ClientRequestContext}. | ||
| * This throwable will be thrown after all decorators are executed, but before the | ||
| * actual client execution starts. | ||
| * | ||
| * <p>For example:<pre>{@code | ||
| * final RuntimeException e = new RuntimeException(); | ||
| * final WebClient webClient = | ||
| * WebClient.builder(SessionProtocol.HTTP, endpointGroup) | ||
| * .contextCustomizer(ctx -> setPendingThrowable(ctx, e)) | ||
| * .decorator(LoggingClient.newDecorator()) // the request is logged | ||
| * .build(); | ||
| * assertThatThrownBy(() -> webClient.blocking().get("/")) | ||
| * .isInstanceOf(UnprocessedRequestException.class) | ||
| * .hasCause(e); | ||
| * }</pre> | ||
| */ | ||
| public final class ClientPendingThrowableUtil { | ||
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| private static final AttributeKey<Throwable> CLIENT_PENDING_THROWABLE = | ||
| AttributeKey.valueOf(ClientPendingThrowableUtil.class, "CLIENT_PENDING_THROWABLE"); | ||
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| /** | ||
| * Sets a pending {@link Throwable} for the specified {@link ClientRequestContext}. | ||
| * Note that the throwable will be peeled via {@link Exceptions#peel(Throwable)} | ||
| * before being set. | ||
| * | ||
| * <p>For example:<pre>{@code | ||
| * final RuntimeException e = new RuntimeException(); | ||
| * final CompletionException wrapper = new CompletionException(e); | ||
| * final ClientRequestContext ctx = ... | ||
| * setPendingThrowable(ctx, wrapper); | ||
| * final Throwable throwable = pendingThrowable(ctx); | ||
| * assert throwable != null; | ||
| * assertThat(throwable).isEqualTo(e); | ||
| * }</pre> | ||
| */ | ||
| public static void setPendingThrowable(ClientRequestContext ctx, Throwable cause) { | ||
| requireNonNull(ctx, "ctx"); | ||
| requireNonNull(cause, "cause"); | ||
| cause = Exceptions.peel(cause); | ||
| ctx.setAttr(CLIENT_PENDING_THROWABLE, cause); | ||
| } | ||
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| /** | ||
| * Retrieves the pending {@link Throwable} for the specified {@link ClientRequestContext}. | ||
| * Note that the derived context will also contain this attribute by default, and can fail | ||
| * requests immediately. The pending {@link Throwable} can be removed by | ||
| * {@link #removePendingThrowable(ClientRequestContext)}. | ||
| * | ||
| * <p>For example:<pre>{@code | ||
| * ClientRequestContext ctx = ...; | ||
| * Throwable t = ...; | ||
| * final Throwable t1 = pendingThrowable(ctx); | ||
| * assert t1 == null; | ||
| * setPendingThrowable(ctx, t); | ||
| * final Throwable t2 = pendingThrowable(ctx); | ||
| * assert t2 == t; | ||
| * final ClientRequestContext derived = ctx.newDerivedContext(id, req, rpcReq, endpoint); | ||
| * final Throwable t3 = pendingThrowable(derived); | ||
| * assert t3 == t; | ||
| * }</pre> | ||
| */ | ||
| @Nullable | ||
| public static Throwable pendingThrowable(ClientRequestContext ctx) { | ||
| requireNonNull(ctx, "ctx"); | ||
| return ctx.attr(CLIENT_PENDING_THROWABLE); | ||
| } | ||
|
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| /** | ||
| * Removes the pending throwable set by {@link #setPendingThrowable(ClientRequestContext, Throwable)}. | ||
| * | ||
| * <p>For example:<pre>{@code | ||
| * final Throwable throwable = pendingThrowable(ctx); | ||
| * assert throwable != null; | ||
| * assertThat(throwable).isEqualTo(e); | ||
| * removePendingThrowable(ctx); | ||
| * assertThat(pendingThrowable(ctx)).isNull(); | ||
| * }</pre> | ||
| */ | ||
| public static void removePendingThrowable(ClientRequestContext ctx) { | ||
| requireNonNull(ctx, "ctx"); | ||
| if (!ctx.hasAttr(CLIENT_PENDING_THROWABLE)) { | ||
| return; | ||
| } | ||
| ctx.setAttr(CLIENT_PENDING_THROWABLE, null); | ||
| } | ||
|
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| private ClientPendingThrowableUtil() {} | ||
| } |
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