RFR: 8371903: HttpClient: improve handling of HTTP/2 GOAWAY frames with error code [v7]

[Christoph Läubrich]

On Wed, 10 Dec 2025 23:34:02 GMT, EunHyunsu <duke at openjdk.org> wrote:

>> ### Problem
>> 
>>   When the HTTP/2 client receives a GOAWAY frame with a non-zero error code, the current implementation discards both the error code and debug data. Users only see generic "Connection closed by peer" errors without any information about why the server terminated the connection.
>> 
>>   ### Solution
>> 
>>   Per [RFC 9113 §5.4.1](https://www.rfc-editor.org/rfc/rfc9113.html#section-5.4.1), a GOAWAY frame with a non-zero error code indicates a connection error requiring immediate closure. This fix:
>> 
>>   1. **Distinguishes** graceful shutdown (NO_ERROR) from connection errors
>>   2. **Preserves** error code and debug data in exception messages
>>   3. **Categorizes** streams based on `lastStreamId`:
>>      - Streams with ID > `lastStreamId`: Marked as unprocessed for automatic retry
>>      - Streams with ID ≤ `lastStreamId`: Failed with detailed error information
>> 
>>   ### Changes
>> 
>>   **Core Implementation** (`Http2Connection.java`):
>>   - Modified `handleGoAway()` to check error code and route appropriately
>>   - Added `handleGoAwayWithError()` method that:
>>     - Extracts error code and debug data from GOAWAY frame
>>     - Creates meaningful error messages with error name, hex code, and debug data
>>     - Properly categorizes streams for retry or failure
>> 
>>   **Test Infrastructure**:
>>   - `Http2TestServerConnection.sendGoAway(int, int, byte[])`: Supports custom error codes
>>   - `Http2TestExchangeImpl.getServerConnection()`: Accessor for test handlers
>>   - `GoAwayWithErrorTest`: Verifies proper error propagation
>> 
>>   ### Example
>> 
>>   **Before:**
>>   IOException: Connection closed by peer
>> 
>>   **After:**
>>   IOException: Received GOAWAY with error code Protocol error (0x1): Invalid HEADERS frame
>> 
>>   ### Testing
>> 
>>   - New `GoAwayWithErrorTest` passes
>>   - Existing HTTP/2 tests unaffected (NO_ERROR path unchanged)
>>   - Backward compatible (no public API changes)
>
> EunHyunsu has updated the pull request incrementally with one additional commit since the last revision:
> 
>   8371903: Use Utils.adjustTimeout() in GoAwayWithErrorTest

test/jdk/java/net/httpclient/http2/GoAwayWithErrorTest.java line 162:

> 160:                         && goawayError.getMessage().contains("0x1")
> 161:                         && goawayError.getMessage().contains(DEBUG_MESSAGE),
> 162:                 "Failed request should contain GOAWAY error details: " + goawayError.getMessage());

I think this test assertion alone already shows that a client has only the chance to use String parsing what I think is bad (both for test and for production code).

If its not planned to have an own public type, can it at least be an internal exception type that can be used in the test?
Maybe a Http2ProtocolError?

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PR Review Comment: https://git.openjdk.org/jdk/pull/28632#discussion_r2616080209