[refactor](session) Bind a ConnectContext to one ProtocolAdapter instead of a Flight subclass

[morningman]

What problem does this PR solve?

Issue Number: #67577 -- the tracking issue for the protocol-agnostic session and execution
layer. This is the second PR of its Stage 1 (after the golden baseline #67789) and does not close it.

The shape after this PR:

  +---------------------------+                             +-----------------------------+
  |       MySQL client        |                             |   Arrow Flight SQL client   |
  +-------------+-------------+                             +--------------+--------------+
                |                                                          |
                v                                                          v
  +---------------------------+                             +-----------------------------+
  | MysqlServer               |                             | DorisFlightSqlProducer      |
  |   AcceptListener          |                             |   every call goes through   |
  |   ReadListener            |                             |   adapter.runCommand()      |
  |   (xnio: one command      |                             |   (lock: one command        |
  |    at a time)             |                             |    at a time)               |
  +-------------+-------------+                             +--------------+--------------+
                |                                                          |
                v                                                          v
  +---------------------------+                             +-----------------------------+
  |   MysqlConnectProcessor   |                             |  FlightSqlConnectProcessor  |
  +-------------+-------------+                             +--------------+--------------+
                |                                                          |
                +----------------------------+-----------------------------+
                                             |
                                             v
  +-------------------------------------------------------------------------------------------+
  | ConnectContext  --  the session, one per connection                                       |
  |                                                                                           |
  |   user, catalog / db, SessionVariable, transaction, prepared statements,                  |
  |   queryId / stmtId, executor, audit, ...                                                  |
  |                                                                                           |
  |   protocolAdapter : ProtocolAdapter                                                       |
  |       bound once, by  forMysql() | forMysqlProxy() | forFlight() | new ConnectContext()   |
  |                                                                                           |
  |   getMysqlChannel()  getCapability()  getFlightSqlChannel()  isReturnResultFromLocal() .. |
  |       same signatures as before, now delegate to protocolAdapter                          |
  +---------------------------------------------+---------------------------------------------+
                                                |
                                                v
                       +-----------------------------------------------+
                       |  <<interface>>  qe.protocol.ProtocolAdapter   |
                       |                                               |
                       |   type()                                      |
                       |   remoteHostPortString(ctx)                   |
                       |   resultSinkType()                            |
                       |   connectPool(scheduler)                      |
                       |   afterStatement(ctx)                         |
                       |   closeConnection(ctx)                        |
                       +-----------------------+-----------------------+
                                               |
                          +--------------------+----------------------------+
                          |                                                 |
  +-----------------------+----------------------+  +-----------------------+----------------------+
  | mysql.protocol.MysqlProtocolAdapter          |  | service.arrowflight.protocol                 |
  |                                              |  |   .FlightProtocolAdapter                     |
  |   MysqlChannel:                              |  |                                              |
  |     a socket                                 |  |   peerIdentity (the bearer token)            |
  |     ProxyMysqlChannel (statement forwarded   |  |   FlightSqlChannel (FE-side result cache)    |
  |       to the master)                         |  |   endpoints of the last query                |
  |     DummyMysqlChannel (internal context)     |  |   returnResultFromLocal                      |
  |   server / negotiated MysqlCapability        |  |   prepared queries                           |
  |   handshake packet, MysqlSslContext          |  |   deferred executors + idle bound            |
  |   COM_STMT_EXECUTE packet, cursor flag       |  |     (#62259, #67503)                         |
  |   clientConsumesCursorMetadataTerminator()   |  |   per-session command lock:                  |
  |   accept-query loop                          |  |     runCommand() / callCommand()             |
  |     (start / suspend / resume / stop)        |  |                                              |
  +----------------------------------------------+  +----------------------------------------------+

  Not touched by this PR: ConnectProcessor / StmtExecutor / Coordinator keep calling the
  ConnectContext getters. The result-encoding half (ResultSender) and the capability
  predicates that replace the remaining ConnectType branches come in the next PRs.

In plain terms. A client session in the frontend is a ConnectContext. Today that one class
holds the state of both wire protocols at the same time: the MySQL socket, the capabilities
negotiated with the MySQL client, the handshake and SSL state, the prepared-statement packet being
executed -- and, next to them, the Arrow Flight SQL result cache, the backend endpoints of the last
Flight query, the prepared queries and the deferred coordinators. Which half is real is decided by a
subclass, FlightSqlConnectContext, that overrides six methods and leaves every other Flight member
sitting on the base class, where a MySQL connection carries it as dead weight and a Flight session
throws from the MySQL ones. This PR gives each protocol its own object, a ProtocolAdapter, and
binds a session to exactly one of them when it is created. Nothing a client sees changes: the golden
byte-for-byte baseline recorded in #67789 is identical before and after.

Problem Summary:

ConnectContext mixes three things: the session (user, catalog and database, session variables,
transaction, prepared statements, the running statement), the MySQL protocol state, and the Arrow
Flight SQL protocol state. The next steps of #67577 move the result path of both protocols onto one
shared implementation, which needs a place for "what only this protocol knows" that is not the
session itself. This PR creates that place and moves the state, without touching the execution layer
yet: StmtExecutor, ConnectProcessor and the coordinators still call the same ConnectContext
getters, which now delegate.

What is changed?

qe/protocol/ProtocolAdapter -- the wire-protocol half of a connection: type(), the client
address for processlist and the audit log, the result sink type the backend must use, the pool the
connection is registered in (there is still one per protocol), a per-statement cleanup hook and
closeConnection. qe/protocol holds only the interface; each front end implements it in a
protocol subpackage of its own package (mysql/protocol, service/arrowflight/protocol), which is
also where the result senders of the next step go.

mysql/protocol/MysqlProtocolAdapter -- owns the MysqlChannel (a socket, the
ProxyMysqlChannel of a forwarded statement on the master, or the DummyMysqlChannel of an
internal context), the server and negotiated capabilities, the handshake packet, the SSL context,
the COM_STMT_EXECUTE packet and its cursor flag, and the xnio accept-query loop that
AcceptListener / ReadListener drive. It also owns the decision StmtExecutor and FEOpExecutor
used to compute from ConnectContext fields -- whether the Connector/J release on the other end
consumes the metadata terminator of a cursor result (#67520) -- as
clientConsumesCursorMetadataTerminator.

service/arrowflight/protocol/FlightProtocolAdapter -- owns the peer identity (bearer token), the
FlightSqlChannel, the prepared queries, the endpoints of the last query, returnResultFromLocal
and the deferred executors of #62259 / #67503, together with their idle bound. ConnectContext
keeps checkTimeout and the idle reaper unchanged; only the list moved.

It also serializes the commands of a session. gRPC runs each call of a session on whatever thread it
likes and nothing in the Flight transport orders them, while ConnectContext is not thread-safe
(the existing DorisFlightSqlProducerTest spells that out). runCommand / callCommand take a
per-session lock, make the session the thread's current ConnectContext for the duration, restore
the previous one afterwards, and give up with UNAVAILABLE after the session's query timeout if
another command is still running. DorisFlightSqlProducer runs statement execution, prepared
statement creation and close, DoGet of a frontend-side result and the catalog / schema / table
metadata requests through it. DoGet of a frontend-side result streams under the lock on purpose: the
next statement of the session resets the channel, whose removal listener closes the
VectorSchemaRoot being streamed. Session teardown (token expiry, CloseSession, KILL) does not
take the lock; that path is reworked when the token becomes the session credential.

ConnectContext -- gets protocolAdapter and three factories: forMysql(StreamConnection),
forMysqlProxy(sessionId) (replaces the new ConnectContext(null, true, sessionId) call in
FrontendServiceImpl) and forFlight(peerIdentity) (replaces the subclass in
FlightSessionsManager). The existing constructors stay as thin wrappers, so the ~115 test files that
call new ConnectContext() are untouched. Every protocol-specific getter keeps its signature and
delegates: getMysqlChannel(), getCapability(), getFlightSqlChannel(), isReturnResultFromLocal()
and so on. A getter that only makes sense on the other protocol throws IllegalStateException
naming the actual protocol (the subclass used to throw a RuntimeException for getMysqlChannel();
the base class used to return null / an empty list for the Flight ones, which no caller relied on).
FlightSqlConnectContext is deleted: its getClientIP / getRemoteHostPortString /
closeChannel / setQueryId overrides are the adapter's remoteHostPortString / closeConnection
/ connectPool, and its kill override only differed in log text.

Removed as dead code while touching the class: isSend / setIsSend (nothing read them; the real
flag lives on MysqlChannel), cloneContext() (no caller, and it would have to share a channel
between two adapters), and the two lines of resetConnection() that cleared Flight-only fields
(COM_RESET_CONNECTION is only sent by MySQL clients).

Not in this PR, deliberately: the execution layer still branches on ConnectType, and an internal
context is still a MySQL context over a DummyMysqlChannel, exactly as before. Both go away in the
follow-up PRs that introduce the result sender and the capability bits.

Verification

• Golden baseline of [test](protocol) Record a golden baseline of MySQL packets and Arrow Flight results #67789: MysqlPacketGoldenTest (27 cases, byte for byte) and
  FlightResultGoldenTest pass unchanged. Not a byte of the recorded traffic moved.
• New unit tests: FlightProtocolAdapterTest (commands of one session run one at a time, a waiting
  command fails with UNAVAILABLE after the query timeout, the thread's current context is set and
  restored, a failing command releases the session, KILL unregisters the session from the Flight
  pool, the trace id lands in the Flight pool) and MysqlProtocolAdapterTest (internal and proxy
  contexts, the cursor-terminator decision and its per-statement reset, the accept-query loop and
  close going through the channel).
• Existing tests adjusted to the factories: the ones that built a FlightSqlConnectContext, poked
  mysqlChannel / connectType through reflection, or used a plain new ConnectContext() as a
  Flight session (ShortCircuitPointQueryTest, AuditLogWorkloadGroupTest, StmtExecutorTest,
  ConnectContextTest, MysqlProtoTest, ConnectionExceedTest). 26 test classes around the
  session, the MySQL channel and the Flight producer: 166 tests, 0 failures.
• Regression on a local cluster built from this branch: arrow_flight_sql_p0 (8 suites, including
  the forward-to-master, query-release, point-query, SQL cache and DatabaseMetaData.getColumns
  paths) and prepared_stmt_p0 (cursor fetch and server-side prepare over MySQL).
• checkstyle:check on fe-core (main and test sources): 0 violations.

Release note

None.

Check List (For Author)

• Test

  • Regression test
  • Unit Test
  • Manual test (add detailed scripts or steps below)
  • No need to test or manual test. Explain why:

• Behavior changed:

  • No.
  • Yes.

• Does this need documentation?

  • No.
  • Yes.

Check List (For Reviewer who merge this PR)

• Confirm the release note
• Confirm test cases
• Confirm document
• Add branch pick label

🤖 Generated with Claude Code

https://claude.ai/code/session_01QFwVuLmK8e7sEdKVKB6QZJ

[hello-stephen]

Thank you for your contribution to Apache Doris.
Don't know what should be done next? See How to process your PR.

Please clearly describe your PR:

1. What problem was fixed (it's best to include specific error reporting information). How it was fixed.
2. Which behaviors were modified. What was the previous behavior, what is it now, why was it modified, and what possible impacts might there be.
3. What features were added. Why was this function added?
4. Which code was refactored and why was this part of the code refactored?
5. Which functions were optimized and what is the difference before and after the optimization?

[morningman]

run buildall

[morningman]

run buildall

[morningman]

run buildall

[morningman]

Local pipeline review — ✅ PASS

schema: doris-repo-review/v1
status: PASS
pr: apache/doris#67835
commit: 22b9306171e097555946d8b9778d7cba13f7e036
base: b78724a75f704b059bf07cab4e7fa6601bdd8a79
reviewed_at: 2026-09-11T13:15+08:00
reviewer: morningman
model: claude-opus-5[1m]
effort: max
findings: {blocker: 0, major: 0, minor: 1, nit: 7}
rounds: 1
converged: true

Notes for maintainers

• fe/fe-core/src/main/java/org/apache/doris/service/arrowflight/protocol/FlightProtocolAdapter.java:270 — the only Minor: a command waiting for the session lock gives up after query_timeout, while the command holding it may be a sync-load statement allowed getExecTimeoutS() = max(insert_timeout, query_timeout); a concurrent metadata/prepare call during a long INSERT gets UNAVAILABLE too early. One-line fix: bound the wait with ctx.getExecTimeoutS().
• fe/fe-core/src/main/java/org/apache/doris/service/arrowflight/DorisFlightSqlProducer.java:320 — the busy-session UNAVAILABLE reaches clients as UNAVAILABLE, INTERNAL, or INTERNAL with an empty description depending on the entry point (getFlightInfoStatement and the three metadata streams re-wrap it); consider passing a FlightRuntimeException through unchanged.
• fe/fe-core/src/main/java/org/apache/doris/service/arrowflight/protocol/FlightProtocolAdapter.java:120 — teardown (closeSession, token expiry, KILL) still runs unregisterConnection concurrently with a command holding the lock; pre-existing and stated in the javadoc, but the next PR of [Tracking] Protocol-agnostic session and execution layer: MySQL and Arrow Flight SQL as equal front ends #67577 should close it.
• The deleted Flight kill override also changed the cancel reason a killed Flight query reports ("arrow flight query killed by user" -> "cancel query by user from "), not only the log text; nothing asserts either string.
• Not verified locally: no build, unit test, regression or cluster run. CheckStyle is green; TeamCity FE UT build 1043145 on this exact commit was still running with 7118 passed / 0 failed when this comment was posted; the golden baselines under fe/fe-core/src/test/resources/protocol-golden/ are untouched by the diff.

_{Reviewed locally with the doris-repo-review pipeline. Repository policy may accept this receipt for the matching commit; it is not a human Apache approval.}

[hello-stephen]

TPC-H: Total hot run time: 16798 ms

machine: 'aliyun_ecs.c7a.8xlarge_32C64G'
scripts: https://github.com/apache/doris/tree/master/tools/tpch-tools
Tpch sf100 test result on commit 22b9306171e097555946d8b9778d7cba13f7e036, data reload: false

------ Round 1 ----------------------------------
============================================
q1	17626	3051	3023	3023
q2	2072	255	220	220
q3	10254	914	529	529
q4	4676	252	206	206
q5	7670	567	394	394
q6	141	118	95	95
q7	542	493	382	382
q8	9236	869	919	869
q9	3462	2417	2427	2417
q10	6496	858	703	703
q11	406	201	182	182
q12	614	262	202	202
q13	18135	1565	1180	1180
q14	163	149	143	143
q15	q16	451	405	382	382
q17	1310	903	756	756
q18	3108	2317	2318	2317
q19	1278	921	731	731
q20	394	285	205	205
q21	5583	1630	1879	1630
q22	332	269	232	232
Total cold run time: 93949 ms
Total hot run time: 16798 ms

----- Round 2, with runtime_filter_mode=off -----
============================================
q1	3421	3373	3335	3335
q2	502	396	380	380
q3	2239	2450	2199	2199
q4	1199	1187	896	896
q5	2232	2151	2139	2139
q6	168	129	88	88
q7	1031	924	864	864
q8	1582	1407	1407	1407
q9	3172	3138	3135	3135
q10	1883	1811	1654	1654
q11	357	269	251	251
q12	453	441	346	346
q13	1491	1543	1163	1163
q14	164	182	153	153
q15	q16	397	409	365	365
q17	3714	3351	3309	3309
q18	4902	4493	4913	4493
q19	1020	877	865	865
q20	1015	961	839	839
q21	3873	3203	3268	3203
q22	395	346	329	329
Total cold run time: 35210 ms
Total hot run time: 31413 ms

[hello-stephen]

TPC-DS: Total hot run time: 83222 ms

machine: 'aliyun_ecs.c7a.8xlarge_32C64G'
scripts: https://github.com/apache/doris/tree/master/tools/tpcds-tools
TPC-DS sf100 test result on commit 22b9306171e097555946d8b9778d7cba13f7e036, data reload: false

query5	4267	421	335	335
query6	376	132	126	126
query7	4952	440	228	228
query8	286	132	120	120
query9	8684	2920	2872	2872
query10	402	216	186	186
query11	5377	1049	936	936
query12	119	75	68	68
query13	1192	443	347	347
query14	6176	2221	2133	2133
query14_1	2007	1990	1980	1980
query15	180	127	111	111
query16	923	388	367	367
query17	807	478	364	364
query18	2335	350	228	228
query19	158	136	103	103
query20	80	67	69	67
query21	198	100	84	84
query22	5404	5347	5406	5347
query23	6980	6405	6241	6241
query23_1	6181	6318	6246	6246
query24	7299	1093	776	776
query24_1	774	783	778	778
query25	401	287	228	228
query26	1218	228	132	132
query27	2788	424	252	252
query28	4664	1507	1519	1507
query29	904	425	332	332
query30	251	155	132	132
query31	823	397	332	332
query32	129	72	70	70
query33	448	215	177	177
query34	985	842	496	496
query35	398	402	335	335
query36	564	562	531	531
query37	130	78	66	66
query38	1001	867	850	850
query39	505	476	500	476
query39_1	484	474	481	474
query40	198	88	76	76
query41	54	52	51	51
query42	76	70	71	70
query43	240	241	212	212
query44	971	535	544	535
query45	105	111	101	101
query46	779	847	554	554
query47	767	771	727	727
query48	337	314	235	235
query49	540	259	191	191
query50	745	273	199	199
query51	8376	8304	8160	8160
query52	65	72	58	58
query53	202	198	151	151
query54	239	178	162	162
query55	74	59	61	59
query56	196	166	158	158
query57	678	661	660	660
query58	199	161	156	156
query59	1218	1233	1149	1149
query60	253	211	188	188
query61	132	147	123	123
query62	372	212	185	185
query63	175	158	146	146
query64	2889	818	734	734
query65	1678	1584	1615	1584
query66	1787	317	196	196
query67	9904	9823	9713	9713
query68	2747	1232	738	738
query69	333	222	205	205
query70	670	641	613	613
query71	259	176	157	157
query72	2294	1709	1542	1542
query73	662	617	354	354
query74	1577	1235	1151	1151
query75	1171	1117	971	971
query76	2293	728	550	550
query77	263	273	214	214
query78	4135	3708	3282	3282
query79	2977	838	608	608
query80	1604	319	281	281
query81	517	161	148	148
query82	615	124	100	100
query83	271	210	193	193
query84	293	113	87	87
query85	794	364	288	288
query86	472	195	157	157
query87	1024	997	912	912
query88	3118	2122	2129	2122
query89	272	200	177	177
query90	2162	131	128	128
query91	134	119	101	101
query92	100	68	62	62
query93	2504	1051	713	713
query94	641	246	228	228
query95	518	317	230	230
query96	860	562	272	272
query97	1134	1071	1041	1041
query98	174	137	138	137
query99	414	349	308	308
Total cold run time: 180639 ms
Total hot run time: 83222 ms

[hello-stephen]

ClickBench: Total hot run time: 14.9 s

machine: 'aliyun_ecs.c7a.8xlarge_32C64G'
scripts: https://github.com/apache/doris/tree/master/tools/clickbench-tools
ClickBench test result on commit 22b9306171e097555946d8b9778d7cba13f7e036, data reload: false

query1	0.00	0.00	0.00
query2	0.09	0.05	0.04
query3	0.25	0.10	0.11
query4	1.60	0.10	0.10
query5	0.18	0.16	0.16
query6	1.25	0.69	0.71
query7	0.03	0.01	0.00
query8	0.04	0.04	0.03
query9	0.30	0.22	0.22
query10	0.36	0.34	0.35
query11	0.16	0.12	0.12
query12	0.14	0.12	0.12
query13	0.32	0.32	0.32
query14	0.48	0.45	0.45
query15	0.36	0.35	0.36
query16	0.24	0.23	0.24
query17	0.68	0.71	0.69
query18	0.17	0.17	0.18
query19	1.21	1.11	1.15
query20	0.01	0.02	0.02
query21	15.45	0.16	0.14
query22	5.04	0.04	0.05
query23	16.16	0.26	0.10
query24	3.07	0.31	0.23
query25	0.09	0.05	0.04
query26	0.73	0.16	0.12
query27	0.04	0.04	0.03
query28	3.62	0.57	0.27
query29	12.45	3.23	2.63
query30	0.26	0.12	0.13
query31	2.76	0.39	0.17
query32	3.50	0.32	0.23
query33	1.41	1.55	1.42
query34	15.39	2.18	1.82
query35	1.79	1.79	1.76
query36	0.44	0.29	0.29
query37	0.06	0.04	0.04
query38	0.05	0.03	0.03
query39	0.04	0.02	0.02
query40	0.12	0.07	0.08
query41	0.08	0.03	0.02
query42	0.03	0.02	0.03
query43	0.03	0.03	0.03
Total cold run time: 90.48 s
Total hot run time: 14.9 s