multi-schema-change ADD INDEX may be blocked

[lance6716]

Bug Report

Please answer these questions before submitting your issue. Thanks!

1. Minimal reproduce step (Required)

diff --git a/pkg/ddl/ingest/env.go b/pkg/ddl/ingest/env.go
index c74d7f69fa..1c014b4f29 100644
--- a/pkg/ddl/ingest/env.go
+++ b/pkg/ddl/ingest/env.go
@@ -19,6 +19,7 @@ import (
        "path/filepath"
        "strconv"

+       "github.com/pingcap/failpoint"
        "github.com/pingcap/tidb/pkg/config"
        "github.com/pingcap/tidb/pkg/ddl/logutil"
        "github.com/pingcap/tidb/pkg/lightning/log"
@@ -68,6 +69,10 @@ func InitGlobalLightningEnv(filterProcessingJobIDs FilterProcessingJobIDsFunc) {
        } else {
                memTotal = memTotal / 2
        }
+       failpoint.Inject("setMemTotalInMB", func(val failpoint.Value) {
+               i := val.(int)
+               memTotal = uint64(i) * size.MB
+       })
        LitBackCtxMgr = NewLitBackendCtxMgr(sortPath, memTotal, filterProcessingJobIDs)
        litRLimit = util.GenRLimit("ddl-ingest")
        LitInitialized = true

$ GO_FAILPOINTS="github.com/pingcap/tidb/pkg/ddl/ingest/setMemTotalInMB=return(1100)" bin/tidb-server -store tikv -path 127.0.0.1:2379 -log-file /tmp/tidb.log

mysql> create table t (c int, c2 int, c3 int, c4 int);
Query OK, 0 rows affected (0.05 sec)

mysql> insert into t values (1,1,1,1), (2,2,2,2), (3,3,3,3);
Query OK, 3 rows affected (0.00 sec)
Records: 3  Duplicates: 0  Warnings: 0

mysql> alter table t add index i(c), add index i2(c2);

2. What did you expect to see? (Required)

fail or success

3. What did you see instead (Required)

blocked

4. What is your TiDB version? (Required)

[lance6716]

tidb-test.log

there are errors in stdout/err

{"level":"warn","ts":"2024-06-04T14:23:03.321545+0800","logger":"etcd-client","caller":"v3@v3.5.12/retry_interceptor.go:62","msg":"retrying of unary invoker failed","target":"etcd-endpoints://0x1400b222a80/","attempt":0,"error":"rpc error: code = DeadlineExceeded desc = latest balancer error: last connection error: connection error: desc = \"transport: Error while dialing: dial tcp: missing address\""}
{"level":"warn","ts":"2024-06-04T14:23:09.32308+0800","logger":"etcd-client","caller":"v3@v3.5.12/retry_interceptor.go:62","msg":"retrying of unary invoker failed","target":"etcd-endpoints://0x1400b222a80/","attempt":0,"error":"rpc error: code = DeadlineExceeded desc = latest balancer error: last connection error: connection error: desc = \"transport: Error while dialing: dial tcp: missing address\""}
{"level":"warn","ts":"2024-06-04T14:23:15.323772+0800","logger":"etcd-client","caller":"v3@v3.5.12/retry_interceptor.go:62","msg":"retrying of unary invoker failed","target":"etcd-endpoints://0x1400b222a80/","attempt":0,"error":"rpc error: code = DeadlineExceeded desc = latest balancer error: last connection error: connection error: desc = \"transport: Error while dialing: dial tcp: missing address\""}