DevStack master branch single-node deployment on Ubuntu 24.04 fails frequently due to MySQL default max_connections (1024) being exceeded by concurrent service connections.

Environment

    OS: Ubuntu 24.04
    Deployment: DevStack master branch (single-node deployment)
    Database: MySQL with default connection limit (max_connections = 1024)
    Networking: Neutron OVS provider network (full local.conf attached below)
    Hardware: 128-core CPU, 256GB memory, 22TB RAID disk (sufficient resources for single-node deployment)

Actual Result
During DevStack deployment (via ./stack.sh), all OpenStack core services (Keystone/Neutron/Nova/Cinder/Glance etc.) establish concurrent, non-pooled connections to the single local MySQL instance. The connection count rapidly exceeds MySQL’s default limit of 1024 (verified via Max_used_connections = 1025 in MySQL status), leading to:

1.Glance service initialization failure (cannot connect to MySQL for metadata setup);
2.Image upload stage (05:22:34) triggers critical errors:
prove chain:
    Failed to contact the endpoint at http://10.126.41.229/image for discovery. Fallback to using that endpoint as the base url.
result:"
    Deployment aborts with Error on exit at the image upload step, resulting in a high failure rate for single-node DevStack master branch deployment.

Expected Result
DevStack master branch should natively adapt to single-node deployment scenarios by:

1.Optimizing service connection strategies (e.g., enabling connection pooling) to avoid exhausting MySQL connections;
2.Or dynamically adjusting MySQL’s max_connections limit for single-node deployments;
3.Ensuring Glance (and all core services) initializes successfully and image upload completes without errors.

Deployment Timeline & Key Error Details
1. Deployment Sequence (Critical Stages)
plaintext

2026-03-21 05:13:22 | Configuring and starting MySQL (max_connections=1024 by default)
2026-03-21 05:13:59 - 05:22:05 | Starting Keystone/Neutron/Nova/Cinder (connections to MySQL accumulate)
2026-03-21 05:22:25 | Starting Glance (MySQL connections already exhausted)
2026-03-21 05:22:34 | Uploading images (deployment fails at this step)

2. MySQL Connection Verification
sql

mysql> show status like 'max_used_connections';
+----------------------+-------+
| Variable_name | Value |
+----------------------+-------+
| Max_used_connections | 1025 |
+----------------------+-------+

Confirmed: MySQL connections exceed the default 1024 limit during deployment.
3. Mitigation Validation
Increasing MySQL’s max_connections (e.g., to 2048) completely resolves the issue—DevStack deployment completes successfully, Glance initializes normally, and image upload works without errors.

Local.conf (Full Configuration)

[[local|localrc]]
# Git configuration
GIT_BASE="https://github.com"

# Network & Path configuration
HOST_IP=10.126.41.229
DEST=/opt/stack
LOGDIR=$DEST/logs
LOGFILE=$LOGDIR/stack.sh.log

# Credentials (shared for all services)
ADMIN_PASSWORD=suma123456
DATABASE_PASSWORD=$ADMIN_PASSWORD
RABBIT_PASSWORD=$ADMIN_PASSWORD
SERVICE_PASSWORD=$ADMIN_PASSWORD

# Service endpoints
SERVICE_HOST=10.126.41.229
MYSQL_HOST=$SERVICE_HOST
RABBIT_HOST=$SERVICE_HOST
GLANCE_HOSTPORT=$SERVICE_HOST:9292

# Neutron (OVS provider network)
Q_USE_SECGROUP=True
FLOATING_RANGE="10.126.40.0/21"
Q_FLOATING_ALLOCATION_POOL=start=10.126.47.240,end=10.126.47.250
PUBLIC_NETWORK_GATEWAY="10.126.40.1"
PUBLIC_INTERFACE=eno1

Q_USE_PROVIDERNET_FOR_PUBLIC=True
OVS_PHYSICAL_BRIDGE=br-ex
PUBLIC_PHYSICAL_NETWORK=public
PUBLIC_BRIDGE=br-ex
OVS_BRIDGE_MAPPINGS=public:br-ex