Linux Ops Essentials: Gray Release, DNS, RabbitMQ, LVS, MySQL & Keepalived

What is Gray Release?

Gray release is a smooth transition deployment method between black and white, allowing gradual rollout. AB testing is a type of gray release where a portion of users see version A and the rest see version B, expanding B if no objections.

DNS Resolution Process

When accessing www.baidu.com, the system checks the local hosts file, then the configured DNS server, then root servers, followed by TLD, second‑level, and third‑level name servers until the final IP is obtained and cached.

What is RabbitMQ?

RabbitMQ is a message‑queue middleware that stores messages during transmission, acting as an intermediary between producers and consumers, providing routing and ensuring delivery even if the receiver is temporarily unavailable.

How Keepalived Works

In a virtual router group, the MASTER VRRP router continuously sends VRRP advertisements. BACKUP routers do not send advertisements; if they stop receiving them, the highest‑priority BACKUP takes over as MASTER within less than a second. VRRP packets are encrypted for security.

LVS Load‑Balancing Modes

LVS supports three modes: NAT (VS‑NAT), IP‑tunnel (VS‑TUN), and Direct‑Routing (VS‑DR). Each mode’s principle, advantages, and disadvantages are described.

MySQL InnoDB Lock Diagnosis & Replication Lag Reduction

Use SHOW ENGINE INNODB STATUS and the information_schema tables innodb_trx, innodb_locks, innodb_lock_waits to locate lock issues. To reduce master‑slave replication delay, check hardware, single‑threaded replication, slow queries, network latency, and adjust parameters such as --slave-net-timeout and --master-connect-retry.

Resetting MySQL Root Password

If the current password is known, change it with mysqladmin -u root -p password "new_password" or by updating the mysql.user table. If the password is forgotten, stop MySQL, start it with --skip-grant-tables, and reset the password.

Nginx vs. LVS vs. HAProxy

Summarize advantages and disadvantages of Nginx, LVS, and HAProxy in terms of layer, configuration complexity, performance, health‑check capabilities, and protocol support.

MySQL Backup Tools

Tools include mysqldump, LVM snapshots, tar archives, and Percona XtraBackup for hot physical backups, supporting full and incremental backups.

Keepalived Health‑Check Configuration

Keepalived implements VRRP for high availability and provides health‑check modules (core, check, vrrp). Example configuration:

HTTP_GET|SSL_GET {
    url {
        path /# HTTP/SSL check URL(s)
    }
    digest   # generated with genhash
    status_code 200
}
connect_port 80
connect_timeout 3
nb_get_retry 3
delay_before_retry 2