The failure is caused by resource exhaustion at the Linux kernel level, specifically involving file descriptors and network sockets under high load.

Key Root Causes:

File Descriptor Exhaustion:
In Linux, everything like files, sockets, and network connections is handled using file descriptors. The error "too many open files" indicates that the process or system has exceeded the ulimit (open file descriptor limit) configured in the kernel.

Socket Exhaustion:
Each database connection uses a TCP socket, which also consumes file descriptors. Under heavy load, too many simultaneous connections can exhaust available kernel socket resources.

Kernel Resource Limits (ulimit / sysctl constraints):
The Linux kernel enforces several limits such as:

• Maximum open files per process (ulimit -n)
• System-wide file descriptor limit
• TCP socket backlog limits

When these limits are reached, the system can no longer accept new connections, causing failures or timeouts.

Connection Leak / Poor Connection Pooling:
If the application does not properly close database connections or lacks efficient connection pooling, open sockets accumulate over time, eventually exhausting available resources.

Why Timeouts Occur:

• New TCP connections cannot be created due to resource limits
• Connection requests remain in SYN queue or wait state
• Database requests fail, leading to timeout errors

Overall, the root cause is Linux kernel-level resource exhaustion, mainly due to hitting file descriptor and socket limits under peak load, often worsened by poor connection management at the application level.