Original, source-backed articles about running small systems, static sites, HTTP, DNS, TLS, and operations.
Posts are original articles written for this site. Each one is script-free, source-backed, and tied to the same operational reality the rest of the site records: how a small, static, publicly served system is built, secured, and kept honest.
systemd supervises process lifecycles
A service manager turns process startup, failure, and shutdown into observable state transitions. With systemd, a unit can name the foreground command, its restart policy, and its output destination. That removes the need for a shell loop that repeatedly launches a daemon without recording why it stopped. It does not prove that the running application can answer requests or that restarting repairs the underlying fault.
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Put the unit in the metric name
A metric named request_duration leaves readers guessing whether 250 means seconds, milliseconds, or something else. A Prometheus-facing name such as http_request_duration_seconds carries that contract into queries, recording rules, and alerts. The contract still needs a correct implementation. Appending _seconds to measurements collected in milliseconds changes the spelling, not the magnitude, and can create a thousandfold monitoring error.
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Rate limiting needs a stable client identifier
A rate-limit key defines which requests share a budget. An account, API credential, address, tenant, and authenticated session are different identities, not interchangeable spellings of “client.” Choosing the wrong grouping can punish unrelated users or let one workload obtain fresh allowance simply by changing a field.
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EDNS advertises UDP capacity without guaranteeing path delivery
EDNS extends DNS through an OPT pseudo-record. Among other information, a request can advertise the UDP payload size its sender is prepared to receive. This allows answers beyond the traditional 512-byte DNS limit. It is an advertisement within a DNS exchange, not a network path-MTU discovery protocol or a promise that every intervening device will deliver a datagram of that size.
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Transport balancing keeps a connection together; HTTP routing can split its requests
The useful distinction between transport and HTTP balancing is where a routing decision can be made. A TCP relay can select a backend for a connection and forward its byte stream without interpreting HTTP requests. An HTTP proxy parses requests and can choose an upstream using their paths or headers. Several requests on one client connection can therefore have different routing outcomes.
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Diagnose descriptor exhaustion in the process that fails
A process needs file descriptors for more than ordinary files. Network sockets, pipes, event interfaces, and duplicated references all compete for entries in its descriptor table. RLIMIT_NOFILE limits the descriptor numbers available to new allocations: the soft limit is one greater than the maximum permitted number. A service can therefore fail to accept work even while the machine has plenty of disk space and memory.
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OOM investigation starts with the allocation scope
Linux can invoke an out-of-memory killer when an allocation cannot be satisfied within its relevant constraints after appropriate reclaim attempts. It is a last-resort recovery mechanism, not an application priority scheduler. Some allocations fail without a kill, and configuration can instead lead to panic behavior. Start an investigation by identifying the allocation scope and recorded event, rather than declaring that the machine must have exhausted every byte of RAM.
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Cookie scope keeps the session where it belongs
A cookie’s host and path scope controls which destinations are eligible to receive its name and value. It is useful to minimize that set, but scope is not authorization, and cookies do not follow the browser’s full origin boundary. This article concentrates on Domain and Path; transport and request context add separate restrictions.
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