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Leave a feedback > userver uses coroutines to operate. A coroutine has its own system stack, a stack per coroutine. The stack size is 256KB by default. This is enough for most users, but sometimes larger stack is required to operate. The stack size is set via coro_pool.stack_size option of components::ManagerControllerComponent in static config:
Stack overflow is an issue for any program written in any framework/language. It is a very tricky case to debug, so userver has matters for proactive stack overflow detection. It can detect and log coroutine stacktrace in case of NN% stack usage. engine.coro-pool.stack-usage.max-usage-percent metric stores the maximum stack usage percent during the task processor lifespan. If you see this metric approaches values close to 100% then it's time to either reduce stack usage or increase stack size in config. Userver uses guard pages to protect against stack overflows, but it is not a complete solution. If you ignore the metric you might face a disaster anyway. In case of stack overflow the process gets a SIGSEGV on attempt to access missing memory page or even writes garbage to a random memory page. So you might want to use a metric to avoid the UB.
