view src/core/ngx_array.c @ 8045:aa28c802409f

Resolver: make TCP write timer event cancelable. Similar to 70e65bf8dfd7, the change is made to ensure that the ability to cancel resolver tasks is fully controlled by the caller. As mentioned in the referenced commit, it is safe to make this timer cancelable because resolve tasks can have their own timeouts that are not cancelable. The scenario where this may become a problem is a periodic background resolve task (not tied to a specific request or a client connection), which receives a response with short TTL, large enough to warrant fallback to a TCP query. With each event loop wakeup, we either have a previously set write timer instance or schedule a new one. The non-cancelable write timer can delay or block graceful shutdown of a worker even if the ngx_resolver_ctx_t->cancelable flag is set by the API user, and there are no other tasks or connections. We use the resolver API in this way to maintain the list of upstream server addresses specified with the 'resolve' parameter, and there could be third-party modules implementing similar logic.
author Aleksei Bavshin <a.bavshin@f5.com>
date Wed, 01 Jun 2022 20:17:23 -0700
parents 4fef8ed52389
children
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/*
 * Copyright (C) Igor Sysoev
 * Copyright (C) Nginx, Inc.
 */


#include <ngx_config.h>
#include <ngx_core.h>


ngx_array_t *
ngx_array_create(ngx_pool_t *p, ngx_uint_t n, size_t size)
{
    ngx_array_t *a;

    a = ngx_palloc(p, sizeof(ngx_array_t));
    if (a == NULL) {
        return NULL;
    }

    if (ngx_array_init(a, p, n, size) != NGX_OK) {
        return NULL;
    }

    return a;
}


void
ngx_array_destroy(ngx_array_t *a)
{
    ngx_pool_t  *p;

    p = a->pool;

    if ((u_char *) a->elts + a->size * a->nalloc == p->d.last) {
        p->d.last -= a->size * a->nalloc;
    }

    if ((u_char *) a + sizeof(ngx_array_t) == p->d.last) {
        p->d.last = (u_char *) a;
    }
}


void *
ngx_array_push(ngx_array_t *a)
{
    void        *elt, *new;
    size_t       size;
    ngx_pool_t  *p;

    if (a->nelts == a->nalloc) {

        /* the array is full */

        size = a->size * a->nalloc;

        p = a->pool;

        if ((u_char *) a->elts + size == p->d.last
            && p->d.last + a->size <= p->d.end)
        {
            /*
             * the array allocation is the last in the pool
             * and there is space for new allocation
             */

            p->d.last += a->size;
            a->nalloc++;

        } else {
            /* allocate a new array */

            new = ngx_palloc(p, 2 * size);
            if (new == NULL) {
                return NULL;
            }

            ngx_memcpy(new, a->elts, size);
            a->elts = new;
            a->nalloc *= 2;
        }
    }

    elt = (u_char *) a->elts + a->size * a->nelts;
    a->nelts++;

    return elt;
}


void *
ngx_array_push_n(ngx_array_t *a, ngx_uint_t n)
{
    void        *elt, *new;
    size_t       size;
    ngx_uint_t   nalloc;
    ngx_pool_t  *p;

    size = n * a->size;

    if (a->nelts + n > a->nalloc) {

        /* the array is full */

        p = a->pool;

        if ((u_char *) a->elts + a->size * a->nalloc == p->d.last
            && p->d.last + size <= p->d.end)
        {
            /*
             * the array allocation is the last in the pool
             * and there is space for new allocation
             */

            p->d.last += size;
            a->nalloc += n;

        } else {
            /* allocate a new array */

            nalloc = 2 * ((n >= a->nalloc) ? n : a->nalloc);

            new = ngx_palloc(p, nalloc * a->size);
            if (new == NULL) {
                return NULL;
            }

            ngx_memcpy(new, a->elts, a->nelts * a->size);
            a->elts = new;
            a->nalloc = nalloc;
        }
    }

    elt = (u_char *) a->elts + a->size * a->nelts;
    a->nelts += n;

    return elt;
}