Dynamic modules.

The auto/module script is extended to understand ngx_module_link=DYNAMIC.
When set, it links the module as a shared object rather than statically
into nginx binary.  The module can later be loaded using the "load_module"
directive.

New auto/module parameter ngx_module_order allows to define module loading
order in complex cases.  By default the order is set based on ngx_module_type.

3rd party modules can be compiled dynamically using the --add-dynamic-module
configure option, which will preset ngx_module_link to "DYNAMIC" before
calling the module config script.

Win32 support is rudimentary, and only works when using MinGW gcc (which
is able to handle exports/imports automatically).

In collaboration with Ruslan Ermilov.

1 files changed, 302 insertions, 6 deletions

diff --git a/src/core/ngx_module.c b/src/core/ngx_module.c
index df3cfde5d..1e947c906 100644
--- a/src/core/ngx_module.c
+++ b/src/core/ngx_module.c
@@ -10,7 +10,16 @@
 #include <ngx_core.h>
 
 
-ngx_uint_t  ngx_max_module;
+#define NGX_MAX_DYNAMIC_MODULES  128
+
+
+static ngx_uint_t ngx_module_index(ngx_cycle_t *cycle);
+static ngx_uint_t ngx_module_ctx_index(ngx_cycle_t *cycle, ngx_uint_t type,
+    ngx_uint_t index);
+
+
+ngx_uint_t         ngx_max_module;
+static ngx_uint_t  ngx_modules_n;
 
 
 ngx_int_t
@@ -20,9 +29,36 @@ ngx_preinit_modules()
 
     ngx_max_module = 0;
     for (i = 0; ngx_modules[i]; i++) {
-        ngx_modules[i]->index = ngx_max_module++;
+        ngx_modules[i]->index = i;
+        ngx_modules[i]->name = ngx_module_names[i];
     }
 
+    ngx_modules_n = i;
+    ngx_max_module = ngx_modules_n + NGX_MAX_DYNAMIC_MODULES;
+
+    return NGX_OK;
+}
+
+
+ngx_int_t
+ngx_cycle_modules(ngx_cycle_t *cycle)
+{
+    /*
+     * create a list of modules to be used for this cycle,
+     * copy static modules to it
+     */
+
+    cycle->modules = ngx_pcalloc(cycle->pool, (ngx_max_module + 1)
+                                              * sizeof(ngx_module_t *));
+    if (cycle->modules == NULL) {
+        return NGX_ERROR;
+    }
+
+    ngx_memcpy(cycle->modules, ngx_modules,
+               ngx_modules_n * sizeof(ngx_module_t *));
+
+    cycle->modules_n = ngx_modules_n;
+
     return NGX_OK;
 }
 
@@ -47,19 +83,279 @@ ngx_init_modules(ngx_cycle_t *cycle)
 ngx_int_t
 ngx_count_modules(ngx_cycle_t *cycle, ngx_uint_t type)
 {
-    ngx_uint_t  i, max;
+    ngx_uint_t     i, next, max;
+    ngx_module_t  *module;
 
+    next = 0;
     max = 0;
 
     /* count appropriate modules, set up their indices */
 
     for (i = 0; cycle->modules[i]; i++) {
-        if (cycle->modules[i]->type != type) {
+        module = cycle->modules[i];
+
+        if (module->type != type) {
+            continue;
+        }
+
+        if (module->ctx_index != NGX_MODULE_UNSET_INDEX) {
+
+            /* if ctx_index was assigned, preserve it */
+
+            if (module->ctx_index > max) {
+                max = module->ctx_index;
+            }
+
+            if (module->ctx_index == next) {
+                next++;
+            }
+
+            continue;
+        }
+
+        /* search for some free index */
+
+        module->ctx_index = ngx_module_ctx_index(cycle, type, next);
+
+        if (module->ctx_index > max) {
+            max = module->ctx_index;
+        }
+
+        next = module->ctx_index + 1;
+    }
+
+    /*
+     * make sure the number returned is big enough for previous
+     * cycle as well, else there will be problems if the number
+     * will be stored in a global variable (as it's used to be)
+     * and we'll have to roll back to the previous cycle
+     */
+
+    if (cycle->old_cycle && cycle->old_cycle->modules) {
+
+        for (i = 0; cycle->old_cycle->modules[i]; i++) {
+            module = cycle->old_cycle->modules[i];
+
+            if (module->type != type) {
+                continue;
+            }
+
+            if (module->ctx_index > max) {
+                max = module->ctx_index;
+            }
+        }
+    }
+
+    /* prevent loading of additional modules */
+
+    cycle->modules_used = 1;
+
+    return max + 1;
+}
+
+
+ngx_int_t
+ngx_add_module(ngx_conf_t *cf, ngx_str_t *file, ngx_module_t *module,
+    char **order)
+{
+    void               *rv;
+    ngx_uint_t          i, m, before;
+    ngx_core_module_t  *core_module;
+
+    if (cf->cycle->modules_n >= ngx_max_module) {
+        ngx_conf_log_error(NGX_LOG_EMERG, cf, 0,
+                           "too many modules loaded");
+        return NGX_ERROR;
+    }
+
+    if (module->version != nginx_version) {
+        ngx_conf_log_error(NGX_LOG_EMERG, cf, 0,
+                           "module \"%V\" version %ui instead of %ui",
+                           file, module->version, nginx_version);
+        return NGX_ERROR;
+    }
+
+    if (ngx_strcmp(module->signature, NGX_MODULE_SIGNATURE) != 0) {
+        ngx_conf_log_error(NGX_LOG_EMERG, cf, 0,
+                           "module \"%V\" is not binary compatible",
+                           file);
+        return NGX_ERROR;
+    }
+
+    for (m = 0; cf->cycle->modules[m]; m++) {
+        if (ngx_strcmp(cf->cycle->modules[m]->name, module->name) == 0) {
+            ngx_conf_log_error(NGX_LOG_EMERG, cf, 0,
+                               "module \"%s\" is already loaded",
+                               module->name);
+            return NGX_ERROR;
+        }
+    }
+
+    /*
+     * if the module wasn't previously loaded, assign an index
+     */
+
+    if (module->index == NGX_MODULE_UNSET_INDEX) {
+        module->index = ngx_module_index(cf->cycle);
+
+        if (module->index >= ngx_max_module) {
+            ngx_conf_log_error(NGX_LOG_EMERG, cf, 0,
+                               "too many modules loaded");
+            return NGX_ERROR;
+        }
+    }
+
+    /*
+     * put the module into the cycle->modules array
+     */
+
+    before = cf->cycle->modules_n;
+
+    if (order) {
+        for (i = 0; order[i]; i++) {
+            if (ngx_strcmp(order[i], module->name) == 0) {
+                i++;
+                break;
+            }
+        }
+
+        for ( /* void */ ; order[i]; i++) {
+
+#if 0
+            ngx_log_debug2(NGX_LOG_DEBUG_CORE, cf->log, 0,
+                           "module: %s before %s",
+                           module->name, order[i]);
+#endif
+
+            for (m = 0; m < before; m++) {
+                if (ngx_strcmp(cf->cycle->modules[m]->name, order[i]) == 0) {
+
+                    ngx_log_debug3(NGX_LOG_DEBUG_CORE, cf->log, 0,
+                                   "module: %s before %s:%i",
+                                   module->name, order[i], m);
+
+                    before = m;
+                    break;
+                }
+            }
+        }
+    }
+
+    /* put the module before modules[before] */
+
+    if (before != cf->cycle->modules_n) {
+        ngx_memmove(&cf->cycle->modules[before + 1],
+                    &cf->cycle->modules[before],
+                    (cf->cycle->modules_n - before) * sizeof(ngx_module_t *));
+    }
+
+    cf->cycle->modules[before] = module;
+    cf->cycle->modules_n++;
+
+    if (module->type == NGX_CORE_MODULE) {
+
+        /*
+         * we are smart enough to initialize core modules;
+         * other modules are expected to be loaded before
+         * initialization - e.g., http modules must be loaded
+         * before http{} block
+         */
+
+        core_module = module->ctx;
+
+        if (core_module->create_conf) {
+            rv = core_module->create_conf(cf->cycle);
+            if (rv == NULL) {
+                return NGX_ERROR;
+            }
+
+            cf->cycle->conf_ctx[module->index] = rv;
+        }
+    }
+
+    return NGX_OK;
+}
+
+
+static ngx_uint_t
+ngx_module_index(ngx_cycle_t *cycle)
+{
+    ngx_uint_t     i, index;
+    ngx_module_t  *module;
+
+    index = 0;
+
+again:
+
+    /* find an unused index */
+
+    for (i = 0; cycle->modules[i]; i++) {
+        module = cycle->modules[i];
+
+        if (module->index == index) {
+            index++;
+            goto again;
+        }
+    }
+
+    /* check previous cycle */
+
+    if (cycle->old_cycle && cycle->old_cycle->modules) {
+
+        for (i = 0; cycle->old_cycle->modules[i]; i++) {
+            module = cycle->old_cycle->modules[i];
+
+            if (module->index == index) {
+                index++;
+                goto again;
+            }
+        }
+    }
+
+    return index;
+}
+
+
+static ngx_uint_t
+ngx_module_ctx_index(ngx_cycle_t *cycle, ngx_uint_t type, ngx_uint_t index)
+{
+    ngx_uint_t     i;
+    ngx_module_t  *module;
+
+again:
+
+    /* find an unused ctx_index */
+
+    for (i = 0; cycle->modules[i]; i++) {
+        module = cycle->modules[i];
+
+        if (module->type != type) {
             continue;
         }
 
-        cycle->modules[i]->ctx_index = max++;
+        if (module->ctx_index == index) {
+            index++;
+            goto again;
+        }
+    }
+
+    /* check previous cycle */
+
+    if (cycle->old_cycle && cycle->old_cycle->modules) {
+
+        for (i = 0; cycle->old_cycle->modules[i]; i++) {
+            module = cycle->old_cycle->modules[i];
+
+            if (module->type != type) {
+                continue;
+            }
+
+            if (module->ctx_index == index) {
+                index++;
+                goto again;
+            }
+        }
     }
 
-    return max;
+    return index;
 }