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MINOR: promex: use watcher to iterate over backend instances

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Ensures proxies iteration in promex applet is safe via a new watcher
member. The principle is similar to the one already used for servers
iteration.

Note that ctx.p[0] is not updated anymore at the end of a function, as
this is automatically done via the watcher itself.
This commit is contained in:
Amaury Denoyelle 2026-02-24 16:22:12 +01:00
parent 20376c54e2
commit dd1990a97a
1 changed files with 60 additions and 26 deletions
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86
addons/promex/service-prometheus.c
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@ -83,6 +83,7 @@ struct promex_ctx {
unsigned field_num; /* current field number (ST_I_PX_* etc) */
unsigned mod_field_num; /* first field number of the current module (ST_I_PX_* etc) */
int obj_state; /* current state among PROMEX_{FRONT|BACK|SRV|LI}_STATE_* */
struct watcher px_watch; /* watcher to automatically update next pointer */
struct watcher srv_watch; /* watcher to automatically update next pointer */
struct list modules; /* list of promex modules to export */
struct eb_root filters; /* list of filters to apply on metrics name */
@ -940,9 +941,6 @@ static int promex_dump_back_metrics(struct appctx *appctx, struct htx *htx)
if (promex_filter_metric(appctx, prefix, name))
continue;
if (!px)
px = proxies_list;
while (px) {
struct promex_label labels[PROMEX_MAX_LABELS-1] = {};
unsigned int srv_state_count[PROMEX_SRV_STATE_COUNT] = { 0 };
@ -1097,9 +1095,16 @@ static int promex_dump_back_metrics(struct appctx *appctx, struct htx *htx)
&val, labels, &out, max))
goto full;
next_px:
px = px->next;
px = watcher_next(&ctx->px_watch, px->next);
}
watcher_detach(&ctx->px_watch);
ctx->flags |= PROMEX_FL_METRIC_HDR;
/* Prepare a new iteration for the next stat column.
* Update ctx.p[0] via watcher.
*/
watcher_attach(&ctx->px_watch, proxies_list);
px = proxies_list;
}
/* Skip extra counters */
@ -1122,9 +1127,6 @@ static int promex_dump_back_metrics(struct appctx *appctx, struct htx *htx)
if (promex_filter_metric(appctx, prefix, name))
continue;
if (!px)
px = proxies_list;
while (px) {
struct promex_label labels[PROMEX_MAX_LABELS-1] = {};
struct promex_metric metric;
@ -1159,25 +1161,39 @@ static int promex_dump_back_metrics(struct appctx *appctx, struct htx *htx)
goto full;
next_px2:
px = px->next;
px = watcher_next(&ctx->px_watch, px->next);
}
watcher_detach(&ctx->px_watch);
ctx->flags |= PROMEX_FL_METRIC_HDR;
/* Prepare a new iteration for the next stat column.
* Update ctx.p[0] via watcher.
*/
watcher_attach(&ctx->px_watch, proxies_list);
px = proxies_list;
}
ctx->field_num += mod->stats_count;
ctx->mod_field_num = 0;
}
px = NULL;
mod = NULL;
end:
if (out.len) {
if (!htx_add_data_atonce(htx, out))
return -1; /* Unexpected and unrecoverable error */
if (ret) {
watcher_detach(&ctx->px_watch);
mod = NULL;
}
/* Save pointers (0=current proxy, 1=current stats module) of the current context */
ctx->p[0] = px;
if (out.len) {
if (!htx_add_data_atonce(htx, out)) {
watcher_detach(&ctx->px_watch);
return -1; /* Unexpected and unrecoverable error */
}
}
/* Save pointers of the current context for dump resumption :
* 0=current proxy, 1=current stats module
* Note that p[0] is already automatically updated via px_watch.
*/
ctx->p[1] = mod;
return ret;
full:
@ -1393,19 +1409,22 @@ static int promex_dump_srv_metrics(struct appctx *appctx, struct htx *htx)
next_px:
watcher_detach(&ctx->srv_watch);
px = px->next;
px = watcher_next(&ctx->px_watch, px->next);
if (px) {
/* Update ctx.p[1] via watcher. */
watcher_attach(&ctx->srv_watch, px->srv);
sv = ctx->p[1];
}
}
watcher_detach(&ctx->px_watch);
ctx->flags |= PROMEX_FL_METRIC_HDR;
/* Prepare a new iteration for the next stat column. */
/* Prepare a new iteration for the next stat column.
* Update ctx.p[0]/p[1] via px_watch/srv_watch.
*/
watcher_attach(&ctx->px_watch, proxies_list);
px = proxies_list;
if (likely(px)) {
/* Update ctx.p[1] via watcher. */
watcher_attach(&ctx->srv_watch, px->srv);
sv = ctx->p[1];
}
@ -1478,19 +1497,22 @@ static int promex_dump_srv_metrics(struct appctx *appctx, struct htx *htx)
next_px2:
watcher_detach(&ctx->srv_watch);
px = px->next;
px = watcher_next(&ctx->px_watch, px->next);
if (px) {
/* Update ctx.p[1] via watcher. */
watcher_attach(&ctx->srv_watch, px->srv);
sv = ctx->p[1];
}
}
watcher_detach(&ctx->px_watch);
ctx->flags |= PROMEX_FL_METRIC_HDR;
/* Prepare a new iteration for the next stat column. */
/* Prepare a new iteration for the next stat column.
* Update ctx.p[0]/p[1] via px_watch/srv_watch.
*/
watcher_attach(&ctx->px_watch, proxies_list);
px = proxies_list;
if (likely(px)) {
/* Update ctx.p[1] via watcher. */
watcher_attach(&ctx->srv_watch, px->srv);
sv = ctx->p[1];
}
@ -1502,8 +1524,8 @@ static int promex_dump_srv_metrics(struct appctx *appctx, struct htx *htx)
end:
if (ret) {
watcher_detach(&ctx->px_watch);
watcher_detach(&ctx->srv_watch);
px = NULL;
mod = NULL;
}
@ -1514,9 +1536,8 @@ static int promex_dump_srv_metrics(struct appctx *appctx, struct htx *htx)
/* Save pointers of the current context for dump resumption :
* 0=current proxy, 1=current server, 2=current stats module
* Note that p[1] is already automatically updated via srv_watch.
* Note that p[0]/p[1] are already automatically updated via px_watch/srv_watch.
*/
ctx->p[0] = px;
ctx->p[2] = mod;
return ret;
full:
@ -1524,6 +1545,7 @@ static int promex_dump_srv_metrics(struct appctx *appctx, struct htx *htx)
goto end;
error:
watcher_detach(&ctx->px_watch);
watcher_detach(&ctx->srv_watch);
return -1;
}
@ -1746,6 +1768,11 @@ static int promex_dump_metrics(struct appctx *appctx, struct htx *htx)
ctx->field_num = ST_I_PX_PXNAME;
ctx->mod_field_num = 0;
appctx->st1 = PROMEX_DUMPER_BACK;
if (ctx->flags & PROMEX_FL_SCOPE_BACK) {
/* Update ctx.p[0] via watcher. */
watcher_attach(&ctx->px_watch, proxies_list);
}
__fallthrough;
case PROMEX_DUMPER_BACK:
@ -1765,7 +1792,8 @@ static int promex_dump_metrics(struct appctx *appctx, struct htx *htx)
appctx->st1 = PROMEX_DUMPER_SRV;
if (ctx->flags & PROMEX_FL_SCOPE_SERVER) {
ctx->p[0] = proxies_list;
/* Update ctx.p[0] via watcher. */
watcher_attach(&ctx->px_watch, proxies_list);
if (likely(proxies_list)) {
/* Update ctx.p[1] via watcher. */
watcher_attach(&ctx->srv_watch, proxies_list->srv);
@ -2048,6 +2076,7 @@ static int promex_appctx_init(struct appctx *appctx)
LIST_INIT(&ctx->modules);
ctx->filters = EB_ROOT;
appctx->st0 = PROMEX_ST_INIT;
watcher_init(&ctx->px_watch, &ctx->p[0], offsetof(struct proxy, watcher_list));
watcher_init(&ctx->srv_watch, &ctx->p[1], offsetof(struct server, watcher_list));
return 0;
}
@ -2062,6 +2091,11 @@ static void promex_appctx_release(struct appctx *appctx)
struct promex_metric_filter *flt;
struct eb32_node *node, *next;
if (appctx->st1 == PROMEX_DUMPER_BACK ||
appctx->st1 == PROMEX_DUMPER_SRV) {
watcher_detach(&ctx->px_watch);
}
if (appctx->st1 == PROMEX_DUMPER_SRV)
watcher_detach(&ctx->srv_watch);