Support setlocale via CONFIG operation. (#11059)

Till now Redis officially supported tuning it via environment variable see #1074.
But we had other requests to allow changing it at runtime, see #799, and #11041.

Note that `strcoll()` is used as Lua comparison function and also for comparison of
certain string objects in Redis, which leads to a problem that, in different regions,
for some characters, the result may be different. Below is an example.
```
127.0.0.1:6333> SORT test alpha
1) "<"
2) ">"
3) ","
4) "*"
127.0.0.1:6333> CONFIG GET locale-collate
1) "locale-collate"
2) ""
127.0.0.1:6333> CONFIG SET locale-collate 1
(error) ERR CONFIG SET failed (possibly related to argument 'locale')
127.0.0.1:6333> CONFIG SET locale-collate C
OK
127.0.0.1:6333> SORT test alpha
1) "*"
2) ","
3) "<"
4) ">"
```
That will cause accidental code compatibility issues for Lua scripts and some
Redis commands. This commit creates a new config parameter to control the
local environment which only affects `Collate` category. Above shows how it
affects `SORT` command, and below shows the influence on Lua scripts.
```
127.0.0.1:6333> CONFIG GET locale-collate
1) " locale-collate"
2) "C"
127.0.0.1:6333> EVAL "return ',' < '*'" 0
(nil)
127.0.0.1:6333> CONFIG SET locale-collate ""
OK
127.0.0.1:6333> EVAL "return ',' < '*'" 0
(integer) 1
```

Co-authored-by: calvincjli <calvincjli@tencent.com>
Co-authored-by: Oran Agra <oran@redislabs.com>

1 files changed, 11 insertions, 0 deletions

diff --git a/src/config.c b/src/config.c
index 0ffe65a61..f98225cbe 100644
--- a/src/config.c
+++ b/src/config.c
@@ -35,6 +35,7 @@
 #include <sys/stat.h>
 #include <glob.h>
 #include <string.h>
+#include <locale.h>
 
 /*-----------------------------------------------------------------------------
  * Config file name-value maps.
@@ -2400,6 +2401,15 @@ static int isValidProcTitleTemplate(char *val, const char **err) {
     return 1;
 }
 
+static int updateLocaleCollate(const char **err) {
+    const char *s = setlocale(LC_COLLATE, server.locale_collate);
+    if (s == NULL) {
+        *err = "Invalid locale name";
+        return 0;
+    }
+    return 1;
+}
+
 static int updateProcTitleTemplate(const char **err) {
     if (redisSetProcTitle(NULL) == C_ERR) {
         *err = "failed to set process title";
@@ -2995,6 +3005,7 @@ standardConfig static_configs[] = {
     createStringConfig("proc-title-template", NULL, MODIFIABLE_CONFIG, ALLOW_EMPTY_STRING, server.proc_title_template, CONFIG_DEFAULT_PROC_TITLE_TEMPLATE, isValidProcTitleTemplate, updateProcTitleTemplate),
     createStringConfig("bind-source-addr", NULL, MODIFIABLE_CONFIG, EMPTY_STRING_IS_NULL, server.bind_source_addr, NULL, NULL, NULL),
     createStringConfig("logfile", NULL, IMMUTABLE_CONFIG, ALLOW_EMPTY_STRING, server.logfile, "", NULL, NULL),
+    createStringConfig("locale-collate", NULL, MODIFIABLE_CONFIG, ALLOW_EMPTY_STRING, server.locale_collate, "", NULL, updateLocaleCollate),
 
     /* SDS Configs */
     createSDSConfig("masterauth", NULL, MODIFIABLE_CONFIG | SENSITIVE_CONFIG, EMPTY_STRING_IS_NULL, server.masterauth, NULL, NULL, NULL),