Add CONFIG SET and GET loglevel feature in Sentinel (redis#11214)

Till now Sentinel allowed modifying the log level in the config file, but not at runtime.
this makes it possible to tune the log level at runtime

sentinel.conf

@@ -19,6 +19,14 @@ daemonize no
 # location here.
 pidfile /var/run/redis-sentinel.pid
 
+# Specify the server verbosity level.
+# This can be one of:
+# debug (a lot of information, useful for development/testing)
+# verbose (many rarely useful info, but not a mess like the debug level)
+# notice (moderately verbose, what you want in production probably)
+# warning (only very important / critical messages are logged)
+loglevel notice
+
 # Specify the log file name. Also the empty string can be used to force
 # Sentinel to log on the standard output. Note that if you use standard
 # output for logging but daemonize, logs will be sent to /dev/null

src/sentinel.c

@@ -3182,7 +3182,17 @@ void sentinelSendPeriodicCommands(sentinelRedisInstance *ri) {
 
 /* =========================== SENTINEL command ============================= */
 
-/* SENTINEL CONFIG SET <option> */
+const char* getLogLevel() {
+   switch (server.verbosity) {
+    case LL_DEBUG: return "debug";
+    case LL_VERBOSE: return "verbose";
+    case LL_NOTICE: return "notice";
+    case LL_WARNING: return "warning";
+    }
+    return "unknown";
+}
+
+/* SENTINEL CONFIG SET <option> <value>*/
 void sentinelConfigSetCommand(client *c) {
     robj *o = c->argv[3];
     robj *val = c->argv[4];
@@ -3213,6 +3223,17 @@ void sentinelConfigSetCommand(client *c) {
         sentinel.sentinel_auth_pass = sdslen(val->ptr) == 0 ?
             NULL : sdsdup(val->ptr);
         drop_conns = 1;
+    } else if (!strcasecmp(o->ptr, "loglevel")) {
+        if (!strcasecmp(val->ptr, "debug"))
+            server.verbosity = LL_DEBUG;
+        else if (!strcasecmp(val->ptr, "verbose"))
+            server.verbosity = LL_VERBOSE;
+        else if (!strcasecmp(val->ptr, "notice"))
+            server.verbosity = LL_NOTICE;
+        else if (!strcasecmp(val->ptr, "warning"))
+            server.verbosity = LL_WARNING;
+        else
+            goto badfmt;
     } else {
         addReplyErrorFormat(c, "Invalid argument '%s' to SENTINEL CONFIG SET",
                             (char *) o->ptr);
@@ -3275,6 +3296,11 @@ void sentinelConfigGetCommand(client *c) {
         matches++;
     }
 
+    if (stringmatch(pattern, "loglevel", 1)) {
+        addReplyBulkCString(c, "loglevel");
+        addReplyBulkCString(c, getLogLevel());
+        matches++;
+    }
     setDeferredMapLen(c, replylen, matches);
 }
 

tests/sentinel/tests/01-conf-update.tcl

@@ -37,3 +37,11 @@ test "After Sentinel 1 is restarted, its config gets updated" {
 test "New master [join $addr {:}] role matches" {
     assert {[RI $master_id role] eq {master}}
 }
+
+test "Update log level" {
+    set current_loglevel [S 0 SENTINEL CONFIG GET loglevel]
+    assert {[lindex $current_loglevel 1] == {notice}}
+    S 0 SENTINEL CONFIG SET loglevel warning
+    set updated_loglevel [S 0 SENTINEL CONFIG GET loglevel]
+    assert {[lindex $updated_loglevel 1] == {warning}}
+}