feat: json log format

Introduce a json log format that can be invoked by passing `log-format json` in your config.

Signed-off-by: Johan Bergström <bugs@bergstroem.nu>

Author: jbergstroem

src/config.c

@@ -153,7 +153,7 @@ configEnum propagation_error_behavior_enum[] = {
     {"panic-on-replicas", PROPAGATION_ERR_BEHAVIOR_PANIC_ON_REPLICAS},
     {NULL, 0}};
 
-configEnum log_format_enum[] = {{"legacy", LOG_FORMAT_LEGACY}, {"logfmt", LOG_FORMAT_LOGFMT}, {NULL, 0}};
+configEnum log_format_enum[] = {{"legacy", LOG_FORMAT_LEGACY}, {"logfmt", LOG_FORMAT_LOGFMT}, {"json", LOG_FORMAT_JSON}, {NULL, 0}};
 
 configEnum log_timestamp_format_enum[] = {{"legacy", LOG_TIMESTAMP_LEGACY},
                                           {"iso8601", LOG_TIMESTAMP_ISO8601},

src/server.c

@@ -177,6 +177,8 @@ void serverLogRaw(int level, const char *msg) {
     const char *verbose_level[] = {"debug", "info", "notice", "warning"};
     const char *roles[] = {"sentinel", "RDB/AOF", "replica", "primary"};
     const char *role_chars = "XCSM";
+    const char *json_format = "{\"pid\":%d,\"role\":\"%s\",\"timestamp\":\"%s\",\"level\":\"%s\",\"message\":\"%s\"}\n";
+    const char *logfmt_format = "pid=%d role=%s timestamp=\"%s\" level=%s message=\"%s\"\n";
     FILE *fp;
     char buf[64];
     int rawmode = (level & LL_RAW);
@@ -229,13 +231,14 @@ void serverLogRaw(int level, const char *msg) {
         }
         switch (server.log_format) {
         case LOG_FORMAT_LOGFMT:
+        case LOG_FORMAT_JSON:
             if (hasInvalidLogfmtChar(msg)) {
                 char safemsg[LOG_MAX_LEN];
                 filterInvalidLogfmtChar(safemsg, LOG_MAX_LEN, msg);
-                fprintf(fp, "pid=%d role=%s timestamp=\"%s\" level=%s message=\"%s\"\n", (int)getpid(), roles[role_index],
+                fprintf(fp, server.log_format == LOG_FORMAT_LOGFMT ? logfmt_format : json_format, (int)getpid(), roles[role_index],
                         buf, verbose_level[level], safemsg);
             } else {
-                fprintf(fp, "pid=%d role=%s timestamp=\"%s\" level=%s message=\"%s\"\n", (int)getpid(), roles[role_index],
+                fprintf(fp, server.log_format == LOG_FORMAT_LOGFMT ? logfmt_format : json_format, (int)getpid(), roles[role_index],
                         buf, verbose_level[level], msg);
             }
             break;

src/server.h

@@ -595,7 +595,8 @@ typedef enum {
 
 /* Sets log format */
 typedef enum { LOG_FORMAT_LEGACY = 0,
-               LOG_FORMAT_LOGFMT } log_format_type;
+               LOG_FORMAT_LOGFMT,
+               LOG_FORMAT_JSON } log_format_type;
 
 /* Sets log timestamp format */
 typedef enum { LOG_TIMESTAMP_LEGACY = 0,

valkey.conf

@@ -401,6 +401,7 @@ loglevel notice
 #
 # - legacy: the default, traditional log format
 # - logfmt: a structured log format; see https://www.brandur.org/logfmt
+# - json: a structured log format; see https://json.org/
 #
 # log-format legacy