in_http: add configurable health endpoint

Add optional health endpoint accessible via GET /health when enabled.
The endpoint returns JSON with status, version, git hash and timestamp
instead of the original Matrix movie quote. The endpoint is disabled
by default for security.

The health_check configuration directive enables the endpoint:
  health_check true

Fixes #10003
Supersedes PR #10020

Author: niedbalski

plugins/in_http/http.c

@@ -234,6 +234,11 @@ static struct flb_config_map config_map[] = {
      "Set successful response code. 200, 201 and 204 are supported."
     },
 
+    {
+     FLB_CONFIG_MAP_BOOL, "health_check", "false",
+     0, FLB_TRUE, offsetof(struct flb_http, enable_health_endpoint),
+     "Enable health check endpoint accessible via GET /health"
+    },
 
     /* EOF */
     {0}

plugins/in_http/http.h

@@ -61,6 +61,9 @@ struct flb_http {
     struct mk_server *server;
 
     int collector_id;
+
+    /* Health endpoint configuration */
+    int enable_health_endpoint;
 };
 
 

plugins/in_http/http_prot.c

@@ -34,6 +34,7 @@
 
 #define HTTP_CONTENT_JSON       0
 #define HTTP_CONTENT_URLENCODED 1
+#define HTTP_HEALTH_ENDPOINT    "/health"
 
 static inline char hex2nibble(char c)
 {
@@ -95,18 +96,19 @@ cfl_sds_t get_health_message()
              tm_time.tm_year + 1900, tm_time.tm_mon + 1, tm_time.tm_mday,
              tm_time.tm_hour, tm_time.tm_min, tm_time.tm_sec, tm.tm.tv_nsec);
 
-    msg = cfl_sds_create_size(256);
+    msg = cfl_sds_create_size(512);
     if (!msg) {
         return NULL;
     }
 
     cfl_sds_printf(&msg,
                   "{\n"
                   "  \"status\": \"ok\",\n"
-                  "  \"message\": \"I can only show you the door. You're the one that has to walk through it.\",\n"
+                  "  \"version\": \"%s\",\n"
+                  "  \"git_hash\": \"%s\",\n"
                   "  \"timestamp\": \"%s\"\n"
                   "}\n",
-                  time_str);
+                  FLB_VERSION_STR, FLB_GIT_HASH, time_str);
 
     return msg;
 }
@@ -990,7 +992,7 @@ int http_prot_handle(struct flb_http *ctx, struct http_conn *conn,
         request->_content_length.data = NULL;
     }
 
-    if (request->method == MK_METHOD_GET && strcmp(uri, "/health") == 0) {
+    if (request->method == MK_METHOD_GET && strcmp(uri, HTTP_HEALTH_ENDPOINT) == 0 && ctx->enable_health_endpoint) {
         flb_sds_destroy(tag);
         mk_mem_free(uri);
         health = get_health_message();
@@ -1324,7 +1326,7 @@ int http_prot_handle_ng(struct flb_http_request *request,
         return -1;
     }
 
-    if (request->method == HTTP_METHOD_GET && strcmp(request->path, "/health") == 0) {
+    if (request->method == HTTP_METHOD_GET && strcmp(request->path, HTTP_HEALTH_ENDPOINT) == 0 && ctx->enable_health_endpoint) {
         flb_sds_destroy(tag);
         health = get_health_message();
         send_response_ng(response, 200, health);