[agroal#335] Disambiguate connection errors from data errors in commands

This commit introduces a few constants to indicate if the
communication over the management socket has failed due to a
connection error or because the data received is not valid.
So far, only `config-get` returns a different value to indicate
invalid data over the socket, but other commands can take advanatge of
this too.

The `pgagroal-cli` main loop has been refactored to distinguish the
new cases, and now it prints the "connection error" message only when
the low level function reports such an error.

All the functions now return a specific value among those defined.

Close agroal#335

src/cli.c

@@ -621,9 +621,18 @@ main(int argc, char** argv)
 
    if (configuration_path != NULL)
    {
-      if (action != ACTION_UNKNOWN && exit_code != 0)
+      if (action != ACTION_UNKNOWN)
       {
-         printf("Connection error on %s\n", config->unix_socket_dir);
+         switch (exit_code)
+         {
+            case EXIT_STATUS_CONNECTION_ERROR:
+               printf("Connection error on %s\n", config->unix_socket_dir);
+               break;
+            case EXIT_STATUS_DATA_ERROR:
+            case EXIT_STATUS_OK:
+               break;
+         }
+
       }
    }
 
@@ -637,7 +646,7 @@ main(int argc, char** argv)
 
    if (verbose)
    {
-      warnx("%s (%d)\n", exit_code == 0 ? "Success" : "Error", exit_code);
+      warnx("%s (%d)\n", exit_code == EXIT_STATUS_OK ? "Success" : "Error", exit_code);
    }
 
    return exit_code;
@@ -648,65 +657,65 @@ flush(SSL* ssl, int socket, int32_t mode, char* database)
 {
    if (pgagroal_management_flush(ssl, socket, mode, database))
    {
-      return 1;
+      return EXIT_STATUS_CONNECTION_ERROR;
    }
 
-   return 0;
+   return EXIT_STATUS_OK;
 }
 
 static int
 enabledb(SSL* ssl, int socket, char* database)
 {
    if (pgagroal_management_enabledb(ssl, socket, database))
    {
-      return 1;
+      return EXIT_STATUS_CONNECTION_ERROR;
    }
 
-   return 0;
+   return EXIT_STATUS_OK;
 }
 
 static int
 disabledb(SSL* ssl, int socket, char* database)
 {
    if (pgagroal_management_disabledb(ssl, socket, database))
    {
-      return 1;
+      return EXIT_STATUS_CONNECTION_ERROR;
    }
 
-   return 0;
+   return EXIT_STATUS_OK;
 }
 
 static int
 gracefully(SSL* ssl, int socket)
 {
    if (pgagroal_management_gracefully(ssl, socket))
    {
-      return 1;
+      return EXIT_STATUS_CONNECTION_ERROR;
    }
 
-   return 0;
+   return EXIT_STATUS_OK;
 }
 
 static int
 stop(SSL* ssl, int socket)
 {
    if (pgagroal_management_stop(ssl, socket))
    {
-      return 1;
+      return EXIT_STATUS_CONNECTION_ERROR;
    }
 
-   return 0;
+   return EXIT_STATUS_OK;
 }
 
 static int
 cancel_shutdown(SSL* ssl, int socket)
 {
    if (pgagroal_management_cancel_shutdown(ssl, socket))
    {
-      return 1;
+      return EXIT_STATUS_CONNECTION_ERROR;
    }
 
-   return 0;
+   return EXIT_STATUS_OK;
 }
 
 static int
@@ -718,7 +727,7 @@ status(SSL* ssl, int socket)
    }
    else
    {
-      return 1;
+      return EXIT_STATUS_CONNECTION_ERROR;
    }
 }
 
@@ -734,7 +743,7 @@ details(SSL* ssl, int socket)
    }
 
    // if here, an error occurred
-   return 1;
+   return EXIT_STATUS_CONNECTION_ERROR;
 
 }
 
@@ -747,64 +756,64 @@ isalive(SSL* ssl, int socket)
    {
       if (pgagroal_management_read_isalive(ssl, socket, &status))
       {
-         return 1;
+         return EXIT_STATUS_CONNECTION_ERROR;
       }
 
       if (status != 1 && status != 2)
       {
-         return 1;
+         return EXIT_STATUS_CONNECTION_ERROR;
       }
    }
    else
    {
-      return 1;
+      return EXIT_STATUS_CONNECTION_ERROR;
    }
 
-   return 0;
+   return EXIT_STATUS_OK;
 }
 
 static int
 reset(SSL* ssl, int socket)
 {
    if (pgagroal_management_reset(ssl, socket))
    {
-      return 1;
+      return EXIT_STATUS_CONNECTION_ERROR;
    }
 
-   return 0;
+   return EXIT_STATUS_OK;
 }
 
 static int
 reset_server(SSL* ssl, int socket, char* server)
 {
    if (pgagroal_management_reset_server(ssl, socket, server))
    {
-      return 1;
+      return EXIT_STATUS_CONNECTION_ERROR;
    }
 
-   return 0;
+   return EXIT_STATUS_OK;
 }
 
 static int
 switch_to(SSL* ssl, int socket, char* server)
 {
    if (pgagroal_management_switch_to(ssl, socket, server))
    {
-      return 1;
+      return EXIT_STATUS_CONNECTION_ERROR;
    }
 
-   return 0;
+   return EXIT_STATUS_OK;
 }
 
 static int
 reload(SSL* ssl, int socket)
 {
    if (pgagroal_management_reload(ssl, socket))
    {
-      return 1;
+      return EXIT_STATUS_CONNECTION_ERROR;
    }
 
-   return 0;
+   return EXIT_STATUS_OK;
 }
 
 /**
@@ -818,7 +827,7 @@ reload(SSL* ssl, int socket)
  * @param config_key the key of the configuration parameter, that is the name
  * of the configuration parameter to read.
  * @param verbose if true the function will print on STDOUT also the config key
- * @returns 0 on success, 1 on failure
+ * @returns 0 on success, 1 on network failure, 2 on data failure
  */
 static int
 config_get(SSL* ssl, int socket, char* config_key, bool verbose)
@@ -844,9 +853,9 @@ config_get(SSL* ssl, int socket, char* config_key, bool verbose)
          goto error;
       }
 
-      // assume an empty response is ok,
-      // do not throw an error to indicate no configuration
-      // setting with such name as been found
+      // an empty response means that the
+      // requested configuration parameter has not been
+      // found, so throw an error
       if (buffer && strlen(buffer))
       {
          if (verbose)
@@ -858,13 +867,17 @@ config_get(SSL* ssl, int socket, char* config_key, bool verbose)
             printf("%s\n", buffer);
          }
       }
+      else
+      {
+         free(buffer);
+         return EXIT_STATUS_DATA_ERROR;
+      }
 
       free(buffer);
-      return 0;
    }
 
-   return 0;
+   return EXIT_STATUS_OK;
 
 error:
-   return 1;
+   return EXIT_STATUS_CONNECTION_ERROR;
 }

src/include/pgagroal.h

@@ -141,6 +141,15 @@ extern "C" {
 #define UPDATE_PROCESS_TITLE_MINIMAL 2
 #define UPDATE_PROCESS_TITLE_VERBOSE 3
 
+/**
+ * Constants used to manage the exit code
+ * of a command sent over the socket in the
+ * management stuff, e.g., `pgagroal-cli`.
+ */
+#define EXIT_STATUS_OK               0
+#define EXIT_STATUS_CONNECTION_ERROR 1
+#define EXIT_STATUS_DATA_ERROR       2
+
 #define likely(x)    __builtin_expect (!!(x), 1)
 #define unlikely(x)  __builtin_expect (!!(x), 0)
 

src/libpgagroal/management.c

@@ -1552,7 +1552,7 @@ pgagroal_management_write_config_get(int socket, char* config_key)
    if (pgagroal_write_config_value(&data[0], config_key))
    {
       pgagroal_log_warn("pgagroal_management_write_config_get: unknwon configuration key <%s>", config_key);
-      goto error;
+      // leave the payload empty, so a zero filled payload will be sent
    }
 
    // send the size of the payload