config: postgres: add multiple database functionality

This commit contains the necessary changes to implement
a multiple same-database system, utilizing a linked-list.
Each linked list represents a database system, with each
node being a different database.

Changelog:
	- For each section parsed in the config file, create
	  a node. If the config contains multiple of the same
	  section, i.e. multiple databases of the same type,
	  then allocate memory for a new node that will hold
	  the config for each database.
	- Changed `db_t` struct to take a `void *` argument
	  instead of a specific database structure, and also
	  change some functions in a similar way. This change
	  was necessary in order to leverage generic programming
	  for the main functions (connect, replicate, close).
	- Added some helper function for the linked list.
	- Added more thread safe functionality to critical sections
	  of the codebase.
	- Changed the structure of the `configs` file, added `.ini`
	  files for testing single/multple databases

Signed-off-by: Panagiotis Foliadis <pfoliadis@hotmail.com>
Co-developed-by: Charalampos Mitrodimas <charmitro@posteo.net>

configs/example.ini

@@ -0,0 +1,32 @@
+[general]
+log_filepath=
+
+[postgres]
+enabled=
+
+origin_host=
+origin_user=
+origin_password=
+origin_port=
+origin_database=
+
+target_host=
+target_user=
+target_password=
+target_port=
+target_database=
+
+backup_type=
+email=
+
+[smtp]
+username= 
+password=
+smtp_host=
+smtp_port=
+auth_mode=
+enabled=
+
+from=
+to=
+cc=

configs/tests/multiple_db_config.ini

@@ -0,0 +1,47 @@
+[postgres]
+enabled=true
+
+origin_host=localhost
+origin_user=postgres
+origin_password=password
+origin_port=5432
+origin_database=postgres_origin
+
+target_host=localhost
+target_user=postgres
+target_password=password
+target_port=5432
+target_database=postgres_origin
+
+backup_type=full
+email=false
+
+[postgres]
+enabled=true
+
+origin_host=localhost
+origin_user=postgres
+origin_password=password
+origin_port=5433
+origin_database=postgres_origin
+
+target_host=localhost
+target_user=postgres
+target_password=password
+target_port=5433
+target_database=postgres_origin
+
+backup_type=full
+email=false
+
+[smtp]
+username = test@posteo.net
+password = 123
+smtp_host = posteo.de
+smtp_port = 587
+auth_mode = tls
+enabled=true
+
+from = charmitro@posteo.net
+to = charmitro@pm.me, trsbisb@gmail.com
+cc = charmitro@gmail.com, charmitro@terrasync.net

configs/test.ini → configs/tests/single_db_config.ini

@@ -5,16 +5,16 @@ origin_host=localhost
 origin_user=postgres
 origin_password=password
 origin_port=5432
-origin_database=postgres
+origin_database=postgres_origin
 
 target_host=localhost
 target_user=postgres
 target_password=password
 target_port=5432
-target_database=postgres
+target_database=postgres_origin
 
 backup_type=full
-email=true
+email=false
 
 [smtp]
 username = test@posteo.net

include/config.h

@@ -14,7 +14,7 @@ typedef enum backup_type {
 	FULL,
 } backup_type;
 
-typedef struct postgres_t {
+typedef struct postgres_node_t {
 	bool enabled;
 
 	d_str_t host;
@@ -25,7 +25,9 @@ typedef struct postgres_t {
 
 	backup_type backup_type;
 	bool email;
-} postgres_t;
+
+	struct postgres_node_t *next;
+} postgres_node_t;
 
 typedef enum auth_mode_t {
 	SSL = 1,
@@ -53,7 +55,7 @@ typedef struct general_t {
 } general_t;
 
 typedef struct config_t {
-	postgres_t *postgres_config;
+	postgres_node_t *postgres_config;
 	smtp_t *smtp_config;
 	general_t *general_config;
 } config_t;

include/db/db.h

@@ -2,6 +2,7 @@
 #define DB_H
 
 #include <stdio.h>
+#include <pthread.h>
 
 #include "config.h"
 
@@ -10,6 +11,7 @@ typedef int (*init_db_func)(void);
 
 extern init_db_func init_functions[MAX_AVAILABLE_DBS];
 extern int num_init_functions;
+extern pthread_mutex_t mutex;
 
 #define ADD_FUNC(init_func)                                               \
 	void __attribute__((constructor)) init_func##_register(void)      \
@@ -28,13 +30,13 @@ extern int num_init_functions;
 /* struct db_t
  * Holds the information every database will need.
  *
- * * postgres_t *pg_conf - inherited from the config
+ * * postgres_node_t *pg_conf - inherited from the config
  * * void *host_conn     - host connection, should be
  *                         allocated based on the target (e.g. PGconn *)
  * * void *target_conn   - target connection (same logic as host_conn)
  */
 struct db_t {
-	postgres_t *pg_conf;
+	void *db_conf;
 
 	void *origin_conn;
 	void *target_conn;
@@ -73,6 +75,14 @@ struct db_operations {
 	int (*replicate)(struct db_t *);
 };
 
+/*
+ * execute_db_operations
+ *
+ * Returns:
+ *   0 Success
+ *  -2 Error creating thread
+ *  -ENOMEM Error allocating memory
+ */
 int execute_db_operations(void);
 
 #endif

include/db/postgres.h

@@ -17,6 +17,7 @@
  *
  *  Returns:
  *  0 on success
+ * -1 Maximum number of available databases reached
  * -ENOMEM Error allocating memory
  *
  */
@@ -34,4 +35,8 @@ int connect_pg(struct db_t *);
 void close_pg(struct db_t *pg_db_t);
 int replicate(struct db_t *pg_db_t);
 
+bool is_enabled(void *);
+const char *get_origin(void *);
+void *get_next(void *);
+
 #endif

include/util.h

@@ -5,6 +5,7 @@
 #include <stdio.h>
 
 #include "log.h"
+#include "db/db.h"
 
 #ifdef _POSIX_C_SOURCE
 #include <limits.h>
@@ -90,4 +91,18 @@ static inline int cnc_strdup(char **string, char *string_to_dup)
  */
 void construct_filepath(char *path, char *filename);
 
+/*
+ * Append `.sql` to a string, mainly to create dump files for SQL-like databases
+ */
+void construct_sql_dump_file(char *backup_filename, const char *database_name);
+
+/*
+ * This function is responsible for iterating through a linked list and for
+ * each node, allocating the correct db structs and populating the `available_dbs` array.
+ */
+int construct_db(void *db_config, bool (*is_enabled)(void *),
+		 void *(*get_next)(void *), const char *(*get_origin)(void *),
+		 int (*connect_func)(struct db_t *),
+		 void (*close_func)(struct db_t *),
+		 int (*replicate_func)(struct db_t *), size_t size_of_node);
 #endif

scripts/postgres-down.sh

@@ -1,9 +1,17 @@
 #! /bin/bash
 
-if docker ps --format "{{.Names}}" | grep -q "cnc-postgres"; then
-    docker stop cnc-postgres
-    docker rm cnc-postgres
-    echo "PostgreSQL Docker container was successfully removed."
+if docker ps --format "{{.Names}}" | grep -q "cnc-postgres-origin"; then
+    docker stop cnc-postgres-origin
+    docker rm cnc-postgres-origin
+    echo "Postgres-origin docker container was successfully removed."
 else
-    echo "PostgreSQL Docker container is not currently running."
+    echo "Postgre-origin docker container is not currently running."
+fi
+
+if docker ps --format "{{.Names}}" | grep -q "cnc-postgres-target"; then
+    docker stop cnc-postgres-target
+    docker rm cnc-postgres-target
+    echo "Postgres-target docker container was successfully removed."
+else
+    echo "Postgres-target docker container is not currently running."
 fi

scripts/postgres-up.sh

@@ -9,13 +9,26 @@ To install docker visit (https://docs.docker.com/engine/install/)."
     exit 1
 fi
 
-docker_args="--name cnc-postgres -d \
-		  -e POSTGRES_PASSWORD=password \
-		  -p 5432:5432 postgres:15"
+docker_args_origin="--name cnc-postgres-origin -d \
+		  -e POSTGRES_PASSWORD=password   \
+                  -e POSTGRES_DB=postgres_origin \
+		  -p 5432:5432 postgres:14"
 
-if docker run $docker_args; then
-    echo "Postgres container was successfully set up."
+if docker run $docker_args_origin; then
+    echo "Postgres-origin container was successfully set up."
 else
-    echo "Failed to start the Postgres container."
+    echo "Failed to start the Postgres-origin container."
+    exit 1
+fi
+
+docker_args_target="--name cnc-postgres-target -d \
+                    -e POSTGRES_PASSWORD=password \
+                    -e POSTGRES_DB=postgres_target \
+                    -p 5433:5432 postgres:14"
+
+if docker run $docker_args_target; then
+    echo "Postgres-target container was successfully set up."
+else
+    echo "Failed to start the Postgres-target container."
     exit 1
 fi

src/cnc.c

@@ -42,6 +42,9 @@ int process_args(int argc, char **argv)
 	int c;
 	char *config_file = NULL;
 
+	// This is needed to access the localtime in a thread-safe manner
+	tzset();
+
 	optind = 0;
 	while ((c = getopt_long(argc, argv, "f:vhV", options, NULL)) != -1) {
 		switch (c) {

src/config.c

@@ -9,6 +9,7 @@
 
 config_t *ini_config;
 char *log_filepath;
+bool new_node = false;
 
 #define CHECK_SECTION(s) strcmp(section, s) == 0
 #define MATCH(s, n) strcmp(section, s) == 0 && strcmp(name, n) == 0
@@ -47,6 +48,14 @@ int handler(void *user, const char *section, const char *name,
 	}
 
 	if (CHECK_SECTION("postgres")) {
+		// If true, create a new node, and change the head of our linked list.
+		if (new_node) {
+			postgres_node_t *temp_node =
+				CNC_MALLOC(sizeof(postgres_node_t));
+			temp_node->next = ini_config->postgres_config;
+			ini_config->postgres_config = temp_node;
+			new_node = false;
+		}
 		if (MATCH("postgres", "enabled")) {
 			if (strcmp("true", value) == 0) {
 				ini_config->postgres_config->enabled = true;
@@ -108,6 +117,12 @@ int handler(void *user, const char *section, const char *name,
 					"Accepted `enabled` values are \"true\" or \"false\".\n");
 				return 0;
 			}
+			/*
+			 * Since we reached the end of the `postgres` section, we need to change
+			 * the flag so we can create a new node the next time we enter to
+			 * this section.
+			 */
+			new_node = true;
 		} else {
 			return 0;
 		}
@@ -164,7 +179,8 @@ int initialize_config(const char *config_file)
 	int ret = 0;
 
 	ini_config = CNC_MALLOC(sizeof(config_t));
-	ini_config->postgres_config = CNC_MALLOC(sizeof(postgres_t));
+	ini_config->postgres_config = CNC_MALLOC(sizeof(postgres_node_t));
+	ini_config->postgres_config->next = NULL;
 	ini_config->smtp_config = CNC_MALLOC(sizeof(smtp_t));
 	ini_config->general_config = CNC_MALLOC(sizeof(general_t));
 	ini_config->general_config->log_filepath = NULL;
@@ -183,28 +199,38 @@ int initialize_config(const char *config_file)
 	return ret;
 }
 
+/*
+ * A helper function to free each node that we allocated. We iterate through the list
+ * and free all the fields that we have parsed from the `.ini` file.
+ */
+void config_free_linked_list(postgres_node_t *head)
+{
+	postgres_node_t *temp;
+	while (head != NULL) {
+		temp = head;
+		head = head->next;
+		free((void *)temp->host.origin);
+		free((void *)temp->user.origin);
+		free((void *)temp->password.origin);
+		free((void *)temp->port.origin);
+		free((void *)temp->database.origin);
+		free((void *)temp->host.target);
+		free((void *)temp->user.target);
+		free((void *)temp->password.target);
+		free((void *)temp->port.target);
+		free((void *)temp->database.target);
+		free(temp);
+	}
+}
+
 void free_config(void)
 {
-	free((void *)ini_config->postgres_config->host.origin);
-	free((void *)ini_config->postgres_config->user.origin);
-	free((void *)ini_config->postgres_config->password.origin);
-	free((void *)ini_config->postgres_config->port.origin);
-	free((void *)ini_config->postgres_config->database.origin);
-
-	free((void *)ini_config->postgres_config->host.target);
-	free((void *)ini_config->postgres_config->user.target);
-	free((void *)ini_config->postgres_config->password.target);
-	free((void *)ini_config->postgres_config->port.target);
-	free((void *)ini_config->postgres_config->database.target);
+	config_free_linked_list(ini_config->postgres_config);
 
 	free((void *)ini_config->smtp_config->username);
 	free((void *)ini_config->smtp_config->password);
 	free((void *)ini_config->smtp_config->smtp_port);
 	free((void *)ini_config->smtp_config->smtp_host);
-
-	if (ini_config->general_config->log_filepath != NULL) {
-		free((void *)ini_config->general_config->log_filepath);
-	}
 	free((void *)ini_config->smtp_config->from);
 
 	for (int i = 0; i < ini_config->smtp_config->to_len; i++) {
@@ -214,8 +240,9 @@ void free_config(void)
 		free(ini_config->smtp_config->cc[i]);
 	}
 
+	free((void *)ini_config->general_config->log_filepath);
+
 	free(ini_config->smtp_config);
-	free(ini_config->postgres_config);
 	free(ini_config->general_config);
 	free(ini_config);
 	free(log_filepath);