[#361] Add a max_connection_age setting

This defines how long a connection will live in seconds
- Add a `max_connection_age` member to `struct configuration`. It will be checked upon returned to the pool, or during idle timeout.
- Add new STATE, TRACKER, and Prometheus metric for `max_connection_age`
- Add documentation for `max_connection_age`
- Add a `start_time` member to `struct connection`. Its implementation is similar to `timestamp`

doc/ARCHITECTURE.md

@@ -35,6 +35,7 @@ connection, and move them around in the connection state diagram. The state diag
 | `STATE_GRACEFULLY` | The connection will be killed upon return to the pool |
 | `STATE_FLUSH` | The connection is being flushed |
 | `STATE_IDLE_CHECK` | The connection is being idle timeout checked |
+| `STATE_MAX_CONNECTION_AGE` | The connection is being max connection age checked |
 | `STATE_VALIDATION` | The connection is being validated |
 | `STATE_REMOVE` | The connection is being removed |
 

doc/CONFIGURATION.md

@@ -61,6 +61,7 @@ The available keys and their accepted values are reported in the table below.
 | log_disconnections | `off` | Bool | No | Log disconnects |
 | blocking_timeout | 30 | Int | No | The number of seconds the process will be blocking for a connection (disable = 0) |
 | idle_timeout | 0 | Int | No | The number of seconds a connection is been kept alive (disable = 0) |
+| max_connection_age | 0 | Int | No | The maximum number of seconds that a connection will live (disable = 0) |
 | validation | `off` | String | No | Should connection validation be performed. Valid options: `off`, `foreground` and `background` |
 | background_interval | 300 | Int | No | The interval between background validation scans in seconds |
 | max_retries | 5 | Int | No | The maximum number of iterations to obtain a connection |

doc/PIPELINES.md

@@ -97,8 +97,8 @@ latency.
 __Important__
 
 Make sure that the `blocking_timeout` settings to set to 0. Otherwise active clients
-may timeout during their workload. Likewise it is best to disable idle connection timeout by
-setting `idle_timeout` to 0.
+may timeout during their workload. Likewise it is best to disable idle connection timeout 
+and max connection age by setting `idle_timeout` and `max_connection_age` to 0.
 
 It is highly recommended that you prefill all connections for each user.
 

doc/man/pgagroal.conf.5.rst

@@ -95,6 +95,9 @@ blocking_timeout
 idle_timeout
   The number of seconds a connection is been kept alive (disable = 0). Default is 0
 
+max_connection_age
+  The maximum number of seconds that a connection will live (disable = 0). Default is 0
+
 validation
   Should connection validation be performed. Valid options: off, foreground and background. Default is off
 

src/include/pgagroal.h

@@ -92,15 +92,16 @@ extern "C" {
 
 #define NUMBER_OF_SECURITY_MESSAGES 5
 
-#define STATE_NOTINIT    -2
-#define STATE_INIT       -1
-#define STATE_FREE        0
-#define STATE_IN_USE      1
-#define STATE_GRACEFULLY  2
-#define STATE_FLUSH       3
-#define STATE_IDLE_CHECK  4
-#define STATE_VALIDATION  5
-#define STATE_REMOVE      6
+#define STATE_NOTINIT           -2
+#define STATE_INIT              -1
+#define STATE_FREE               0
+#define STATE_IN_USE             1
+#define STATE_GRACEFULLY         2
+#define STATE_FLUSH              3
+#define STATE_IDLE_CHECK         4
+#define STATE_MAX_CONNECTION_AGE 5
+#define STATE_VALIDATION         6
+#define STATE_REMOVE             7
 
 #define SECURITY_INVALID  -2
 #define SECURITY_REJECT   -1
@@ -280,6 +281,7 @@ struct connection
    int backend_secret; /**< The backend secret */
 
    signed char limit_rule; /**< The limit rule used */
+   time_t start_time;      /**< The start timestamp */
    time_t timestamp;       /**< The last used timestamp */
    pid_t pid;              /**< The associated process id */
    int fd;                 /**< The descriptor */
@@ -359,16 +361,17 @@ struct prometheus
    atomic_ulong session_time[HISTOGRAM_BUCKETS]; /**< The histogram buckets */
    atomic_ulong session_time_sum;                /**< Total session time */
 
-   atomic_ulong connection_error;       /**< The number of error calls */
-   atomic_ulong connection_kill;        /**< The number of kill calls */
-   atomic_ulong connection_remove;      /**< The number of remove calls */
-   atomic_ulong connection_timeout;     /**< The number of timeout calls */
-   atomic_ulong connection_return;      /**< The number of return calls */
-   atomic_ulong connection_invalid;     /**< The number of invalid calls */
-   atomic_ulong connection_get;         /**< The number of get calls */
-   atomic_ulong connection_idletimeout; /**< The number of idle timeout calls */
-   atomic_ulong connection_flush;       /**< The number of flush calls */
-   atomic_ulong connection_success;     /**< The number of success calls */
+   atomic_ulong connection_error;              /**< The number of error calls */
+   atomic_ulong connection_kill;               /**< The number of kill calls */
+   atomic_ulong connection_remove;             /**< The number of remove calls */
+   atomic_ulong connection_timeout;            /**< The number of timeout calls */
+   atomic_ulong connection_return;             /**< The number of return calls */
+   atomic_ulong connection_invalid;            /**< The number of invalid calls */
+   atomic_ulong connection_get;                /**< The number of get calls */
+   atomic_ulong connection_idletimeout;        /**< The number of idle timeout calls */
+   atomic_ulong connection_max_connection_age; /**< The number of max connection age calls */
+   atomic_ulong connection_flush;              /**< The number of flush calls */
+   atomic_ulong connection_success;            /**< The number of success calls */
 
    /**< The number of connection awaiting due to `blocking_timeout` */
    atomic_ulong connections_awaiting[NUMBER_OF_LIMITS];
@@ -451,6 +454,7 @@ struct configuration
 
    int blocking_timeout;         /**< The blocking timeout in seconds */
    int idle_timeout;             /**< The idle timeout in seconds */
+   int max_connection_age;       /**< The max connection age in seconds */
    int validation;               /**< Validation mode */
    int background_interval;      /**< Background validation timer in seconds */
    int max_retries;              /**< The maximum number of retries */

src/include/pool.h

@@ -77,6 +77,12 @@ pgagroal_kill_connection(int slot, SSL* ssl);
 void
 pgagroal_idle_timeout(void);
 
+/**
+ * Perform max connection age check
+ */
+void
+pgagroal_max_connection_age(void);
+
 /**
  * Perform connection validation
  */

src/include/prometheus.h

@@ -125,6 +125,12 @@ pgagroal_prometheus_connection_get(void);
 void
 pgagroal_prometheus_connection_idletimeout(void);
 
+/**
+ * Connection max connection age
+ */
+void
+pgagroal_prometheus_connection_max_connection_age(void);
+
 /**
  * Connection awaiting due to `blocking_timeout`.
  * Tracks the total awaiting connections and also the

src/include/tracker.h

@@ -51,17 +51,18 @@ extern "C" {
 
 #define TRACKER_BAD_CONNECTION              9
 #define TRACKER_IDLE_TIMEOUT               10
-#define TRACKER_INVALID_CONNECTION         11
-#define TRACKER_FLUSH                      12
-#define TRACKER_REMOVE_CONNECTION          13
-
-#define TRACKER_PREFILL                    14
-#define TRACKER_PREFILL_RETURN             15
-#define TRACKER_PREFILL_KILL               16
-#define TRACKER_WORKER_RETURN1             17
-#define TRACKER_WORKER_RETURN2             18
-#define TRACKER_WORKER_KILL1               19
-#define TRACKER_WORKER_KILL2               20
+#define TRACKER_MAX_CONNECTION_AGE         11
+#define TRACKER_INVALID_CONNECTION         12
+#define TRACKER_FLUSH                      13
+#define TRACKER_REMOVE_CONNECTION          14
+
+#define TRACKER_PREFILL                    15
+#define TRACKER_PREFILL_RETURN             16
+#define TRACKER_PREFILL_KILL               17
+#define TRACKER_WORKER_RETURN1             18
+#define TRACKER_WORKER_RETURN2             19
+#define TRACKER_WORKER_KILL1               20
+#define TRACKER_WORKER_KILL2               21
 
 #define TRACKER_TX_RETURN_CONNECTION_START 30
 #define TRACKER_TX_RETURN_CONNECTION_STOP  31

src/libpgagroal/configuration.c

@@ -132,6 +132,7 @@ pgagroal_init_configuration(void* shm)
 
    config->blocking_timeout = 30;
    config->idle_timeout = 0;
+   config->max_connection_age = 0;
    config->validation = VALIDATION_OFF;
    config->background_interval = 300;
    config->max_retries = 5;
@@ -645,6 +646,11 @@ pgagroal_validate_configuration(void* shm, bool has_unix_socket, bool has_main_s
          pgagroal_log_warn("pgagroal: Using idle_timeout for the transaction pipeline is not recommended");
       }
 
+      if (config->max_connection_age > 0)
+      {
+         pgagroal_log_warn("pgagroal: Using max_connection_age for the transaction pipeline is not recommended");
+      }
+
       if (config->validation == VALIDATION_FOREGROUND)
       {
          pgagroal_log_warn("pgagroal: Using foreground validation for the transaction pipeline is not recommended");
@@ -2262,6 +2268,7 @@ transfer_configuration(struct configuration* config, struct configuration* reloa
 
    config->blocking_timeout = reload->blocking_timeout;
    config->idle_timeout = reload->idle_timeout;
+   config->max_connection_age = reload->max_connection_age;
    config->validation = reload->validation;
    config->background_interval = reload->background_interval;
    config->max_retries = reload->max_retries;
@@ -3190,6 +3197,10 @@ pgagroal_write_config_value(char* buffer, char* config_key, size_t buffer_size)
       {
          return to_int(buffer, config->idle_timeout);
       }
+      else if (!strncmp(key, "max_connection_age", MISC_LENGTH))
+      {
+         return to_int(buffer, config->max_connection_age);
+      }
       else if (!strncmp(key, "validation", MISC_LENGTH))
       {
          return to_validation(buffer, config->validation);
@@ -3998,6 +4009,13 @@ pgagroal_apply_main_configuration(struct configuration* config,
          unknown = true;
       }
    }
+   else if (key_in_section("max_connection_age", section, key, true, &unknown))
+   {
+       if (as_int(value, &config->max_connection_age))
+       {
+           unknown = true;
+       }
+   }
    else if (key_in_section("validation", section, key, true, &unknown))
    {
       config->validation = as_validation(value);

src/libpgagroal/management.c

@@ -648,6 +648,7 @@ pgagroal_management_write_status(int socket, bool graceful)
          case STATE_FREE:
          case STATE_FLUSH:
          case STATE_IDLE_CHECK:
+         case STATE_MAX_CONNECTION_AGE:
          case STATE_VALIDATION:
          case STATE_REMOVE:
             total++;
@@ -914,6 +915,7 @@ pgagroal_management_write_details(int socket)
 
       memset(&details, 0, sizeof(details));
 
+      pgagroal_write_long(details, (long)config->connections[i].start_time);
       pgagroal_write_long(details, (long)config->connections[i].timestamp);
       pgagroal_write_int32(details + 8, (int)config->connections[i].pid);
       pgagroal_write_int32(details + 12, (int)config->connections[i].fd);