[agroal#285] Introduce update_process_title setting

This commit adds the `update_process_title` configuration setting.
Values for such setting are:
- `never` or `off`, means the user does not want to update the process
title at all;
- `strict` (used on Linux and systems that do no provide a native call
to update the process title) allows for changing the process title
without overflowing the length of the initial command line;
- `minimal` sets the process title to `user/database` even if this
exceeds the initial command line length;
- `verbose` sets the process title to `user@host:port/database` even
if this overflows the initial command line length.

By default the setting is configured as `verbose`, but this could
break some aggressively secured environments, where no native way to
set the process title is provided.

The `pgagroal_set_proc_title` function has been refactored so that, if
the update policy is set to `never` the process title will never be
updated. This can be confusing because even the "main" process will
not have a title update.
Likely, if the policy is `strict`, the function will never try to
overflow the initial command line length.

When set to `verbose` or leaved as default, the process title is built
with information about the hostname, port, username and database.
This can produce a very long title, that is in any case cut at
`MAX_PROCESS_TITLE_LENGTH` (256 bytes, including the terminator).
In the unluckily case the primary server cannot be determined, the
`verbose` mode is set back to `minimal`, but this indicates there is
something wrong somewhere else.

On those systems that do provide a native way to set the process
title, there is no difference between `strict` and `minimal` and the
`minmal` policy is always adopted.

Documentation updated.

Close agroal#285

doc/CONFIGURATION.md

@@ -77,6 +77,7 @@ See a more complete [sample](./etc/pgagroal.conf) configuration for running `pga
 | tracker | off | Bool | No | Track connection lifecycle |
 | track_prepared_statements | off | Bool | No | Track prepared statements (transaction pooling) |
 | pidfile | | String | No | Path to the PID file. If omitted, automatically set to `unix_socket_dir`/pgagroal.`port`.pid |
+| update_process_title | `verbose` | No | The behavior for updating the operating system process title, mainly related to connection processes. Allowed settings are: `never` (or `off`), does not update the process title; `strict` to set the process title without overriding the existing initial process title length; `minimal` to set the process title to `username/database`; `verbose` (or `full`) to set the process title to `user@host:port/database`. Please note that `strict` and `minimal` are honored only on those systems that do not provide a native way to set the process title (e.g., Linux). On other systems, there is no difference between `strict` and `minimal` and the assumed behaviour is `minimal` even if `strict` is used. `never` and `verbose` are always honored, on every system. On Linux systems the process title is always trimmed to 255 characters, while on system that provide a natve way to set the process title it can be longer. |
 
 __Danger zone__
 

src/include/pgagroal.h

@@ -62,6 +62,7 @@ extern "C" {
 #define PGAGROAL_DEFAULT_ADMINS_FILE PGAGROAL_DEFAULT_CONFIGURATION_PATH "pgagroal_admins.conf"
 #define PGAGROAL_DEFAULT_SUPERUSER_FILE PGAGROAL_DEFAULT_CONFIGURATION_PATH "pgagroal_superuser.conf"
 
+#define MAX_PROCESS_TITLE_LENGTH 256
 
 #define MAX_BUFFER_SIZE      65535
 #define DEFAULT_BUFFER_SIZE  65535
@@ -134,6 +135,11 @@ extern "C" {
 #define HUGEPAGE_TRY 1
 #define HUGEPAGE_ON  2
 
+#define UPDATE_PROCESS_TITLE_NEVER 0
+#define UPDATE_PROCESS_TITLE_STRICT 1
+#define UPDATE_PROCESS_TITLE_MINIMAL 2
+#define UPDATE_PROCESS_TITLE_VERBOSE 3
+
 #define likely(x)    __builtin_expect (!!(x), 1)
 #define unlikely(x)  __builtin_expect (!!(x), 0)
 
@@ -399,6 +405,8 @@ struct configuration
    char log_line_prefix[MISC_LENGTH]; /**< The logging prefix */
    atomic_schar log_lock;             /**< The logging lock */
 
+   unsigned int update_process_title;  /**< Behaviour for updating the process title */
+
    bool authquery; /**< Is authentication query enabled */
 
    bool tls;                        /**< Is TLS enabled */

src/include/utils.h

@@ -245,7 +245,22 @@ int
 pgagroal_base64_decode(char* encoded, size_t encoded_length, char** raw, int* raw_length);
 
 /**
- * Set process title
+ * Set process title.
+ *
+ * The function will autonomously check the update policy set
+ * via the configuration option `update_process_title` and
+ * will do nothing if the setting is `never`.
+ * In the case the policy is set to `strict`, the process title
+ * will not overflow the initial command line length (i.e., strlen(argv[*]))
+ * otherwise it will do its best to set the title to the desired string.
+ *
+ * The policies `strict` and `minimal` will be honored only on Linux platforms
+ * where a native call to set the process title is not available.
+ *
+ *
+ * The resulting process title will be set to either `s1` or `s1/s2` if there
+ * both strings and the length is allowed by the policy.
+ *
  * @param argc The number of arguments
  * @param argv The argv pointer
  * @param s1 The first string
@@ -261,6 +276,10 @@ pgagroal_set_proc_title(int argc, char** argv, char* s1, char* s2);
  * with the form
  *    user@host:port/database
  *
+ * This means that all the policies honored by the latter function and
+ * set via the `update_process_title` configuration paramter will be
+ * honored.
+ *
  * @param argc the number of arguments
  * @param argv command line arguments
  * @param connection the struct connection pointer for the established connection.

src/libpgagroal/configuration.c

@@ -66,6 +66,7 @@ static int as_logging_rotation_age(char* str, unsigned int* age);
 static int as_validation(char* str);
 static int as_pipeline(char* str);
 static int as_hugepage(char* str);
+static unsigned int as_update_process_title(char* str, unsigned int* policy, unsigned int default_policy);
 static int extract_value(char* str, int offset, char** value);
 static void extract_hba(char* str, char** type, char** database, char** user, char** address, char** method);
 static void extract_limit(char* str, int server_max, char** database, char** user, int* max_size, int* initial_size, int* min_size);
@@ -141,6 +142,8 @@ pgagroal_init_configuration(void* shm)
 
    atomic_init(&config->su_connection, STATE_FREE);
 
+   config->update_process_title = UPDATE_PROCESS_TITLE_VERBOSE;
+
    return 0;
 }
 
@@ -570,6 +573,13 @@ pgagroal_read_configuration(void* shm, char* filename, bool emitWarnings)
                      unknown = true;
                   }
                }
+               else if (key_in_section("update_process_title", section, key, true, &unknown))
+               {
+                  if (as_update_process_title(value, &config->update_process_title, UPDATE_PROCESS_TITLE_VERBOSE))
+                  {
+                     unknown = false;
+                  }
+               }
                else
                {
                   unknown = true;
@@ -2416,6 +2426,9 @@ transfer_configuration(struct configuration* config, struct configuration* reloa
    config->metrics_cache_max_age = reload->metrics_cache_max_age;
    restart_int("metrics_cache_max_size", config->metrics_cache_max_size, reload->metrics_cache_max_size);
    config->management = reload->management;
+
+   config->update_process_title = reload->update_process_title;
+
    /* gracefully */
 
    /* disabled */
@@ -3133,3 +3146,53 @@ as_bytes(char* str, unsigned int* bytes, unsigned int default_bytes)
       return 1;
    }
 }
+
+/**
+ * Utility function to understand the setting for updating
+ * the process title.
+ *
+ * @param str the value obtained by the configuration parsing
+ * @param policy the pointer to the value where the setting will be stored
+ * @param default_policy a value to set when the configuration cannot be
+ * understood
+ *
+ * @return 0 on success, 1 on error. In any case the `policy` variable is set to
+ * `default_policy`.
+ */
+static unsigned int
+as_update_process_title(char* str, unsigned int* policy, unsigned int default_policy)
+{
+   if (is_empty_string(str))
+   {
+      *policy = default_policy;
+      return 1;
+   }
+
+   if (!strncmp(str, "never", MISC_LENGTH) || !strncmp(str, "off", MISC_LENGTH))
+   {
+      *policy = UPDATE_PROCESS_TITLE_NEVER;
+      return 0;
+   }
+   else if (!strncmp(str, "strict", MISC_LENGTH))
+   {
+      *policy = UPDATE_PROCESS_TITLE_STRICT;
+      return 0;
+   }
+   else if (!strncmp(str, "minimal", MISC_LENGTH))
+   {
+      *policy = UPDATE_PROCESS_TITLE_MINIMAL;
+      return 0;
+   }
+   else if (!strncmp(str, "verbose", MISC_LENGTH) || !strncmp(str, "full", MISC_LENGTH))
+   {
+      *policy = UPDATE_PROCESS_TITLE_VERBOSE;
+      return 0;
+   }
+   else
+   {
+      // not a valid setting
+      *policy = default_policy;
+      return 1;
+   }
+
+}

src/libpgagroal/utils.c

@@ -720,10 +720,20 @@ void
 pgagroal_set_proc_title(int argc, char** argv, char* s1, char* s2)
 {
 #ifdef HAVE_LINUX
-   char title[256];
+   char title[MAX_PROCESS_TITLE_LENGTH];
    size_t size;
    char** env = environ;
    int es = 0;
+   struct configuration* config;
+
+   config = (struct configuration*)shmem;
+
+   // sanity check: if the user does not want to
+   // update the process title, do nothing
+   if (config->update_process_title == UPDATE_PROCESS_TITLE_NEVER)
+   {
+      return;
+   }
 
    if (!env_changed)
    {
@@ -772,11 +782,21 @@ pgagroal_set_proc_title(int argc, char** argv, char* s1, char* s2)
             s1 != NULL && s2 != NULL ? "/" : "",
             s2 != NULL ? s2 : "");
 
-   size = strlen(title) + 1;
-
    // nuke the command line info
    memset(*argv, 0, max_process_title_size);
 
+   // copy the new title over argv checking
+   // the update_process_title policy
+   if (config->update_process_title == UPDATE_PROCESS_TITLE_STRICT)
+   {
+      size = max_process_title_size;
+   }
+   else
+   {
+      // here we can set the title to a full description
+      size = strlen(title) + 1;
+   }
+
    memcpy(*argv, title, size);
    memset(*argv + size, 0, 1);
 
@@ -797,13 +817,19 @@ pgagroal_set_connection_proc_title(int argc, char** argv, struct connection* con
 {
    struct configuration* config;
    int primary;
-   char info[MISC_LENGTH];
+   char info[MAX_PROCESS_TITLE_LENGTH];
 
    config = (struct configuration*)shmem;
 
-   pgagroal_get_primary(&primary);
+   if (pgagroal_get_primary(&primary))
+   {
+      // cannot find the primary, this is a problem!
+      pgagroal_set_proc_title(argc, argv, connection->username, connection->database);
+      return;
+   }
 
-   snprintf(info, MISC_LENGTH, "%s@%s:%d",
+   memset(&info, 0, sizeof(info));
+   snprintf(info, MAX_PROCESS_TITLE_LENGTH - 1, "%s@%s:%d",
             connection->username,
             config->servers[primary].host,
             config->servers[primary].port);

src/libpgagroal/worker.c

@@ -106,7 +106,19 @@ pgagroal_worker(int client_fd, char* address, char** argv)
       pgagroal_prometheus_client_active_add();
 
       pgagroal_pool_status();
-      pgagroal_set_connection_proc_title(1, argv, &config->connections[slot]);
+
+      // do we have to update the process title?
+      switch (config->update_process_title)
+      {
+         case UPDATE_PROCESS_TITLE_MINIMAL:
+         case UPDATE_PROCESS_TITLE_STRICT:
+            // pgagroal_set_proc_title will check the policy
+            pgagroal_set_proc_title(1, argv, config->connections[slot].username, config->connections[slot].database);
+            break;
+         case UPDATE_PROCESS_TITLE_VERBOSE:
+            pgagroal_set_connection_proc_title(1, argv, &config->connections[slot]);
+            break;
+      }
 
       if (config->pipeline == PIPELINE_PERFORMANCE)
       {