Adjust MySQL socket file name generation so that no socket parameter to the client is required for a standard installation

README.md

@@ -624,8 +624,8 @@ these values as parameters, but a more convenient way is to instrument the
 `createCredentials` function -- the above `processes.nix` expression propagates
 the entire `ids` attribute set as a parameter to the constructors.
 
-The constructors expression indirectly composes the `createCredentials` as
-follows:
+The constructors expression indirectly composes the `createCredentials` function
+as follows:
 
 ```nix
 {pkgs, ids ? {}, ...}:
@@ -640,10 +640,10 @@ follows:
 }
 ```
 
-It propagates the `ids` to the function that composes the `createCredentials`
-function. As a result, it will automatically assign the UIDs and GIDs in the
-`ids.nix` expression when the user configures a user or group with a name that
-exists in the `uids` and `gids` resource pools.
+The `ids` attribute set is propagated to the function that composes the
+`createCredentials` function. As a result, it will automatically assign the UIDs
+and GIDs in the `ids.nix` expression when the user configures a user or group
+with a name that exists in the `uids` and `gids` resource pools.
 
 To make these UIDs and GIDs assignments go smoothly, it is recommended to give
 a process the same process name, instance name, user and group names.

examples/service-containers-agnostic/mysql.nix

@@ -2,12 +2,22 @@
 {port ? 3306, instanceSuffix ? "", instanceName ? "mysql${instanceSuffix}", containerName ? "mysql-database${instanceSuffix}", type}:
 
 let
-  mysqlSocket = "${runtimeDir}/${instanceName}/${instanceName}.sock";
+  # By default, the socket file resides in $runtimeDir/mysqld/mysqld.sock.
+  # We only change the path component: 'mysqld' into the instance name if no
+  # instanceSuffix parameter is specified. Otherwise, we append the
+  # instanceSuffix to 'mysqld'.
+  #
+  # This construction is used to allow the mysql client executable to work
+  # without a socket parameter for the default configuration.
+
+  mysqlSocket =
+    if instanceName != "mysql" && instanceSuffix == "" then "${runtimeDir}/${instanceName}/mysqld.sock"
+    else "${runtimeDir}/mysqld${instanceSuffix}/mysqld.sock";
 
   mysqlUsername = "root";
 
   pkg = mysqlConstructorFun {
-    inherit port instanceName;
+    inherit port instanceName instanceSuffix;
     postInstall = ''
       # Add Dysnomia container configuration file for MySQL database
       mkdir -p $out/etc/dysnomia/containers

examples/services-agnostic/mysql.nix

@@ -1,9 +1,21 @@
 {createManagedProcess, stdenv, mysql, stateDir, runtimeDir, forceDisableUserChange}:
-{port ? 3306, instanceSuffix ? "", instanceName ? "mysqld${instanceSuffix}", postInstall ? ""}:
+{port ? 3306, instanceSuffix ? "", instanceName ? "mysql${instanceSuffix}", postInstall ? ""}:
 
 let
   dataDir = "${stateDir}/db/${instanceName}";
-  instanceRuntimeDir = "${runtimeDir}/${instanceName}";
+
+  # By default, the socket file resides in $runtimeDir/mysqld/mysqld.sock.
+  # We only change the path component: 'mysqld' into the instance name if no
+  # instanceSuffix parameter is specified. Otherwise, we append the
+  # instanceSuffix to 'mysqld'.
+  #
+  # This construction is used to allow the mysql client executable to work
+  # without a socket parameter for the default configuration.
+
+  instanceRuntimeDir =
+    if instanceName != "mysql" && instanceSuffix == "" then "${runtimeDir}/${instanceName}"
+    else "${runtimeDir}/mysqld${instanceSuffix}";
+
   user = instanceName;
   group = instanceName;
 in
@@ -27,7 +39,7 @@ createManagedProcess {
   '';
 
   foregroundProcess = "${mysql}/bin/mysqld";
-  foregroundProcessArgs = [ "--basedir" mysql "--datadir" dataDir "--port" port "--socket" "${instanceRuntimeDir}/${instanceName}.sock" ]
+  foregroundProcessArgs = [ "--basedir" mysql "--datadir" dataDir "--port" port "--socket" "${instanceRuntimeDir}/mysqld.sock" ]
     ++ stdenv.lib.optionals (!forceDisableUserChange) [ "--user" user ];
 
   credentials = {