4 files changed, 191 insertions, 0 deletions
diff --git a/config/client.go b/config/client.go
new file mode 100644
index 0000000..1515aae
--- /dev/null
+++ b/config/client.go
@@ -0,0 +1,11 @@
+package config
+
+// ClientConfig represents a DTail client configuration (empty as of now as there
+// are no available config options yet, but that may changes in the future).
+type ClientConfig struct {
+}
+
+// Create a new default client configuration.
+func newDefaultClientConfig() *ClientConfig {
+	return &ClientConfig{}
+}
diff --git a/config/common.go b/config/common.go
new file mode 100644
index 0000000..8c07710
--- /dev/null
+++ b/config/common.go
@@ -0,0 +1,42 @@
+package config
+
+// CommonConfig stores configuration keys shared by DTail server and client.
+type CommonConfig struct {
+	// The SSH server port number.
+	SSHPort int
+	// Enable experimental features.
+	ExperimentalFeaturesEnable bool `json:",omitempty"`
+	// Enable extra debug logging (used for deevlopment or debugging purpes only).
+	DebugEnable bool `json:",omitempty"`
+	// Enable extra trace logging (used for deevlopment or debugging purpes only).
+	TraceEnable bool `json:",omitempty"`
+	// The log strategy to use, one of
+	//   stdout: only log to stdout (useful when used with systemd)
+	//   daily: create a log file for every day
+	LogStrategy string
+	// The log directory
+	LogDir string
+	// The cache directory
+	CacheDir string
+	// Do we want to enable pperf http server?
+	PProfEnable bool `json:",omitempty"`
+	// The HTTP port used by PProf
+	PProfPort int `json:",omitempty"`
+	// The PProf HTTP server bind address
+	PProfBindAddress string `json:",omitempty"`
+}
+
+// Create a new default configuration.
+func newDefaultCommonConfig() *CommonConfig {
+	return &CommonConfig{
+		SSHPort:                    2222,
+		DebugEnable:                false,
+		TraceEnable:                false,
+		ExperimentalFeaturesEnable: false,
+		LogDir:                     "log",
+		CacheDir:                   "cache",
+		PProfEnable:                false,
+		PProfPort:                  6060,
+		PProfBindAddress:           "0.0.0.0",
+	}
+}
diff --git a/config/config.go b/config/config.go
new file mode 100644
index 0000000..5463c5f
--- /dev/null
+++ b/config/config.go
@@ -0,0 +1,72 @@
+package config
+
+import (
+	"encoding/json"
+	"io/ioutil"
+	"os"
+)
+
+// ControlUser is used for various DTail specific operations.
+const ControlUser string = "DTAIL-CONTROL-USER"
+
+// Client holds a DTail client configuration.
+var Client *ClientConfig
+
+// Server holds a DTail server configuration.
+var Server *ServerConfig
+
+// Common holds common configs of both both, client and server.
+var Common *CommonConfig
+
+// Used to initialize the configuration.
+type configInitializer struct {
+	Common *CommonConfig
+	Server *ServerConfig
+	Client *ClientConfig
+}
+
+// Parse and read a given config file in JSON format.
+func (c *configInitializer) parseConfig(configFile string) {
+	fd, err := os.Open(configFile)
+	if err != nil {
+		panic(err)
+	}
+	defer fd.Close()
+
+	cfgBytes, err := ioutil.ReadAll(fd)
+	if err != nil {
+		panic(err)
+	}
+
+	err = json.Unmarshal([]byte(cfgBytes), c)
+	if err != nil {
+		panic(err)
+	}
+}
+
+// Init the DTail configuration.
+func Init(configFile string) {
+	initializer := configInitializer{
+		Common: newDefaultCommonConfig(),
+		Server: newDefaultServerConfig(),
+		Client: newDefaultClientConfig(),
+	}
+
+	if configFile == "" {
+		configFile = "./cfg/dtail.json"
+	}
+
+	if _, err := os.Stat(configFile); !os.IsNotExist(err) {
+		initializer.parseConfig(configFile)
+	}
+
+	// Assign pointers to global variables, so that we can access the
+	// configuration from any place of the program.
+	Common = initializer.Common
+	Server = initializer.Server
+	Client = initializer.Client
+
+	if Server.MapreduceLogFormat == "" {
+		Server.MapreduceLogFormat = "default"
+	}
+}
diff --git a/config/server.go b/config/server.go
new file mode 100644
index 0000000..7883b33
--- /dev/null
+++ b/config/server.go
@@ -0,0 +1,66 @@
+package config
+
+import (
+	"errors"
+)
+
+// Permissions map. Each SSH user has a list of permissions which
+// log files it is allowed to follow and which ones not.
+type Permissions struct {
+	// The default user permissions.
+	Default []string
+	// The per user special permissions.
+	Users map[string][]string
+}
+
+// ServerConfig represents the server configuration.
+type ServerConfig struct {
+	// The SSH server bind port.
+	SSHBindAddress string
+	// The max amount of concurrent user connection allowed to connect to the server.
+	MaxConnections int
+	// The max amount of concurrent cats per server.
+	MaxConcurrentCats int
+	// The max amount of concurrent tails per server.
+	MaxConcurrentTails int
+	// The user permissions.
+	Permissions Permissions `json:",omitempty"`
+	// The mapr log format
+	MapreduceLogFormat string `json:",omitempty"`
+	// The default path of the server host key
+	HostKeyFile string
+	// The host key size in bits
+	HostKeyBits int
+}
+
+// Create a new default server configuration.
+func newDefaultServerConfig() *ServerConfig {
+	defaultPermissions := []string{"^/.*"}
+	defaultBindAddress := "0.0.0.0"
+
+	return &ServerConfig{
+		SSHBindAddress:     defaultBindAddress,
+		MaxConnections:     10,
+		MaxConcurrentCats:  2,
+		MaxConcurrentTails: 50,
+		HostKeyFile:        "./cache/ssh_host_key",
+		HostKeyBits:        4096,
+		Permissions: Permissions{
+			Default: defaultPermissions,
+		},
+	}
+}
+
+// ServerUserPermissions retrieves the permission set of a given user.
+func ServerUserPermissions(userName string) (permissions []string, err error) {
+	permissions = Server.Permissions.Default
+	if p, ok := Server.Permissions.Users[userName]; ok {
+		permissions = p
+	}
+
+	if len(permissions) == 0 {
+		err = errors.New("Empty set of permission, user won't be able to open any files")
+	}
+
+	return
+}