Documentation ¶
Index ¶
Constants ¶
This section is empty.
Variables ¶
This section is empty.
Functions ¶
func SetRefreshInterval ¶ added in v0.2.0
SetRefreshInterval is used to set the refresh interval
Types ¶
type CassandraConfigManager ¶
type CassandraConfigManager struct {
// contains filtered or unexported fields
}
CassandraConfigManager is an implementation of ConfigManager backed by a config store that's built on top of Cassandra.
func (*CassandraConfigManager) Get ¶
func (cfgMgr *CassandraConfigManager) Get(svc string, version string, sku string, host string) (interface{}, error)
Get returns the config value that best matches the given input criteria. svc param cannot be empty.
func (*CassandraConfigManager) Start ¶
func (cfgMgr *CassandraConfigManager) Start()
Start starts the config manager
func (*CassandraConfigManager) Stop ¶
func (cfgMgr *CassandraConfigManager) Stop()
Stop stops the config manager
func (*CassandraConfigManager) String ¶
func (cfgMgr *CassandraConfigManager) String() string
type ConfigManager ¶
type ConfigManager interface { // Get fetches and returns a config object that // best matches the specified input criteria. The // input parameters refer to the 4 levels in the // config hierarchy Get(svc string, version string, sku string, host string) (interface{}, error) //Start starts the config manager Start() //Stop stops the running config manager Stop() }
ConfigManager refers to any implementation that vends config, backed by a config store which supports a hierarchial config structure with 4 pre-defined levels : (service, serviceVersion, sku, hostname)
func NewCassandraConfigManager ¶
func NewCassandraConfigManager(mClient m.TChanMetadataService, configTypes map[string]interface{}, logger bark.Logger) ConfigManager
NewCassandraConfigManager constructs and returns an implementation of config managed backed by a store that's built on top of cassandra. The underlying config store supports configuration of key,values in a tree like structure with 4 pre-defined levels:
serviceName.serviceVersion.sku.hostname.key=value
where serviceName is the name of the service (ex - inputhost,outputhost, etc) serviceVersion identifes software version (ex - manyrocks, v1.0 etc) sku identifies the hardware sku (ex - ec2.m1.12) hostname identifies a specific host (ex - cherami14)
The underlying config store supports wildcards to specify default values that apply to a broad category, subject to the following constraints:
(1) serviceName cannot be a wildcard (2) if sku is a wildcard, hostname MUST also be a wildcard
Config Evaluation:
In general, the config evaluator ALWAYS returns the most specific config value that matches the given input constraints. The config levels from most to least specific are (hostname, sku, serviceVersion, serviceName) Example config: inputhost.*.*.*.maxExtents=111 inputhost.*.ec2m112.*.maxExtents=222 inputhost.v1.*.*.maxExtents=333 inputhost.v1.m1large.*.maxExtents=444 Example Queries: Get(inputhost, *, *, *) = 111 Get(inputhost, v1, *, *) = 333 Get(inputhost, v1, ec2m112, *) = 222 --> BEWARE, defaults applied Get(inputhost, v1, m1large, *) = 444
The constructor to this class takes a configTypes param, which is a map of serviceName to configObjects. The config object MUST be of struct type and all members must be PUBLIC. The ConfigObject supports two pre-defined struct tags - name and default. name refers to the name of the config on the underlying store and default refers to the default value for that config param. Following are the data types supported for config params within the struct:
Int64
Float64
String
String slice ([]string - raw config value must be a csv)
Example ConfigObject and config manager initialization
type InputConfig struct { MaxExtents int64 `name:"max-extents" default:"50"` AdminStatus string `name:"admin-status" default:"enabled"` }
cfgTypes := []map[string]interface{}{"inputhost": InputConfig{}} cfgMgr := NewCassandraConfigManager(mClient, cfgTypes, logger)
Automatic Refresh:
The returned config manager automatically syncs with the underlying config store every minute. Callers must AVOID caching the result of configManager.Get() to be able to respond to config changes.
Future Work:
Notifications to observers on config changes