Best way to declare and define global variables in DolphinDB-CodePudding

I’d like to define some global configuration parameters to share them across sessions. How do I declare and define global variables in DolphinDB?

CodePudding user response：

Solution #1:

You can create a thread-safe dictionary which is shared across sessions. For example, create a global configuration file:

config = syncDict(STRING, STRING, `config)
config[`key1]=`value1
config[`key2]=`value2

Solution #2:

The first solution can only take effect on one node. To share configuration among nodes while maintaining the consistency, it is recommended to use a high-availability stream table.

colNames = `key`value`modifyTs
colTypes = [STRING, STRING, TIMESTAMP]
t=table(1000:0,colNames,colTypes)
haStreamTable(2, t,`global_config,10000000, keyColumn=`key, retentionMinutes=9999999)

In this case, you can even use DolphinDB as ZooKeeper. The configuration can be shared across the cluster, and can be restored after crash.

CodePudding user response：

you can define global variables using the global keyword.

global x = 1