CLI Tutorial: Server Scaling

When the environment is already created, in some cases it may be required to change its topology - for example, to scale a particular server or the whole environment layer (using the vertical and/or horizontal scaling respectively) due to the changed incoming load. This may be accomplished with the corresponding changetopology CLI method:

~/jelastic/environment/control/changetopology --envName {env_name} --env '{"engine" : "{engine_type}"}' --nodes ['{"nodeType" : "{node_type}","count" : {nodes_amount}, "fixedCloudlets" : {cloudlets_amount}, "flexibleCloudlets" : {cloudlets_amount}}, {"nodeType" : "{node_type}", "count" : {nodes_amount}, "fixedCloudlets" : {cloudlets_amount}, "flexibleCloudlets" :  {cloudlets_amount}}']

Jelastic CLI change topology

The whole set of possible parameters is the same as for the createenvironment method, except the –envName {env_name} - here it is used to point to the already existing environment, that should be adjusted.

As for the rest of options, in this example we use the following ones:

  • {engine_type} - engine the instances of the chosen environment are powered by (an obligatory string)
  • {node_type} - stack type identifier, according to the list
  • {nodes_amount} - amount of nodes to be set (applies horizontal scaling)
  • {cloudlets_amount} - number of fixed (fixedCloudlets) and/or flexible (flexibleCloudlets) cloudlets to be allocated for the specified node type (applies vertical scaling)

Note: For the proper work of horizontally scaled application server, do not miss to add a load balancing node to your environment topology beforehand (if it’s absent).
Reconfiguration of environment topology may take several minutes in order to be accomplished.

What’s next?

More CLI usage examples can be found in the following documents: