IPC mechanism in AppScope library for Cli

[michalbiesek]

The need for a mechanism for the connection between cli and AppScope process:

• we have a way to set our data in the loaded process but we don't have any reliable way to get data from scoped/loaded process
• For example scenario: there is a need for proper support detach and reattach to ask the application about the state are you scoped?/ are you loaded?
• the general mechanism can be utilized in more scenarios: ask about the configuration/ set the configuration
• initial approach is to utilize message-queue API (mq_open...)
• should be nonblock no library side

[michalbiesek]

Pull Request #1219 introduced the IPC mechanism.
Currently, 3 messages are supported:

• get Scope status - allows retrieval of information from the scoped process status (Active,Latent, Setup) in other words we can distinguish process after detaching from scoped process. Used by cli via scope ps

• get Scope configuration - allows retrieval of runtime configuration used in the scoped process. Used by cli via scope inspect <PID>

• set Scope configuration - allows retrieval of runtime configuration used in the scoped process. Used by cli via scope update <PID> --config <configFilePath>

[michalbiesek]

Open questions:

• Bug in the current implementation of REQ_SET_CFG? In the following part of code we do not free the memory pointed by g_staticfg we overwrite it.

                case REQ_SET_CFG:
                    if (req->cfg) {
                        // Apply the config
                        doConfig(req->cfg);
                        g_staticfg = req->cfg;
                    } else {
                        DBG(NULL);
                    }

• Unify types in CLI and library regarding configuration: ScopeConfig and jsonConfigurationObject. E.g. in CLI the enable metric property is type of boolean:
  Done in 3b1de89

[jrcheli]

@abetones: this is adding two new new cli commands (subcommands?) in v1.3.0. "scope inspect" and "scope update". We think that the cli-reference will need to be updated accordingly.