Expert Advisor to work after shutdown

Can you please write here, from your experience, what are your best precautions to add to an Expert Advisor code lines, so it will resume the best way, after restarting the metatrader4/computer?

In other words:
What are the scenarios you may think that could happen after EA starts working again, if metatrader 4 platform needed to restart?
I know Global Variables (GV), but please elaborate on some scenes that may happen and how can the EA overcome these cases if they happen in real?

1) Check for MT4 connectivity
2) Wait for downloading historical data to load so it calculate any indicator values correctly ( i had this issue)
3) May be trading signal on new candle bar. it dosn't fire up trade straight away

When the server/platform restarts the task is to restore the exact original state your EA has been in before the shutdown.

To do this as a first step you need to specify what defines the runtime state your EA. Typically that's external order state (open positions, pending orders, limits) and internal EA state (variables defining trading conditions/logic).

The next step is to separate these state conditions into ones that can be restored from account data and the ones that cannot. External state can be easily restored from the account itself. Restoring internal state depends on the complexity of your EA and can be anything from easy to difficult. You have to decide whether you can easily restore a condition by a few iCustom() calls or not.

At the end of that separation you may have a number of internal variables you don't know how to restore easily. Those variables not easily to be restored (NERV) need to be stored separately and outside of the EA. After a restart you will have to restore them from the external storage. You may use the terminal's GlobalVariable* functions but I recommend plain text or .ini file (more stable and better maintainable). When making a decision keep in mind that a hard server shutdown or a crashing terminal may not provide enough time to write GlobalVariables* to disk.

Regular runtime procedure: Each time a NERV in your EA changes you immediately write the change to external storage. You don't wait with writing until MetaTrader shuts down in a (hopefully) clean way.

Restart procedure: In EA::OnInit() you restore all variables that make-up your EA's runtime state from (1) the account and from (2) external storage.


ps: To be able to run multiple EAs in parallel you may assign different magic numbers to each of them and use "symbol-magic-number" to create a namespace for GlobalVariables* or the name of a file.

Thank you very much for your great ideas.

Side note , I running MT4 on my Mac , Do I need to restart my MT every weekend in order for my robots to work well?

Too many factors. It just depends on the type of strategy and how you approach every task.

From my point of view, what emmzett has indicated to you is amazing. A really good advice.

Depending on the complexity of the state you need to restore, using external files or any database-like alternative would be best. You may create data structures that are passed to text and back to your code structures by some mechanism (simply created by your own, JSON-live, XML-like).