ProfilesCache does not handle race conditions

[traeok]

Describe the bug

Although JavaScript and Node.js are single-threaded, multiple VS Code extensions can activate in parallel. Extensions that grab the static ProfilesCache instance from Zowe Explorer might compete with one another when performing operations on the cache (such as refresh), causing undefined behavior in the cache (such as missing or incorrect profile values, etc.)

To Reproduce

Have two or more extensions that access the ProfilesCache instance through Zowe Explorer's extension exports (vscode.extensions.getExtension("zowe.vscode-extension-for-zowe").exports). Try to call refresh on this cache instance for each extension, as soon as the extensions are activated.

Expected behavior

The ProfilesCache instance should fill the cache successfully during refresh, and return an instance with valid profiles.

Desktop (please complete the following information):

• OS: Windows
• Zowe Explorer Version: 2.15.2

Additional context

A few internal developers have reported this issue. Due to the nature of VS Code extensions and asynchronous code in Node.js, we likely need to add multi-threading support to prevent any problems that may surface from ProfilesCache race conditions.

[github-actions]

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[roman-kupriyanov]

Hi @traeok ! Thanks for creating the issue 🙏

I would like to add also that initForZowe() call itself can produce a multiple unnecessary refresh calls by the structure of its arguments.

The signature of this function expects a profileType and an optional list of the schemas:

public async initForZowe(
  profileType: string,
  profileTypeConfigurations?: zowe.imperative.ICommandProfileTypeConfiguration[]
): Promise<void> { }

This forces the extenders to call something like code below for each type they want to register (and some extensions include more than one types, including ours):

for (const profileType of extensionProfileTypes) {
  await zoweExplorerExtenderApi.initForZowe(profileType, [profileSchemas[profileType]];
  cache.registerCustomProfilesType(profileType);
}

To avoid re-registering of the same profile schemas on each iteration we have to run the initForZowe multiple times for each profile type and its schema and this, in its order, causes multiple unnecessary refreshes and disk re-reading, which might interrupt other extensions init process and also takes more time.

If it is possible, it would be great to be able to pass all the schemas and register them at once, thus to have only one refresh for all of them at once. The updated signature may look just like this:

public async initForZoweNew(
  profileTypeConfigurations: zowe.imperative.ICommandProfileTypeConfiguration[]
): Promise<void> { }

The schemas themselves already include the type field that may be taken from there. So extenders may just call it simply like this:

await zoweExplorerExtenderApi.initForZoweNew(profileSchemas);
profileSchemas.forEach(({ type }) => cache.registerCustomProfilesType(type))

Again, just an idea. Thanks for taking a look at this problem 😃