/// <inheritdoc />
/// <remarks>
/// This function should ideally queue up the work
/// </remarks>
public override async Task <Possible <PackageDownloadResult> > DownloadPackage(
string weakPackageFingerprint,
PackageIdentity package,
AbsolutePath packageTargetFolder,
Func <Task <Possible <IReadOnlyList <RelativePath> > > > producePackage)
{
// Check if we can reuse a package that is layed out on disk already.
// If the hash file is present packageHash variable will contain the content of it.
if (TryGetPackageFromFromDisk(package, packageTargetFolder, weakPackageFingerprint, out var possiblePackageFromDisk, out var packageHash))
{
return(possiblePackageFromDisk);
}
// Slower path: checking the cache first
var targetLocation = packageTargetFolder.ToString(PathTable);
var friendlyName = package.GetFriendlyName();
using (var pm = PerformanceMeasurement.StartWithoutStatistic(
LoggingContext,
nestedLoggingContext => m_logger.StartRetrievingPackage(nestedLoggingContext, friendlyName, targetLocation),
nestedLoggingContext => m_logger.EndRetrievingPackage(nestedLoggingContext, friendlyName)))
{
var loggingContext = pm.LoggingContext;
// Getting the package content from the cache
var packageFromCache = await TryGetPackageFromCache(loggingContext, weakPackageFingerprint, package, packageTargetFolder, packageHash);
if (!packageFromCache.Succeeded || packageFromCache.Result.IsValid)
{
// Cache failure or package was successfully obtained from the cache.
return(packageFromCache);
}
// Cache miss
m_logger.PackageNotFoundInCacheAndStartedDownloading(loggingContext, package.Id, package.Version);
// Step: We couldn't retrieve the package from the cache, or some blobs were missing, generate the package with the given function
var possiblePackageContents = await producePackage();
if (!possiblePackageContents.Succeeded)
{
return(possiblePackageContents.Failure);
}
// Now we can save the content to the cache
Analysis.IgnoreResult(
await TryAddPackageToCache(
loggingContext,
weakPackageFingerprint,
package,
packageTargetFolder,
possiblePackageContents.Result),
justification: "Okay to ignore putting in cache failure, will happen next time"
);
// Step: Return descriptor indicating it wasn't restored from the cache
return(PackageDownloadResult.FromRemote(package, packageTargetFolder, possiblePackageContents.Result));
}
}
