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Fixed more races and edge cases I found.

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This commit is contained in:
Patrick LeBlanc
2019-07-03 13:31:49 -05:00
parent 2722da0b40
commit 56a51605af
5 changed files with 84 additions and 25 deletions
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51
src/Cache.cpp
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@@ -132,7 +132,7 @@ void Cache::populate()
lru.push_back(p.filename().string());
auto last = lru.end();
m_lru.insert(--last);
currentCacheSize += bf::file_size(p);
currentCacheSize += bf::file_size(*dir);
}
else
logger->log(LOG_WARNING, "Cache: found something in the cache that does not belong '%s'", p.string().c_str());
@@ -147,7 +147,7 @@ void Cache::populate()
if (bf::is_regular_file(p))
{
if (p.extension() == ".journal")
currentCacheSize += bf::file_size(p);
currentCacheSize += bf::file_size(*dir);
else
logger->log(LOG_WARNING, "Cache: found a file in the journal dir that does not belong '%s'", p.string().c_str());
}
@@ -286,8 +286,17 @@ void Cache::read(const vector<string> &keys)
}
else
{
// There's window where the file has been downloaded but is not yet
// added to the lru structs. However it is in the DNE. If it is in the DNE, then it is also
// in Downloader's map. So, this thread needs to start the download if it's not in the
// DNE or if there's an existing download that hasn't finished yet. Starting the download
// includes waiting for an existing download to finish, which from this class's pov is the
// same thing.
if (doNotEvict.find(key) == doNotEvict.end() || downloader.inProgress(key))
keysToFetch.push_back(&key);
else
cout << "Cache: detected and stopped a racey download" << endl;
addToDNE(key);
keysToFetch.push_back(&key);
}
}
if (keysToFetch.empty())
@@ -301,13 +310,22 @@ void Cache::read(const vector<string> &keys)
// downloads with size 0 didn't actually happen, either because it
// was a preexisting download (another read() call owns it), or because
// there was an error downloading it. Use size == 0 as an indication of
// what to add to the cache
// what to add to the cache. Also needs to verify that the file was not deleted,
// indicated by existence in doNotEvict.
if (dlSizes[i] != 0)
{
sum_sizes += dlSizes[i];
lru.push_back(*keysToFetch[i]);
LRU_t::iterator lit = lru.end();
m_lru.insert(--lit); // I dislike this way of grabbing the last iterator in a list.
if (doNotEvict.find(*keysToFetch[i]) != doNotEvict.end())
{
sum_sizes += dlSizes[i];
lru.push_back(*keysToFetch[i]);
LRU_t::iterator lit = lru.end();
m_lru.insert(--lit); // I dislike this way of grabbing the last iterator in a list.
}
else // it was downloaded, but a deletion happened so we have to toss it
{
cout << "removing a file that was deleted by another thread during download" << endl;
bf::remove(prefix / (*keysToFetch[i]));
}
}
}
@@ -329,9 +347,14 @@ void Cache::doneReading(const vector<string> &keys)
boost::unique_lock<boost::mutex> s(lru_mutex);
for (const string &key : keys)
{
const auto &it = m_lru.find(key);
if (it != m_lru.end())
removeFromDNE(it->lit);
removeFromDNE(key);
// most should be in the map.
// debateable whether it's faster to look up the list iterator and use it
// or whether it's faster to bypass that and use strings only.
//const auto &it = m_lru.find(key);
//if (it != m_lru.end())
// removeFromDNE(it->lit);
}
_makeSpace(0);
}
@@ -588,12 +611,6 @@ int Cache::ifExistsThenDelete(const string &key)
auto it = m_lru.find(key);
if (it != m_lru.end())
{
if (doNotEvict.find(it->lit) != doNotEvict.end())
{
cout << "almost deleted a file being read, are we really doing that somewhere?" << endl;
return 0;
}
if (toBeDeleted.find(it->lit) == toBeDeleted.end())
{
doNotEvict.erase(it->lit);