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libstore: collect effective url and cachedness earlier

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this will let us return metadata for a transfer without having to wait
for the entire transfer to complete. more importantly for current uses
though is that we could now send retries to the effective url directly
instead of retreading the entire redirect path. this improves latency,
and in such cases where redirects change while we're downloading it'll
also improve correctness (previously we'd silently download bad data).

Change-Id: I6fcd920eb96fbdb2e960b73773c0b854e0300e99
This commit is contained in:
eldritch horrors 2024-10-27 18:27:11 +01:00
parent 97c76c4655
commit 2b3bdda027
1 changed files with 38 additions and 10 deletions
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48
src/libstore/filetransfer.cc
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@ -50,7 +50,17 @@ struct curlFileTransfer : public FileTransfer
std::optional<std::string> uploadData;
std::string downloadData;
bool noBody = false; // \equiv HTTP HEAD, don't download data
bool done = false; // whether either the success or failure function has been called
enum {
/// nothing has been transferred yet
initialSetup,
/// at least some metadata has already been transferred,
/// but the transfer did not succeed and is now retrying
retrySetup,
/// data transfer in progress
transferring,
/// transfer complete, result or failure reported
transferComplete,
} phase = initialSetup;
std::packaged_task<
std::pair<FileTransferResult, std::string>(std::exception_ptr, FileTransferResult)>
callback;
@ -129,7 +139,7 @@ struct curlFileTransfer : public FileTransfer
curl_easy_cleanup(req);
if (requestHeaders) curl_slist_free_all(requestHeaders);
try {
if (!done)
if (phase != transferComplete)
fail(FileTransferError(Interrupted, {}, "download of '%s' was interrupted", uri));
} catch (...) {
ignoreExceptionInDestructor();
@ -138,8 +148,8 @@ struct curlFileTransfer : public FileTransfer
void failEx(std::exception_ptr ex)
{
assert(!done);
done = true;
assert(phase != transferComplete);
phase = transferComplete;
callback(ex, std::move(result));
}
@ -149,6 +159,22 @@ struct curlFileTransfer : public FileTransfer
failEx(std::make_exception_ptr(std::forward<T>(e)));
}
void maybeFinishSetup()
{
if (phase > retrySetup) {
return;
}
char * effectiveUriCStr = nullptr;
curl_easy_getinfo(req, CURLINFO_EFFECTIVE_URL, &effectiveUriCStr);
if (effectiveUriCStr)
result.effectiveUri = effectiveUriCStr;
result.cached = getHTTPStatus() == 304;
phase = transferring;
}
std::exception_ptr writeException;
size_t writeCallback(void * contents, size_t size, size_t nmemb)
@ -156,6 +182,8 @@ struct curlFileTransfer : public FileTransfer
const size_t realSize = size * nmemb;
try {
maybeFinishSetup();
bodySize += realSize;
if (successfulStatuses.count(getHTTPStatus()) && this->dataCallback) {
@ -268,6 +296,10 @@ struct curlFileTransfer : public FileTransfer
void init()
{
if (phase > initialSetup) {
phase = retrySetup;
}
curl_easy_reset(req);
if (verbosity >= lvlVomit) {
@ -337,10 +369,7 @@ struct curlFileTransfer : public FileTransfer
{
auto httpStatus = getHTTPStatus();
char * effectiveUriCStr = nullptr;
curl_easy_getinfo(req, CURLINFO_EFFECTIVE_URL, &effectiveUriCStr);
if (effectiveUriCStr)
result.effectiveUri = effectiveUriCStr;
maybeFinishSetup();
debug("finished %s of '%s'; curl status = %d, HTTP status = %d, body = %d bytes",
verb(), uri, code, httpStatus, bodySize);
@ -358,9 +387,8 @@ struct curlFileTransfer : public FileTransfer
else if (code == CURLE_OK && successfulStatuses.count(httpStatus))
{
result.cached = httpStatus == 304;
act.progress(bodySize, bodySize);
done = true;
phase = transferComplete;
callback(nullptr, std::move(result));
}