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Fix 'error 9 while decompressing xz file'

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Once we've started writing data to a Sink, we can't restart a download
request, because then we end up writing duplicate data to the
Sink. Therefore we shouldn't handle retries in Downloader but at a
higher level (in particular, in copyStorePath()).

Fixes #2952.

(cherry picked from commit a67cf5a358)
This commit is contained in:
Eelco Dolstra 2019-06-24 21:48:52 +02:00
parent 2fef4dd296
commit 78fa47a7f0
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GPG key ID: 8170B4726D7198DE
7 changed files with 156 additions and 119 deletions
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67
src/libstore/download.cc
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@ -8,6 +8,7 @@
#include "compression.hh"
#include "pathlocks.hh"
#include "finally.hh"
#include "retry.hh"
#ifdef ENABLE_S3
#include <aws/core/client/ClientConfiguration.h>
@ -19,11 +20,9 @@
#include <curl/curl.h>
#include <algorithm>
#include <cmath>
#include <cstring>
#include <iostream>
#include <queue>
#include <random>
#include <thread>
using namespace std::string_literals;
@ -62,9 +61,6 @@ struct CurlDownloader : public Downloader
{
CURLM * curlm = 0;
std::random_device rd;
std::mt19937 mt19937;
struct DownloadItem : public std::enable_shared_from_this<DownloadItem>
{
CurlDownloader & downloader;
@ -77,12 +73,6 @@ struct CurlDownloader : public Downloader
bool active = false; // whether the handle has been added to the multi object
std::string status;
unsigned int attempt = 0;
/* Don't start this download until the specified time point
has been reached. */
std::chrono::steady_clock::time_point embargo;
struct curl_slist * requestHeaders = 0;
std::string encoding;
@ -401,9 +391,7 @@ struct CurlDownloader : public Downloader
}
}
attempt++;
auto exc =
fail(
code == CURLE_ABORTED_BY_CALLBACK && _isInterrupted
? DownloadError(Interrupted, fmt("%s of '%s' was interrupted", request.verb(), request.uri))
: httpStatus != 0
@ -414,31 +402,15 @@ struct CurlDownloader : public Downloader
)
: DownloadError(err,
fmt("unable to %s '%s': %s (%d)",
request.verb(), request.uri, curl_easy_strerror(code), code));
/* If this is a transient error, then maybe retry the
download after a while. */
if (err == Transient && attempt < request.tries) {
int ms = request.baseRetryTimeMs * std::pow(2.0f, attempt - 1 + std::uniform_real_distribution<>(0.0, 0.5)(downloader.mt19937));
printError(format("warning: %s; retrying in %d ms") % exc.what() % ms);
embargo = std::chrono::steady_clock::now() + std::chrono::milliseconds(ms);
downloader.enqueueItem(shared_from_this());
}
else
fail(exc);
request.verb(), request.uri, curl_easy_strerror(code), code)));
}
}
};
struct State
{
struct EmbargoComparator {
bool operator() (const std::shared_ptr<DownloadItem> & i1, const std::shared_ptr<DownloadItem> & i2) {
return i1->embargo > i2->embargo;
}
};
bool quit = false;
std::priority_queue<std::shared_ptr<DownloadItem>, std::vector<std::shared_ptr<DownloadItem>>, EmbargoComparator> incoming;
std::vector<std::shared_ptr<DownloadItem>> incoming;
};
Sync<State> state_;
@ -451,7 +423,6 @@ struct CurlDownloader : public Downloader
std::thread workerThread;
CurlDownloader()
: mt19937(rd())
{
static std::once_flag globalInit;
std::call_once(globalInit, curl_global_init, CURL_GLOBAL_ALL);
@ -545,9 +516,7 @@ struct CurlDownloader : public Downloader
nextWakeup = std::chrono::steady_clock::time_point();
/* Add new curl requests from the incoming requests queue,
except for requests that are embargoed (waiting for a
retry timeout to expire). */
/* Add new curl requests from the incoming requests queue. */
if (extraFDs[0].revents & CURL_WAIT_POLLIN) {
char buf[1024];
auto res = read(extraFDs[0].fd, buf, sizeof(buf));
@ -556,22 +525,9 @@ struct CurlDownloader : public Downloader
}
std::vector<std::shared_ptr<DownloadItem>> incoming;
auto now = std::chrono::steady_clock::now();
{
auto state(state_.lock());
while (!state->incoming.empty()) {
auto item = state->incoming.top();
if (item->embargo <= now) {
incoming.push_back(item);
state->incoming.pop();
} else {
if (nextWakeup == std::chrono::steady_clock::time_point()
|| item->embargo < nextWakeup)
nextWakeup = item->embargo;
break;
}
}
std::swap(state->incoming, incoming);
quit = state->quit;
}
@ -598,7 +554,7 @@ struct CurlDownloader : public Downloader
{
auto state(state_.lock());
while (!state->incoming.empty()) state->incoming.pop();
state->incoming.clear();
state->quit = true;
}
}
@ -614,7 +570,7 @@ struct CurlDownloader : public Downloader
auto state(state_.lock());
if (state->quit)
throw nix::Error("cannot enqueue download request because the download thread is shutting down");
state->incoming.push(item);
state->incoming.push_back(item);
}
writeFull(wakeupPipe.writeSide.get(), " ");
}
@ -697,7 +653,9 @@ std::future<DownloadResult> Downloader::enqueueDownload(const DownloadRequest &
DownloadResult Downloader::download(const DownloadRequest & request)
{
return enqueueDownload(request).get();
return retry<DownloadResult>(request.tries, [&]() {
return enqueueDownload(request).get();
});
}
void Downloader::download(DownloadRequest && request, Sink & sink)
@ -883,7 +841,7 @@ CachedDownloadResult Downloader::downloadCached(ref<Store> store, const string &
writeFile(dataFile, url + "\n" + res.etag + "\n" + std::to_string(time(0)) + "\n");
} catch (DownloadError & e) {
if (storePath.empty()) throw;
printError(format("warning: %1%; using cached result") % e.msg());
warn("%s; using cached result", e.msg());
result.etag = expectedETag;
}
}
@ -933,5 +891,4 @@ bool isUri(const string & s)
return scheme == "http" || scheme == "https" || scheme == "file" || scheme == "channel" || scheme == "git" || scheme == "s3" || scheme == "ssh";
}
}