nix-super/src/libstore/filetransfer.hh
Eelco Dolstra 1ad3328c5e Allow tarball URLs to redirect to a lockable immutable URL
Previously, for tarball flakes, we recorded the original URL of the
tarball flake, rather than the URL to which it ultimately
redirects. Thus, a flake URL like
http://example.org/patchelf-latest.tar that redirects to
http://example.org/patchelf-<revision>.tar was not really usable. We
couldn't record the redirected URL, because sites like GitHub redirect
to CDN URLs that we can't rely on to be stable.

So now we use the redirected URL only if the server returns the
`x-nix-is-immutable` or `x-amz-meta-nix-is-immutable` headers in its
response.
2023-06-13 14:17:45 +02:00

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#pragma once
///@file
#include "types.hh"
#include "hash.hh"
#include "config.hh"
#include <string>
#include <future>
namespace nix {
struct FileTransferSettings : Config
{
Setting<bool> enableHttp2{this, true, "http2",
"Whether to enable HTTP/2 support."};
Setting<std::string> userAgentSuffix{this, "", "user-agent-suffix",
"String appended to the user agent in HTTP requests."};
Setting<size_t> httpConnections{
this, 25, "http-connections",
R"(
The maximum number of parallel TCP connections used to fetch
files from binary caches and by other downloads. It defaults
to 25. 0 means no limit.
)",
{"binary-caches-parallel-connections"}};
Setting<unsigned long> connectTimeout{
this, 0, "connect-timeout",
R"(
The timeout (in seconds) for establishing connections in the
binary cache substituter. It corresponds to `curl`s
`--connect-timeout` option. A value of 0 means no limit.
)"};
Setting<unsigned long> stalledDownloadTimeout{
this, 300, "stalled-download-timeout",
R"(
The timeout (in seconds) for receiving data from servers
during download. Nix cancels idle downloads after this
timeout's duration.
)"};
Setting<unsigned int> tries{this, 5, "download-attempts",
"How often Nix will attempt to download a file before giving up."};
};
extern FileTransferSettings fileTransferSettings;
struct FileTransferRequest
{
std::string uri;
Headers headers;
std::string expectedETag;
bool verifyTLS = true;
bool head = false;
size_t tries = fileTransferSettings.tries;
unsigned int baseRetryTimeMs = 250;
ActivityId parentAct;
bool decompress = true;
std::optional<std::string> data;
std::string mimeType;
std::function<void(std::string_view data)> dataCallback;
FileTransferRequest(std::string_view uri)
: uri(uri), parentAct(getCurActivity()) { }
std::string verb()
{
return data ? "upload" : "download";
}
};
struct FileTransferResult
{
bool cached = false;
std::string etag;
std::string effectiveUri;
std::string data;
uint64_t bodySize = 0;
/* An "immutable" URL for this resource (i.e. one whose contents
will never change), as returned by the `Link: <url>;
rel="immutable"` header. */
std::optional<std::string> immutableUrl;
};
class Store;
struct FileTransfer
{
virtual ~FileTransfer() { }
/**
* Enqueue a data transfer request, returning a future to the result of
* the download. The future may throw a FileTransferError
* exception.
*/
virtual void enqueueFileTransfer(const FileTransferRequest & request,
Callback<FileTransferResult> callback) = 0;
std::future<FileTransferResult> enqueueFileTransfer(const FileTransferRequest & request);
/**
* Synchronously download a file.
*/
FileTransferResult download(const FileTransferRequest & request);
/**
* Synchronously upload a file.
*/
FileTransferResult upload(const FileTransferRequest & request);
/**
* Download a file, writing its data to a sink. The sink will be
* invoked on the thread of the caller.
*/
void download(FileTransferRequest && request, Sink & sink);
enum Error { NotFound, Forbidden, Misc, Transient, Interrupted };
};
/**
* @return a shared FileTransfer object.
*
* Using this object is preferred because it enables connection reuse
* and HTTP/2 multiplexing.
*/
ref<FileTransfer> getFileTransfer();
/**
* @return a new FileTransfer object
*
* Prefer getFileTransfer() to this; see its docs for why.
*/
ref<FileTransfer> makeFileTransfer();
class FileTransferError : public Error
{
public:
FileTransfer::Error error;
/// intentionally optional
std::optional<std::string> response;
template<typename... Args>
FileTransferError(FileTransfer::Error error, std::optional<std::string> response, const Args & ... args);
};
}