Fix 'error 9 while decompressing xz file'

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 a67cf5a3585c41dd9f219a2c7aa9cf67fa69520b)

1 files changed, 49 insertions, 45 deletions

diff --git a/src/libstore/store-api.cc b/src/libstore/store-api.cc
index c13ff11564ec..28ad7c019a94 100644
--- a/src/libstore/store-api.cc
+++ b/src/libstore/store-api.cc
@@ -6,10 +6,11 @@
 #include "thread-pool.hh"
 #include "json.hh"
 #include "derivations.hh"
+#include "retry.hh"
+#include "download.hh"
 
 #include <future>
 
-
 namespace nix {
 
 
@@ -572,54 +573,57 @@ void Store::buildPaths(const PathSet & paths, BuildMode buildMode)
 void copyStorePath(ref<Store> srcStore, ref<Store> dstStore,
     const Path & storePath, RepairFlag repair, CheckSigsFlag checkSigs)
 {
-    auto srcUri = srcStore->getUri();
-    auto dstUri = dstStore->getUri();
-
-    Activity act(*logger, lvlInfo, actCopyPath,
-        srcUri == "local" || srcUri == "daemon"
-          ? fmt("copying path '%s' to '%s'", storePath, dstUri)
-          : dstUri == "local" || dstUri == "daemon"
-            ? fmt("copying path '%s' from '%s'", storePath, srcUri)
-            : fmt("copying path '%s' from '%s' to '%s'", storePath, srcUri, dstUri),
-        {storePath, srcUri, dstUri});
-    PushActivity pact(act.id);
-
-    auto info = srcStore->queryPathInfo(storePath);
-
-    uint64_t total = 0;
-
-    if (!info->narHash) {
-        StringSink sink;
-        srcStore->narFromPath({storePath}, sink);
-        auto info2 = make_ref<ValidPathInfo>(*info);
-        info2->narHash = hashString(htSHA256, *sink.s);
-        if (!info->narSize) info2->narSize = sink.s->size();
-        if (info->ultimate) info2->ultimate = false;
-        info = info2;
-
-        StringSource source(*sink.s);
-        dstStore->addToStore(*info, source, repair, checkSigs);
-        return;
-    }
+    retry<void>(downloadSettings.tries, [&]() {
 
-    if (info->ultimate) {
-        auto info2 = make_ref<ValidPathInfo>(*info);
-        info2->ultimate = false;
-        info = info2;
-    }
+        auto srcUri = srcStore->getUri();
+        auto dstUri = dstStore->getUri();
+
+        Activity act(*logger, lvlInfo, actCopyPath,
+            srcUri == "local" || srcUri == "daemon"
+              ? fmt("copying path '%s' to '%s'", storePath, dstUri)
+              : dstUri == "local" || dstUri == "daemon"
+                ? fmt("copying path '%s' from '%s'", storePath, srcUri)
+                : fmt("copying path '%s' from '%s' to '%s'", storePath, srcUri, dstUri),
+            {storePath, srcUri, dstUri});
+        PushActivity pact(act.id);
+
+        auto info = srcStore->queryPathInfo(storePath);
+
+        uint64_t total = 0;
+
+        if (!info->narHash) {
+            StringSink sink;
+            srcStore->narFromPath({storePath}, sink);
+            auto info2 = make_ref<ValidPathInfo>(*info);
+            info2->narHash = hashString(htSHA256, *sink.s);
+            if (!info->narSize) info2->narSize = sink.s->size();
+            if (info->ultimate) info2->ultimate = false;
+            info = info2;
 
-    auto source = sinkToSource([&](Sink & sink) {
-        LambdaSink wrapperSink([&](const unsigned char * data, size_t len) {
-            sink(data, len);
-            total += len;
-            act.progress(total, info->narSize);
+            StringSource source(*sink.s);
+            dstStore->addToStore(*info, source, repair, checkSigs);
+            return;
+        }
+
+        if (info->ultimate) {
+            auto info2 = make_ref<ValidPathInfo>(*info);
+            info2->ultimate = false;
+            info = info2;
+        }
+
+        auto source = sinkToSource([&](Sink & sink) {
+            LambdaSink wrapperSink([&](const unsigned char * data, size_t len) {
+                sink(data, len);
+                total += len;
+                act.progress(total, info->narSize);
+            });
+            srcStore->narFromPath({storePath}, wrapperSink);
+        }, [&]() {
+            throw EndOfFile("NAR for '%s' fetched from '%s' is incomplete", storePath, srcStore->getUri());
         });
-        srcStore->narFromPath({storePath}, wrapperSink);
-    }, [&]() {
-        throw EndOfFile("NAR for '%s' fetched from '%s' is incomplete", storePath, srcStore->getUri());
-    });
 
-    dstStore->addToStore(*info, *source, repair, checkSigs);
+        dstStore->addToStore(*info, *source, repair, checkSigs);
+    });
 }