Add support for s3:// URIs

This adds support for s3:// URIs in all places where Nix allows URIs,
e.g. in builtins.fetchurl, builtins.fetchTarball, <nix/fetchurl.nix>
and NIX_PATH. It allows fetching resources from private S3 buckets,
using credentials obtained from the standard places (i.e. AWS_*
environment variables, ~/.aws/credentials and the EC2 metadata
server). This may not be super-useful in general, but since we already
depend on aws-sdk-cpp, it's a cheap feature to add.

1 files changed, 80 insertions, 61 deletions

diff --git a/src/libstore/s3-binary-cache-store.cc b/src/libstore/s3-binary-cache-store.cc
index cc1b331042..ac083410b3 100644
--- a/src/libstore/s3-binary-cache-store.cc
+++ b/src/libstore/s3-binary-cache-store.cc
@@ -1,6 +1,6 @@
 #if ENABLE_S3
-#if __linux__
 
+#include "s3.hh"
 #include "s3-binary-cache-store.hh"
 #include "nar-info.hh"
 #include "nar-info-disk-cache.hh"
@@ -18,15 +18,6 @@
 
 namespace nix {
 
-struct istringstream_nocopy : public std::stringstream
-{
-    istringstream_nocopy(const std::string & s)
-    {
-        rdbuf()->pubsetbuf(
-            (char *) s.data(), s.size());
-    }
-};
-
 struct S3Error : public Error
 {
     Aws::S3::S3Errors err;
@@ -60,21 +51,81 @@ static void initAWS()
     });
 }
 
+S3Helper::S3Helper()
+    : config(makeConfig())
+    , client(make_ref<Aws::S3::S3Client>(*config))
+{
+}
+
+ref<Aws::Client::ClientConfiguration> S3Helper::makeConfig()
+{
+    initAWS();
+    auto res = make_ref<Aws::Client::ClientConfiguration>();
+    res->region = Aws::Region::US_EAST_1; // FIXME: make configurable
+    res->requestTimeoutMs = 600 * 1000;
+    return res;
+}
+
+S3Helper::DownloadResult S3Helper::getObject(
+    const std::string & bucketName, const std::string & key)
+{
+    debug("fetching ‘s3://%s/%s’...", bucketName, key);
+
+    auto request =
+        Aws::S3::Model::GetObjectRequest()
+        .WithBucket(bucketName)
+        .WithKey(key);
+
+    request.SetResponseStreamFactory([&]() {
+        return Aws::New<std::stringstream>("STRINGSTREAM");
+    });
+
+    DownloadResult res;
+
+    auto now1 = std::chrono::steady_clock::now();
+
+    try {
+
+        auto result = checkAws(fmt("AWS error fetching ‘%s’", key),
+            client->GetObject(request));
+
+        res.data = std::make_shared<std::string>(
+            dynamic_cast<std::stringstream &>(result.GetBody()).str());
+
+    } catch (S3Error & e) {
+        if (e.err != Aws::S3::S3Errors::NO_SUCH_KEY) throw;
+    }
+
+    auto now2 = std::chrono::steady_clock::now();
+
+    res.durationMs = std::chrono::duration_cast<std::chrono::milliseconds>(now2 - now1).count();
+
+    return res;
+}
+
+#if __linux__
+
+struct istringstream_nocopy : public std::stringstream
+{
+    istringstream_nocopy(const std::string & s)
+    {
+        rdbuf()->pubsetbuf(
+            (char *) s.data(), s.size());
+    }
+};
+
 struct S3BinaryCacheStoreImpl : public S3BinaryCacheStore
 {
     std::string bucketName;
 
-    ref<Aws::Client::ClientConfiguration> config;
-    ref<Aws::S3::S3Client> client;
-
     Stats stats;
 
+    S3Helper s3Helper;
+
     S3BinaryCacheStoreImpl(
         const Params & params, const std::string & bucketName)
         : S3BinaryCacheStore(params)
         , bucketName(bucketName)
-        , config(makeConfig())
-        , client(make_ref<Aws::S3::S3Client>(*config))
     {
         diskCache = getNarInfoDiskCache();
     }
@@ -84,15 +135,6 @@ struct S3BinaryCacheStoreImpl : public S3BinaryCacheStore
         return "s3://" + bucketName;
     }
 
-    ref<Aws::Client::ClientConfiguration> makeConfig()
-    {
-        initAWS();
-        auto res = make_ref<Aws::Client::ClientConfiguration>();
-        res->region = Aws::Region::US_EAST_1; // FIXME: make configurable
-        res->requestTimeoutMs = 600 * 1000;
-        return res;
-    }
-
     void init() override
     {
         if (!diskCache->cacheExists(getUri(), wantMassQuery_, priority)) {
@@ -100,7 +142,7 @@ struct S3BinaryCacheStoreImpl : public S3BinaryCacheStore
             /* Create the bucket if it doesn't already exists. */
             // FIXME: HeadBucket would be more appropriate, but doesn't return
             // an easily parsed 404 message.
-            auto res = client->GetBucketLocation(
+            auto res = s3Helper.client->GetBucketLocation(
                 Aws::S3::Model::GetBucketLocationRequest().WithBucket(bucketName));
 
             if (!res.IsSuccess()) {
@@ -108,7 +150,7 @@ struct S3BinaryCacheStoreImpl : public S3BinaryCacheStore
                     throw Error(format("AWS error checking bucket ‘%s’: %s") % bucketName % res.GetError().GetMessage());
 
                 checkAws(format("AWS error creating bucket ‘%s’") % bucketName,
-                    client->CreateBucket(
+                    s3Helper.client->CreateBucket(
                         Aws::S3::Model::CreateBucketRequest()
                         .WithBucket(bucketName)
                         .WithCreateBucketConfiguration(
@@ -146,7 +188,7 @@ struct S3BinaryCacheStoreImpl : public S3BinaryCacheStore
     {
         stats.head++;
 
-        auto res = client->HeadObject(
+        auto res = s3Helper.client->HeadObject(
             Aws::S3::Model::HeadObjectRequest()
             .WithBucket(bucketName)
             .WithKey(path));
@@ -179,7 +221,7 @@ struct S3BinaryCacheStoreImpl : public S3BinaryCacheStore
         auto now1 = std::chrono::steady_clock::now();
 
         auto result = checkAws(format("AWS error uploading ‘%s’") % path,
-            client->PutObject(request));
+            s3Helper.client->PutObject(request));
 
         auto now2 = std::chrono::steady_clock::now();
 
@@ -198,42 +240,18 @@ struct S3BinaryCacheStoreImpl : public S3BinaryCacheStore
         sync2async<std::shared_ptr<std::string>>(success, failure, [&]() {
             debug(format("fetching ‘s3://%1%/%2%’...") % bucketName % path);
 
-            auto request =
-                Aws::S3::Model::GetObjectRequest()
-                .WithBucket(bucketName)
-                .WithKey(path);
-
-            request.SetResponseStreamFactory([&]() {
-                return Aws::New<std::stringstream>("STRINGSTREAM");
-            });
-
             stats.get++;
 
-            try {
-
-                auto now1 = std::chrono::steady_clock::now();
-
-                auto result = checkAws(format("AWS error fetching ‘%s’") % path,
-                    client->GetObject(request));
-
-                auto now2 = std::chrono::steady_clock::now();
+            auto res = s3Helper.getObject(bucketName, path);
 
-                auto res = dynamic_cast<std::stringstream &>(result.GetBody()).str();
+            stats.getBytes += res.data ? res.data->size() : 0;
+            stats.getTimeMs += res.durationMs;
 
-                auto duration = std::chrono::duration_cast<std::chrono::milliseconds>(now2 - now1).count();
+            if (res.data)
+                printTalkative("downloaded ‘s3://%s/%s’ (%d bytes) in %d ms",
+                    bucketName, path, res.data->size(), res.durationMs);
 
-                printMsg(lvlTalkative, format("downloaded ‘s3://%1%/%2%’ (%3% bytes) in %4% ms")
-                    % bucketName % path % res.size() % duration);
-
-                stats.getBytes += res.size();
-                stats.getTimeMs += duration;
-
-                return std::make_shared<std::string>(res);
-
-            } catch (S3Error & e) {
-                if (e.err == Aws::S3::S3Errors::NO_SUCH_KEY) return std::shared_ptr<std::string>();
-                throw;
-            }
+            return res.data;
         });
     }
 
@@ -246,7 +264,7 @@ struct S3BinaryCacheStoreImpl : public S3BinaryCacheStore
             debug(format("listing bucket ‘s3://%s’ from key ‘%s’...") % bucketName % marker);
 
             auto res = checkAws(format("AWS error listing bucket ‘%s’") % bucketName,
-                client->ListObjects(
+                s3Helper.client->ListObjects(
                     Aws::S3::Model::ListObjectsRequest()
                     .WithBucket(bucketName)
                     .WithDelimiter("/")
@@ -281,7 +299,8 @@ static RegisterStoreImplementation regStore([](
     return store;
 });
 
+#endif
+
 }
 
 #endif
-#endif