libstore: asyncify BinaryCacheStore::fileExists

Change-Id: I7574f61bf222389606be87bbaff486b386cdbecd

lix/libstore/binary-cache-store.cc

@@ -19,6 +19,7 @@
 #include "lix/libutil/strings.hh"
 
 #include <chrono>
+#include <functional>
 #include <regex>
 #include <fstream>
 #include <sstream>
@@ -214,7 +215,10 @@ try {
 
             ThreadPool threadPool("write debuginfo pool", 25);
 
-            auto doFile = [&](std::string member, std::string key, std::string target) {
+            auto doFile = [&](AsyncIoRoot & aio,
+                              std::string member,
+                              std::string key,
+                              std::string target) {
                 checkInterrupt();
 
                 JSON json;
@@ -223,7 +227,9 @@ try {
 
                 // FIXME: or should we overwrite? The previous link may point
                 // to a GC'ed file, so overwriting might be useful...
-                if (fileExists(key)) return;
+                if (aio.blockOn(fileExists(key))) {
+                    return;
+                }
 
                 printMsg(lvlTalkative, "creating debuginfo link from '%s' to '%s'", key, target);
 
@@ -251,7 +257,9 @@ try {
                     std::string key = "debuginfo/" + buildId;
                     std::string target = "../" + narInfo->url;
 
-                    threadPool.enqueue(std::bind(doFile, std::string(debugPath, 1), key, target));
+                    threadPool.enqueueWithAio(std::bind(
+                        doFile, std::placeholders::_1, std::string(debugPath, 1), key, target
+                    ));
                 }
             }
 
@@ -260,13 +268,14 @@ try {
     }
 
     /* Atomically write the NAR file. */
-    if (repair || !fileExists(narInfo->url)) {
+    if (repair || !TRY_AWAIT(fileExists(narInfo->url))) {
         stats.narWrite++;
         upsertFile(narInfo->url,
             std::make_shared<std::fstream>(fnTemp, std::ios_base::in | std::ios_base::binary),
             "application/x-nix-nar");
-    } else
+    } else {
         stats.narWriteAverted++;
+    }
 
     stats.narWriteBytes += info.narSize;
     stats.narWriteCompressedBytes += fileSize;
@@ -347,7 +356,7 @@ try {
     // FIXME: this only checks whether a .narinfo with a matching hash
     // part exists. So ‘f4kb...-foo’ matches ‘f4kb...-bar’, even
     // though they shouldn't. Not easily fixed.
-    co_return fileExists(narInfoFileFor(storePath));
+    co_return TRY_AWAIT(fileExists(narInfoFileFor(storePath)));
 } catch (...) {
     co_return result::current_exception();
 }

lix/libstore/binary-cache-store.hh

@@ -73,7 +73,7 @@ public:
     BinaryCacheStoreConfig & config() override = 0;
     const BinaryCacheStoreConfig & config() const override = 0;
 
-    virtual bool fileExists(const std::string & path) = 0;
+    virtual kj::Promise<Result<bool>> fileExists(const std::string & path) = 0;
 
     virtual void upsertFile(const std::string & path,
         std::shared_ptr<std::basic_iostream<char>> istream,

lix/libstore/http-binary-cache-store.cc

@@ -120,16 +120,18 @@ protected:
         throw SubstituterDisabled("substituter '%s' is disabled", getUri());
     }
 
-    bool fileExists(const std::string & path) override
-    {
+    kj::Promise<Result<bool>> fileExists(const std::string & path) override
+    try {
         checkEnabled();
 
         try {
-            return getFileTransfer()->exists(makeURI(path));
+            co_return getFileTransfer()->exists(makeURI(path));
         } catch (FileTransferError & e) {
             maybeDisable();
             throw;
         }
+    } catch (...) {
+        co_return result::current_exception();
     }
 
     void upsertFile(const std::string & path,

lix/libstore/local-binary-cache-store.cc

@@ -57,7 +57,7 @@ public:
 
 protected:
 
-    bool fileExists(const std::string & path) override;
+    kj::Promise<Result<bool>> fileExists(const std::string & path) override;
 
     void upsertFile(const std::string & path,
         std::shared_ptr<std::basic_iostream<char>> istream,
@@ -125,9 +125,11 @@ try {
     co_return result::current_exception();
 }
 
-bool LocalBinaryCacheStore::fileExists(const std::string & path)
-{
-    return pathExists(binaryCacheDir + "/" + path);
+kj::Promise<Result<bool>> LocalBinaryCacheStore::fileExists(const std::string & path)
+try {
+    return {pathExists(binaryCacheDir + "/" + path)};
+} catch (...) {
+    return {result::current_exception()};
 }
 
 std::set<std::string> LocalBinaryCacheStore::uriSchemes()

lix/libstore/s3-binary-cache-store.cc

@@ -324,8 +324,8 @@ struct S3BinaryCacheStoreImpl : public S3BinaryCacheStore
         co_return result::current_exception();
     }
 
-    bool fileExists(const std::string & path) override
-    {
+    kj::Promise<Result<bool>> fileExists(const std::string & path) override
+    try {
         stats.head++;
 
         auto res = s3Helper.client->HeadObject(
@@ -339,11 +339,13 @@ struct S3BinaryCacheStoreImpl : public S3BinaryCacheStore
                 || error.GetErrorType() == Aws::S3::S3Errors::NO_SUCH_KEY
                 // If bucket listing is disabled, 404s turn into 403s
                 || error.GetErrorType() == Aws::S3::S3Errors::ACCESS_DENIED)
-                return false;
+                return {false};
             throw Error("AWS error fetching '%s': %s", path, error.GetMessage());
         }
 
-        return true;
+        return {true};
+    } catch (...) {
+        return {result::current_exception()};
     }
 
     std::shared_ptr<TransferManager> transferManager;