* build.cc: only use a substituter if it returns info for a path.

src/libstore/build.cc

@@ -2187,14 +2187,34 @@ void SubstitutionGoal::init()
         return;
     }
 
-    if (!worker.store.querySubstitutablePathInfo(storePath, info)) {
+    subs = substituters;
+    
+    tryNext();
+}
+
+
+void SubstitutionGoal::tryNext()
+{
+    trace("trying next substituter");
+
+    if (subs.size() == 0) {
+        /* None left.  Terminate this goal and let someone else deal
+           with it. */
         printMsg(lvlError,
-            format("path `%1%' is required, but there is no substituter that knows anything about it")
+            format("path `%1%' is required, but there is no substituter that can build it")
             % storePath);
         amDone(ecFailed);
         return;
     }
 
+    sub = subs.front();
+    subs.pop_front();
+
+    if (!worker.store.querySubstitutablePathInfo(sub, storePath, info)) {
+        tryNext();
+        return;
+    }
+
     /* To maintain the closure invariant, we first have to realise the
        paths referenced by this one. */
     foreach (PathSet::iterator, i, info.references)
@@ -2223,29 +2243,6 @@ void SubstitutionGoal::referencesValid()
         if (*i != storePath) /* ignore self-references */
             assert(worker.store.isValidPath(*i));
 
-    subs = substituters;
-
-    tryNext();
-}
-
-
-void SubstitutionGoal::tryNext()
-{
-    trace("trying next substituter");
-
-    if (subs.size() == 0) {
-        /* None left.  Terminate this goal and let someone else deal
-           with it. */
-        printMsg(lvlError,
-            format("path `%1%' is required, but there is no substituter that can build it")
-            % storePath);
-        amDone(ecFailed);
-        return;
-    }
-
-    sub = subs.front();
-    subs.pop_front();
-
     state = &SubstitutionGoal::tryToRun;
     worker.waitForBuildSlot(shared_from_this());
 }

src/libstore/local-store.cc

@@ -541,12 +541,11 @@ bool LocalStore::hasSubstitutes(const Path & path)
 }
 
 
-bool LocalStore::querySubstitutablePathInfo(const Path & path,
-    SubstitutablePathInfo & info)
+bool LocalStore::querySubstitutablePathInfo(const Path & substituter,
+    const Path & path, SubstitutablePathInfo & info)
 {
-    foreach (Paths::iterator, i, substituters) {
-        RunningSubstituter & run(runningSubstituters[*i]);
-        startSubstituter(*i, run);
+    RunningSubstituter & run(runningSubstituters[substituter]);
+    startSubstituter(substituter, run);
 
     *run.to << "info\n" << path << "\n" << std::flush;
         
@@ -556,7 +555,8 @@ bool LocalStore::querySubstitutablePathInfo(const Path & path,
     getline(*run.from, s);
     if (!string2Int(s, res)) abort();
 
-        if (res) {
+    if (!res) return false;
+    
     getline(*run.from, info.deriver);
     int nrRefs;
     getline(*run.from, s);
@@ -569,10 +569,16 @@ bool LocalStore::querySubstitutablePathInfo(const Path & path,
     long long size;
     if (!string2Int(s, size)) abort();
     info.downloadSize = size;
+    
     return true;
 }
-    }
 
+
+bool LocalStore::querySubstitutablePathInfo(const Path & path,
+    SubstitutablePathInfo & info)
+{
+    foreach (Paths::iterator, i, substituters)
+        if (querySubstitutablePathInfo(*i, path, info)) return true;
     return false;
 }
 

src/libstore/local-store.hh

@@ -86,6 +86,9 @@ public:
     bool querySubstitutablePathInfo(const Path & path,
         SubstitutablePathInfo & info);
     
+    bool querySubstitutablePathInfo(const Path & substituter,
+        const Path & path, SubstitutablePathInfo & info);
+    
     Path addToStore(const Path & srcPath, bool fixed = false,
         bool recursive = false, string hashAlgo = "",
         PathFilter & filter = defaultPathFilter);