Store: Add a method for getting build logs

This allows various Store implementations to provide different ways to
get build logs. For example, BinaryCacheStore can get the build logs
from the binary cache.

Also, remove the log-servers option since we can use substituters for
this.

6 files changed, 44 insertions, 11 deletions

diff --git a/src/libstore/build.cc b/src/libstore/build.cc
index fd1f5dc3a4..2b0f8e592d 100644
--- a/src/libstore/build.cc
+++ b/src/libstore/build.cc
@@ -3048,9 +3048,6 @@ void DerivationGoal::registerOutputs()
 }
 
 
-string drvsLogDir = "drvs";
-
-
 Path DerivationGoal::openLogFile()
 {
     logSize = 0;
@@ -3060,7 +3057,7 @@ Path DerivationGoal::openLogFile()
     string baseName = baseNameOf(drvPath);
 
     /* Create a log file. */
-    Path dir = (format("%1%/%2%/%3%/") % worker.store.logDir % drvsLogDir % string(baseName, 0, 2)).str();
+    Path dir = (format("%1%/%2%/%3%/") % worker.store.logDir % worker.store.drvsLogDir % string(baseName, 0, 2)).str();
     createDirs(dir);
 
     Path logFileName = (format("%1%/%2%%3%")
diff --git a/src/libstore/globals.cc b/src/libstore/globals.cc
index df537a5125..012b3d5b8b 100644
--- a/src/libstore/globals.cc
+++ b/src/libstore/globals.cc
@@ -179,7 +179,6 @@ void Settings::update()
     _get(envKeepDerivations, "env-keep-derivations");
     _get(sshSubstituterHosts, "ssh-substituter-hosts");
     _get(useSshSubstituter, "use-ssh-substituter");
-    _get(logServers, "log-servers");
     _get(enableImportNative, "allow-unsafe-native-code-during-evaluation");
     _get(useCaseHack, "use-case-hack");
     _get(preBuildHook, "pre-build-hook");
diff --git a/src/libstore/globals.hh b/src/libstore/globals.hh
index 7a9a9f6c0c..4627216819 100644
--- a/src/libstore/globals.hh
+++ b/src/libstore/globals.hh
@@ -181,9 +181,6 @@ struct Settings {
     /* Whether to show a stack trace if Nix evaluation fails. */
     bool showTrace;
 
-    /* A list of URL prefixes that can return Nix build logs. */
-    Strings logServers;
-
     /* Whether the importNative primop should be enabled */
     bool enableImportNative;
 
diff --git a/src/libstore/local-fs-store.cc b/src/libstore/local-fs-store.cc
index 4571a2211c..c5da73dba3 100644
--- a/src/libstore/local-fs-store.cc
+++ b/src/libstore/local-fs-store.cc
@@ -2,6 +2,8 @@
 #include "fs-accessor.hh"
 #include "store-api.hh"
 #include "globals.hh"
+#include "compression.hh"
+#include "derivations.hh"
 
 namespace nix {
 
@@ -84,4 +86,37 @@ void LocalFSStore::narFromPath(const Path & path, Sink & sink)
     dumpPath(getRealStoreDir() + std::string(path, storeDir.size()), sink);
 }
 
+const string LocalFSStore::drvsLogDir = "drvs";
+
+std::shared_ptr<std::string> LocalFSStore::getBuildLog(const Path & path_)
+{
+    auto path(path_);
+
+    assertStorePath(path);
+
+    if (!isDerivation(path)) {
+        path = queryPathInfo(path)->deriver;
+        if (path == "") return nullptr;
+    }
+
+    string baseName = baseNameOf(path);
+
+    for (int j = 0; j < 2; j++) {
+
+        Path logPath =
+            j == 0
+            ? (format("%1%/%2%/%3%/%4%") % logDir % drvsLogDir % string(baseName, 0, 2) % string(baseName, 2)).str()
+            : (format("%1%/%2%/%3%") % logDir % drvsLogDir % baseName).str();
+        Path logBz2Path = logPath + ".bz2";
+
+        if (pathExists(logPath))
+            return std::make_shared<std::string>(readFile(logPath));
+
+        else if (pathExists(logBz2Path))
+            return decompress("bzip2", readFile(logBz2Path));
+    }
+
+    return nullptr;
+}
+
 }
diff --git a/src/libstore/local-store.hh b/src/libstore/local-store.hh
index 511209d840..49a0d7e0d6 100644
--- a/src/libstore/local-store.hh
+++ b/src/libstore/local-store.hh
@@ -21,9 +21,6 @@ namespace nix {
 const int nixSchemaVersion = 10;
 
 
-extern string drvsLogDir;
-
-
 struct Derivation;
 
 
diff --git a/src/libstore/store-api.hh b/src/libstore/store-api.hh
index 481d0b7990..3aea30c286 100644
--- a/src/libstore/store-api.hh
+++ b/src/libstore/store-api.hh
@@ -566,6 +566,11 @@ public:
        if they lack a signature. */
     virtual bool isTrusted() { return false; }
 
+    /* Return the build log of the specified store path, if available,
+       or null otherwise. */
+    virtual std::shared_ptr<std::string> getBuildLog(const Path & path)
+    { return nullptr; }
+
 protected:
 
     Stats stats;
@@ -579,6 +584,7 @@ public:
     const Path rootDir;
     const Path stateDir;
     const Path logDir;
+    const static string drvsLogDir;
 
     LocalFSStore(const Params & params);
 
@@ -595,6 +601,8 @@ public:
     {
         return getRealStoreDir() + "/" + baseNameOf(storePath);
     }
+
+    std::shared_ptr<std::string> getBuildLog(const Path & path) override;
 };