From 7a3e7d0e61a651cb929b88a23f930785cfef3774 Mon Sep 17 00:00:00 2001
From: Eelco Dolstra <edolstra@gmail.com>
Date: Tue, 6 Dec 2016 17:43:39 +0100
Subject: [PATCH] nix-store --serve: Suppress log output on stderr when
 repeating a build

---
 src/libstore/build.cc      | 3 ++-
 src/libstore/globals.hh    | 5 +++++
 src/nix-store/nix-store.cc | 1 +
 3 files changed, 8 insertions(+), 1 deletion(-)

diff --git a/src/libstore/build.cc b/src/libstore/build.cc
index ba51f8591..89d363a09 100644
--- a/src/libstore/build.cc
+++ b/src/libstore/build.cc
@@ -3047,7 +3047,8 @@ void DerivationGoal::handleEOF(int fd)
 
 void DerivationGoal::flushLine()
 {
-    if (settings.verboseBuild)
+    if (settings.verboseBuild &&
+        (settings.printRepeatedBuilds || curRound == 1))
         printError(filterANSIEscapes(currentLogLine, true));
     else {
         logTail.push_back(currentLogLine);
diff --git a/src/libstore/globals.hh b/src/libstore/globals.hh
index 3194193bc..a423b4e5c 100644
--- a/src/libstore/globals.hh
+++ b/src/libstore/globals.hh
@@ -149,6 +149,11 @@ struct Settings {
        before being killed (0 means no limit). */
     unsigned long maxLogSize;
 
+    /* When build-repeat > 0 and verboseBuild == true, whether to
+       print repeated builds (i.e. builds other than the first one) to
+       stderr. Hack to prevent Hydra logs from being polluted. */
+    bool printRepeatedBuilds = true;
+
     /* How often (in seconds) to poll for locks. */
     unsigned int pollInterval;
 
diff --git a/src/nix-store/nix-store.cc b/src/nix-store/nix-store.cc
index 2e530ae52..77ad517a7 100644
--- a/src/nix-store/nix-store.cc
+++ b/src/nix-store/nix-store.cc
@@ -842,6 +842,7 @@ static void opServe(Strings opFlags, Strings opArgs)
             settings.maxLogSize = readInt(in);
         if (GET_PROTOCOL_MINOR(clientVersion) >= 3)
             settings.set("build-repeat", std::to_string(readInt(in)));
+        settings.printRepeatedBuilds = false;
     };
 
     while (true) {