1 files changed, 49 insertions, 0 deletions
diff --git a/src/mds/balancers/greedyspill.lua b/src/mds/balancers/greedyspill.lua
new file mode 100644
index 000000000..20576cdb8
--- /dev/null
+++ b/src/mds/balancers/greedyspill.lua
@@ -0,0 +1,49 @@
+local metrics = {"auth.meta_load", "all.meta_load", "req_rate", "queue_len", "cpu_load_avg"}
+
+-- Metric for balancing is the workload; also dumps metrics
+local function mds_load()
+  for rank, mds in pairs(mds) do
+    local s = "MDS"..rank..": < "
+    for _, metric in ipairs(metrics) do
+      s = s..metric.."="..mds[metric].." "
+    end
+    mds.load = mds["all.meta_load"]
+    BAL_LOG(5, s.."> load="..mds.load)
+  end
+end
+
+-- Shed load when you have load and your neighbor doesn't
+local function when()
+  if not mds[whoami+1] then
+    -- i'm the last rank
+    BAL_LOG(5, "when: not migrating! I am the last rank, nothing to spill to.");
+    return false
+  end
+  my_load = mds[whoami]["load"]
+  his_load = mds[whoami+1]["load"]
+  if my_load > 0.01 and his_load < 0.01 then
+    BAL_LOG(5, "when: migrating! my_load="..my_load.." hisload="..his_load)
+    return true
+  end
+  BAL_LOG(5, "when: not migrating! my_load="..my_load.." hisload="..his_load)
+  return false
+end
+
+-- Shed half your load to your neighbor
+-- neighbor=whoami+2 because Lua tables are indexed starting at 1
+local function where(targets)
+  targets[whoami+1] = mds[whoami]["load"]/2
+  return targets
+end
+
+local targets = {}
+for rank in pairs(mds) do
+  targets[rank] = 0
+end
+
+mds_load()
+if when() then
+  where(targets)
+end
+
+return targets