modules/predict: turn off prediction by setting empty period

diff --git a/modules/predict/README.rst b/modules/predict/README.rst
index e24598e853bbe148c79721fc2408173d1ee8f177..e1c9ab78b8bf0e52094442b1f627b8cc4e943f44 100644 (file)
--- a/modules/predict/README.rst
+++ b/modules/predict/README.rst
@@ -28,6 +28,8 @@ Example configuration
 
 Defaults are 15 minutes window, 6 hours period.
 
+.. tip:: Use period 0 to turn off prediction and just do prefetching of expiring records.
+
 Exported metrics
 ^^^^^^^^^^^^^^^^
 

diff --git a/modules/predict/predict.lua b/modules/predict/predict.lua
index 223ceec0d6c59c1091adc2f1d27825d2cfcbf7b9..bc80d11c8b9a77a0f97846beb1c1828a4feb6d35 100644 (file)
--- a/modules/predict/predict.lua
+++ b/modules/predict/predict.lua
@@ -1,13 +1,13 @@
 -- Speculative prefetching for repetitive and soon-expiring records to reduce latency.
 -- @module predict
--- @field queue table of scheduled records
--- @field queue_max maximum length of the queue
--- @field window length of the coalescing window
+-- @field queue queue of scheduled queries
+-- @field queue_len number of scheduled queries
+-- @field period length of prediction history (number of windows)
+-- @field window length of the prediction window
 local predict = {
        queue = {},
        queue_len = 0,
        batch = 0,
-       epoch = 0,
        period = 24,
        window = 15,
        log = {},
@@ -15,6 +15,7 @@ local predict = {
 
 -- Calculate current epoch (which window fits current time)
 local function current_epoch()
+       if not predict.period or predict.period <= 1 then return nil end
        return (os.date('%H')*(60/predict.window) +
                math.floor(os.date('%M')/predict.window)) % predict.period + 1
 end
@@ -70,7 +71,7 @@ end
 
 -- Sample current epoch, return number of sampled queries
 function predict.sample(epoch_now)
-       if not epoch_now then return end
+       if not epoch_now then return 0, 0 end
        local queries = stats.frequent()
        stats.clear_frequent()
        local queued = 0
@@ -93,6 +94,7 @@ end
 
 -- Predict queries for the upcoming epoch
 local function generate(epoch_now)
+       if not epoch_now then return 0 end
        local queued = 0
        local period = predict.period + 1
        for i = 1, predict.period / 2 - 1 do
@@ -110,7 +112,6 @@ local function generate(epoch_now)
        return queued
 end
 
--- Process current epoch
 function predict.process(ev)
        -- Start a new epoch, or continue sampling
        predict.ev_sample = nil
@@ -118,6 +119,7 @@ function predict.process(ev)
        local nr_learned, nr_queued = predict.sample(epoch_now)
        -- End of epoch, predict next
        if predict.epoch ~= epoch_now then
+               stats['predict.epoch'] = epoch_now
                predict.epoch = epoch_now
                nr_queued = nr_queued + generate(epoch_now)
        end
@@ -132,14 +134,13 @@ function predict.process(ev)
                end
        end
        predict.ev_sample = event.after(next_event(), predict.process)
-       stats['predict.epoch'] = epoch_now
        stats['predict.queue'] = predict.queue_len
        stats['predict.learned'] = nr_learned
        collectgarbage()
 end
 
 function predict.init(module)
-       if predict.window > 0 and predict.period > 0 then
+       if predict.window > 0 then
                predict.epoch = current_epoch()
                predict.ev_sample = event.after(next_event(), predict.process)
        end