automover algo python script

external algorithm testing thing.

1 files changed, 208 insertions, 0 deletions

diff --git a/scripts/memcached-automove b/scripts/memcached-automove
new file mode 100755
index 0000000..98ba6dc
--- /dev/null
+++ b/scripts/memcached-automove
@@ -0,0 +1,208 @@
+#!/usr/bin/python3
+# Copyright 2017 Facebook.
+# Licensed under the same terms as memcached itself.
+
+import argparse
+import socket
+import sys
+import re
+import traceback
+from time import sleep
+
+parser = argparse.ArgumentParser(description="daemon for rebalancing slabs")
+parser.add_argument("--host", help="host to connect to",
+        default="localhost:11211", metavar="HOST:PORT")
+parser.add_argument("-s", "--sleep", help="seconds between runs",
+                    type=int, default="1")
+parser.add_argument("-v", "--verbose", action="store_true")
+parser.add_argument("-a", "--automove", action="store_true", default=False,
+                    help="enable automatic page rebalancing")
+parser.add_argument("-w", "--window", type=int, default="30",
+                    help="rolling window size for decision history")
+parser.add_argument("-r", "--ratio", type=float, default=0.8,
+                    help="ratio limiting distance between low/high class ages")
+
+# TODO:
+# - age adjuster function
+#   - by ratio of get_hits
+#   - by ratio of chunk size
+
+args = parser.parse_args()
+
+host, port = args.host.split(':')
+
+def window_check(history, sid, key):
+    total = 0
+    for window in history['w']:
+        s = window.get(sid)
+        if s and s.get(key):
+            total += s.get(key)
+    return total
+
+def determine_move(history, diffs, totals):
+    """ Figure out of a page move is in order.
+
+    - if > 2.5 pages of free space without free chunks reducing for N trials,
+      and no evictions for N trials, free to global.
+    - use ratio of how far apart age can be between slab classes
+    - if get_hits exists, allowable distance in age from the *youngest* slab
+      class is based on the percentage of get_hits the class gets, against the
+      factored max distance, ie:
+      1% max delta. youngest is 900, oldest allowable is 900+90
+      if class has 30% of get_hits, it can be 930
+    - youngest evicting slab class gets page moved to it, if outside ratio max
+    """
+    w = history['w'][-1]
+    oldest = (-1, 0)
+    youngest = (-1, sys.maxsize)
+    decision = (-1, -1)
+    for sid, slab in diffs.items():
+        w[sid] = {}
+        if 'evicted_d' not in slab:
+            continue
+        # mark this window as dirty if total pages increases or evictions
+        # happened
+        if slab['total_pages_d'] > 0:
+            w[sid]['dirty'] = 1
+        if slab['evicted_d'] > 0:
+            w[sid]['dirty'] = 1
+            w[sid]['ev'] = 1
+
+        # if > 2.5 pages free, and not dirty, reassign to global page pool and
+        # break.
+        if slab['free_chunks'] > slab['chunks_per_page'] * 2.5:
+            if window_check(history, sid, 'dirty') == 0:
+                decision = (sid, 0)
+                break
+
+        # are we the oldest slab class? (and a valid target)
+        if slab['age'] > oldest[1] and slab['total_pages'] > 5:
+            oldest = (sid, slab['age'])
+
+        # are we the youngest evicting slab class?
+        if slab['age'] < youngest[1] and window_check(history, sid, 'ev') > args.window / 2:
+            youngest = (sid, slab['age'])
+
+    # is the youngest slab class too young?
+    if args.verbose:
+        print("old, young:", oldest, youngest)
+    if youngest[0] != -1 and oldest[0] != -1:
+        if youngest[1] < oldest[1] * args.ratio:
+            decision = (oldest[0], youngest[0])
+
+    # rotate windows
+    history['w'].append({})
+    # TODO: Configurable window size
+    if (len(history['w']) > args.window):
+        history['w'].pop(0)
+    return decision
+
+
+def run_move(s, decision):
+    s.write("slabs reassign " + str(decision[0]) + " " + str(decision[1]) + "\r\n")
+    line = s.readline().rstrip()
+    if args.verbose:
+        print("move result:", line)
+
+
+def diff_stats(before, after):
+    diffs = {}
+    totals = {}
+    for slabid in after.keys():
+        sb = before.get(slabid)
+        sa = after.get(slabid)
+        if not (sb and sa):
+            continue
+        slab = sa.copy()
+        for k in sa.keys():
+            if k not in sb:
+                continue
+            if k not in totals:
+                totals[k] = 0
+                totals[k + '_d'] = 0
+            if k + '_d' not in slab:
+                slab[k + '_d'] = 0
+            if re.search(r"^\d+$", sa[k]):
+                totals[k] += int(sa[k])
+                slab[k] = int(sa[k])
+                slab[k + '_d'] = int(sa[k]) - int(sb[k])
+                totals[k + '_d'] += int(sa[k]) - int(sb[k])
+        slab['slab'] = slabid
+        diffs[slabid] = slab
+    return (diffs, totals)
+
+
+def read_stats(s):
+    slabs = {}
+    for statcmd in ['items', 'slabs']:
+        #print("stat cmd: " + statcmd)
+        # FIXME: Formatting
+        s.write("stats " + statcmd + "\r\n")
+        while True:
+            line = s.readline().rstrip()
+            if line.startswith("END"):
+                break
+
+            m = re.match(r"^STAT (?:items:)?(\d+):(\S+) (\S+)", line)
+            if m:
+                (slab, var, val) = m.groups()
+                if slab not in slabs:
+                    slabs[slab] = {}
+                slabs[slab][var] = val
+            #print("line: " + line)
+    return slabs
+
+
+def pct(num, divisor):
+    if not divisor:
+        return 0
+    return (num / divisor)
+
+
+def show_detail(diffs, totals):
+    print("  {:2s}: {:8s} (pct  ) {:10s} (pct    ) {:6s} (pct)".format('sb',
+                'evicted', 'items', 'pages'))
+
+    for sid, slab in diffs.items():
+        if 'evicted_d' not in slab:
+            continue
+        print("  {:2d}: {:8d} ({:.2f}%) {:10d} ({:.4f}%) {:6d} ({:.2f}%)".format(
+              int(sid), slab['evicted_d'], pct(slab['evicted_d'], totals['evicted_d']),
+              slab['number'], pct(slab['number'], totals['number']),
+              slab['total_pages'], pct(slab['total_pages'], totals['total_pages'])))
+
+
+stats_pre = {}
+history = { 'w': [{}] }
+while True:
+    try:
+        with socket.create_connection((host, port), 5) as c:
+            s = c.makefile(mode="rw", buffering=1)
+            s.write("slabs automove 0\r\n")
+            print(s.readline().rstrip())
+            while True:
+                stats_post = read_stats(s)
+                (diffs, totals) = diff_stats(stats_pre, stats_post)
+                if args.verbose:
+                    show_detail(diffs, totals)
+                decision = determine_move(history, diffs, totals)
+                if decision[0] != -1 and decision[1] != -1:
+                    print("moving page from, to:", decision)
+                    if args.automove:
+                        run_move(s, decision)
+
+                # Minimize sleeping if we just moved a page to global pool.
+                # Improves responsiveness during flushes/quick changes.
+                if decision[1] == 0:
+                    sleep(0.05)
+                else:
+                    sleep(args.sleep)
+                stats_pre = stats_post
+    except:
+        err = sys.exc_info()
+        print("disconnected:", err[0], err[1])
+        traceback.print_exc()
+        stats_pre = {}
+        history = { 'w': [{}] }
+        sleep(args.sleep)
+