fatelei · January 9, 2016 15:56 · May 14, 2015
diff --git a/migrate-redis.py b/migrate-redis.py
@@ -0,0 +1,94 @@
+"""
+Copies all keys from the source Redis host to the destination Redis host.
+Useful to migrate Redis instances where commands like SLAVEOF and MIGRATE are
+restricted (e.g. on Amazon ElastiCache).
+
+The script scans through the keyspace of the given database number and uses
+a pipeline of DUMP and RESTORE commands to migrate the keys.
+
+Requires Redis 2.8.0 or higher.
+
+Python requirements:
+click==4.0
+progressbar==2.3
+redis==2.10.3
+"""
+
+import click
+from progressbar import ProgressBar
+from progressbar.widgets import Percentage, Bar, ETA
+import redis
+from redis.exceptions import ResponseError
+
+@click.command()
+@click.argument('srchost')
+@click.argument('dsthost')
+@click.option('--db', default=0, help='Redis db number, default 0')
+@click.option('--flush', default=False, is_flag=True, help='Delete all keys from destination before migrating')
+def migrate(srchost, dsthost, db, flush):
+    if srchost == dsthost:
+        print 'Source and destination must be different.'
+        return
+
+    source = redis.Redis(srchost, db=db)
+    dest = redis.Redis(dsthost, db=db)
+
+    if flush:
+        dest.flushdb()
+
+    size = source.dbsize()
+
+    if size == 0:
+        print 'No keys found.'
+        return
+
+    progress_widgets = ['%d keys: ' % size, Percentage(), ' ', Bar(), ' ', ETA()]
+    pbar = ProgressBar(widgets=progress_widgets, maxval=size).start()
+
+    COUNT = 2000 # scan size
+
+    cnt = 0
+    non_existing = 0
+    already_existing = 0
+    cursor = 0
+
+    while True:
+        cursor, keys = source.scan(cursor, count=COUNT)
+        pipeline = source.pipeline()
+        for key in keys:
+            pipeline.pttl(key)
+            pipeline.dump(key)
+        result = pipeline.execute()
+
+        pipeline = dest.pipeline()
+
+        for key, ttl, data in zip(keys, result[::2], result[1::2]):
+            if ttl is None:
+                ttl = 0
+            if data != None:
+                pipeline.restore(key, ttl, data)
+            else:
+                non_existing += 1
+
+        results = pipeline.execute(False)
+        for key, result in zip(keys, results):
+            if result != 'OK':
+                e = result
+                if hasattr(e, 'message') and (e.message == 'BUSYKEY Target key name already exists.' or e.message == 'Target key name is busy.'):
+                    already_existing += 1
+                else:
+                    print 'Key failed:', key, `data`, `result`
+                    raise e
+
+        if cursor == 0:
+            break
+
+        cnt += len(keys)
+        pbar.update(min(size, cnt))
+
+    pbar.finish()
+    print 'Keys disappeared on source during scan:', non_existing
+    print 'Keys already existing on destination:', already_existing
+
+if __name__ == '__main__':
+    migrate()
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