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69 lines
2.7 KiB
Python
69 lines
2.7 KiB
Python
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# -*- coding: utf-8 -*-
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# Copyright 2015 OpenMarket Ltd
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#
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# Licensed under the Apache License, Version 2.0 (the "License");
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# you may not use this file except in compliance with the License.
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# You may obtain a copy of the License at
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#
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# http://www.apache.org/licenses/LICENSE-2.0
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#
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# Unless required by applicable law or agreed to in writing, software
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# distributed under the License is distributed on an "AS IS" BASIS,
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# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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# See the License for the specific language governing permissions and
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# limitations under the License.
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"""
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This module controls the reliability for application service transactions.
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The nominal flow through this module looks like:
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___________
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\O/ --- event -->| | +--------------+
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| - event ---->| EventPool |<-- poll 1/s for events ---| EventSorter |
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/ \ ---- event ->|___________| +--------------+
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USERS ____________________________|
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| | |
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V V V
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ASa ASb ASc
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[e,e] [e] [e,e,e]
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V
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-````````- +------------+
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|````````|<--StoreTxn-|Transaction |
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|Database| | Maker |---> SEND TO AS
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`--------` +------------+
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What happens on SEND TO AS depends on the state of the Application Service:
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- If the AS is marked as DOWN, do nothing.
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- If the AS is marked as UP, send the transaction.
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* SUCCESS : Increment where the AS is up to txn-wise and nuke the txn
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contents from the db.
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* FAILURE : Marked AS as DOWN and start Recoverer.
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Recoverer attempts to recover ASes who have died. The flow for this looks like:
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,--------------------- backoff++ --------------.
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V |
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START ---> Wait exp ------> Get oldest txn ID from ----> FAILURE
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backoff DB and try to send it
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^ |__________
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Mark AS as | V
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UP & quit +---------- YES SUCCESS
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NO <--- Have more txns? <------ Mark txn success & nuke -+
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from db; incr AS pos.
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"""
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class EventPool(object):
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pass
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class EventSorter(object):
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pass
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class TransactionMaker(object):
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pass
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class Recoverer(object):
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pass
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