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/*
* Licensed to the Apache Software Foundation (ASF) under one
* or more contributor license agreements. See the NOTICE file
* distributed with this work for additional information
* regarding copyright ownership. The ASF licenses this file
* to you under the Apache License, Version 2.0 (the
* "License"); you may not use this file except in compliance
* with the License. You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing,
* software distributed under the License is distributed on an
* "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
* KIND, either express or implied. See the License for the
* specific language governing permissions and limitations
* under the License.
*/
/* $Rev$ $Date$ */
/**
* A partitioner component implementation which forwards data access requests to a
* dynamically selected data store component. The selection is externalized, performed
* by a selector component, responsible for selecting the target data store given the
* data access request key and a list of references to available data store components.
* This pattern can be used for sharding or load balancing for example.
*/
#define WANT_HTTPD_LOG 1
#include "string.hpp"
#include "function.hpp"
#include "list.hpp"
#include "value.hpp"
#include "monad.hpp"
namespace tuscany {
namespace partitioner {
/**
* Return the target partition for a key.
*/
const failable<lambda<value(const list<value>&)> > partition(const value& key, const lambda<value(const list<value>&)> selector, const list<value>& partitions) {
// Call the selector component to convert the given key to a partition number
const value p = selector(mklist<value>("get", key, partitions));
if (isNil(p)) {
ostringstream os;
os << "Couldn't get partition number: " << key;
return mkfailure<lambda<value(const list<value>&)> >(str(os), false);
}
return (const lambda<value(const list<value>&)>)p;
}
/**
* Get an item from a partition.
*/
const failable<value> get(const value& key, const lambda<value(const list<value>&)> selector, const list<value>& partitions) {
// Select partition
const failable<lambda<value(const list<value>&)> > p = partition(key, selector, partitions);
if (!hasContent(p))
return mkfailure<value>(reason(p));
// Get from selected partition
const value val = content(p)(mklist<value>("get", key));
if (isNil(val)) {
ostringstream os;
os << "Couldn't get entry from partition: " << key;
return mkfailure<value>(str(os), false);
}
return val;
}
/**
* Post an item to a partition.
*/
const failable<value> post(const value& key, const value& val, const lambda<value(const list<value>&)> selector, const list<value>& partitions) {
const value id = append<value>(key, mklist(mkuuid()));
// Select partition
const failable<lambda<value(const list<value>&)> > p = partition(id, selector, partitions);
if (!hasContent(p))
return mkfailure<value>(reason(p));
// Put into select partition
content(p)(mklist<value>("put", id, val));
return id;
}
/**
* Put an item into a partition.
*/
const failable<value> put(const value& key, const value& val, const lambda<value(const list<value>&)> selector, const list<value>& partitions) {
// Select partition
const failable<lambda<value(const list<value>&)> > p = partition(key, selector, partitions);
if (!hasContent(p))
return mkfailure<value>(reason(p));
// Put into selected partition
content(p)(mklist<value>("put", key, val));
return value(true);
}
/**
* Delete an item from a partition.
*/
const failable<value> del(const value& key, const lambda<value(const list<value>&)> selector, const list<value>& partitions) {
// Select partition
const failable<lambda<value(const list<value>&)> > p = partition(key, selector, partitions);
if (!hasContent(p))
return mkfailure<value>(reason(p));
// Delete from selected partition
content(p)(mklist<value>("delete", key));
return value(true);
}
}
}
extern "C" {
const tuscany::value apply(const tuscany::list<tuscany::value>& params) {
const tuscany::value func(car(params));
if (func == "get")
return tuscany::partitioner::get(cadr(params), caddr(params), cdddr(params));
if (func == "post")
return tuscany::partitioner::post(cadr(params), caddr(params), cadddr(params), cddddr(params));
if (func == "put")
return tuscany::partitioner::put(cadr(params), caddr(params), cadddr(params), cddddr(params));
if (func == "delete")
return tuscany::partitioner::del(cadr(params), caddr(params), cdddr(params));
return tuscany::mkfailure<tuscany::value>();
}
}
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