165 lines
6.5 KiB
C++
Executable File
165 lines
6.5 KiB
C++
Executable File
/**
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* @file _httpinternal.h
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* @brief Implementation constants and magic numbers
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*
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* $LicenseInfo:firstyear=2012&license=viewerlgpl$
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* Second Life Viewer Source Code
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* Copyright (C) 2012-2013, Linden Research, Inc.
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*
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* This library is free software; you can redistribute it and/or
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* modify it under the terms of the GNU Lesser General Public
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* License as published by the Free Software Foundation;
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* version 2.1 of the License only.
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*
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* This library is distributed in the hope that it will be useful,
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* but WITHOUT ANY WARRANTY; without even the implied warranty of
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
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* Lesser General Public License for more details.
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*
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* You should have received a copy of the GNU Lesser General Public
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* License along with this library; if not, write to the Free Software
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* Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
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*
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* Linden Research, Inc., 945 Battery Street, San Francisco, CA 94111 USA
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* $/LicenseInfo$
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*/
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#ifndef _LLCORE_HTTP_INTERNAL_H_
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#define _LLCORE_HTTP_INTERNAL_H_
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// If you find this included in a public interface header,
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// something wrong is probably happening.
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// --------------------------------------------------------------------
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// General library to-do list
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//
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// - Implement policy classes. Structure is mostly there just didn't
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// need it for the first consumer. [Classes are there. More
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// advanced features, like borrowing, aren't there yet.]
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// - Consider Removing 'priority' from the request interface. Its use
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// in an always active class can lead to starvation of low-priority
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// requests. Requires coodination of priority values across all
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// components that share a class. Changing priority across threads
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// is slightly expensive (relative to gain) and hasn't been completely
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// implemented. And the major user of priority, texture fetches,
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// may not really need it.
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// - Set/get for global policy and policy classes is clumsy. Rework
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// it heading in a direction that allows for more dynamic behavior.
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// [Mostly fixed]
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// - Move HttpOpRequest::prepareRequest() to HttpLibcurl for the
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// pedantic.
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// - Update downloader and other long-duration services are going to
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// need a progress notification. Initial idea is to introduce a
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// 'repeating request' which can piggyback on another request and
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// persist until canceled or carrier completes. Current queue
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// structures allow an HttpOperation object to be enqueued
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// repeatedly, so...
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// - Investigate making c-ares' re-implementation of a resolver library
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// more resilient or more intelligent on Mac. Part of the DNS failure
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// lies in here. The mechanism also looks a little less dynamic
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// than needed in an environments where networking is changing.
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// - Global optimizations: 'borrowing' connections from other classes,
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// HTTP pipelining.
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// - Dynamic/control system stuff: detect problems and self-adjust.
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// This won't help in the face of the router problems we've looked
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// at, however. Detect starvation due to UDP activity and provide
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// feedback to it.
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// - Change the transfer timeout scheme. We're less interested in
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// absolute time, in most cases, than in continuous progress.
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// - Many of the policy class settings are currently applied to the
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// entire class. Some, like connection limits, would be better
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// applied to each destination target making multiple targets
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// independent.
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//
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// Integration to-do list
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// - LLTextureFetch still needs a major refactor. The use of
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// LLQueuedThread makes it hard to inspect workers and do the
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// resource waiting we're now doing. Rebuild along simpler lines
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// some of which are suggested in new commentary at the top of
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// the main source file.
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// - Expand areas of usage eventually leading to the removal of LLCurl.
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// Rough order of expansion:
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// . Avatar names
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// . Group membership lists
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// . Caps access in general
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// . 'The rest'
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// - Adapt texture cache, image decode and other image consumers to
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// the BufferArray model to reduce data copying. Alternatively,
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// adapt this library to something else.
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//
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// --------------------------------------------------------------------
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// If '1', internal ready queues will not order ready
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// requests by priority, instead it's first-come-first-served.
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// Reprioritization requests have the side-effect of then
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// putting the modified request at the back of the ready queue.
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#define LLCORE_HTTP_READY_QUEUE_IGNORES_PRIORITY 1
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namespace LLCore
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{
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// Maxium number of policy classes that can be defined.
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// *TODO: Currently limited to the default class + 1, extend.
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const int HTTP_POLICY_CLASS_LIMIT = 8;
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// Debug/informational tracing. Used both
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// as a global option and in per-request traces.
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const int HTTP_TRACE_OFF = 0;
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const int HTTP_TRACE_LOW = 1;
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const int HTTP_TRACE_CURL_HEADERS = 2;
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const int HTTP_TRACE_CURL_BODIES = 3;
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const int HTTP_TRACE_MIN = HTTP_TRACE_OFF;
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const int HTTP_TRACE_MAX = HTTP_TRACE_CURL_BODIES;
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// Request retry limits
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//
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// At a minimum, retries need to extend past any throttling
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// window we're expecting from central services. In the case
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// of Linden services running through the caps routers, there's
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// a five-second or so window for throttling with some spillover.
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// We want to span a few windows to allow transport to slow
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// after onset of the throttles and then recover without a final
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// failure. Other systems may need other constants.
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const int HTTP_RETRY_COUNT_DEFAULT = 8;
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const int HTTP_RETRY_COUNT_MIN = 0;
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const int HTTP_RETRY_COUNT_MAX = 100;
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const int HTTP_REDIRECTS_DEFAULT = 10;
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// Timeout value used for both connect and protocol exchange.
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// Retries and time-on-queue are not included and aren't
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// accounted for.
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const long HTTP_REQUEST_TIMEOUT_DEFAULT = 30L;
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const long HTTP_REQUEST_XFER_TIMEOUT_DEFAULT = 0L;
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const long HTTP_REQUEST_TIMEOUT_MIN = 0L;
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const long HTTP_REQUEST_TIMEOUT_MAX = 3600L;
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// Limits on connection counts
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const int HTTP_CONNECTION_LIMIT_DEFAULT = 8;
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const int HTTP_CONNECTION_LIMIT_MIN = 1;
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const int HTTP_CONNECTION_LIMIT_MAX = 256;
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// Miscellaneous defaults
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const long HTTP_PIPELINING_DEFAULT = 0L;
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const bool HTTP_USE_RETRY_AFTER_DEFAULT = true;
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const long HTTP_THROTTLE_RATE_DEFAULT = 0L;
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// Tuning parameters
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// Time worker thread sleeps after a pass through the
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// request, ready and active queues.
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const int HTTP_SERVICE_LOOP_SLEEP_NORMAL_MS = 2;
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// Block allocation size (a tuning parameter) is found
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// in bufferarray.h.
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} // end namespace LLCore
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#endif // _LLCORE_HTTP_INTERNAL_H_
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