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Developing Applications with APR
Paul Querna pquerna@apache.org July 21, 2005 http://www.outoforder.cc/presentations/
A.P.R.
- Apache Portable Runtime
- Origin: httpd
- Platforms: Unix, Netware, OS/2, Windows.
Developing Applications with APR Paul Querna pquerna@apache.org - - PowerPoint PPT Presentation
Developing Applications with APR Paul Querna pquerna@apache.org - - PowerPoint PPT Presentation
Developing Applications with APR Paul Querna pquerna@apache.org July 21, 2005 http://www.outoforder.cc/presentations/ A.P.R. Apache Portable Runtime Origin: httpd Platforms: Unix, Netware, OS/2, Windows. Your Application APR-Util
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Your Application APR-Util APR Operating System Libraries
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Integration Points
- Modules
- Wrap Areas that use APR/Pools
- C++ Objects
- Entire Application
- Memory pools everywhere
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Layers
- Memory Allocation
- OS Portability Functions
- Library/Utility Functions (APR-Util)
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Memory Allocation.
- Memory Pools
- No free()
- Less overhead than Garbage Collection
- Still requires thinking!
- Loops
- Long running tasks
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apr_pool_create(&pool, NULL); for (i=0; i > n; ++i) { do_something(pool, i); apr_pool_clear(pool); } apr_pool_destroy(&pool, NULL);
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3.75 7.50 11.25 15.00
App Use Pool Size
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Not Perfect.
- Unbounded Memory Usage:
- ‘leaks’
- Pools will not free() to the OS.
- Can be handled with sub-pools.
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18.75 37.50 56.25 75.00
App Use Pool Size
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void use_lots_of_ram(apr_pool_t* pool) { do { void* data = apr_palloc(pool, 500); .... } while(cond_true()); }
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void use_lots_of_ram(apr_pool_t* pool) { apr_pool_create(&subpool, pool); do { void* data = apr_palloc(subpool, 500); ... } while(cond_true()); apr_pool_destroy(subpool); }
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void use_lots_of_ram(apr_pool_t* pool) { apr_pool_create(&subpool, pool); do { void* data = apr_palloc(subpool, 500); ... apr_pool_clear(subpool); } while(cond_true()); apr_pool_destroy(subpool); }
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Integration Points
- Modules
- Wrap Areas that use APR/Pools
- C++ Objects
- Entire Application
- Memory pools everywhere
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Simple Applications
- Few Calls to initialize APR
- Cleanup
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#include "apr.h" #include "apr_file_io.h" int main(int argc, char *argv[]) { apr_pool_t *p; apr_file_t *fp; apr_initialize(); atexit(apr_terminate); apr_pool_create(&p, NULL); apr_file_open_stdout(&fp, p); apr_file_printf(fp, "Hello World\n”); return 0; }
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Data Structures
- apr_array_header_t
- apr_table_t
- apr_hash_t
- APR Rings
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Arrays
- apr_array_make()
- initial size
- apr_array_push()
- returns pointer to new memory
- nelts
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Tables
- Keys &
Values
- Used for HTTP Headers
- apr_table_do
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Hashes
- Keys &
Values
- Arbitrary (void*)
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Rings
- Double Linked List
- Optional Debugging
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apr_status_t
- 0 == APR_SUCCESS
- Always use APR_STATUS_IS_* macros
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File IO
- read, write, writev, sendfile, seek, locking
- functions for stderr/stdout/stdin
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Network IO
- read, write, writev, sendfile
- sockaddr
- pollset
- kqueue/epoll/event ports
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Threading
- Similar to pthreads
- threads
- mutex
- thread
- process
- global
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APR-Util
- Everything that doesn’t have a home?
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Bucket Brigades
- Complicated -- entire sessions in past AC
are on them
- Buckets contain:
- Files
- Pipes
- Sockets
- Custom
- Uses APR_RING_*
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DBM
- iterate, fetch, insert
- must be explicitly closed -- no cleanup
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apr_reslist
- Pooling of Resources made easy
- Proxy
- DBI
- Timeouts
- Creation
- Destruction
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apr_dbd
- One API:
- MySQL
- Postrgres
- SQLite v2 & v3
- Oracle (in progress)
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apr_dbd_driver_t* driver = NULL; apr_dbd_t* handle = NULL; apr_dbd_get_driver(pool, "sqlite3", &driver); apr_dbd_open(driver, pool, “db", &handle); apr_dbd_query(driver, handle, &nrows, sql);
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Questions?
- http://www.outoforder.cc/presentations/