diff options
Diffstat (limited to 'doc/hacker-guide/hacker-guide.tex')
| -rw-r--r-- | doc/hacker-guide/hacker-guide.tex | 309 |
1 files changed, 0 insertions, 309 deletions
diff --git a/doc/hacker-guide/hacker-guide.tex b/doc/hacker-guide/hacker-guide.tex deleted file mode 100644 index c2d7255d7..000000000 --- a/doc/hacker-guide/hacker-guide.tex +++ /dev/null @@ -1,309 +0,0 @@ -\documentclass{book}[12pt] -\usepackage{graphicx} -% \usepackage{fancyhdr} - -% \pagestyle{fancy} -\begin{document} - -% \headheight 117pt -% \rhead{\includegraphics{zr-logo.eps}} - -\author{Gluster} -\title{GlusterFS 1.3 Hacker's Guide} -\date{June 1, 2007} - -\maketitle -\frontmatter -\tableofcontents - -\mainmatter -\chapter{Introduction} - -\section{Coding guidelines} -GlusterFS uses Git for version control. To get the latest source do: -\begin{verbatim} - $ git clone git://git.gluster.com/glusterfs.git glusterfs -\end{verbatim} -\noindent -GlusterFS follows the GNU coding -standards\footnote{http://www.gnu.org/prep/standards\_toc.html} for the -most part. - -\chapter{Major components} -\section{libglusterfs} -\texttt{libglusterfs} contains supporting code used by all the other components. -The important files here are: - -\texttt{dict.c}: This is an implementation of a serializable dictionary type. It is -used by the protocol code to send requests and replies. It is also used to pass options -to translators. - -\texttt{logging.c}: This is a thread-safe logging library. The log messages go to a -file (default \texttt{/usr/local/var/log/glusterfs/*}). - -\texttt{protocol.c}: This file implements the GlusterFS on-the-wire -protocol. The protocol itself is a simple ASCII protocol, designed to -be easy to parse and be human readable. - -A sample GlusterFS protocol block looks like this: -\begin{verbatim} - Block Start header - 0000000000000023 callid - 00000001 type - 00000016 op - xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx human-readable name - 00000000000000000000000000000ac3 block size - <...> block - Block End -\end{verbatim} - -\texttt{stack.h}: This file defines the \texttt{STACK\_WIND} and -\texttt{STACK\_UNWIND} macros which are used to implement the parallel -stack that is maintained for inter-xlator calls. See the \textsl{Taking control -of the stack} section below for more details. - -\texttt{spec.y}: This contains the Yacc grammar for the GlusterFS -specification file, and the parsing code. - - -Draw diagrams of trees -Two rules: -(1) directory structure is same -(2) file can exist only on one node - -\section{glusterfs-fuse} -\section{glusterfsd} -\section{transport} -\section{scheduler} -\section{xlator} - -\chapter{xlators} -\section{Taking control of the stack} -One can think of STACK\_WIND/UNWIND as a very specific RPC mechanism. - -% \includegraphics{stack.eps} - -\section{Overview of xlators} - -\flushleft{\LARGE\texttt{cluster/}} -\vskip 2ex -\flushleft{\Large\texttt{afr}} -\vskip 2ex -\flushleft{\Large\texttt{stripe}} -\vskip 2ex -\flushleft{\Large\texttt{unify}} - -\vskip 4ex -\flushleft{\LARGE\texttt{debug/}} -\vskip 2ex -\flushleft{\Large\texttt{trace}} -\vskip 2ex -The trace xlator simply logs all fops and mops, and passes them through to its child. - -\vskip 4ex -\flushleft{\LARGE\texttt{features/}} -\flushleft{\Large\texttt{posix-locks}} -\vskip 2ex -This xlator implements \textsc{posix} record locking semantics over -any kind of storage. - -\vskip 4ex -\flushleft{\LARGE\texttt{performance/}} - -\flushleft{\Large\texttt{io-threads}} -\vskip 2ex -\flushleft{\Large\texttt{read-ahead}} -\vskip 2ex -\flushleft{\Large\texttt{stat-prefetch}} -\vskip 2ex -\flushleft{\Large\texttt{write-behind}} -\vskip 2ex - -\vskip 4ex -\flushleft{\LARGE\texttt{protocol/}} -\vskip 2ex - -\flushleft{\Large\texttt{client}} -\vskip 2ex - -\flushleft{\Large\texttt{server}} -\vskip 2ex - -\vskip 4ex -\flushleft{\LARGE\texttt{storage/}} -\flushleft{\Large\texttt{posix}} -\vskip 2ex -The \texttt{posix} xlator is the one which actually makes calls to the -on-disk filesystem. Currently this is the only storage xlator available. However, -plans to develop other storage xlators, such as one for Amazon's S3 service, are -on the roadmap. - -\chapter{Writing a simple xlator} -\noindent -In this section we're going to write a rot13 xlator. ``Rot13'' is a -simple substitution cipher which obscures a text by replacing each -letter with the letter thirteen places down the alphabet. So `a' (0) -would become `n' (12), `b' would be 'm', and so on. Rot13 applied to -a piece of ciphertext yields the plaintext again, because rot13 is its -own inverse, since: - -\[ -x_c = x + 13\; (mod\; 26) -\] -\[ -x_c + 13\; (mod\; 26) = x + 13 + 13\; (mod\; 26) = x -\] - -First we include the requisite headers. - -\begin{verbatim} -#include <ctype.h> -#include <sys/uio.h> - -#include "glusterfs.h" -#include "xlator.h" -#include "logging.h" - -/* - * This is a rot13 ``encryption'' xlator. It rot13's data when - * writing to disk and rot13's it back when reading it. - * This xlator is meant as an example, not for production - * use ;) (hence no error-checking) - */ - -\end{verbatim} - -Then we write the rot13 function itself. For simplicity, we only transform lower case -letters. Any other byte is passed through as it is. - -\begin{verbatim} -/* We only handle lower case letters for simplicity */ -static void -rot13 (char *buf, int len) -{ - int i; - for (i = 0; i < len; i++) { - if (isalpha (buf[i])) - buf[i] = (buf[i] - 'a' + 13) % 26; - else if (buf[i] <= 26) - buf[i] = (buf[i] + 13) % 26 + 'a'; - } -} -\end{verbatim} - -Next comes a utility function whose purpose will be clear after looking at the code -below. - -\begin{verbatim} -static void -rot13_iovec (struct iovec *vector, int count) -{ - int i; - for (i = 0; i < count; i++) { - rot13 (vector[i].iov_base, vector[i].iov_len); - } -} -\end{verbatim} - -\begin{verbatim} -static int32_t -rot13_readv_cbk (call_frame_t *frame, - call_frame_t *prev_frame, - xlator_t *this, - int32_t op_ret, - int32_t op_errno, - struct iovec *vector, - int32_t count) -{ - rot13_iovec (vector, count); - - STACK_UNWIND (frame, op_ret, op_errno, vector, count); - return 0; -} - -static int32_t -rot13_readv (call_frame_t *frame, - xlator_t *this, - dict_t *ctx, - size_t size, - off_t offset) -{ - STACK_WIND (frame, - rot13_readv_cbk, - FIRST_CHILD (this), - FIRST_CHILD (this)->fops->readv, - ctx, size, offset); - return 0; -} - -static int32_t -rot13_writev_cbk (call_frame_t *frame, - call_frame_t *prev_frame, - xlator_t *this, - int32_t op_ret, - int32_t op_errno) -{ - STACK_UNWIND (frame, op_ret, op_errno); - return 0; -} - -static int32_t -rot13_writev (call_frame_t *frame, - xlator_t *this, - dict_t *ctx, - struct iovec *vector, - int32_t count, - off_t offset) -{ - rot13_iovec (vector, count); - - STACK_WIND (frame, - rot13_writev_cbk, - FIRST_CHILD (this), - FIRST_CHILD (this)->fops->writev, - ctx, vector, count, offset); - return 0; -} - -\end{verbatim} - -Every xlator must define two functions and two external symbols. The functions are -\texttt{init} and \texttt{fini}, and the symbols are \texttt{fops} and \texttt{mops}. -The \texttt{init} function is called when the xlator is loaded by GlusterFS, and -contains code for the xlator to initialize itself. Note that if an xlator is present -multiple times in the spec tree, the \texttt{init} function will be called each time -the xlator is loaded. - -\begin{verbatim} -int32_t -init (xlator_t *this) -{ - if (!this->children) { - gf_log ("rot13", GF_LOG_ERROR, - "FATAL: rot13 should have exactly one child"); - return -1; - } - - gf_log ("rot13", GF_LOG_DEBUG, "rot13 xlator loaded"); - return 0; -} -\end{verbatim} - -\begin{verbatim} - -void -fini (xlator_t *this) -{ - return; -} - -struct xlator_fops fops = { - .readv = rot13_readv, - .writev = rot13_writev -}; - - -\end{verbatim} - -\end{document} - |