Inferno Distributed Programming With Inferno®Larry RauMember of Technical Staff Inferno Network Software Solutions Lucent Technologies, Inclarryr@lucent.com http://www.lucent.com/inferno
The Inferno OS • Lightweight OS for networked devices • portable -- StrongARM, PowerPC, x86, MIPS, SPARC. • Integrated DIS™ VM -- supports portable machine independent code modules. • Provides “distributed computing” capability through Namespace and Styx™ Technologies • Authentication and Encryption between nodes.
Distributed Computing Capabilities • The Inferno OS is built around a unique method of distributed computing • All resources represented as files • A dynamically adjustable namespace • The Styx™ file access protocol
Inferno File Systems • Inferno views virtually everything as a file system • network interface: /dev/tcp, /dev/udp,... • process information: /prog • window system: /dev/draw • information: /dev/user, /dev/time, /dev/sysname, /dev/random,….
Example: TCP Interface Access a TCP/IP network by manipulating the following files: puck$ ls /net/tcp/0 /net/tcp/0/ctl /net/tcp/0/data /net/tcp/0/listen /net/tcp/0/local /net/tcp/0/remote /net/tcp/0/status
Example: /dev/draw Access to the Inferno windowing system is via another file system: puck$ ls /dev/draw/2 /dev/draw/2/ctl /dev/draw/2/data /dev/draw/2/refresh
Other existing file systems • telfs: interface to telephony device • Mfs: message store file system • asr: interface to speech recognition
Why file systems? • Simple concept • familiar access methods: open, read, write, etc. • language neutral access • Easy to distribute
The Inferno Namespace • The Inferno Namespace is a hierarchical collection of files (I.e. resources). • Every process accesses its resources via its own namespace • can inherit from parent • share with other processes • Local and remote resources are bound into the namespace.
Primary Namespace Operations • BIND • MOUNT • EXPORT
The BIND Namespace Operation • Attaches local resources to the namespace • Moves a resource within the namespace • Can hide resources by binding over • Binding a directory can result in a Union Directory
Union Directories • A directory whose contents are a combination of the source and destination • Directories can be stacked where the contents of one hide the contents of others. • When binding you have the option of adding before or after the current contents
tmp / Y A Z F1 A1 A2 ... F1 F2 F3 F2 A1 B1 ... ... Union Directories ... ...
Z F2 A1 B1 A A Y / A ... ... F1 A1 A2 ... F1 A1 A2 F1 F2 F3 Union Directories bind -b /tmp/Y /A bind -a /tmp/Z /A
The MOUNT Namespace Operation • Attaches a remote file system to the namespace • Equivalent to a remote attach to obtain the remote file system’s root followed by a BIND operation • Mount initiates a Styx connection over an established network connection • Net connection can be authenticated
Node1 Node2 Mounting A Remote Node • Establish a network connection: TCP, Serial, ATM, etc. • [optional] Mutually authenticate the connection and establish session keys for encryption of all communication • Establish a Styx session: this obtains the root of the remote file system
The EXPORT Namespace Operation • Present the current namespace to remote clients • Listens on a network connection for a Styx session request • Accepts the mount by providing access to the root of the namespace • Continually responds to client file requests via the Styx protocol
Node1 Node2 Exporting a Namespace • Obtain a network connection: TCP Listen, etc • [optional] Perform mutual authentication and encryption key setup • Wait for Styx session request
Mini-Summary • Represent all local resources as file systems • Namespace provides a single, dynamically configured, hierarchical view of all resources (I.e. file systems) • Remote resources attached to the namespace
Writing Applications • Applications access resources by accessing files within the namespace • Use familiar file access functions • Access is independent of how the files got in the namespace -- local,remote, who cares!
Writing File Systems • Inferno drivers: C modules linked with the kernel • Limbo programs using the file2chan() system call • makes use of srv device (I.e. file system) • Limbo written Synthetic File Systems • InfernoSpaces • Java class library • C library
Application Advantages • Applications can assume location of resources: open(“/x/y”,…) • Resources can be configured prior to running the applications -- (I.e. an administrative chore) • No explicit networking code required • Allows for network independent distributed computing
The Styx™ Protocol • A simple file access protocol • Message passing: transmit-reply (a Styx Transaction) • Synchronous • 13 message pairs + 1 error reply • Assumes a reliable transport • Allows overlapped transactions • Mostly fixed length messages
Styx Message Structure Indicates message type: initial transmission (T-message) or reply message (R-message) Unique identifier used to track commands Unsigned integer that represents “current” file Message specific data type tag fid Contents
NOP FLUSH CLONE WALK OPEN CREATE READ WRITE CLUNK REMOVE STAT WSTAT ATTACH Styx Transactions
Summary Everything is a file + A method to organize files + A remote file access protocol = A Distributed Programming Model
How is it being used • Telephony • Call setup • Device control • Text to Speech • Network Gateways