init code

Makefile

@@ -0,0 +1,57 @@
+all: server tweakfs
+
+clean:
+#	make -f Makefile.fuse_rpc clean
+	rm *.o
+	rm bbfs.log
+	rm -f fuse_rpc_client
+	rm -f fuse_rpc_server
+	rm -f tweakfs
+	rm -rf mountdir
+	rm -rf rootdir
+
+create:
+	mkdir mountdir
+	mkdir rootdir
+	touch rootdir/secret.txt
+	touch rootdir/secret_file.txt
+	touch rootdir/bogus.txt
+	echo "hello world" > rootdir/bogus.txt
+	echo "secret" > rootdir/secret.txt
+	echo "secret_file" > rootdir/secret_file.txt
+	mkdir rootdir/testdir
+
+header: fuse_rpc.x
+#	rpcgen -M -a -C fuse_rpc.x
+	rpcgen -M fuse_rpc.x
+
+server: fuse_rpc.h fuse_rpc_svc.c fuse_rpc_server.c fuse_rpc_xdr.c fuse_rpc_clnt.c
+	gcc -g3 -pthread fuse_rpc_svc.c fuse_rpc_server.c fuse_rpc_xdr.c fuse_rpc_clnt.c -o fuse_rpc_server
+
+tweakfs: tweakfs.c log.c fuse_rpc_clnt.o fuse_rpc_xdr.o
+	gcc -g3 -pthread $^ `pkg-config fuse --cflags --libs` -o $@
+
+mount:
+	./tweakfs -d -s rootdir/ mountdir/ localhost
+#	./tweakfs rootdir/ mountdir/ localhost
+
+debug:
+#	valgrind ./tweakfs -d -s rootdir/ mountdir localhost	
+	valgrind ./tweakfs -d -s rootdir/ mountdir 67.159.88.71 10.148.54.200
+
+unmount:
+	fusermount -u mountdir
+
+rpc:
+#	rpcgen -a -C fuse_rpc.x
+	make -f Makefile.fuse_rpc
+
+run_server:
+	sudo ./fuse_rpc_server
+#	sudo ./fuse_rpc_server 2>/dev/null
+
+new:
+	make unmount
+	make clean
+	make
+	make create

Makefile.fuse_rpc

@@ -0,0 +1,47 @@
+
+# This is a template Makefile generated by rpcgen
+
+# Parameters
+
+CLIENT = fuse_rpc_client
+SERVER = fuse_rpc_server
+
+SOURCES_CLNT.c = 
+SOURCES_CLNT.h = 
+SOURCES_SVC.c = 
+SOURCES_SVC.h = 
+SOURCES.x = fuse_rpc.x
+
+TARGETS_SVC.c = fuse_rpc_svc.c fuse_rpc_server.c fuse_rpc_xdr.c 
+TARGETS_CLNT.c = fuse_rpc_clnt.c fuse_rpc_client.c fuse_rpc_xdr.c 
+TARGETS = fuse_rpc.h fuse_rpc_xdr.c fuse_rpc_clnt.c fuse_rpc_svc.c fuse_rpc_client.c fuse_rpc_server.c
+
+OBJECTS_CLNT = $(SOURCES_CLNT.c:%.c=%.o) $(TARGETS_CLNT.c:%.c=%.o)
+OBJECTS_SVC = $(SOURCES_SVC.c:%.c=%.o) $(TARGETS_SVC.c:%.c=%.o)
+# Compiler flags 
+
+CPPFLAGS += -D_REENTRANT
+CFLAGS += -g 
+LDLIBS += -lnsl -lpthread 
+ RPCGENFLAGS = 
+
+# Targets 
+
+all : $(CLIENT) $(SERVER)
+
+$(TARGETS) : $(SOURCES.x) 
+	rpcgen $(RPCGENFLAGS) $(SOURCES.x)
+
+$(OBJECTS_CLNT) : $(SOURCES_CLNT.c) $(SOURCES_CLNT.h) $(TARGETS_CLNT.c) 
+
+$(OBJECTS_SVC) : $(SOURCES_SVC.c) $(SOURCES_SVC.h) $(TARGETS_SVC.c) 
+
+$(CLIENT) : $(OBJECTS_CLNT) 
+	$(LINK.c) -o $(CLIENT) $(OBJECTS_CLNT) $(LDLIBS) 
+
+$(SERVER) : $(OBJECTS_SVC) 
+	$(LINK.c) -o $(SERVER) $(OBJECTS_SVC) $(LDLIBS)
+
+ clean:
+	 $(RM) core $(TARGETS) $(OBJECTS_CLNT) $(OBJECTS_SVC) $(CLIENT) $(SERVER)
+

README.md

@@ -1,2 +1,89 @@
-# Distributed-File-System
-Distributed File Sytem
+### Distributed File system
+This project is distributed file system based on [FUSE](https://github.com/libfuse/libfuse). Currently the cluster contains only two servers, one primary and one secondary, but it could be extended to more.
+
+#### How to run the program
+Before compiling the project, make sure the environment is set-up.
+```
+sudo apt update 
+sudo apt dist-upgrade 
+sudo apt install build-essential pkg-config libfuse-dev
+```
+This repo has provided Makefile, but several places needs to be updated.
+`make header` compiles and updates the RPC header and stab files.
+`make all` compiles client-side and server-side executable file `tweakfs` and `fuse_rpc_server` respectively.
+`make create` generates the rootdir and mountdir automatically, which is the pre-requisite for the program.
+`make debug` needs a little update: the last two arguments are IP addresses for primary and secondary server.
+`make unmount` unmount the mountdir off rootdir.
+`make clean` cleans all generated object files and rootdir, mountdir.
+Additionally, on server-side, I did a hard code of secondary server IP address, ``connect_server``which needs to be corrected.
+System configuration file `/etc/hosts` should also appended the target server IP. Example:
+```
+127.0.0.1       localhost
+127.0.1.1       ubuntu
+
+# For RPC.
+67.159.88.71 [email protected]
+10.148.54.200 [email protected]
+
+# The following lines are desirable for IPv6 capable hosts
+::1     localhost ip6-localhost ip6-loopback
+ff02::1 ip6-allnodes
+ff02::2 ip6-allrouters
+```
+
+#### Implementation details
+1. On client side, every file system operation will be transmitted to server side via RPC. In this project, I select [Sun RPC](https://docs.oracle.com/cd/E19683-01/816-1435/6m7rrfn9k/index.html). Client side always tries to connect primary server first, then secondary server if fails.
+2. `.x` file is the communication protocal for RPC.
+Naming pattern:
+- client-to-server message structs are named as function_arg, server-to-client message structs are named as function_ret.
+- Every server-to-client response includes a data member ret, it returns 0 if RPC succeeds, otherwise it'd be assigned -errno.
+- For r/w requests, a len member is included, which indicates the actual bytes completes.
+- Every *_arg has a data member called ip, which is used to differentiate seperate path for distinct clients. To create path at server side, it's represented as a unsigned integer.
+3. Server handles every RPC requests from client side.
+For primary server, several updating operation needs to be completed on secondary server for replication and availability, say, `write`, `mkdir`, `rmdir`, etc. It first transmit these requests to secondary server, and handle the request whatever the second one succeeds or fails. Other read-only requests will only be handled on primary server.
+4. Primary server goes through the "handle flow" of `opendir` - `readdir` - `releasedir`, `open` - `read` - `release`, so it could use the fd acquired from previous operations, while the secondary server have to rely on full path.
+5. All operations are executed in the order of:
+
+(1) transmit request to primary server, if possible
+
+(2) check rwx validility, if needed
+
+(3) lock the file or directory, if needed
+
+(4) execute the operation
+
+(5) unlock the locked resource
+
+(6) set return value, and send back response back to client via RPC
+
+6. Server stores all files under the root directory `/DFS`, and create it at the very beginning it doesn't exist. All files are considered visible by all user mounted, but other operations, like updating, removing, reading needs further authentication.
+
+7. About access authentication:
+
+(1) file open is checked by read and write bit
+
+(2) directory listing is checked by read bit, open is checked by execute bit
+
+(3) file creation, rename and deletion need the rwx bits of parent directory, related operations include operation: unlink, mkdir, rmdir, mknod, rename, symlink, link
+
+(4) chown needs root, chmod needs owner, utime needs owner
+
+8. Locking mechanism:
+
+(1) add shared lock for file read and directory read
+
+(2) add exclusive lock for file write
+
+(3) add exclusive lock for directory mutation, eg: rename, unlink, etc
+
+9. About server recovery, we have provided a python script which does cold restoration. Eg, you could simply `sudo python rsync.py [email protected]:/9962309 /`
+
+#### Special handling
+1. `chown` needs root identity, users calling it will get a "permission deny" error message.
+2. `/DFS` is a special root directory in Ddistributed File System. Anyone can create file or directory inside of it, but only owner of the file can delete or rename. 
+
+#### Known bugs
+1. We have handled the cases where primary server or secondary one cannot be reached. But if the client goes down, fd won't be released, thus system resource is leaked.
+2. `symlink` and `link` operations are not yet thread-safe.
+3. `fd .` should show the file system attribute, but my program cannot.
+4. server failover test doesn't pass; currently it can only handle the case when server program is killed, and machine is still alive; it doesn't go well when secondary server is rebooted.