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diff --git a/extras/cliutils/README.md b/extras/cliutils/README.md new file mode 100644 index 00000000000..ccb60802c3d --- /dev/null +++ b/extras/cliutils/README.md @@ -0,0 +1,233 @@ +# CLI utility for creating Cluster aware CLI tools for Gluster +cliutils is a Python library which provides wrapper around `gluster system:: +execute` command to extend the functionalities of Gluster. + +Example use cases: +- Start a service in all peer nodes of Cluster +- Collect the status of a service from all peer nodes +- Collect the config values from each peer nodes and display latest + config based on version. +- Copy a file present in GLUSTERD_WORKDIR from one peer node to all + other peer nodes.(Geo-replication create push-pem is using this to + distribute the SSH public keys from all master nodes to all slave + nodes) +- Generate pem keys in all peer nodes and collect all the public keys + to one place(Geo-replication gsec_create is doing this) +- Provide Config sync CLIs for new features like `gluster-eventsapi`, + `gluster-restapi`, `gluster-mountbroker` etc. + +## Introduction + +If a executable file present in `$GLUSTER_LIBEXEC` directory in all +peer nodes(Filename startswith `peer_`) then it can be executed by +running `gluster system:: execute` command from any one peer node. + +- This command will not copy any executables to peer nodes, Script + should exist in all peer nodes to use this infrastructure. Raises + error in case script not exists in any one of the peer node. +- Filename should start with `peer_` and should exist in + `$GLUSTER_LIBEXEC` directory. +- This command can not be called from outside the cluster. + +To understand the functionality, create a executable file `peer_hello` +under $GLUSTER_LIBEXEC directory and copy to all peer nodes. + + #!/usr/bin/env bash + echo "Hello from $(gluster system:: uuid get)" + +Now run the following command from any one gluster node, + + gluster system:: execute hello + +**Note:** Gluster will not copy the executable script to all nodes, + copy `peer_hello` script to all peer nodes to use `gluster system:: + execute` infrastructure. + +It will run `peer_hello` executable in all peer nodes and shows the +output from each node(Below example shows output from my two nodes +cluster) + + Hello from UUID: e7a3c5c8-e7ad-47ad-aa9c-c13907c4da84 + Hello from UUID: c680fc0a-01f9-4c93-a062-df91cc02e40f + +## cliutils +A Python wrapper around `gluster system:: execute` command is created +to address the following issues + +- If a node is down in the cluster, `system:: execute` just skips it + and runs only in up nodes. +- `system:: execute` commands are not user friendly +- It captures only stdout, so handling errors is tricky. + +**Advantages of cliutils:** + +- Single executable file will act as node component as well as User CLI. +- `execute_in_peers` utility function will merge the `gluster system:: + execute` output with `gluster peer status` to identify offline nodes. +- Easy CLI Arguments handling. +- If node component returns non zero return value then, `gluster + system:: execute` will fail to aggregate the output from other + nodes. `node_output_ok` or `node_output_notok` utility functions + returns zero both in case of success or error, but returns json + with ok: true or ok:false respectively. +- Easy to iterate on the node outputs. +- Better error handling - Geo-rep CLIs `gluster system:: execute + mountbroker`, `gluster system:: execute gsec_create` and `gluster + system:: add_secret_pub` are suffering from error handling. These + tools are not notifying user if any failures during execute or if a node + is down during execute. + +### Hello World +Create a file in `$LIBEXEC/glusterfs/peer_message.py` with following +content. + + #!/usr/bin/env python + from gluster.cliutils import Cmd, runcli, execute_in_peers, node_output_ok + + class NodeHello(Cmd): + name = "node-hello" + + def run(self, args): + node_output_ok("Hello") + + class Hello(Cmd): + name = "hello" + + def run(self, args): + out = execute_in_peers("node-hello") + for row in out: + print ("{0} from {1}".format(row.output, row.hostname)) + + if __name__ == "__main__": + runcli() + +When we run `python peer_message.py`, it will have two subcommands, +"node-hello" and "hello". This file should be copied to +`$LIBEXEC/glusterfs` directory in all peer nodes. User will call +subcommand "hello" from any one peer node, which internally call +`gluster system:: execute message.py node-hello`(This runs in all peer +nodes and collect the outputs) + +For node component do not print the output directly, use +`node_output_ok` or `node_output_notok` functions. `node_output_ok` +additionally collects the node UUID and prints in JSON +format. `execute_in_peers` function will collect this output and +merges with `peers list` so that we don't miss the node information if +that node is offline. + +If you observed already, function `args` is optional, if you don't +have arguments then no need to create a function. When we run the +file, we will have two subcommands. For example, + + python peer_message.py hello + python peer_message.py node-hello + +First subcommand calls second subcommand in all peer nodes. Basically +`execute_in_peers(NAME, ARGS)` will be converted into + + CMD_NAME = FILENAME without "peers_" + gluster system:: execute <CMD_NAME> <SUBCOMMAND> <ARGS> + +In our example, + + filename = "peer_message.py" + cmd_name = "message.py" + gluster system:: execute ${cmd_name} node-hello + +Now create symlink in `/usr/bin` or `/usr/sbin` directory depending on +the usecase.(Optional step for usability) + + ln -s /usr/libexec/glusterfs/peer_message.py /usr/bin/gluster-message + +Now users can use `gluster-message` instead of calling +`/usr/libexec/glusterfs/peer_message.py` + + gluster-message hello + +### Showing CLI output as Table + +Following example uses prettytable library, which can be installed +using `pip install prettytable` or `dnf install python-prettytable` + + #!/usr/bin/env python + from prettytable import PrettyTable + from gluster.cliutils import Cmd, runcli, execute_in_peers, node_output_ok + + class NodeHello(Cmd): + name = "node-hello" + + def run(self, args): + node_output_ok("Hello") + + class Hello(Cmd): + name = "hello" + + def run(self, args): + out = execute_in_peers("node-hello") + # Initialize the CLI table + table = PrettyTable(["ID", "NODE", "NODE STATUS", "MESSAGE"]) + table.align["NODE STATUS"] = "r" + for row in out: + table.add_row([row.nodeid, + row.hostname, + "UP" if row.node_up else "DOWN", + row.output if row.ok else row.error]) + + print table + + if __name__ == "__main__": + runcli() + + +Example output, + + +--------------------------------------+-----------+-------------+---------+ + | ID | NODE | NODE STATUS | MESSAGE | + +--------------------------------------+-----------+-------------+---------+ + | e7a3c5c8-e7ad-47ad-aa9c-c13907c4da84 | localhost | UP | Hello | + | bb57a4c4-86eb-4af5-865d-932148c2759b | vm2 | UP | Hello | + | f69b918f-1ffa-4fe5-b554-ee10f051294e | vm3 | DOWN | N/A | + +--------------------------------------+-----------+-------------+---------+ + +## How to package in Gluster +If the project is created in `$GLUSTER_SRC/tools/message` + +Add "message" to SUBDIRS list in `$GLUSTER_SRC/tools/Makefile.am` + +and then create a `Makefile.am` in `$GLUSTER_SRC/tools/message` +directory with following content. + + EXTRA_DIST = peer_message.py + + peertoolsdir = $(libexecdir)/glusterfs/ + peertools_SCRIPTS = peer_message.py + + install-exec-hook: + $(mkdir_p) $(DESTDIR)$(bindir) + rm -f $(DESTDIR)$(bindir)/gluster-message + ln -s $(libexecdir)/glusterfs/peer_message.py \ + $(DESTDIR)$(bindir)/gluster-message + + uninstall-hook: + rm -f $(DESTDIR)$(bindir)/gluster-message + +Thats all. Add following files in `glusterfs.spec.in` if packaging is +required.(Under `%files` section) + + %{_libexecdir}/glusterfs/peer_message.py* + %{_bindir}/gluster-message + +## Who is using cliutils +- gluster-mountbroker http://review.gluster.org/14544 +- gluster-eventsapi http://review.gluster.org/14248 +- gluster-georep-sshkey http://review.gluster.org/14732 +- gluster-restapi https://github.com/aravindavk/glusterfs-restapi + +## Limitations/TODOs +- Not yet possible to create CLI without any subcommand, For example + `gluster-message` without any arguments +- Hiding node subcommands in `--help`(`gluster-message --help` will + show all subcommands including node subcommands) +- Only positional arguments supported for node arguments, Optional + arguments can be used for other commands. +- API documentation |