Resending this as my last message accidentally included some html and got rejected by the listserv On 27 Jan 2022, at 16:04, John Cai wrote: > Hey Phillip, > > First of all thank you for the thorough review—it really helps someone who’s learning how to contribute! > > On 27 Jan 2022, at 6:25, Phillip Wood wrote: > >> Hi John >> >> On 25/01/2022 22:50, John Cai wrote: >>> This RFC patch proposes a new flag --stdin-cmd that works with >>> git-cat-file --batch. Similar to git-update-ref --stdin, it will accept >>> commands and arguments from stdin. >>> >>> The start of this idea was discussed in [1], where the original >>> motivation was to be able to control when the buffer was flushed to >>> stdout in --buffer mode. >>> >>> However, this can actually be much more useful in situations when >>> git-cat-file --batch is being used as a long lived backend query >>> process. At GitLab, we use a pair of cat-file processes. One for >>> iterating over object metadata with --batch-check, and the other to grab >>> object contents with --batch. However, if we had --stdin-cmd, we could >>> get rid of the second --batch-check process, and just have one progress >>> where we can flip between getting object info, and getting object contents. >>> This can lead to huge savings. >>> >>> git cat-file --batch --stdin-cmd >>> >>> $ <command> [arg1] [arg2] NL >>> >>> We can also add a -z mode to allow for NUL-terminated lines >>> >>> $ <command> [arg1] [arg2] NUL >>> >>> This patch adds three commands: object, info, fflush >>> >>> $ object <sha1> NL >>> $ info <sha1> NL >>> $ fflush NL >>> >>> These three would be immediately useful in GitLab's context, but one can >>> imagine this mode to be further extended for other things. >>> >>> For instance, a non-trivial part of "cat-file --batch" time is spent >>> on parsing its argument and seeing if it's a revision, ref etc. So we >>> could add a command that only accepts a full-length 40 >>> character SHA-1. >>> >>> This would be the first step in adding such an interface to >>> git-cat-file. >>> >>> [1] https://lore.kernel.org/git/pull.1124.git.git.1636149400.gitgitgadget@xxxxxxxxx/ >>> >>> Helped-by: Ævar Arnfjörð Bjarmason <avarab@xxxxxxxxx> >>> Signed-off-by: John Cai <johncai86@xxxxxxxxx> >>> --- >>> Changes from v1: >>> >>> - changed option name to batch-command. >>> - changed command function interface to receive the whole line after the command >>> name to put the onus of parsing arguments to each individual command function. >>> - pass in whole line to batch_one_object in both parse_cmd_object and >>> parse_cmd_info to support spaces in the object reference. >>> - removed addition of -z to include in a separate patch series >>> - added documentation. >> >> I've left some comments below, they're mostly small details, I like the new option name and the changes you've made to the command parsing. >> >>> --- >>> Documentation/git-cat-file.txt | 15 +++++ >>> builtin/cat-file.c | 114 ++++++++++++++++++++++++++++++++- >>> strvec.c | 23 +++++++ >>> strvec.h | 8 +++ >>> t/t1006-cat-file.sh | 32 +++++++++ >>> 5 files changed, 191 insertions(+), 1 deletion(-) >>> >>> diff --git a/Documentation/git-cat-file.txt b/Documentation/git-cat-file.txt >>> index bef76f4dd0..8aefa45e4c 100644 >>> --- a/Documentation/git-cat-file.txt >>> +++ b/Documentation/git-cat-file.txt >>> @@ -96,6 +96,21 @@ OPTIONS >>> need to specify the path, separated by whitespace. See the >>> section `BATCH OUTPUT` below for details. >>> +-batch-command:: >> >> is this missing a '-'? >> >>> + Enter a command mode that reads from stdin. May not be combined with any >>> + other options or arguments except `--textconv` or `--filters`, in which >>> + case the input lines also need to specify the path, separated by >>> + whitespace. See the section `BATCH OUTPUT` below for details. >>> + >>> +object <object>:: >>> + Print object contents for object reference <object> >>> + >>> +info <object>:: >>> + Print object info for object reference <object> >>> + >>> +flush:: >>> + Flush to stdout immediately when used with --buffer >>> + >>> --batch-all-objects:: >>> Instead of reading a list of objects on stdin, perform the >>> requested batch operation on all objects in the repository and >>> diff --git a/builtin/cat-file.c b/builtin/cat-file.c >>> index 7b3f42950e..30794284d5 100644 >>> --- a/builtin/cat-file.c >>> +++ b/builtin/cat-file.c >>> @@ -16,6 +16,7 @@ >>> #include "packfile.h" >>> #include "object-store.h" >>> #include "promisor-remote.h" >>> +#include "strvec.h" >>> struct batch_options { >>> int enabled; >>> @@ -26,7 +27,10 @@ struct batch_options { >>> int unordered; >>> int cmdmode; /* may be 'w' or 'c' for --filters or --textconv */ >>> const char *format; >>> + int stdin_cmd; >> >> Now that the option has been renamed it would be nice to rename the corresponding variable to match > > I was trying to find a good name. There is already a cmdmode variable. I’m thinking stdin_cmd is not such a > bad name since we are receiving commands from stdin. suggestions welcome! > >> >>> + int end_null; >> >> If you're not adding '-z' here then you don't need this or the addition below. >> >>> }; >>> +static char line_termination = '\n'; >>> static const char *force_path; >>> @@ -508,6 +512,102 @@ static int batch_unordered_packed(const struct object_id *oid, >>> data); >>> } >>> +enum batch_state { >>> + /* Non-transactional state open for commands. */ >>> + BATCH_STATE_OPEN, >>> +}; >> >> I forgot to ask what the idea behind the batch state is last time - what's it for? > > This is to support transactional semantics for commands we want to support in the future, but > since this is already a biggish change, we can leave this out of this series. > >> >>> +static void parse_cmd_object(struct batch_options *opt, >>> + const char *line, >>> + struct strbuf *output, >>> + struct expand_data *data) >>> +{ >>> + opt->print_contents = 1; >>> + batch_one_object(line, output, opt, data); >>> +} >>> + >>> +static void parse_cmd_info(struct batch_options *opt, >>> + const char *line, >>> + struct strbuf *output, >>> + struct expand_data *data) >>> +{ >>> + opt->print_contents = 0; >>> + batch_one_object(line, output, opt, data); >>> +} >>> + >>> +static void parse_cmd_fflush(struct batch_options *opt, >>> + const char *line, >>> + struct strbuf *output, >>> + struct expand_data *data) >>> +{ >>> + fflush(stdout); >>> +} >>> + >>> +typedef void (*parse_cmd_fn_t)(struct batch_options *, const char *, >>> + struct strbuf *, struct expand_data *); >>> + >>> +static const struct parse_cmd { >>> + const char *prefix; >>> + parse_cmd_fn_t fn; >>> + unsigned args; >> >> This is now a flag so maybe 'takes_args' would better describe its purpose. >> >>> + enum batch_state state; >>> +} commands[] = { >>> + { "object", parse_cmd_object, 1, BATCH_STATE_OPEN }, >>> + { "info", parse_cmd_info, 1, BATCH_STATE_OPEN }, >>> + { "fflush", parse_cmd_fflush, 0, BATCH_STATE_OPEN }, >>> +}; >>> + >>> +static void batch_objects_stdin_cmd(struct batch_options *opt, >>> + struct strbuf *output, >>> + struct expand_data *data) >>> +{ >>> + struct strbuf input = STRBUF_INIT; >>> + enum batch_state state = BATCH_STATE_OPEN; >>> + >>> + /* Read each line dispatch its command */ >>> + while (!strbuf_getwholeline(&input, stdin, line_termination)) { >>> + int i; >>> + const struct parse_cmd *cmd = NULL; >>> + const char *p; >>> + >>> + if (*input.buf == line_termination) >>> + die("empty command in input"); >>> + else if (isspace(*input.buf)) >>> + die("whitespace before command: %s", input.buf); >>> + >>> + for (i = 0; i < ARRAY_SIZE(commands); i++) { >>> + const char *prefix = commands[i].prefix; >>> + char c; >>> + const char *cmd_name; >> >> skip_prefix() sets this to the end of the name so maybe 'cmd_end' would be clearer? >> >>> + if (!skip_prefix(input.buf, prefix, &cmd_name)) >>> + continue; >>> + /* >>> + * If the command has arguments, verify that it's >>> + * followed by a space. Otherwise, it shall be followed >>> + * by a line terminator. >>> + */ >>> + c = commands[i].args ? ' ' : line_termination; >>> + if (input.buf[strlen(prefix)] != c) >> >> Now that you're using skip_prefix() you can write this as >> if (*cmd_end != c) >> >>> + continue; >>> + >>> + cmd = &commands[i]; >>> + break; >>> + } >>> + if (!cmd) >>> + die("unknown command: %s", input.buf); >>> + >>> + p = input.buf + strlen(cmd->prefix) + 1; >> >> This can be simplified to >> p = cmd_end + 1; >> >>> + const char *pos = strstr(p, &line_termination); >> >> This isn't needed without '-z'. If it were required then using strchrnul() would prevent a NULL pointer dereference when the last input line does not end with a terminator. I think we typically call a pointer to the end of the line 'eol' or 'end'. Also variables should be declared at the top of the function. >> >>> + switch (state) { >>> + case BATCH_STATE_OPEN: >>> + break; >>> + } >>> + cmd->fn(opt, xstrndup(p, pos-p), output, data); >> >> Is there a reason this is passing a copy of the string? >> >>> + } >>> + strbuf_release(&input); >>> +} >>> + >>> static int batch_objects(struct batch_options *opt) >>> { >>> struct strbuf input = STRBUF_INIT; >>> @@ -515,6 +615,7 @@ static int batch_objects(struct batch_options *opt) >>> struct expand_data data; >>> int save_warning; >>> int retval = 0; >>> + const int stdin_cmd = opt->stdin_cmd; >>> if (!opt->format) >>> opt->format = "%(objectname) %(objecttype) %(objectsize)"; >>> @@ -590,7 +691,8 @@ static int batch_objects(struct batch_options *opt) >>> save_warning = warn_on_object_refname_ambiguity; >>> warn_on_object_refname_ambiguity = 0; >>> - while (strbuf_getline(&input, stdin) != EOF) { >>> + while (!stdin_cmd && >> >> If you moved the 'if (stdin_cmd)' block above this block we could loose this change. I'm not sure if that is possible without looking at the whole function though. >> >>> + strbuf_getline(&input, stdin) != EOF) { >>> if (data.split_on_whitespace) { >>> /* >>> * Split at first whitespace, tying off the beginning >>> @@ -608,6 +710,9 @@ static int batch_objects(struct batch_options *opt) >>> batch_one_object(input.buf, &output, opt, &data); >>> } >>> + if (stdin_cmd) >>> + batch_objects_stdin_cmd(opt, &output, &data); >>> + >>> strbuf_release(&input); >>> strbuf_release(&output); >>> warn_on_object_refname_ambiguity = save_warning; >>> @@ -636,6 +741,7 @@ static int batch_option_callback(const struct option *opt, >>> bo->enabled = 1; >>> bo->print_contents = !strcmp(opt->long_name, "batch"); >>> + bo->stdin_cmd = !strcmp(opt->long_name, "batch-command"); >>> bo->format = arg; >>> return 0; >>> @@ -683,6 +789,10 @@ int cmd_cat_file(int argc, const char **argv, const char *prefix) >>> N_("like --batch, but don't emit <contents>"), >>> PARSE_OPT_OPTARG | PARSE_OPT_NONEG, >>> batch_option_callback), >>> + OPT_CALLBACK_F(0, "batch-command", &batch, N_(""), >>> + N_("enters batch mode that accepts commands"), >>> + PARSE_OPT_NOARG | PARSE_OPT_NONEG, >>> + batch_option_callback), >>> OPT_CMDMODE(0, "batch-all-objects", &opt, >>> N_("with --batch[-check]: ignores stdin, batches all known objects"), 'b'), >>> /* Batch-specific options */ >>> @@ -738,6 +848,8 @@ int cmd_cat_file(int argc, const char **argv, const char *prefix) >>> /* Batch defaults */ >>> if (batch.buffer_output < 0) >>> batch.buffer_output = batch.all_objects; >>> + if (batch.end_null) >>> + line_termination = '\0'; >>> /* Return early if we're in batch mode? */ >>> if (batch.enabled) { >>> diff --git a/strvec.c b/strvec.c >>> index 61a76ce6cb..7dca04bf7a 100644 >>> --- a/strvec.c >>> +++ b/strvec.c >>> [...] >> >> We don't need any strvec changes now that we don't split the input lines to --bactch-command >> >>> +F='%s\0' >> >> This isn't used now >> >>> +test_expect_success 'batch-command unknown command' ' >>> + echo unknown_command >cmd && >>> + test_expect_code 128 git cat-file --batch-command < cmd 2>err && >>> + grep -E "^fatal:.*unknown command.*" err >>> +' >>> + >>> +test_expect_success 'setup object data' ' >>> + content="Object Data" && >>> + size=$(strlen "$content") && >>> + sha1=$(echo_without_newline "$content" | git hash-object -w --stdin) >>> +' >>> + >>> +test_expect_success 'batch-command calling object works' ' >>> + echo "object $sha1" | git cat-file --batch-command >actual && >>> + echo "$sha1 blob $size" >expect && >>> + echo `git cat-file -p "$sha1"` >>expect && >>> + test_cmp expect actual >>> +' >>> + >>> +test_expect_success 'batch-command calling info works' ' >>> + echo "info $sha1" | git cat-file --batch-command >actual && >>> + echo "$sha1 blob $size" >expect && >>> + test_cmp expect actual >>> +' >> >> I had a quick look at this test file and there is a loop at the top that runs some --batch tests on various inputs, I wonder if these two tests could go in there. >> >>> +test_expect_success 'batch-command fflush works' ' >>> + printf "fflush\n" > cmd && >>> + test_expect_code 0 git cat-file --batch-command < cmd 2>err >>> +' >> >> It'd be nice to check this actually flushes the output. > > could you give me some ideas on how to do this? Ok, after filling around I think it can be something like this (copied over from an example in t9300-fast-import.sh run_buffer_test () { type=$1 sha1=$2 size=$3 mkfifo V.input exec 8<>V.input rm V.input mkfifo V.output exec 9<>V.output rm V.output ( git cat-file --buffer --batch-command <&8 >&9 & echo $! >&9 && wait $! ) & sh_pid=$! read fi_pid <&9 test_when_finished " exec 8>&-; exec 9>&-; kill $sh_pid && wait $sh_pid kill $fi_pid && wait $fi_pid true" expect=$(echo "$sha1 $type $size") echo "info $sha1" >&8 echo "fflush" >&8 read actual <&9 test "$actual" = "$expect" } Not sure if there's a simpler way since we need to simulate writing to and reading from the process. Thanks > >> >> Best Wishes >> >> Phillip >> >>> test_done
