Re: [PATCH v4 3/4] trace2: don't overload target directories

[Johannes Schindelin <Johannes.Schindelin@gmx.de>]

Hi Josh,

On Thu, 3 Oct 2019, Josh Steadmon wrote:

> [...]
> diff --git a/trace2/tr2_dst.c b/trace2/tr2_dst.c
> index 5dda0ca1cd..af3405f179 100644
> --- a/trace2/tr2_dst.c
> +++ b/trace2/tr2_dst.c
> @@ -1,3 +1,5 @@
> +#include <dirent.h>
> +

This completely breaks the Windows build:

	In file included from trace2/tr2_dst.c:1:
	compat/win32/dirent.h:13:14: error: 'MAX_PATH' undeclared here (not in a
	function)
	   13 |  char d_name[MAX_PATH * 3]; /* file name (* 3 for UTF-8 conversion) */
	      |              ^~~~~~~~

See the full build log in all its glory here:

https://dev.azure.com/gitgitgadget/git/_build/results?buildId=17409&view=logs&jobId=fd490c07-0b22-5182-fac9-6d67fe1e939b&taskId=ce91d5d6-0c55-50f5-8ab9-6695c03ab102&lineStart=252&lineEnd=255&colStart=1&colEnd=30

The fix is as easy as probably surprising: simply delete that
`#include`. It is redundant anyway:
https://github.com/git/git/blob/v2.23.0/git-compat-util.h#L184

Deleting that `#include` line from your patch not only lets the file
compile cleanly on Windows, it also conforms to our coding style where
`cache.h` or `git-compat-util.h` need to be the first `#include`. That
rule's purpose is precisely to prevent platform-specific compile errors
like the one shown above.

Ciao,
Johannes

>  #include "cache.h"
>  #include "trace2/tr2_dst.h"
>  #include "trace2/tr2_sid.h"
> @@ -8,6 +10,19 @@
>   */
>  #define MAX_AUTO_ATTEMPTS 10
>
> +/*
> + * Sentinel file used to detect when we're overloading a directory with too many
> + * trace files.
> + */
> +#define OVERLOAD_SENTINEL_NAME "git-trace2-overload"
> +
> +/*
> + * When set to zero, disables directory overload checking. Otherwise, controls
> + * how many files we can write to a directory before entering overload mode.
> + * This can be overridden via the TR2_SYSENV_MAX_FILES setting.
> + */
> +static int tr2env_max_files = 0;
> +
>  static int tr2_dst_want_warning(void)
>  {
>  	static int tr2env_dst_debug = -1;
> @@ -32,6 +47,67 @@ void tr2_dst_trace_disable(struct tr2_dst *dst)
>  	dst->need_close = 0;
>  }
>
> +/*
> + * Check to make sure we're not overloading the target directory with too many
> + * files. First get the threshold (if present) from the config or envvar. If
> + * it's zero or unset, disable this check.  Next check for the presence of a
> + * sentinel file, then check file count. If we are overloaded, create the
> + * sentinel file if it doesn't already exist.
> + *
> + * We expect that some trace processing system is gradually collecting files
> + * from the target directory; after it removes the sentinel file we'll start
> + * writing traces again.
> + */
> +static int tr2_dst_overloaded(const char *tgt_prefix)
> +{
> +	int file_count = 0, max_files = 0, ret = 0;
> +	const char *max_files_var;
> +	DIR *dirp;
> +	struct strbuf path = STRBUF_INIT, sentinel_path = STRBUF_INIT;
> +	struct stat statbuf;
> +
> +	/* Get the config or envvar and decide if we should continue this check */
> +	max_files_var = tr2_sysenv_get(TR2_SYSENV_MAX_FILES);
> +	if (max_files_var && *max_files_var && ((max_files = atoi(max_files_var)) >= 0))
> +		tr2env_max_files = max_files;
> +
> +	if (!tr2env_max_files) {
> +		ret = 0;
> +		goto cleanup;
> +	}
> +
> +	strbuf_addstr(&path, tgt_prefix);
> +	if (!is_dir_sep(path.buf[path.len - 1])) {
> +		strbuf_addch(&path, '/');
> +	}
> +
> +	/* check sentinel */
> +	strbuf_addbuf(&sentinel_path, &path);
> +	strbuf_addstr(&sentinel_path, OVERLOAD_SENTINEL_NAME);
> +	if (!stat(sentinel_path.buf, &statbuf)) {
> +		ret = 1;
> +		goto cleanup;
> +	}
> +
> +	/* check file count */
> +	dirp = opendir(path.buf);
> +	while (file_count < tr2env_max_files && dirp && readdir(dirp))
> +		file_count++;
> +	if (dirp)
> +		closedir(dirp);
> +
> +	if (file_count >= tr2env_max_files) {
> +		creat(sentinel_path.buf, 0666);
> +		ret = 1;
> +		goto cleanup;
> +	}
> +
> +cleanup:
> +	strbuf_release(&path);
> +	strbuf_release(&sentinel_path);
> +	return ret;
> +}
> +
>  static int tr2_dst_try_auto_path(struct tr2_dst *dst, const char *tgt_prefix)
>  {
>  	int fd;
> @@ -50,6 +126,16 @@ static int tr2_dst_try_auto_path(struct tr2_dst *dst, const char *tgt_prefix)
>  	strbuf_addstr(&path, sid);
>  	base_path_len = path.len;
>
> +	if (tr2_dst_overloaded(tgt_prefix)) {
> +		strbuf_release(&path);
> +		if (tr2_dst_want_warning())
> +			warning("trace2: not opening %s trace file due to too "
> +				"many files in target directory %s",
> +				tr2_sysenv_display_name(dst->sysenv_var),
> +				tgt_prefix);
> +		return 0;
> +	}
> +
>  	for (attempt_count = 0; attempt_count < MAX_AUTO_ATTEMPTS; attempt_count++) {
>  		if (attempt_count > 0) {
>  			strbuf_setlen(&path, base_path_len);
> diff --git a/trace2/tr2_sysenv.c b/trace2/tr2_sysenv.c
> index 5958cfc424..3c3792eca2 100644
> --- a/trace2/tr2_sysenv.c
> +++ b/trace2/tr2_sysenv.c
> @@ -49,6 +49,9 @@ static struct tr2_sysenv_entry tr2_sysenv_settings[] = {
>  				       "trace2.perftarget" },
>  	[TR2_SYSENV_PERF_BRIEF]    = { "GIT_TRACE2_PERF_BRIEF",
>  				       "trace2.perfbrief" },
> +
> +	[TR2_SYSENV_MAX_FILES]     = { "GIT_TRACE2_MAX_FILES",
> +				       "trace2.maxfiles" },
>  };
>  /* clang-format on */
>
> diff --git a/trace2/tr2_sysenv.h b/trace2/tr2_sysenv.h
> index 8dd82a7a56..d4364a7b85 100644
> --- a/trace2/tr2_sysenv.h
> +++ b/trace2/tr2_sysenv.h
> @@ -24,6 +24,8 @@ enum tr2_sysenv_variable {
>  	TR2_SYSENV_PERF,
>  	TR2_SYSENV_PERF_BRIEF,
>
> +	TR2_SYSENV_MAX_FILES,
> +
>  	TR2_SYSENV_MUST_BE_LAST
>  };
>
> --
> 2.23.0.581.g78d2f28ef7-goog
>
>