Re: [RFC/PATCH v4 30/49] odb-helper: add read_object_process()

> From: Ben Peart <benpeart@microsoft.com>
> 
> Signed-off-by: Ben Peart <benpeart@microsoft.com>
> Signed-off-by: Christian Couder <chriscool@tuxfamily.org>
> ---
>   odb-helper.c | 202 ++++++++++++++++++++++++++++++++++++++++++++++++++++++++---
>   odb-helper.h |   5 ++
>   sha1_file.c  |  33 +++++++++-
>   3 files changed, 227 insertions(+), 13 deletions(-)
> 
> diff --git a/odb-helper.c b/odb-helper.c
> index 5fb56c6135..20e83cb55a 100644
> --- a/odb-helper.c
> +++ b/odb-helper.c
> @@ -4,6 +4,187 @@
>   #include "odb-helper.h"
>   #include "run-command.h"
>   #include "sha1-lookup.h"
> +#include "sub-process.h"
> +#include "pkt-line.h"
> +#include "sigchain.h"
> +
> +struct read_object_process {
> +	struct subprocess_entry subprocess;
> +	unsigned int supported_capabilities;
> +};
> +
> +static int subprocess_map_initialized;
> +static struct hashmap subprocess_map;
> +
> +static void parse_capabilities(char *cap_buf,
> +			       unsigned int *supported_capabilities,
> +			       const char *process_name)
> +{
> +	struct string_list cap_list = STRING_LIST_INIT_NODUP;
> +
> +	string_list_split_in_place(&cap_list, cap_buf, '=', 1);
> +
> +	if (cap_list.nr == 2 && !strcmp(cap_list.items[0].string, "capability")) {
> +		const char *cap_name = cap_list.items[1].string;
> +
> +		if (!strcmp(cap_name, "get")) {
> +			*supported_capabilities |= ODB_HELPER_CAP_GET;
> +		} else if (!strcmp(cap_name, "put")) {
> +			*supported_capabilities |= ODB_HELPER_CAP_PUT;
> +		} else if (!strcmp(cap_name, "have")) {
> +			*supported_capabilities |= ODB_HELPER_CAP_HAVE;
> +		} else {
> +			warning("external process '%s' requested unsupported read-object capability '%s'",
> +				process_name, cap_name);
> +		}
> +	}
> +
> +	string_list_clear(&cap_list, 0);
> +}
> +
> +static int start_read_object_fn(struct subprocess_entry *subprocess)
> +{
> +	int err;
> +	struct read_object_process *entry = (struct read_object_process *)subprocess;
> +	struct child_process *process = &subprocess->process;
> +	char *cap_buf;
> +
> +	sigchain_push(SIGPIPE, SIG_IGN);
> +
> +	err = packet_writel(process->in, "git-read-object-client", "version=1", NULL);
> +	if (err)
> +		goto done;
> +
> +	err = strcmp(packet_read_line(process->out, NULL), "git-read-object-server");
> +	if (err) {
> +		error("external process '%s' does not support read-object protocol version 1", subprocess->cmd);
> +		goto done;
> +	}
> +	err = strcmp(packet_read_line(process->out, NULL), "version=1");
> +	if (err)
> +		goto done;
> +	err = packet_read_line(process->out, NULL) != NULL;
> +	if (err)
> +		goto done;
> +
> +	err = packet_writel(process->in, "capability=get", NULL);
> +	if (err)
> +		goto done;
> +
> +	while ((cap_buf = packet_read_line(process->out, NULL)))
> +		parse_capabilities(cap_buf, &entry->supported_capabilities, subprocess->cmd);
> +
> +done:
> +	sigchain_pop(SIGPIPE);
> +
> +	return err;
> +}
> +
> +static struct read_object_process *launch_read_object_process(const char *cmd)
> +{
> +	struct read_object_process *entry;
> +
> +	if (!subprocess_map_initialized) {
> +		subprocess_map_initialized = 1;
> +		hashmap_init(&subprocess_map, (hashmap_cmp_fn) cmd2process_cmp, 0);
> +		entry = NULL;
> +	} else {
> +		entry = (struct read_object_process *)subprocess_find_entry(&subprocess_map, cmd);
> +	}
> +
> +	fflush(NULL);
> +
> +	if (!entry) {
> +		entry = xmalloc(sizeof(*entry));
> +		entry->supported_capabilities = 0;
> +
> +		if (subprocess_start(&subprocess_map, &entry->subprocess, cmd, start_read_object_fn)) {
> +			free(entry);
> +			return 0;
> +		}
> +	}
> +
> +	return entry;
> +}
> +
> +static int check_object_process_error(int err,
> +				      const char *status,
> +				      struct read_object_process *entry,
> +				      const char *cmd,
> +				      unsigned int capability)
> +{
> +	if (!err)
> +		return;
> +
> +	if (!strcmp(status, "error")) {
> +		/* The process signaled a problem with the file. */
> +	} else if (!strcmp(status, "notfound")) {
> +		/* Object was not found */
> +		err = -1;
> +	} else if (!strcmp(status, "abort")) {
> +		/*
> +		 * The process signaled a permanent problem. Don't try to read
> +		 * objects with the same command for the lifetime of the current
> +		 * Git process.
> +		 */
> +		if (capability)
> +			entry->supported_capabilities &= ~capability;
> +	} else {
> +		/*
> +		 * Something went wrong with the read-object process.
> +		 * Force shutdown and restart if needed.
> +		 */
> +		error("external object process '%s' failed", cmd);
> +		subprocess_stop(&subprocess_map, &entry->subprocess);
> +		free(entry);
> +	}
> +
> +	return err;
> +}
> +
> +static int read_object_process(const unsigned char *sha1)
> +{
> +	int err;
> +	struct read_object_process *entry;
> +	struct child_process *process;
> +	struct strbuf status = STRBUF_INIT;
> +	const char *cmd = "read-object";
> +	uint64_t start;
> +
> +	start = getnanotime();
> +
> +	entry = launch_read_object_process(cmd);
> +	process = &entry->subprocess.process;
> +
> +	if (!(ODB_HELPER_CAP_GET & entry->supported_capabilities))
> +		return -1;
> +
> +	sigchain_push(SIGPIPE, SIG_IGN);
> +
> +	err = packet_write_fmt_gently(process->in, "command=get\n");
> +	if (err)
> +		goto done;
> +
> +	err = packet_write_fmt_gently(process->in, "sha1=%s\n", sha1_to_hex(sha1));
> +	if (err)
> +		goto done;
> +
> +	err = packet_flush_gently(process->in);
> +	if (err)
> +		goto done;
> +
> +	subprocess_read_status(process->out, &status);
> +	err = strcmp(status.buf, "success");
> +
> +done:
> +	sigchain_pop(SIGPIPE);
> +
> +	err = check_object_process_error(err, status.buf, entry, cmd, ODB_HELPER_CAP_GET);
> +
> +	trace_performance_since(start, "read_object_process");
> +
> +	return err;
> +}
>   
>   struct odb_helper *odb_helper_new(const char *name, int namelen)
>   {
> @@ -350,20 +531,21 @@ static int odb_helper_fetch_git_object(struct odb_helper *o,
>   int odb_helper_fault_in_object(struct odb_helper *o,
>   			       const unsigned char *sha1)
>   {
> -	struct odb_helper_object *obj;
> -	struct odb_helper_cmd cmd;
> +	struct odb_helper_object *obj = odb_helper_lookup(o, sha1);
>   
> -	obj = odb_helper_lookup(o, sha1);
>   	if (!obj)
>   		return -1;
>   
> -	if (odb_helper_start(o, &cmd, 0, "get %s", sha1_to_hex(sha1)) < 0)
> -		return -1;
> -
> -	if (odb_helper_finish(o, &cmd))
> -		return -1;
> -
> -	return 0;
> +	if (o->script_mode) {
> +		struct odb_helper_cmd cmd;
> +		if (odb_helper_start(o, &cmd, 0, "get %s", sha1_to_hex(sha1)) < 0)
> +			return -1;
> +		if (odb_helper_finish(o, &cmd))
> +			return -1;
> +		return 0;
> +	} else {
> +		return read_object_process(sha1);
> +	}
>   }
>   
>   int odb_helper_fetch_object(struct odb_helper *o,
> diff --git a/odb-helper.h b/odb-helper.h
> index 44c98bbf56..b23544aa4a 100644
> --- a/odb-helper.h
> +++ b/odb-helper.h
> @@ -9,11 +9,16 @@ enum odb_helper_fetch_kind {
>   	ODB_FETCH_KIND_FAULT_IN
>   };
>   
> +#define ODB_HELPER_CAP_GET    (1u<<0)
> +#define ODB_HELPER_CAP_PUT    (1u<<1)
> +#define ODB_HELPER_CAP_HAVE   (1u<<2)
> +
>   struct odb_helper {
>   	const char *name;
>   	const char *cmd;
>   	enum odb_helper_fetch_kind fetch_kind;
>   	int script_mode;
> +	unsigned int supported_capabilities;
>   
>   	struct odb_helper_object {
>   		unsigned char sha1[20];
> diff --git a/sha1_file.c b/sha1_file.c
> index 9d8e37432e..38a0404506 100644
> --- a/sha1_file.c
> +++ b/sha1_file.c
> @@ -698,7 +698,17 @@ int check_and_freshen_file(const char *fn, int freshen)
>   
>   static int check_and_freshen_local(const unsigned char *sha1, int freshen)
>   {
> -	return check_and_freshen_file(sha1_file_name(sha1), freshen);
> +	int ret;
> +	int tried_hook = 0;
> +
> +retry:
> +	ret = check_and_freshen_file(sha1_file_name(sha1), freshen);
> +	if (!ret && !tried_hook) {
> +		tried_hook = 1;
> +		if (!external_odb_fault_in_object(sha1))
> +			goto retry;
> +	}
> +	return ret;
>   }
>   
>   static int check_and_freshen_nonlocal(const unsigned char *sha1, int freshen)
> @@ -3000,7 +3010,9 @@ int sha1_object_info_extended(const unsigned char *sha1, struct object_info *oi,
>   	int rtype;
>   	enum object_type real_type;
>   	const unsigned char *real = lookup_replace_object_extended(sha1, flags);
> +	int tried_hook = 0;
>   
> +retry:
>   	co = find_cached_object(real);
>   	if (co) {
>   		if (oi->typep)
> @@ -3026,8 +3038,14 @@ int sha1_object_info_extended(const unsigned char *sha1, struct object_info *oi,
>   
>   		/* Not a loose object; someone else may have just packed it. */
>   		reprepare_packed_git();
> -		if (!find_pack_entry(real, &e))
> +		if (!find_pack_entry(real, &e)) {

> +			if (!tried_hook) {
> +				tried_hook = 1;
> +				if (!external_odb_fault_in_object(sha1))
> +					goto retry;
> +			}
>   			return -1;
> +		}
>   	}
>   
>   	/*
> @@ -3121,7 +3139,9 @@ static void *read_object(const unsigned char *sha1, enum object_type *type,
>   	unsigned long mapsize;
>   	void *map, *buf;
>   	struct cached_object *co;
> +	int tried_hook = 0;
>   
> +retry:
>   	co = find_cached_object(sha1);
>   	if (co) {
>   		*type = co->type;
> @@ -3139,7 +3159,14 @@ static void *read_object(const unsigned char *sha1, enum object_type *type,
>   		return buf;
>   	}
>   	reprepare_packed_git();
> -	return read_packed_sha1(sha1, type, size);
> +	buf = read_packed_sha1(sha1, type, size);
> +	if (!buf && !tried_hook) {
> +		tried_hook = 1;
> +		if (!external_odb_fault_in_object(sha1))
> +			goto retry;
> +	}
> +
> +	return buf;
>   }
>   
>   /*
>