Refactor the filter.<driver>.process code into a separate sub-process
module that can be used to reduce the cost of starting up a sub-process
for multiple commands. It does this by keeping the external process
running and processing all commands by communicating over standard input
and standard output using the packet format (pkt-line) based protocol.
Full documentation is in Documentation/technical/api-sub-process.txt.
This code is refactored from:
Commit edcc85814c ("convert: add filter.<driver>.process option",
2016-10-16)
keeps the external process running and processes all commands
Signed-off-by: Ben Peart <benpe...@microsoft.com>
---
Documentation/technical/api-sub-process.txt | 54 ++++++++++
Makefile | 1 +
convert.c | 160 ++++++----------------------
sub-process.c | 117 ++++++++++++++++++++
sub-process.h | 46 ++++++++
5 files changed, 248 insertions(+), 130 deletions(-)
create mode 100644 Documentation/technical/api-sub-process.txt
create mode 100644 sub-process.c
create mode 100644 sub-process.h
diff --git a/Documentation/technical/api-sub-process.txt
b/Documentation/technical/api-sub-process.txt
new file mode 100644
index 0000000000..eb5005aa72
--- /dev/null
+++ b/Documentation/technical/api-sub-process.txt
@@ -0,0 +1,54 @@
+sub-process API
+===============
+
+The sub-process API makes it possible to run background sub-processes
+that should run until the git command exits and communicate with it
+through stdin and stdout. This reduces the overhead of having to fork
+a new process each time it needs to be communicated with.
+
+The sub-processes are kept in a hashmap by command name and looked up
+via the subprocess_find_entry function. If an existing instance can not
+be found then a new process should be created and started. When the
+parent git command terminates, all sub-processes are also terminated.
+
+This API is based on the run-command API.
+
+Data structures
+---------------
+
+* `struct subprocess_entry`
+
+The sub-process structure. Members should not be accessed directly.
+
+Types
+-----
+
+'int(*subprocess_start_fn)(struct subprocess_entry *entry)'::
+
+ User-supplied function to initialize the sub-process. This is
+ typically used to negoiate the interface version and capabilities.
+
+
+Functions
+---------
+
+`subprocess_start`::
+
+ Start a subprocess and add it to the subprocess hashmap.
+
+`subprocess_stop`::
+
+ Kill a subprocess and remove it from the subprocess hashmap.
+
+`subprocess_find_entry`::
+
+ Find a subprocess in the subprocess hashmap.
+
+`subprocess_get_child_process`::
+
+ Get the underlying `struct child_process` from a subprocess.
+
+`subprocess_read_status`::
+
+ Helper function to read packets looking for the last "status=<foo>"
+ key/value pair.
diff --git a/Makefile b/Makefile
index a5a11e721a..8afe733092 100644
--- a/Makefile
+++ b/Makefile
@@ -830,6 +830,7 @@ LIB_OBJS += streaming.o
LIB_OBJS += string-list.o
LIB_OBJS += submodule.o
LIB_OBJS += submodule-config.o
+LIB_OBJS += sub-process.o
LIB_OBJS += symlinks.o
LIB_OBJS += tag.o
LIB_OBJS += tempfile.o
diff --git a/convert.c b/convert.c
index 8d652bf27c..565a1d0d8c 100644
--- a/convert.c
+++ b/convert.c
@@ -4,6 +4,7 @@
#include "quote.h"
#include "sigchain.h"
#include "pkt-line.h"
+#include "sub-process.h"
/*
* convert.c - convert a file when checking it out and checking it in.
@@ -497,132 +498,30 @@ static int apply_single_file_filter(const char *path,
const char *src, size_t le
#define CAP_SMUDGE (1u<<1)
struct cmd2process {
- struct hashmap_entry ent; /* must be the first member! */
+ struct subprocess_entry subprocess;
unsigned int supported_capabilities;
- const char *cmd;
- struct child_process process;
};
-static int cmd_process_map_initialized;
-static struct hashmap cmd_process_map;
-
-static int cmd2process_cmp(const struct cmd2process *e1,
- const struct cmd2process *e2,
- const void *unused)
+static int start_multi_file_filter_fn(struct subprocess_entry *subprocess)
{
- return strcmp(e1->cmd, e2->cmd);
-}
-
-static struct cmd2process *find_multi_file_filter_entry(struct hashmap
*hashmap, const char *cmd)
-{
- struct cmd2process key;
- hashmap_entry_init(&key, strhash(cmd));
- key.cmd = cmd;
- return hashmap_get(hashmap, &key, NULL);
-}
-
-static int packet_write_list(int fd, const char *line, ...)
-{
- va_list args;
int err;
- va_start(args, line);
- for (;;) {
- if (!line)
- break;
- if (strlen(line) > LARGE_PACKET_DATA_MAX)
- return -1;
- err = packet_write_fmt_gently(fd, "%s\n", line);
- if (err)
- return err;
- line = va_arg(args, const char*);
- }
- va_end(args);
- return packet_flush_gently(fd);
-}
-
-static void read_multi_file_filter_status(int fd, struct strbuf *status)
-{
- struct strbuf **pair;
- char *line;
- for (;;) {
- line = packet_read_line(fd, NULL);
- if (!line)
- break;
- pair = strbuf_split_str(line, '=', 2);
- if (pair[0] && pair[0]->len && pair[1]) {
- /* the last "status=<foo>" line wins */
- if (!strcmp(pair[0]->buf, "status=")) {
- strbuf_reset(status);
- strbuf_addbuf(status, pair[1]);
- }
- }
- strbuf_list_free(pair);
- }
-}
-
-static void kill_multi_file_filter(struct hashmap *hashmap, struct cmd2process
*entry)
-{
- if (!entry)
- return;
-
- entry->process.clean_on_exit = 0;
- kill(entry->process.pid, SIGTERM);
- finish_command(&entry->process);
-
- hashmap_remove(hashmap, entry, NULL);
- free(entry);
-}
-
-static void stop_multi_file_filter(struct child_process *process)
-{
- sigchain_push(SIGPIPE, SIG_IGN);
- /* Closing the pipe signals the filter to initiate a shutdown. */
- close(process->in);
- close(process->out);
- sigchain_pop(SIGPIPE);
- /* Finish command will wait until the shutdown is complete. */
- finish_command(process);
-}
-
-static struct cmd2process *start_multi_file_filter(struct hashmap *hashmap,
const char *cmd)
-{
- int err;
- struct cmd2process *entry;
+ struct cmd2process *entry = (struct cmd2process *)subprocess;
struct child_process *process;
- const char *argv[] = { cmd, NULL };
struct string_list cap_list = STRING_LIST_INIT_NODUP;
char *cap_buf;
const char *cap_name;
- entry = xmalloc(sizeof(*entry));
- entry->cmd = cmd;
- entry->supported_capabilities = 0;
- process = &entry->process;
-
- child_process_init(process);
- process->argv = argv;
- process->use_shell = 1;
- process->in = -1;
- process->out = -1;
- process->clean_on_exit = 1;
- process->clean_on_exit_handler = stop_multi_file_filter;
-
- if (start_command(process)) {
- error("cannot fork to run external filter '%s'", cmd);
- return NULL;
- }
-
- hashmap_entry_init(entry, strhash(cmd));
+ process = subprocess_get_child_process(&entry->subprocess);
sigchain_push(SIGPIPE, SIG_IGN);
- err = packet_write_list(process->in, "git-filter-client", "version=2",
NULL);
+ err = packet_writel(process->in, "git-filter-client", "version=2",
NULL);
if (err)
goto done;
err = strcmp(packet_read_line(process->out, NULL), "git-filter-server");
if (err) {
- error("external filter '%s' does not support filter protocol
version 2", cmd);
+ error("external filter '%s' does not support filter protocol
version 2", subprocess->cmd);
goto done;
}
err = strcmp(packet_read_line(process->out, NULL), "version=2");
@@ -632,7 +531,7 @@ static struct cmd2process *start_multi_file_filter(struct
hashmap *hashmap, cons
if (err)
goto done;
- err = packet_write_list(process->in, "capability=clean",
"capability=smudge", NULL);
+ err = packet_writel(process->in, "capability=clean",
"capability=smudge", NULL);
for (;;) {
cap_buf = packet_read_line(process->out, NULL);
@@ -651,7 +550,7 @@ static struct cmd2process *start_multi_file_filter(struct
hashmap *hashmap, cons
} else {
warning(
"external filter '%s' requested unsupported
filter capability '%s'",
- cmd, cap_name
+ subprocess->cmd, cap_name
);
}
@@ -661,14 +560,10 @@ static struct cmd2process *start_multi_file_filter(struct
hashmap *hashmap, cons
done:
sigchain_pop(SIGPIPE);
- if (err || errno == EPIPE) {
- error("initialization for external filter '%s' failed", cmd);
- kill_multi_file_filter(hashmap, entry);
- return NULL;
- }
+ if (err || errno == EPIPE)
+ err = err ? err : errno;
- hashmap_add(hashmap, entry);
- return entry;
+ return err;
}
static int apply_multi_file_filter(const char *path, const char *src, size_t
len,
@@ -682,22 +577,20 @@ static int apply_multi_file_filter(const char *path,
const char *src, size_t len
struct strbuf filter_status = STRBUF_INIT;
const char *filter_type;
- if (!cmd_process_map_initialized) {
- cmd_process_map_initialized = 1;
- hashmap_init(&cmd_process_map, (hashmap_cmp_fn)
cmd2process_cmp, 0);
- entry = NULL;
- } else {
- entry = find_multi_file_filter_entry(&cmd_process_map, cmd);
- }
+ entry = (struct cmd2process *)subprocess_find_entry(cmd);
fflush(NULL);
if (!entry) {
- entry = start_multi_file_filter(&cmd_process_map, cmd);
- if (!entry)
+ entry = xmalloc(sizeof(*entry));
+ entry->supported_capabilities = 0;
+
+ if (subprocess_start(&entry->subprocess, cmd,
start_multi_file_filter_fn)) {
+ free(entry);
return 0;
+ }
}
- process = &entry->process;
+ process = subprocess_get_child_process(&entry->subprocess);
if (!(wanted_capability & entry->supported_capabilities))
return 0;
@@ -737,7 +630,10 @@ static int apply_multi_file_filter(const char *path, const
char *src, size_t len
if (err)
goto done;
- read_multi_file_filter_status(process->out, &filter_status);
+ err = subprocess_read_status(process->out, &filter_status);
+ if (err)
+ goto done;
+
err = strcmp(filter_status.buf, "success");
if (err)
goto done;
@@ -746,7 +642,10 @@ static int apply_multi_file_filter(const char *path, const
char *src, size_t len
if (err)
goto done;
- read_multi_file_filter_status(process->out, &filter_status);
+ err = subprocess_read_status(process->out, &filter_status);
+ if (err)
+ goto done;
+
err = strcmp(filter_status.buf, "success");
done:
@@ -768,7 +667,8 @@ static int apply_multi_file_filter(const char *path, const
char *src, size_t len
* Force shutdown and restart if another blob requires
filtering.
*/
error("external filter '%s' failed", cmd);
- kill_multi_file_filter(&cmd_process_map, entry);
+ subprocess_stop((struct subprocess_entry *)entry);
+ free(entry);
}
} else {
strbuf_swap(dst, &nbuf);
diff --git a/sub-process.c b/sub-process.c
new file mode 100644
index 0000000000..5a06a9fd1e
--- /dev/null
+++ b/sub-process.c
@@ -0,0 +1,117 @@
+/*
+ * Generic implementation of background process infrastructure.
+ */
+#include "sub-process.h"
+#include "sigchain.h"
+#include "pkt-line.h"
+
+static int subprocess_map_initialized;
+static struct hashmap subprocess_map;
+
+static int name2process_cmp(const struct subprocess_entry *e1,
+ const struct subprocess_entry *e2, const void *unused)
+{
+ return strcmp(e1->cmd, e2->cmd);
+}
+
+static void subprocess_exit_handler(struct child_process *process)
+{
+ sigchain_push(SIGPIPE, SIG_IGN);
+ /* Closing the pipe signals the filter to initiate a shutdown. */
+ close(process->in);
+ close(process->out);
+ sigchain_pop(SIGPIPE);
+ /* Finish command will wait until the shutdown is complete. */
+ finish_command(process);
+}
+
+int subprocess_start(struct subprocess_entry *entry, const char *cmd,
+ subprocess_start_fn startfn)
+{
+ int err;
+ const char *argv[] = { cmd, NULL };
+
+ if (!subprocess_map_initialized) {
+ hashmap_init(&subprocess_map, (hashmap_cmp_fn)name2process_cmp,
0);
+ subprocess_map_initialized = 1;
+ }
+
+ entry->cmd = cmd;
+
+ child_process_init(&entry->process);
+ entry->process.argv = argv;
+ entry->process.use_shell = 1;
+ entry->process.in = -1;
+ entry->process.out = -1;
+ entry->process.clean_on_exit = 1;
+ entry->process.clean_on_exit_handler = subprocess_exit_handler;
+
+ err = start_command(&entry->process);
+ if (err) {
+ error("cannot fork to run sub-process '%s'", entry->cmd);
+ return err;
+ }
+
+ err = startfn(entry);
+ if (err) {
+ error("initialization for sub-process '%s' failed", entry->cmd);
+ subprocess_stop(entry);
+ return err;
+ }
+
+ hashmap_entry_init(entry, strhash(entry->cmd));
+ hashmap_add(&subprocess_map, entry);
+
+ return 0;
+}
+
+void subprocess_stop(struct subprocess_entry *entry)
+{
+ if (!entry)
+ return;
+
+ entry->process.clean_on_exit = 0;
+ kill(entry->process.pid, SIGTERM);
+ finish_command(&entry->process);
+
+ hashmap_remove(&subprocess_map, entry, NULL);
+}
+
+struct subprocess_entry *subprocess_find_entry(const char *cmd)
+{
+ struct subprocess_entry key;
+
+ if (!subprocess_map_initialized) {
+ hashmap_init(&subprocess_map, (hashmap_cmp_fn)name2process_cmp,
0);
+ subprocess_map_initialized = 1;
+ return NULL;
+ }
+
+ hashmap_entry_init(&key, strhash(cmd));
+ key.cmd = cmd;
+ return hashmap_get(&subprocess_map, &key, NULL);
+}
+
+int subprocess_read_status(int fd, struct strbuf *status)
+{
+ struct strbuf **pair;
+ char *line;
+ int len;
+
+ for (;;) {
+ len = packet_read_line_gently(fd, NULL, &line);
+ if ((len == -1) || !line)
+ break;
+ pair = strbuf_split_str(line, '=', 2);
+ if (pair[0] && pair[0]->len && pair[1]) {
+ /* the last "status=<foo>" line wins */
+ if (!strcmp(pair[0]->buf, "status=")) {
+ strbuf_reset(status);
+ strbuf_addbuf(status, pair[1]);
+ }
+ }
+ strbuf_list_free(pair);
+ }
+
+ return len == -1 ? len : 0;
+}
diff --git a/sub-process.h b/sub-process.h
new file mode 100644
index 0000000000..d1492f476d
--- /dev/null
+++ b/sub-process.h
@@ -0,0 +1,46 @@
+#ifndef SUBPROCESS_H
+#define SUBPROCESS_H
+
+#include "git-compat-util.h"
+#include "hashmap.h"
+#include "run-command.h"
+
+/*
+ * Generic implementation of background process infrastructure.
+ * See Documentation/technical/api-background-process.txt.
+ */
+
+ /* data structures */
+
+struct subprocess_entry {
+ struct hashmap_entry ent; /* must be the first member! */
+ struct child_process process;
+ const char *cmd;
+};
+
+/* subprocess functions */
+
+typedef int(*subprocess_start_fn)(struct subprocess_entry *entry);
+int subprocess_start(struct subprocess_entry *entry, const char *cmd,
+ subprocess_start_fn startfn);
+
+void subprocess_stop(struct subprocess_entry *entry);
+
+struct subprocess_entry *subprocess_find_entry(const char *cmd);
+
+/* subprocess helper functions */
+
+static inline struct child_process *subprocess_get_child_process(
+ struct subprocess_entry *entry)
+{
+ return &entry->process;
+}
+
+/*
+ * Helper function that will read packets looking for "status=<foo>"
+ * key/value pairs and return the value from the last "status" packet
+ */
+
+int subprocess_read_status(int fd, struct strbuf *status);
+
+#endif
--
2.12.0.gvfs.1.43.g876ba2a
