libsubprocess: use matchtag instead of pid for flux_subprocess_write()

src/common/libsubprocess/client.c

@@ -44,6 +44,9 @@ struct rexec_ctx {
     json_t *cmd;
     int flags;
     struct rexec_response response;
+    uint32_t matchtag;
+    uint32_t rank;
+    char *service_name;
 };
 
 static void rexec_response_clear (struct rexec_response *resp)
@@ -62,12 +65,16 @@ static void rexec_ctx_destroy (struct rexec_ctx *ctx)
         int saved_errno = errno;
         rexec_response_clear (&ctx->response);
         json_decref (ctx->cmd);
+        free (ctx->service_name);
         free (ctx);
         errno = saved_errno;
     }
 }
 
-static struct rexec_ctx *rexec_ctx_create (flux_cmd_t *cmd, int flags)
+static struct rexec_ctx *rexec_ctx_create (flux_cmd_t *cmd,
+                                           const char *service_name,
+                                           uint32_t rank,
+                                           int flags)
 {
     struct rexec_ctx *ctx;
     int valid_flags = SUBPROCESS_REXEC_STDOUT
@@ -80,10 +87,12 @@ static struct rexec_ctx *rexec_ctx_create (flux_cmd_t *cmd, int flags)
     }
     if (!(ctx = calloc (1, sizeof (*ctx))))
         return NULL;
-    if (!(ctx->cmd = cmd_tojson (cmd)))
+    if (!(ctx->cmd = cmd_tojson (cmd))
+        || !(ctx->service_name = strdup (service_name)))
         goto error;
     ctx->flags = flags;
     ctx->response.pid = -1;
+    ctx->rank = rank;
     return ctx;
 error:
     rexec_ctx_destroy (ctx);
@@ -106,7 +115,7 @@ flux_future_t *subprocess_rexec (flux_t *h,
     }
     if (asprintf (&topic, "%s.exec", service_name) < 0)
         return NULL;
-    if (!(ctx = rexec_ctx_create (cmd, flags)))
+    if (!(ctx = rexec_ctx_create (cmd, service_name, rank, flags)))
         goto error;
     if (!(f = flux_rpc_pack (h,
                              topic,
@@ -122,6 +131,7 @@ flux_future_t *subprocess_rexec (flux_t *h,
         rexec_ctx_destroy (ctx);
         goto error;
     }
+    ctx->matchtag = flux_rpc_get_matchtag (f);
     free (topic);
     return f;
 error:
@@ -223,33 +233,32 @@ bool subprocess_rexec_is_output (flux_future_t *f,
     return false;
 }
 
-int subprocess_write (flux_t *h,
-                      const char *service_name,
-                      uint32_t rank,
-                      pid_t pid,
+int subprocess_write (flux_future_t *f_exec,
                       const char *stream,
                       const char *data,
                       int len,
                       bool eof)
 {
+    struct rexec_ctx *ctx = flux_future_aux_get (f_exec, "flux::rexec");
+    flux_t *h = flux_future_get_flux (f_exec);
     flux_future_t *f = NULL;
     json_t *io;
     char *topic;
     int rc = -1;
 
-    if (!h || pid < 0 || !stream || !service_name) {
+    if (!stream || !ctx) {
         errno = EINVAL;
         return -1;
     }
-    if (asprintf (&topic, "%s.write", service_name) < 0)
+    if (asprintf (&topic, "%s.write", ctx->service_name) < 0)
         return -1;
     if (!(io = ioencode (stream, "0", data, len, eof))
         || !(f = flux_rpc_pack (h,
                                 topic,
-                                rank,
+                                ctx->rank,
                                 FLUX_RPC_NORESPONSE,
                                 "{s:i s:O}",
-                                "pid", pid,
+                                "matchtag", ctx->matchtag,
                                 "io", io)))
         goto out;
     rc = 0;

src/common/libsubprocess/client.h

@@ -40,10 +40,7 @@ bool subprocess_rexec_is_output (flux_future_t *f,
                                  int *len,
                                  bool *eof);
 
-int subprocess_write (flux_t *h,
-                      const char *service_name,
-                      uint32_t rank,
-                      pid_t pid,
+int subprocess_write (flux_future_t *f,
                       const char *stream,
                       const char *data,
                       int len,

src/common/libsubprocess/remote.c

@@ -468,48 +468,6 @@ static int remote_output_buffered (flux_subprocess_t *p,
     return 0;
 }
 
-/* In the event channel had data / closed before process running */
-static int send_channel_data (flux_subprocess_t *p)
-{
-    struct subprocess_channel *c;
-    c = zhash_first (p->channels);
-    while (c) {
-        int bytes = fbuf_bytes (c->write_buffer);
-        if (c->closed || bytes > 0) {
-            const char *ptr = NULL;
-            int len = 0;
-            if (bytes > 0) {
-                if (!(ptr = fbuf_read (c->write_buffer, -1, &len))) {
-                    llog_debug (p,
-                                "error reading buffered data: %s",
-                                strerror (errno));
-                    set_failed (p, "internal fbuf_read error");
-                    return -1;
-                }
-            }
-            if (subprocess_write (p->h,
-                                  p->service_name,
-                                  p->rank,
-                                  p->pid,
-                                  c->name,
-                                  ptr,
-                                  len,
-                                  c->closed) < 0) {
-                llog_debug (p,
-                            "error sending rexec.write request: %s",
-                            strerror (errno));
-                set_failed (p, "internal close error");
-                return -1;
-            }
-            /* Don't need this buffer anymore, reclaim the space */
-            fbuf_destroy (c->write_buffer);
-            c->write_buffer = NULL;
-        }
-        c = zhash_next (p->channels);
-    }
-    return 0;
-}
-
 static void rexec_continuation (flux_future_t *f, void *arg)
 {
     flux_subprocess_t *p = arg;
@@ -543,8 +501,6 @@ static void rexec_continuation (flux_future_t *f, void *arg)
     if (subprocess_rexec_is_started (f, &p->pid)) {
         p->pid_set = true;
         process_new_state (p, FLUX_SUBPROCESS_RUNNING);
-        if (send_channel_data (p) < 0)
-            goto error;
     }
     else if (subprocess_rexec_is_stopped (f)) {
         process_new_state (p, FLUX_SUBPROCESS_STOPPED);

src/common/libsubprocess/server.c

@@ -107,6 +107,30 @@ static flux_subprocess_t *proc_find_bypid (subprocess_server_t *s, pid_t pid)
     return NULL;
 }
 
+/* Find a <service>.exec message with the same sender as msg and matchtag as
+ * specified in the request matchtag field.
+ * N.B. flux_cancel_match() happens to be helpful because RFC 42 subprocess
+ * write works like RFC 6 cancel.
+ */
+static flux_subprocess_t *proc_find_byclient (subprocess_server_t *s,
+                                              const flux_msg_t *request)
+{
+    flux_subprocess_t *p;
+
+    p = zlistx_first (s->subprocesses);
+    while (p) {
+        const flux_msg_t *msg;
+
+        if ((msg = flux_subprocess_aux_get (p, msgkey))
+            && flux_cancel_match (request, msg))
+            return p;
+        p = zlistx_next (s->subprocesses);
+    }
+    errno = ESRCH;
+    return NULL;
+}
+
+
 static void proc_completion_cb (flux_subprocess_t *p)
 {
     subprocess_server_t *s = flux_subprocess_aux_get (p, srvkey);
@@ -390,14 +414,14 @@ static void server_write_cb (flux_t *h,
     char *data = NULL;
     int len = 0;
     bool eof = false;
-    pid_t pid;
+    int matchtag;
     json_t *io = NULL;
     flux_error_t error;
 
     if (flux_request_unpack (msg,
                              NULL,
                              "{ s:i s:o }",
-                             "pid", &pid,
+                             "matchtag", &matchtag,
                              "io", &io) < 0
         || iodecode (io, &stream, NULL, &data, &len, &eof) < 0) {
         llog_error (s,
@@ -415,27 +439,24 @@ static void server_write_cb (flux_t *h,
      * in flight, and is not necessarily an error, and can be common enough
      * that the log messages end up being a nuisance.
      */
-    if (!(p = proc_find_bypid (s, pid))
-        || p->state != FLUX_SUBPROCESS_RUNNING)
+    if (!(p = proc_find_byclient (s, msg))
+        || p->state == FLUX_SUBPROCESS_FAILED
+        || p->state == FLUX_SUBPROCESS_EXITED)
         goto out;
 
     if (data && len) {
         int rc = flux_subprocess_write (p, stream, data, len);
         if (rc < 0) {
             llog_error (s,
-                        "Error writing %d bytes to subprocess pid %d %s",
+                        "Error writing %d bytes to subprocess %s",
                         len,
-                        (int)pid,
                         stream);
             goto error;
         }
     }
     if (eof) {
         if (flux_subprocess_close (p, stream) < 0) {
-            llog_error (s,
-                        "Error writing EOF to subprocess pid %d %s",
-                        (int)pid,
-                        stream);
+            llog_error (s, "Error writing EOF to subprocess %s", stream);
             goto error;
         }
     }

src/common/libsubprocess/subprocess.c

@@ -54,7 +54,6 @@ void channel_destroy (void *arg)
         flux_watcher_destroy (c->buffer_read_stopped_w);
         c->buffer_read_w_started = false;
 
-        fbuf_destroy (c->write_buffer);
         fbuf_destroy (c->read_buffer);
         flux_watcher_destroy (c->out_prep_w);
         flux_watcher_destroy (c->out_idle_w);
@@ -707,42 +706,12 @@ int flux_subprocess_write (flux_subprocess_t *p,
             errno = EPIPE;
             return -1;
         }
-        if (p->state == FLUX_SUBPROCESS_INIT) {
-            if (!c->write_buffer) {
-                int buffer_size;
-                if ((buffer_size = cmd_option_bufsize (p, stream)) < 0) {
-                    log_err ("cmd_option_bufsize: %s", strerror (errno));
-                    return -1;
-                }
-                if (!(c->write_buffer = fbuf_create (buffer_size))) {
-                    log_err ("fbuf_create");
-                    return -1;
-                }
-            }
-            if (fbuf_space (c->write_buffer) < len) {
-                errno = ENOSPC;
-                return -1;
-            }
-            if ((ret = fbuf_write (c->write_buffer, buf, len)) < 0) {
-                log_err ("fbuf_write");
-                return -1;
-            }
-        }
-        else { /* p->state == FLUX_SUBPROCESS_RUNNING */
-            if (subprocess_write (p->h,
-                                  p->service_name,
-                                  p->rank,
-                                  p->pid,
-                                  c->name,
-                                  buf,
-                                  len,
-                                  false) < 0) {
-                log_err ("error sending rexec.write request: %s",
-                         strerror (errno));
-                return -1;
-            }
-            ret = len;
+        if (subprocess_write (p->f, c->name, buf, len, false) < 0) {
+            log_err ("error sending rexec.write request: %s",
+                     strerror (errno));
+            return -1;
         }
+        ret = len;
     }
 
     return ret;
@@ -780,26 +749,12 @@ int flux_subprocess_close (flux_subprocess_t *p, const char *stream)
         c->closed = true;
     }
     else {
-        /* if process isn't running, eof plus any previously written
-         * data will be sent after process converts to running.  See
-         * send_channel_data() in remote.c.  If subprocess has already
-         * exited, this does nothing.
-         */
-        c->closed = true;
-        if (p->state == FLUX_SUBPROCESS_RUNNING) {
-            if (subprocess_write (p->h,
-                                  p->service_name,
-                                  p->rank,
-                                  p->pid,
-                                  c->name,
-                                  NULL,
-                                  0,
-                                  true) < 0) {
-                log_err ("error sending rexec.write request: %s",
-                         strerror (errno));
-                return -1;
-            }
+        if (subprocess_write (p->f, c->name, NULL, 0, true) < 0) {
+            log_err ("error sending rexec.write request: %s",
+                     strerror (errno));
+            return -1;
         }
+        c->closed = true;
     }
 
     return 0;

src/common/libsubprocess/subprocess_private.h

@@ -45,7 +45,6 @@ struct subprocess_channel {
     bool buffer_read_w_started;
 
     /* remote */
-    struct fbuf *write_buffer;  /* buffer pre-running data */
     struct fbuf *read_buffer;
     bool read_eof_received;
     flux_watcher_t *out_prep_w;

src/common/libsubprocess/test/iostress.c

@@ -120,7 +120,7 @@ static void iostress_state_cb (flux_subprocess_t *p,
     }
 }
 
-static int rexec_write (flux_t *h, pid_t pid, const char *buf, int len)
+static int rexec_write (flux_t *h, uint32_t matchtag, const char *buf, int len)
 {
     flux_future_t *f;
     json_t *io;
@@ -133,7 +133,7 @@ static int rexec_write (flux_t *h, pid_t pid, const char *buf, int len)
                              0,
                              FLUX_RPC_NORESPONSE,
                              "{s:i s:O}",
-                             "pid", pid,
+                             "matchtag", matchtag,
                              "io", io))) {
         json_decref (io);
         return -1;
@@ -150,15 +150,18 @@ static void iostress_source_cb (flux_reactor_t *r,
 {
     struct iostress_ctx *ctx = arg;
     char *buf;
+    uint32_t matchtag;
 
     if (!(buf = malloc (ctx->linesize)))
         BAIL_OUT ("out of memory");
     memset (buf, 'F', ctx->linesize - 1);
     buf[ctx->linesize - 1] = '\n';
 
+    matchtag = flux_rpc_get_matchtag (ctx->p->f);
+
     for (int i = 0; i < ctx->batchlines; i++) {
         if (ctx->direct) {
-            if (rexec_write (ctx->h, ctx->pid, buf, ctx->linesize) < 0)
+            if (rexec_write (ctx->h, matchtag, buf, ctx->linesize) < 0)
                 BAIL_OUT ("rexec_write failed");
         }
         else {