Improve error diagnostics

* runcap: Upgrade. This version correctly captures output lines
not terminated with a newline character.
* src/tallyman.1: Update.
* src/tallyman.c (main): Print error diagnostics if unable to run
the program or if it exists with an improper status.

3 files changed, 49 insertions, 5 deletions

diff --git a/runcap b/runcap
-Subproject 048800a78f64808116bb9b943837062a67f586a
+Subproject 1309ae35b1ff7ed26a3ccc2fcdc6bd13bb494ce
diff --git a/src/tallyman.1 b/src/tallyman.1
index ce1d09d..57036e8 100644
--- a/src/tallyman.1
+++ b/src/tallyman.1
@@ -1,2 +1,2 @@
-.TH TALLYMAN 1 "August 13, 2019" "TALLYMAN" "Tallyman User Reference"
+.TH TALLYMAN 1 "August 14, 2019" "TALLYMAN" "Tallyman User Reference"
 .SH NAME
@@ -39,2 +39,30 @@ statement in the
 .PP
+It is supposed that each container is responsible for certain
+.IR service .
+Each service is assigned a name.  Multiple containers can run
+the same service (for example you can have several database
+containers).
+.PP
+Containers are configured to run
+.B tallyman
+as their
+.B HEALTHCHECK
+command.  The
+.I SRVID
+argument supplies the name of the service the container is responsible
+for.  The \fICOMMAND\fR and optional additional arguments supply the
+name of the actual health-checking program and its command line
+arguments.
+.B Tallyman
+will run this command, collect its standard error and standard output,
+pack them along with the program exit code in a JSON packet, and send
+this packet to the predefined address using HTTP POST request. It will
+then exit with the same code as the health-checking program it ran. To
+the container, the effect of running
+.B tallyman
+is the same as if it ran the health-checking program itself: error
+code, standard error and standard output are all preserved. On the
+other hand, they are copied to the collector listening on the
+predefined address outside the container.
+.PP
 The data collector program
@@ -42,4 +70,9 @@ The data collector program
 must be listening at \fIHOST:PORT\fR. See its manual for
-details. Container default gateway is the default \fIHOST\fR.
-Default port is 8990.
+details.
+.PP
+In the absense of the
+.B \-s
+option,
+.B tallyman
+will send statistics to the container's default gateway, port 8990.
 .SH OPTIONS
diff --git a/src/tallyman.c b/src/tallyman.c
index df40fa2..c35cc9e 100644
--- a/src/tallyman.c
+++ b/src/tallyman.c
@@ -300,6 +300,7 @@ main(int argc, char **argv)
 	if (runcap(&rc, rcflags)) {
+		char const *emsg = strerror(errno);
 		json_object_set(obj, "status", json_new_bool(0));
 		json_object_set(obj, "error", json_new_bool(1));
-		json_object_set(obj, "message",
-				json_new_string(strerror(errno)));
+		json_object_set(obj, "message", json_new_string(emsg));
+		error("failed to run %s: %s", argv[0], emsg);
 	} else {
@@ -309,2 +310,11 @@ main(int argc, char **argv)
 				json_new_bool(status == 0));
+			if (status
+			    && rc.rc_cap[RUNCAP_STDERR].sc_nlines == 0) {
+				if (status == 127)
+					error("failed to run %s: %s", argv[0],
+					      "program not found");
+				else
+					error("command %s exited with status %d",
+					      argv[0], status);
+			}
 		} else {
@@ -329,2 +339,3 @@ main(int argc, char **argv)
 
+			error("%s: %s", argv[0], msg);
 			free(msg);