store: Added a generic JSON formatter.

It works by consuming single objects of any type (host, service, metric,
attribute) at a time and appending their JSON serialization to a string
buffer. The current position in the object tree is recorded in an internal
state.

A helper function is provided on top of the base formatter which allows to
handle an full object at a time.

diff --git a/src/Makefile.am b/src/Makefile.am
index c8ad524c12f6809cd01f7b37b7bac6f1df7128ab..64b6ec46c41a4639879357c846e3089f21d6f269 100644 (file)
--- a/src/Makefile.am
+++ b/src/Makefile.am
@@ -72,6 +72,7 @@ libsysdb_la_SOURCES = \
                core/store.c include/core/store.h \
                core/store-private.h \
                core/store_expr.c \
+               core/store_json.c \
                core/store_lookup.c \
                core/data.c include/core/data.h \
                core/timeseries.c include/core/timeseries.h \

diff --git a/src/core/store-private.h b/src/core/store-private.h
index 775057f09e235f9033edc10526a08e65d7f43d47..953a8826c741abbb21e0b8b3e9871922da3e00d8 100644 (file)
--- a/src/core/store-private.h
+++ b/src/core/store-private.h
@@ -106,6 +106,7 @@ typedef struct {
 /*
  * expressions
  */
+
 enum {
        ATTR_VALUE  = -2, /* attr name stored in data.data.string */
        FIELD_VALUE = -1, /* field type stored in data.data.integer */

diff --git a/src/core/store_json.c b/src/core/store_json.c
new file mode 100644 (file)
index 0000000..d9fc37c
--- /dev/null
+++ b/src/core/store_json.c
@@ -0,0 +1,241 @@
+/*
+ * SysDB - src/core/store_json.c
+ * Copyright (C) 2013-2014 Sebastian 'tokkee' Harl <sh@tokkee.org>
+ * All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions
+ * are met:
+ * 1. Redistributions of source code must retain the above copyright
+ *    notice, this list of conditions and the following disclaimer.
+ * 2. Redistributions in binary form must reproduce the above copyright
+ *    notice, this list of conditions and the following disclaimer in the
+ *    documentation and/or other materials provided with the distribution.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+ * ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED
+ * TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
+ * PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDERS OR
+ * CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL,
+ * EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO,
+ * PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS;
+ * OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY,
+ * WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR
+ * OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF
+ * ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+ */
+
+/*
+ * This module implements JSON support.
+ */
+
+#if HAVE_CONFIG_H
+#      include "config.h"
+#endif /* HAVE_CONFIG_H */
+
+#include "sysdb.h"
+#include "core/store-private.h"
+#include "utils/error.h"
+
+#include <assert.h>
+
+#include <stdlib.h>
+
+/*
+ * private data types
+ */
+
+struct sdb_store_json_formatter {
+       sdb_strbuf_t *buf;
+
+       /* The context describes the state of the formatter through
+        * the path pointing to the current object */
+       int context[8];
+       size_t current;
+};
+
+/*
+ * private helper functions
+ */
+
+static int
+json_emit(sdb_store_json_formatter_t *f, sdb_store_obj_t *obj)
+{
+       char time_str[64];
+       char interval_str[64];
+       size_t i;
+
+       assert(f && obj);
+
+       sdb_strbuf_append(f->buf, "{\"name\": \"%s\", ", SDB_OBJ(obj)->name);
+       if (obj->type == SDB_ATTRIBUTE) {
+               char tmp[sdb_data_strlen(&ATTR(obj)->value) + 1];
+               if (sdb_data_format(&ATTR(obj)->value, tmp, sizeof(tmp),
+                                       SDB_DOUBLE_QUOTED) < 0)
+                       snprintf(tmp, sizeof(tmp), "<error>");
+               sdb_strbuf_append(f->buf, "\"value\": %s, ", tmp);
+       }
+
+       /* TODO: make time and interval formats configurable */
+       if (! sdb_strftime(time_str, sizeof(time_str),
+                               "%F %T %z", obj->last_update))
+               snprintf(time_str, sizeof(time_str), "<error>");
+       time_str[sizeof(time_str) - 1] = '\0';
+
+       if (! sdb_strfinterval(interval_str, sizeof(interval_str),
+                               obj->interval))
+               snprintf(interval_str, sizeof(interval_str), "<error>");
+       interval_str[sizeof(interval_str) - 1] = '\0';
+
+       sdb_strbuf_append(f->buf, "\"last_update\": \"%s\", "
+                       "\"update_interval\": \"%s\", \"backends\": [",
+                       time_str, interval_str);
+
+       for (i = 0; i < obj->backends_num; ++i) {
+               sdb_strbuf_append(f->buf, "\"%s\"", obj->backends[i]);
+               if (i < obj->backends_num - 1)
+                       sdb_strbuf_append(f->buf, ",");
+       }
+       sdb_strbuf_append(f->buf, "]");
+       return 0;
+} /* json_emit */
+
+/*
+ * public API
+ */
+
+sdb_store_json_formatter_t *
+sdb_store_json_formatter(sdb_strbuf_t *buf)
+{
+       sdb_store_json_formatter_t *f;
+
+       if (! buf)
+               return NULL;
+
+       f = calloc(1, sizeof(*f));
+       if (! f)
+               return NULL;
+
+       f->buf = buf;
+       f->context[0] = 0;
+       f->current = 0;
+       return f;
+} /* sdb_store_json_formatter */
+
+int
+sdb_store_json_emit(sdb_store_json_formatter_t *f, sdb_store_obj_t *obj)
+{
+       if ((! f) || (! obj))
+               return -1;
+
+       /* first host */
+       if (! f->context[0]) {
+               assert(f->current == 0);
+               f->context[0] = SDB_HOST;
+               return json_emit(f, obj);
+       }
+
+       if (obj->type == f->context[f->current]) {
+               /* new entry of the same type */
+               sdb_strbuf_append(f->buf, "},");
+       }
+       else if ((f->context[f->current] == SDB_HOST)
+                       || (obj->type == SDB_ATTRIBUTE)) {
+               assert(obj->type != SDB_HOST);
+               /* all object types may be children of a host;
+                * attributes may be children of any type */
+               sdb_strbuf_append(f->buf, ", \"%ss\": [",
+                               SDB_STORE_TYPE_TO_NAME(obj->type));
+               ++f->current;
+       }
+       else if (f->current >= 1) {
+               /* new entry of a previous type or a new type on the same level
+                * -> rewind to the right state and then handle the new object */
+               assert(obj->type != SDB_ATTRIBUTE);
+               while (f->current > 0) {
+                       if (f->context[f->current] == obj->type)
+                               break;
+                       assert(f->context[f->current] != SDB_HOST);
+                       sdb_strbuf_append(f->buf, "}]");
+                       --f->current;
+               }
+               return sdb_store_json_emit(f, obj);
+       }
+       else {
+               sdb_log(SDB_LOG_ERR, "store: Unexpected object of type %s "
+                               "on level %zu during JSON serialization",
+                               SDB_STORE_TYPE_TO_NAME(obj->type), f->current);
+               return -1;
+       }
+
+       json_emit(f, obj);
+       assert(f->current < SDB_STATIC_ARRAY_LEN(f->context));
+       f->context[f->current] = obj->type;
+       return 0;
+} /* sdb_store_json_emit */
+
+int
+sdb_store_json_emit_full(sdb_store_json_formatter_t *f, sdb_store_obj_t *obj,
+               sdb_store_matcher_t *filter)
+{
+       sdb_avltree_t *trees[] = { NULL, NULL, NULL };
+       size_t i;
+
+       if (sdb_store_json_emit(f, obj))
+               return -1;
+
+       if (obj->type == SDB_HOST) {
+               trees[0] = HOST(obj)->attributes;
+               trees[1] = HOST(obj)->metrics;
+               trees[2] = HOST(obj)->services;
+       }
+       else if (obj->type == SDB_SERVICE)
+               trees[0] = SVC(obj)->attributes;
+       else if (obj->type == SDB_METRIC)
+               trees[0] = METRIC(obj)->attributes;
+       else if (obj->type == SDB_ATTRIBUTE)
+               return 0;
+       else
+               return -1;
+
+       for (i = 0; i < SDB_STATIC_ARRAY_LEN(trees); ++i) {
+               sdb_avltree_iter_t *iter;
+
+               if (! trees[i])
+                       continue;
+
+               iter = sdb_avltree_get_iter(trees[i]);
+               while (sdb_avltree_iter_has_next(iter)) {
+                       sdb_store_obj_t *child;
+                       child = STORE_OBJ(sdb_avltree_iter_get_next(iter));
+
+                       if (filter && (! sdb_store_matcher_matches(filter, child, NULL)))
+                               continue;
+
+                       if (sdb_store_json_emit_full(f, child, filter)) {
+                               sdb_avltree_iter_destroy(iter);
+                               return -1;
+                       }
+               }
+               sdb_avltree_iter_destroy(iter);
+       }
+       return 0;
+} /* sdb_store_json_emit_full */
+
+int
+sdb_store_json_finish(sdb_store_json_formatter_t *f)
+{
+       if (! f)
+               return -1;
+
+       while (f->current > 0) {
+               sdb_strbuf_append(f->buf, "}]");
+               --f->current;
+       }
+       if (f->context[0])
+               sdb_strbuf_append(f->buf, "}");
+       return 0;
+} /* sdb_store_json_finish */
+
+/* vim: set tw=78 sw=4 ts=4 noexpandtab : */
+

diff --git a/src/include/core/store.h b/src/include/core/store.h
index 2720db472f30abd4c853b7c1c805979749407f25..6dd7d1ade1ca98b952a4ce05a8b1a4f6bc21fa49 100644 (file)
--- a/src/include/core/store.h
+++ b/src/include/core/store.h
@@ -88,6 +88,13 @@ struct sdb_store_matcher;
 typedef struct sdb_store_matcher sdb_store_matcher_t;
 #define SDB_STORE_MATCHER(obj) ((sdb_store_matcher_t *)(obj))
 
+/*
+ * A JSON formatter converts a stored object into the JSON format.
+ * See http://www.ietf.org/rfc/rfc4627.txt
+ */
+struct sdb_store_json_formatter;
+typedef struct sdb_store_json_formatter sdb_store_json_formatter_t;
+
 /*
  * Queryable fields of a stored object.
  */
@@ -612,6 +619,58 @@ int
 sdb_store_host_tojson(sdb_store_obj_t *host, sdb_strbuf_t *buf,
                sdb_store_matcher_t *filter, int flags);
 
+/*
+ * sdb_store_json_formatter:
+ * Create a JSON formatter writing to the specified buffer.
+ */
+sdb_store_json_formatter_t *
+sdb_store_json_formatter(sdb_strbuf_t *buf);
+
+/*
+ * sdb_store_json_emit:
+ * Serialize a single object to JSON adding it to the string buffer associated
+ * with the formatter object. The serialized object will not include
+ * attributes or any child objects. Instead, call the function again for each
+ * of those objects. All attributes have to be emitted before any other
+ * children types. Use sdb_store_json_emit_full() to emit a full (filtered)
+ * object.
+ *
+ * Note that the output might not be valid JSON before calling
+ * sdb_store_json_finish().
+ *
+ * Returns:
+ *  - 0 on success
+ *  - a negative value else
+ */
+int
+sdb_store_json_emit(sdb_store_json_formatter_t *f, sdb_store_obj_t *obj);
+
+/*
+ * sdb_store_json_emit_full:
+ * Serialize a single object including it's attributes and all children to
+ * JSON, adding it to the string buffer associated with the formatter object.
+ * The filter, if specified, is applied to each attribute and child object.
+ * Only matching objects will be included in the output.
+ *
+ * Note that the output might not be valid JSON before calling
+ * sdb_store_json_finish().
+ *
+ * Returns:
+ *  - 0 on success
+ *  - a negative value else
+ */
+int
+sdb_store_json_emit_full(sdb_store_json_formatter_t *f, sdb_store_obj_t *obj,
+               sdb_store_matcher_t *filter);
+
+/*
+ * sdb_store_json_finish:
+ * Finish the JSON output. This function has to be called once after emiting
+ * all objects.
+ */
+int
+sdb_store_json_finish(sdb_store_json_formatter_t *f);
+
 #ifdef __cplusplus
 } /* extern "C" */
 #endif