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renderd: fix PostGIS memory growth with parameterize_style #502

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Merged
hummeltech merged 1 commit into from
Oct 10, 2026
Merged

renderd: fix PostGIS memory growth with parameterize_style #502

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53 changes: 35 additions & 18 deletions src/gen_tile.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -89,6 +89,11 @@ struct projectionconfig {

struct xmlmapconfig {
Map map;
/* Cache of parameterized Map copies keyed by the options string.
* Avoids recreating PostGIS datasource objects (and their connection
* pools) on every render, which would accumulate in Mapnik's global
* ConnectionManager and exhaust memory under sustained load. */
std::map<std::string, mapnik::Map> parameterized_map_cache;
const char *host;
const char *htcphost;
const char *output_format;
Expand Down Expand Up @@ -247,31 +252,43 @@ static enum protoCmd render(struct xmlmapconfig *map, int x, int y, int z, char
unsigned int render_size_tx = MIN(METATILE, map->prj->aspect_x * (1 << z));
unsigned int render_size_ty = MIN(METATILE, map->prj->aspect_y * (1 << z));

map->map.resize(render_size_tx * map->tilesize, render_size_ty * map->tilesize);
map->map.zoom_to_box(tile2prjbounds(map->prj, x, y, z));
/* Select the map to render with: a cached parameterized copy, or the base map. */
mapnik::Map *render_map;

if (map->parameterize_function) {
/* Look up or create a parameterized map for this options string.
* Re-using a cached copy avoids calling set_datasource() on every
* render, which would create a new PostGIS connection pool entry in
* Mapnik's global ConnectionManager each time and leak memory. */
auto it = map->parameterized_map_cache.find(std::string(options));

if (it == map->parameterized_map_cache.end()) {
mapnik::Map parameterized = map->map;
map->parameterize_function(parameterized, options);
parameterized.load_fonts();
auto inserted = map->parameterized_map_cache.emplace(std::string(options), std::move(parameterized));
it = inserted.first;
g_logger(G_LOG_LEVEL_DEBUG, "Cached new parameterized map for options '%s' (cache size: %zu)",
options, map->parameterized_map_cache.size());
}

if (map->map.buffer_size() == 0) { // Only set buffer size if the buffer size isn't explicitly set in the mapnik stylesheet.
map->map.set_buffer_size((map->tilesize >> 1) * map->scale);
render_map = &it->second;
} else {
render_map = &map->map;
}

// m.zoom(size+1);
render_map->resize(render_size_tx * map->tilesize, render_size_ty * map->tilesize);
render_map->zoom_to_box(tile2prjbounds(map->prj, x, y, z));

if (render_map->buffer_size() == 0) { // Only set buffer size if the buffer size isn't explicitly set in the mapnik stylesheet.
render_map->set_buffer_size((map->tilesize >> 1) * map->scale);
}

mapnik::image_32 buf(render_size_tx * map->tilesize, render_size_ty * map->tilesize);

try {
if (map->parameterize_function) {
Map map_parameterized = map->map;

map->parameterize_function(map_parameterized, options);

map_parameterized.load_fonts();

mapnik::agg_renderer<mapnik::image_32> ren(map_parameterized, buf, map->scale);
ren.apply();
} else {
mapnik::agg_renderer<mapnik::image_32> ren(map->map, buf, map->scale);
ren.apply();
}
mapnik::agg_renderer<mapnik::image_32> ren(*render_map, buf, map->scale);
ren.apply();
} catch (std::exception const &ex) {
g_logger(G_LOG_LEVEL_ERROR, "failed to render TILE %s %d %d-%d %d-%d", map->xmlname, z, x, x + render_size_tx - 1, y, y + render_size_ty - 1);
g_logger(G_LOG_LEVEL_ERROR, " reason: %s", ex.what());
Expand Down
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